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  #1   Report Post  
Ken Sterling
 
Posts: n/a
Default A different single-point threading question....

All,
I also have a question concerning single-point threading.
I recently started practicing making a few *small* parts for
a miniature hit n miss engine I'm going to build (never had to
make stuff this small before). One of the pieces is a
downsized "grease cup" as is seen on some bigger
machinery for greasing the bearings. Simply a threaded
fixture to screw into the bearing cap, and a reservoir with a
grease cap to be tightened to force grease down through
a small hole into the bearing.
As I very seldom had to thread mating parts without having the "other
half" to try for fit, I'm in the process of "bettering" my accuracy so
when I make the female thread, the male thread will fit as it should.
I have a nice threading book (using 29 degrees angle) from Sears/Atlas
showing a lot of info, but I also wanted to try something.
Example:
1/4-20 threaded male piece.
Charts show the major diameter of .2500 with a minor diameter of .1850
which corresponds to the National Form Tool Double Depth of Thread
of .0650. (.2500 minus .0650 equals .1850). The manual I have shows
depth of compound feed for the thread to be .037. So all is well
and good so far.
The chart also shows calculations for VEE form tool being Double Depth
of Thread of .0758. Therefore, .2500 minus .0758 leaves minor
diameter of .1742. The compound feed is shown to be .043 for the VEE
thread. Again, okay so far.
Now... I have Guy Lautard's bedside reader showing a formula for
diameter reduction and also length reduction.
Using the VEE form example above, I need to reduct the diameter
of the shaft by .0650 in the threading process. Dividing this number
by 2 for my lathe, I need a "crossslide" infeed of .0325 for the depth
of thread.
Using Lautard's system for small crossslide infeeds by using the
compound, his formula is:
Amount of crossslide infeed needed divided by sin of compound angle
setting. Therefore .0325 divided by sin(29 degrees) should give me
the correct amount of compound infeed to equal the amount of
crossslide infeed I'm attempting to get. Formula yields .0670.
Wrong answer..... what am I overlooking? The charts in the
manual work well and the fit is good, but I was just trying to
use a method which prevents looking up everything.
Thanks.
Ken.

  #2   Report Post  
Bill Darby
 
Posts: n/a
Default A different single-point threading question....

Hi Ken

for a 1/4 " shaft the major diameter is supposed to be a 1/4 ". at the
same time
the thread form says that each of the thread crests should be flat and
the width
of the flat should be equal to 1/8 th of the thread pitch. So that
leaves 7/8 ths of
the thread pitch to form the top of the equilateral triangle that
defines the shape
of the thread.

So in a 1/4-20 threaded male the pitch is .050" and 7/8 ths of that is
..04375"
So all the sides of the equilateral triangle are .04375"
So the distance from first touch (with a sharp tool) using a 29.5 degree
compound is close enough to .04375" to be just that.

If for some reason you need the double depth then it is cos 30 or .866
times the
length of the sides (.04375") which gives the height of the equilateral
triangle and twice that is the double depth. (.866*.04375*2= .075775")

Nothing to look up!

Bill


"Ken Sterling" wrote in message
s.com...
All,
I also have a question concerning single-point threading.
I recently started practicing making a few *small* parts for
a miniature hit n miss engine I'm going to build (never had to
make stuff this small before). One of the pieces is a
downsized "grease cup" as is seen on some bigger
machinery for greasing the bearings. Simply a threaded
fixture to screw into the bearing cap, and a reservoir with a
grease cap to be tightened to force grease down through
a small hole into the bearing.
As I very seldom had to thread mating parts without having the "other
half" to try for fit, I'm in the process of "bettering" my accuracy so
when I make the female thread, the male thread will fit as it should.
I have a nice threading book (using 29 degrees angle) from Sears/Atlas
showing a lot of info, but I also wanted to try something.
Example:
1/4-20 threaded male piece.
Charts show the major diameter of .2500 with a minor diameter of .1850
which corresponds to the National Form Tool Double Depth of Thread
of .0650. (.2500 minus .0650 equals .1850). The manual I have shows
depth of compound feed for the thread to be .037. So all is well
and good so far.
The chart also shows calculations for VEE form tool being Double Depth
of Thread of .0758. Therefore, .2500 minus .0758 leaves minor
diameter of .1742. The compound feed is shown to be .043 for the VEE
thread. Again, okay so far.
Now... I have Guy Lautard's bedside reader showing a formula for
diameter reduction and also length reduction.
Using the VEE form example above, I need to reduct the diameter
of the shaft by .0650 in the threading process. Dividing this number
by 2 for my lathe, I need a "crossslide" infeed of .0325 for the depth
of thread.
Using Lautard's system for small crossslide infeeds by using the
compound, his formula is:
Amount of crossslide infeed needed divided by sin of compound angle
setting. Therefore .0325 divided by sin(29 degrees) should give me
the correct amount of compound infeed to equal the amount of
crossslide infeed I'm attempting to get. Formula yields .0670.
Wrong answer..... what am I overlooking? The charts in the
manual work well and the fit is good, but I was just trying to
use a method which prevents looking up everything.
Thanks.
Ken.



  #3   Report Post  
Harold & Susan Vordos
 
Posts: n/a
Default A different single-point threading question....


"Ken Sterling" wrote in message
s.com...
All,
I also have a question concerning single-point threading.
I recently started practicing making a few *small* parts for
a miniature hit n miss engine I'm going to build (never had to
make stuff this small before). One of the pieces is a
downsized "grease cup" as is seen on some bigger
machinery for greasing the bearings. Simply a threaded
fixture to screw into the bearing cap, and a reservoir with a
grease cap to be tightened to force grease down through
a small hole into the bearing.
As I very seldom had to thread mating parts without having the "other
half" to try for fit, I'm in the process of "bettering" my accuracy so
when I make the female thread, the male thread will fit as it should.
I have a nice threading book (using 29 degrees angle) from Sears/Atlas
showing a lot of info, but I also wanted to try something.
Example:
1/4-20 threaded male piece.
Charts show the major diameter of .2500 with a minor diameter of .1850
which corresponds to the National Form Tool Double Depth of Thread
of .0650. (.2500 minus .0650 equals .1850). The manual I have shows
depth of compound feed for the thread to be .037. So all is well
and good so far.
The chart also shows calculations for VEE form tool being Double Depth
of Thread of .0758. Therefore, .2500 minus .0758 leaves minor
diameter of .1742. The compound feed is shown to be .043 for the VEE
thread. Again, okay so far.
Now... I have Guy Lautard's bedside reader showing a formula for
diameter reduction and also length reduction.
Using the VEE form example above, I need to reduct the diameter
of the shaft by .0650 in the threading process. Dividing this number
by 2 for my lathe, I need a "crossslide" infeed of .0325 for the depth
of thread.
Using Lautard's system for small crossslide infeeds by using the
compound, his formula is:
Amount of crossslide infeed needed divided by sin of compound angle
setting. Therefore .0325 divided by sin(29 degrees) should give me
the correct amount of compound infeed to equal the amount of
crossslide infeed I'm attempting to get. Formula yields .0670.
Wrong answer..... what am I overlooking? The charts in the
manual work well and the fit is good, but I was just trying to
use a method which prevents looking up everything.
Thanks.
Ken.


Hi Ken,
Cutting threads by major and minor diameter is not a good idea due to the
random flat that usually accompanies a threading tool. Without a
comparator to know its width, the formulas are useless. I strongly
recommend you use thread wires and threading charts to cut your threads.
The use of any of the trick calculations are only as reliable as the
information you have concerning your threading tool, and the degree of
precision with which you pick up the surface to be threaded, taking into
account the variation in major diameter. On small threads its entirely
possible you'd have more error than the small amount of tolerance common to
some threads. Relying on threading charts removes all the questions,
because you machine to known dimensions. Pretty much anything you need to
know is published in Machinery's Handbook. This may sound like overkill to
you, but it is a part of learning to cut threads properly.

Harold


  #4   Report Post  
Ken Sterling
 
Posts: n/a
Default A different single-point threading question....

Hi Ken

for a 1/4 " shaft the major diameter is supposed to be a 1/4 ". at the
same time
the thread form says that each of the thread crests should be flat and
the width
of the flat should be equal to 1/8 th of the thread pitch. So that
leaves 7/8 ths of
the thread pitch to form the top of the equilateral triangle that
defines the shape
of the thread.

So in a 1/4-20 threaded male the pitch is .050" and 7/8 ths of that is
.04375"
So all the sides of the equilateral triangle are .04375"
So the distance from first touch (with a sharp tool) using a 29.5 degree
compound is close enough to .04375" to be just that.

If for some reason you need the double depth then it is cos 30 or .866
times the
length of the sides (.04375") which gives the height of the equilateral
triangle and twice that is the double depth. (.866*.04375*2= .075775")

Nothing to look up!

Bill


"Ken Sterling" wrote in message
ws.com...
All,
I also have a question concerning single-point threading.
I recently started practicing making a few *small* parts for
a miniature hit n miss engine I'm going to build (never had to
make stuff this small before). One of the pieces is a
downsized "grease cup" as is seen on some bigger
machinery for greasing the bearings. Simply a threaded
fixture to screw into the bearing cap, and a reservoir with a
grease cap to be tightened to force grease down through
a small hole into the bearing.
As I very seldom had to thread mating parts without having the "other
half" to try for fit, I'm in the process of "bettering" my accuracy so
when I make the female thread, the male thread will fit as it should.
I have a nice threading book (using 29 degrees angle) from Sears/Atlas
showing a lot of info, but I also wanted to try something.
Example:
1/4-20 threaded male piece.
Charts show the major diameter of .2500 with a minor diameter of .1850
which corresponds to the National Form Tool Double Depth of Thread
of .0650. (.2500 minus .0650 equals .1850). The manual I have shows
depth of compound feed for the thread to be .037. So all is well
and good so far.
The chart also shows calculations for VEE form tool being Double Depth
of Thread of .0758. Therefore, .2500 minus .0758 leaves minor
diameter of .1742. The compound feed is shown to be .043 for the VEE
thread. Again, okay so far.
Now... I have Guy Lautard's bedside reader showing a formula for
diameter reduction and also length reduction.
Using the VEE form example above, I need to reduct the diameter
of the shaft by .0650 in the threading process. Dividing this number
by 2 for my lathe, I need a "crossslide" infeed of .0325 for the depth
of thread.
Using Lautard's system for small crossslide infeeds by using the
compound, his formula is:
Amount of crossslide infeed needed divided by sin of compound angle
setting. Therefore .0325 divided by sin(29 degrees) should give me
the correct amount of compound infeed to equal the amount of
crossslide infeed I'm attempting to get. Formula yields .0670.
Wrong answer..... what am I overlooking? The charts in the
manual work well and the fit is good, but I was just trying to
use a method which prevents looking up everything.
Thanks.
Ken.



Thanks, Bill.
I worked out the numbers on a bunch of different thread profiles and
they seem to match the charts in my threading manual for my lathe.
(Some of the numbers in the charts were of course, rounded off, but
working out the formula carries out more decimal places than these
eyes will ever be able to see, :-) )
Thanks for the info - I think it will be handy - Now to find some more
"free" time to get back to the lathe.....
Thanks again.
Ken.

  #5   Report Post  
Ken Sterling
 
Posts: n/a
Default A different single-point threading question....


"Ken Sterling" wrote in message
ws.com...
All,
I also have a question concerning single-point threading.
I recently started practicing making a few *small* parts for
a miniature hit n miss engine I'm going to build (never had to
make stuff this small before). One of the pieces is a
downsized "grease cup" as is seen on some bigger
machinery for greasing the bearings. Simply a threaded
fixture to screw into the bearing cap, and a reservoir with a
grease cap to be tightened to force grease down through
a small hole into the bearing.
As I very seldom had to thread mating parts without having the "other
half" to try for fit, I'm in the process of "bettering" my accuracy so
when I make the female thread, the male thread will fit as it should.
I have a nice threading book (using 29 degrees angle) from Sears/Atlas
showing a lot of info, but I also wanted to try something.
Example:
1/4-20 threaded male piece.
Charts show the major diameter of .2500 with a minor diameter of .1850
which corresponds to the National Form Tool Double Depth of Thread
of .0650. (.2500 minus .0650 equals .1850). The manual I have shows
depth of compound feed for the thread to be .037. So all is well
and good so far.
The chart also shows calculations for VEE form tool being Double Depth
of Thread of .0758. Therefore, .2500 minus .0758 leaves minor
diameter of .1742. The compound feed is shown to be .043 for the VEE
thread. Again, okay so far.
Now... I have Guy Lautard's bedside reader showing a formula for
diameter reduction and also length reduction.
Using the VEE form example above, I need to reduct the diameter
of the shaft by .0650 in the threading process. Dividing this number
by 2 for my lathe, I need a "crossslide" infeed of .0325 for the depth
of thread.
Using Lautard's system for small crossslide infeeds by using the
compound, his formula is:
Amount of crossslide infeed needed divided by sin of compound angle
setting. Therefore .0325 divided by sin(29 degrees) should give me
the correct amount of compound infeed to equal the amount of
crossslide infeed I'm attempting to get. Formula yields .0670.
Wrong answer..... what am I overlooking? The charts in the
manual work well and the fit is good, but I was just trying to
use a method which prevents looking up everything.
Thanks.
Ken.


Hi Ken,
Cutting threads by major and minor diameter is not a good idea due to the
random flat that usually accompanies a threading tool. Without a
comparator to know its width, the formulas are useless. I strongly
recommend you use thread wires and threading charts to cut your threads.
The use of any of the trick calculations are only as reliable as the
information you have concerning your threading tool, and the degree of
precision with which you pick up the surface to be threaded, taking into
account the variation in major diameter. On small threads its entirely
possible you'd have more error than the small amount of tolerance common to
some threads. Relying on threading charts removes all the questions,
because you machine to known dimensions. Pretty much anything you need to
know is published in Machinery's Handbook. This may sound like overkill to
you, but it is a part of learning to cut threads properly.

Harold


Thanks Harold. Your point is understood and well taken. My question
in my original post, though, kind of reflected on the fact that when I
determined Major Dia, and then Minor Dia, I knew how much the diameter
had to be reduced to get to the Minor Dia. What I couldn't understand
is why, using Guy Lautard's Diameter Reduction Formula (amount of
diameter reduction, divided by the sin(29 degrees)) would not give me
the proper amount of compound infeed. Still haven't figured out that
one - I guess it really doesn't matter, but I hate it when I can see
the formula, and it works with the example, but when applied to
another situation - it sucks.
Thanks again for your response.
Ken.



  #6   Report Post  
DoN. Nichols
 
Posts: n/a
Default A different single-point threading question....

In article m,
Ken Sterling Ken Sterling wrote:

[ ... ]

Thanks Harold. Your point is understood and well taken. My question
in my original post, though, kind of reflected on the fact that when I
determined Major Dia, and then Minor Dia, I knew how much the diameter
had to be reduced to get to the Minor Dia. What I couldn't understand
is why, using Guy Lautard's Diameter Reduction Formula (amount of
diameter reduction, divided by the sin(29 degrees)) would not give me
the proper amount of compound infeed.


Is your compound set to 29 degrees? If to some other angle, you
will need to calculate using the sine of whatever angle you are actually
using.

And after all -- the pitch diameter is what really matters.
Hence the measuring over wires.

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---
  #7   Report Post  
Harold & Susan Vordos
 
Posts: n/a
Default A different single-point threading question....


"DoN. Nichols" wrote in message
...
snip-------
And after all -- the pitch diameter is what really matters.
Hence the measuring over wires.

Enjoy,
DoN.



Yep, my point, exactly. All the rest does is cloud the issue. None of it
is close enough to use for proper threading.

Harold


  #8   Report Post  
Ken Sterling
 
Posts: n/a
Default A different single-point threading question....


"DoN. Nichols" wrote in message
...
snip-------
And after all -- the pitch diameter is what really matters.
Hence the measuring over wires.

Enjoy,
DoN.



Yep, my point, exactly. All the rest does is cloud the issue. None of it
is close enough to use for proper threading.

Harold


Points well taken, but in this particular situation, I'm threading
5/16-40, internal, 3/16 deep to a solid bottom. Don't know any
way to check this so just wanted to get the numbers as close as I can.
Thanks.
Ken.

  #9   Report Post  
Harold & Susan Vordos
 
Posts: n/a
Default A different single-point threading question....


"Ken Sterling" wrote in message
s.com...

"DoN. Nichols" wrote in message
...
snip-------
And after all -- the pitch diameter is what really matters.
Hence the measuring over wires.

Enjoy,
DoN.



Yep, my point, exactly. All the rest does is cloud the issue. None of

it
is close enough to use for proper threading.

Harold


Points well taken, but in this particular situation, I'm threading
5/16-40, internal, 3/16 deep to a solid bottom. Don't know any
way to check this so just wanted to get the numbers as close as I can.
Thanks.
Ken.


In a case such as this, what I've done is turn my own plug gage. By using
(proper) wires and cutting the thread to proper form you can enjoy
considerable success, although the gage is subject to change, so it is good
for only a minimum amount of use. It's a good idea to use something like
O6 tool steel (Graph-Mo, for example), which tends to leave a better finish
than carbon steel. A leaded steel might be a good choice for a very small
amount of usage. It is also critical to have the use of a comparator, or
at least good magnification, so the proper amount of flat can be ground on
the threading tool, which, in the case of such a fine thread, is very
slight. If the thread in question is critical (such as having to pass
inspection) the chance of hitting the proper pitch diameter by trusting the
compound movement would be very small due to the minimal tolerance, although
certainly possible. The problem is you don't really have any idea if the
thread being generated is where you think it is, so it's very easy to stop
at the proper number on the dial and be off, either too large or too small
on the pitch diameter.

Hope this helps, Ken. It's not intended to give you a bad time.

Good luck!

Harold


  #10   Report Post  
Ken Sterling
 
Posts: n/a
Default A different single-point threading question....


"Ken Sterling" wrote in message
ws.com...

"DoN. Nichols" wrote in message
...
snip-------
And after all -- the pitch diameter is what really matters.
Hence the measuring over wires.

Enjoy,
DoN.


Yep, my point, exactly. All the rest does is cloud the issue. None of

it
is close enough to use for proper threading.

Harold


Points well taken, but in this particular situation, I'm threading
5/16-40, internal, 3/16 deep to a solid bottom. Don't know any
way to check this so just wanted to get the numbers as close as I can.
Thanks.
Ken.


In a case such as this, what I've done is turn my own plug gage. By using
(proper) wires and cutting the thread to proper form you can enjoy
considerable success, although the gage is subject to change, so it is good
for only a minimum amount of use. It's a good idea to use something like
O6 tool steel (Graph-Mo, for example), which tends to leave a better finish
than carbon steel. A leaded steel might be a good choice for a very small
amount of usage. It is also critical to have the use of a comparator, or
at least good magnification, so the proper amount of flat can be ground on
the threading tool, which, in the case of such a fine thread, is very
slight. If the thread in question is critical (such as having to pass
inspection) the chance of hitting the proper pitch diameter by trusting the
compound movement would be very small due to the minimal tolerance, although
certainly possible. The problem is you don't really have any idea if the
thread being generated is where you think it is, so it's very easy to stop
at the proper number on the dial and be off, either too large or too small
on the pitch diameter.

Hope this helps, Ken. It's not intended to give you a bad time.

Good luck!

Harold


No "bad time" taken, Harold. I appreciate the info and tips. This
application is certainly not critical, but for my own use and I think
(after a couple of different tries) I'm getting the "hang" of it. :-)
I like the idea of a "temporary" plug gauge.... I may just take that
route. Thanks
Ken.




  #11   Report Post  
Ted Edwards
 
Posts: n/a
Default A different single-point threading question....

Bill Darby wrote:

for a 1/4 " shaft the major diameter is supposed to be a 1/4 ".


Bill, you have sadi this many times and now I wonder if we both mean the
same thing by "major diameter". I mean the mesurement I get if I close
a flat faced micrometer over the outside of a male thread having removed
any burrs if present. What do you mean?

I ask because I understand that the only 1/4" thread with a full 0.2500"
o.d. would be one with a sharp V-topped thread. Any comercial 1/4"
thread I have measured has always been rather less than 0.2500 o.d.,
typically by about 1/8 of the nominal thread depth.

Also, any thread I have single pointed has always needed to be cut a
little deeper to fit than you indicate, assuming I understand you
correctly. I would like to understand this better.

Ted


  #12   Report Post  
Ted Edwards
 
Posts: n/a
Default A different single-point threading question....

Harold & Susan Vordos wrote:

Yep, my point, exactly. All the rest does is cloud the issue. None of it
is close enough to use for proper threading.


Guess I'm going to have to cut some music wire and make a holder.
Otherwise this could be awkward with only two hands. :-) Any ideas on
this holder?

Ted


  #13   Report Post  
Robert Swinney
 
Posts: n/a
Default A different single-point threading question....

for a 1/4 " shaft the major diameter is supposed to be a 1/4 ".
Bill, you have sadi this many times and now I wonder if we both mean the
same thing by "major diameter".


This is confusing, to say the least. Here is a good approach:

Always take "diameter" to mean the actual outside, full diameter of the rod
or bolt to be threaded; as in 1/4-20, diameter is 0.250; 3/8-16 diameter is
0.375, etc. For bolt or rod to thread use the formula:

Bolt size = Diameter - ((1.299 x %) / pitch))

Where diameter is as explained above, % is expressed as a decimal, and pitch
is the number of threads per inch.

Bob Swinney


  #14   Report Post  
Harold & Susan Vordos
 
Posts: n/a
Default A different single-point threading question....


"Ted Edwards" wrote in message
...
Harold & Susan Vordos wrote:

Yep, my point, exactly. All the rest does is cloud the issue. None of

it
is close enough to use for proper threading.


Guess I'm going to have to cut some music wire and make a holder.
Otherwise this could be awkward with only two hands. :-) Any ideas on
this holder?

Ted


No holder. The use of thread wires with your object still in a lathe is
very easy, with a holder only adding to problems. One of the problems
would be the influence the holder would have over the wires. That may
sound trivial, but it's not, and a caution of this very thing accompanies
good wires. The wires must be free to conform to the thread. Even a
little tape on one end can influence a reading, especially on larger wires.

People with your ability with math would have no trouble calculating the
proper measurement over wires when choosing random diameters for measuring,
but folks like me, with only a high school education, one that did not
consist of any advanced mathematics, would have a difficult time calculating
the proper readings. Further, and in this case it likely makes no
difference at all, if you were chasing threads that needed acceptance by
inspection, the readings would most likely be disputed by an inspection
department. Standard thread wires (not the little cheap PeeDee sets, but
the wires sold by such firms as Deltronics) are precision instruments, with
diameters held to millionths, and come with certification. The wires are of
such a quality that they can be used for certification of thread gages.
These wires come with a constant that is added to the maximum and minimum
thread pitch, which one fetches from a source such as Machinery's Handbook.
Measuring threads by this method is very simple and is acceptable by
inspection. It is likely well overkill for the home shop type, but is good
and acceptable practice in any shop.

Back to the use of thread wires. To use them, one sets the mike so it's
opened slightly larger than the intended reading, places two wires on the
top side of the item to be measured, spread a distance slightly narrower
than the diameter of the spindle, then straddles the wires with the spindle.
lightly pressing the wires to keep them from falling. The third wire,
which is held in one's lips, is then slid between the anvil and the part,
splitting the distance between the top wires, so a three point reading can
be taken. When the open distance is fairly close, the wires will stay in
place with no trouble at all once the third wire is installed. One then
tightens the spindle, keeping the face parallel with the top two wires,
rocking the mike for feel, until it is measuring the distance over the
wires. Once learned this way, it's very easy, and fast, and requires
no holder.

One word of caution, and it matters not the source of your wires, be they
the expensive commercial wires such as the Deltronics, P&W, or just the
simple set sold be PeeDee: ALWAYS clean out your chip pan when measuring
threads. It's amazing how a long wire looks like the rest of the chips when
you drop them.

Good luck!

Harold


  #15   Report Post  
Harold & Susan Vordos
 
Posts: n/a
Default A different single-point threading question....


"Robert Swinney" wrote in message
...
for a 1/4 " shaft the major diameter is supposed to be a 1/4 ".

Bill, you have sadi this many times and now I wonder if we both mean the
same thing by "major diameter".


This is confusing, to say the least. Here is a good approach:

Always take "diameter" to mean the actual outside, full diameter of the

rod
or bolt to be threaded; as in 1/4-20, diameter is 0.250; 3/8-16 diameter

is
0.375, etc. For bolt or rod to thread use the formula:

Bolt size = Diameter - ((1.299 x %) / pitch))

Where diameter is as explained above, % is expressed as a decimal, and

pitch
is the number of threads per inch.

Bob Swinney


I would assume that, for the home shop types, it may be confusing, but it's
not when a thread is specified. Part of the information provided by
threading charts is the *proper* major diameter, which varies depending on
the nature of a thread. In other words, not all 1/4-20 threads are created
equally.

One example:

1/4-20 2A
Major diameter range: .2489"/.2408"

1/4-20 3A
Major diameter range: .2500"/.2419"

None of the features of threads are left to discretion. Simply referencing
the charts will provide the necessary information in order to chase proper
threads. The only exception is the width of the flat for modified V form
threads, which is not included in most charts, although the minor diameter
is specified.

Harold







  #16   Report Post  
Bill
 
Posts: n/a
Default A different single-point threading question....

Hi Ted

I wonder if we both mean the same thing by "major diameter". I mean the
measurement I get if I close a flat faced micrometer over the outside of a
male thread


Yes I meant that they were one in the same IE : "major diameter. I mean the
measurement I get if I close a flat faced micrometer over the outside of a male
thread"

Yes they are one in the same. In regard to Harold's point depending on the
class of thread the actual measurement will not necessarily be the same as the
designated diameter. (as he elaborated upon) IE: A given class of 1/4" thread
might call for a major diameter something less then .25"

I ask because I understand that the only 1/4" thread with a full 0.2500"
o.d. would be one with a sharp V-topped thread.


No this is not a true assertion. The 1/8 th * pitch flat on the crest of the
thread is supposed to be made at the actual major diameter.

Without getting into various classes of threads and their associated major
diameters (see Harold's post) this is why I wanted to stick to a generic 1/4
thread with a 1/4 major diameter because it illustrates very clearly that the
1/8 * pitch flat occurs at the major diameter.

As I see it the thread form designers were quite smart and cost conscious. They
probably wanted to throw away the very weak pip portion of the V-topped thread
because it meant that the diameter of the stock was quit large to accommodate
the sharp V-tops. So they truncated useless top 1/8 th of the thread height and
made the resulting flat occur at the major diameter which is essentially the
same size of the stock used to form the thread.

Also, any thread I have single pointed has always needed to be cut a
little deeper to fit than you indicate, assuming I understand you
correctly. I would like to understand this better.


I also have had this same experience. The answer lies in the various classes of
thread you may be trying to mate your thread with. What I have said (I believe
to be correct) but it is a generic explanation. As you would be aware, all the
various classes of threads call for various dimensions, Not that the various
dimensions change the thread form but they call for various major diameters.

The Major diameter varies with each class of thread but the one thing about the
thread form that is always constant, is the width of the flat. It is always 1/8
th * the pitch. This means that equilateral triangle that forms the thread shape
is always the same, ie 7/8 ths of the pitch length on edge.

All of which simply means that all classes of external threads are cut the same,
except that the start diameter should conform to the stated major diameter of
the class of thread you want to cut.

Sorry I talked so much I am kind of on the fly!

Bill





Ted Edwards wrote:

Bill Darby wrote:

for a 1/4 " shaft the major diameter is supposed to be a 1/4 ".


Bill, you have sadi this many times and now I wonder if we both mean the
same thing by "major diameter". I mean the mesurement I get if I close
a flat faced micrometer over the outside of a male thread having removed
any burrs if present. What do you mean?

I ask because I understand that the only 1/4" thread with a full 0.2500"
o.d. would be one with a sharp V-topped thread. Any comercial 1/4"
thread I have measured has always been rather less than 0.2500 o.d.,
typically by about 1/8 of the nominal thread depth.

Also, any thread I have single pointed has always needed to be cut a
little deeper to fit than you indicate, assuming I understand you
correctly. I would like to understand this better.

Ted


  #17   Report Post  
Robert Swinney
 
Posts: n/a
Default A different single-point threading question....

Harold sez:

" The only exception is the width of the flat for modified V form
threads, which is not included in most charts, although the minor diameter
is specified."


I didn't do a lot of research on this but, I think the formula I gave is for
the diameter of a bolt for cutting sharp "V" threads on a lathe. Without
going into a lot of "class distinction" I believe the formula will also work
quite well for the basic starting diameter for rods to be threaded (chased
??) with a die. As Harold said, it is OK for us home-shop types. Granted,
it may get into trouble with extremely hard material. Then, one would be
well advised to go to "class".

Bob Swinney




"Harold & Susan Vordos" wrote in message
...

"Robert Swinney" wrote in message
...
for a 1/4 " shaft the major diameter is supposed to be a 1/4 ".
Bill, you have sadi this many times and now I wonder if we both mean

the
same thing by "major diameter".


This is confusing, to say the least. Here is a good approach:

Always take "diameter" to mean the actual outside, full diameter of the

rod
or bolt to be threaded; as in 1/4-20, diameter is 0.250; 3/8-16

diameter
is
0.375, etc. For bolt or rod to thread use the formula:

Bolt size = Diameter - ((1.299 x %) / pitch))

Where diameter is as explained above, % is expressed as a decimal, and

pitch
is the number of threads per inch.

Bob Swinney


I would assume that, for the home shop types, it may be confusing, but

it's
not when a thread is specified. Part of the information provided by
threading charts is the *proper* major diameter, which varies depending on
the nature of a thread. In other words, not all 1/4-20 threads are

created
equally.

One example:

1/4-20 2A
Major diameter range: .2489"/.2408"

1/4-20 3A
Major diameter range: .2500"/.2419"

None of the features of threads are left to discretion. Simply

referencing
the charts will provide the necessary information in order to chase

proper
threads.
Harold







  #18   Report Post  
Robert Swinney
 
Posts: n/a
Default A different single-point threading question....

Bill, Your rationale is quite clear and one that many "thread cutters" would
be the better off to understand. Key to working one's way through the
thread jungle is that originally, depending on how far back you want to go,
all threads were cut on the lathe. I would guess that, originally, they all
started out as sharp "Vs". As I understand it, departures from sharp "Vs"
began in England with Sir Jos. Whitworth's 55 degree thread. Than gradually
after that, standardized types and classes began to appear. Now, with ISO,
I would suppose the standards are now, welll, errr, standardized. From what
I read, standards were not fully defined until after WWII.

Bob Swinney

"Bill" wrote in message
...
Hi Ted

I wonder if we both mean the same thing by "major diameter". I mean the
measurement I get if I close a flat faced micrometer over the outside of

a
male thread


Yes I meant that they were one in the same IE : "major diameter. I

mean the
measurement I get if I close a flat faced micrometer over the outside of a

male
thread"

Yes they are one in the same. In regard to Harold's point depending

on the
class of thread the actual measurement will not necessarily be the same

as the
designated diameter. (as he elaborated upon) IE: A given class of 1/4"

thread
might call for a major diameter something less then .25"

I ask because I understand that the only 1/4" thread with a full 0.2500"
o.d. would be one with a sharp V-topped thread.


No this is not a true assertion. The 1/8 th * pitch flat on the crest of

the
thread is supposed to be made at the actual major diameter.

Without getting into various classes of threads and their associated major
diameters (see Harold's post) this is why I wanted to stick to a generic

1/4
thread with a 1/4 major diameter because it illustrates very clearly that

the
1/8 * pitch flat occurs at the major diameter.

As I see it the thread form designers were quite smart and cost conscious.

They
probably wanted to throw away the very weak pip portion of the V-topped

thread
because it meant that the diameter of the stock was quit large to

accommodate
the sharp V-tops. So they truncated useless top 1/8 th of the thread

height and
made the resulting flat occur at the major diameter which is essentially

the
same size of the stock used to form the thread.

Also, any thread I have single pointed has always needed to be cut a
little deeper to fit than you indicate, assuming I understand you
correctly. I would like to understand this better.


I also have had this same experience. The answer lies in the various

classes of
thread you may be trying to mate your thread with. What I have said (I

believe
to be correct) but it is a generic explanation. As you would be aware, all

the
various classes of threads call for various dimensions, Not that the

various
dimensions change the thread form but they call for various major

diameters.

The Major diameter varies with each class of thread but the one thing

about the
thread form that is always constant, is the width of the flat. It is

always 1/8
th * the pitch. This means that equilateral triangle that forms the thread

shape
is always the same, ie 7/8 ths of the pitch length on edge.

All of which simply means that all classes of external threads are cut the

same,
except that the start diameter should conform to the stated major diameter

of
the class of thread you want to cut.

Sorry I talked so much I am kind of on the fly!

Bill





Ted Edwards wrote:

Bill Darby wrote:

for a 1/4 " shaft the major diameter is supposed to be a 1/4 ".


Bill, you have sadi this many times and now I wonder if we both mean the
same thing by "major diameter". I mean the mesurement I get if I close
a flat faced micrometer over the outside of a male thread having removed
any burrs if present. What do you mean?

I ask because I understand that the only 1/4" thread with a full 0.2500"
o.d. would be one with a sharp V-topped thread. Any comercial 1/4"
thread I have measured has always been rather less than 0.2500 o.d.,
typically by about 1/8 of the nominal thread depth.

Also, any thread I have single pointed has always needed to be cut a
little deeper to fit than you indicate, assuming I understand you
correctly. I would like to understand this better.

Ted




  #19   Report Post  
Ken Cutt
 
Posts: n/a
Default A different single-point threading question....


No holder. The use of thread wires with your object still in a lathe is

very easy, with a holder only adding to problems. One of the problems
would be the influence the holder would have over the wires. That may
sound trivial, but it's not, and a caution of this very thing accompanies
good wires. The wires must be free to conform to the thread. Even a
little tape on one end can influence a reading, especially on larger wires.

People with your ability with math would have no trouble calculating the
proper measurement over wires when choosing random diameters for measuring,
but folks like me, with only a high school education, one that did not
consist of any advanced mathematics, would have a difficult time calculating
the proper readings. Further, and in this case it likely makes no
difference at all, if you were chasing threads that needed acceptance by
inspection, the readings would most likely be disputed by an inspection
department. Standard thread wires (not the little cheap PeeDee sets, but
the wires sold by such firms as Deltronics) are precision instruments, with
diameters held to millionths, and come with certification. The wires are of
such a quality that they can be used for certification of thread gages.
These wires come with a constant that is added to the maximum and minimum
thread pitch, which one fetches from a source such as Machinery's Handbook.
Measuring threads by this method is very simple and is acceptable by
inspection. It is likely well overkill for the home shop type, but is good
and acceptable practice in any shop.

Back to the use of thread wires. To use them, one sets the mike so it's
opened slightly larger than the intended reading, places two wires on the
top side of the item to be measured, spread a distance slightly narrower
than the diameter of the spindle, then straddles the wires with the spindle.
lightly pressing the wires to keep them from falling. The third wire,
which is held in one's lips, is then slid between the anvil and the part,
splitting the distance between the top wires, so a three point reading can
be taken. When the open distance is fairly close, the wires will stay in
place with no trouble at all once the third wire is installed. One then
tightens the spindle, keeping the face parallel with the top two wires,
rocking the mike for feel, until it is measuring the distance over the
wires. Once learned this way, it's very easy, and fast, and requires
no holder.

One word of caution, and it matters not the source of your wires, be they
the expensive commercial wires such as the Deltronics, P&W, or just the
simple set sold be PeeDee: ALWAYS clean out your chip pan when measuring
threads. It's amazing how a long wire looks like the rest of the chips when
you drop them.

Good luck!

Harold


For practical home shops is there any advantage to using wires instead
if a thread Mic ? The cheap imports look a lot more convienient .
Ken Cutt

  #20   Report Post  
 
Posts: n/a
Default A different single-point threading question....

On Sun, 30 May 2004 17:33:36 GMT, Ted Edwards
wrote:

Harold & Susan Vordos wrote:

Yep, my point, exactly. All the rest does is cloud the issue. None of it
is close enough to use for proper threading.


Guess I'm going to have to cut some music wire and make a holder.
Otherwise this could be awkward with only two hands. :-) Any ideas on
this holder?

Ted


A small lump of Plasticene (modelling clay)!

Jim


  #21   Report Post  
M
 
Posts: n/a
Default A different single-point threading question....


"Harold & Susan Vordos" wrote

The third wire,
which is held in one's lips, is then slid between the anvil and the part,
splitting the distance between the top wires, so.......



That's the hard part.... "which is held in one's lips"........ Harold, you
forgot to mention the first step..... turn the lathe off..... !

Mark


  #22   Report Post  
Harold & Susan Vordos
 
Posts: n/a
Default A different single-point threading question....


"M" mark@maxmachinedotcom wrote in message
...

"Harold & Susan Vordos" wrote

The third wire,
which is held in one's lips, is then slid between the anvil and the

part,
splitting the distance between the top wires, so.......



That's the hard part.... "which is held in one's lips"........ Harold,

you
forgot to mention the first step..... turn the lathe off..... !

Mark



Chuckle!

Yep, should have mentioned that, Could prove real interesting otherwise.
:-)

Harold


  #23   Report Post  
Harold & Susan Vordos
 
Posts: n/a
Default A different single-point threading question....


"Ken Cutt" wrote in message
...
snip---


For practical home shops is there any advantage to using wires instead
if a thread Mic ? The cheap imports look a lot more convienient .
Ken Cutt


I don't like thread mikes. Never have, although they are fine for home
usage, probably even so good as to be considered over-kill. My personal
preference is to use wires, not even triangles. Both thread mikes and
triangles have the potential to measure a thread off the pitch diameter when
there's the slightest error in thread form. That's not true with wires.
All of this is probably not all that important as long as you're not trying
to sell threads under government contract, which is where I acquired all my
"bad" habits. In spite of the fact that I closed my commercial shop over
20 years ago, the years of running government contract work still steers my
thinking to this day. I've long maintained that if you choose methods
that are accepted by industry/government, that you'll achieve a level of
excellence that is difficult to challenge, and have a yield that is
consistently better than those that don't. It's worked for me for years, so
I hesitate to abandon my ways. It's hard to relax, and I don't know that
I really want to because it's no more difficult to work to exacting
standards than to be a hack if you always practice working in what I
consider to be a better way. Therefore, I stay the coarse, using wires.
I don't find them any more difficult to use than thread mikes, which, to me,
have a terrible feel. (Proper) wires can be used for calibrating gages,
thread mikes can not. That alone speaks volumes about their ability to
provide erroneous readings.

Harold


  #24   Report Post  
Harold & Susan Vordos
 
Posts: n/a
Default A different single-point threading question....


wrote in message
...
On Sun, 30 May 2004 17:33:36 GMT, Ted Edwards
wrote:

Harold & Susan Vordos wrote:

Yep, my point, exactly. All the rest does is cloud the issue. None

of it
is close enough to use for proper threading.


Guess I'm going to have to cut some music wire and make a holder.
Otherwise this could be awkward with only two hands. :-) Any ideas on
this holder?

Ted


A small lump of Plasticene (modelling clay)!

Jim


That's a bigger pain in the butt than loose wires, and by a long shot.
I've tried any and everything in my years on the machines. There's nothing
that replaces learning how to do it without aids of any sort. Nothing!
That includes a loop of masking tape, by the way. Like I said, I've tried
it all. None of it works as well as free wires.

Harold


  #25   Report Post  
jim rozen
 
Posts: n/a
Default A different single-point threading question....

In article , Harold & Susan Vordos says...

I don't like thread mikes. Never have, although they are fine for home
usage, probably even so good as to be considered over-kill. My personal
preference is to use wires, not even triangles. Both thread mikes and
triangles have the potential to measure a thread off the pitch diameter when
there's the slightest error in thread form. That's not true with wires.


Harold I cannot argue with using the best method for the job, even
at home, but it would seem to me that the wires cannot meausure
properly if there *is* an error in the thread form. For example,
what if the threads were cut to some odd angle, say, 63 degrees
or so. Unless one used a comparator to actually measure the thread
angle, wouldn't the wires give some reading that would allow
one to *think* the threads were properly formed when in fact
they were not?

What role do thread gages play in all this?

Jim

==================================================
please reply to:
JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com
==================================================



  #26   Report Post  
Harold & Susan Vordos
 
Posts: n/a
Default A different single-point threading question....


"jim rozen" wrote in message
...
In article , Harold & Susan Vordos says...

I don't like thread mikes. Never have, although they are fine for home
usage, probably even so good as to be considered over-kill. My personal
preference is to use wires, not even triangles. Both thread mikes and
triangles have the potential to measure a thread off the pitch diameter

when
there's the slightest error in thread form. That's not true with wires.


Harold I cannot argue with using the best method for the job, even
at home, but it would seem to me that the wires cannot meausure
properly if there *is* an error in the thread form. For example,
what if the threads were cut to some odd angle, say, 63 degrees
or so. Unless one used a comparator to actually measure the thread
angle, wouldn't the wires give some reading that would allow
one to *think* the threads were properly formed when in fact
they were not?

What role do thread gages play in all this?

Jim




I fully agree, Jim. The tolerance of the thread form is very much a part
of the equation, and it's relatively narrow. Certainly 3 degrees would
be WAY out of tolerance. It's been a lot of years, but I seem to recall
that the thread form is held to +/- 15 minutes. I think it's safe to say
that most of us, especially us older dudes, can't even see it on a thread
gage unless we're grinding a relatively large threading tool with broad
faces.

The harsh reality is that the wires *will* be measuring at the pitch
diameter, it just won't be right because of form error. I think you can
see that. The problem with triangles is they bear anywhere but at the
pitch line if the angle is off, and it makes no difference which way.
Mikes are slightly different because they have a truncated spindle and anvil
as I recall. If the thread form is too narrow, they will make contact near
the major diameter instead of at the pitch line. Wires always measure the
pitch line, even with bad form.

Actually, thread gages pick up thread form error to some degree.
Considering the no go is generally truncated, if a go gage fits, but the
form is off, the no go is likely to go on as well, depending on the thread
form angle. Other features may be off, so it won't go. Because the gage
checks angle to some degree, when you finally get a thread to fit the gage
that is off form, it is usually off so far in other features that the no go
betrays the bad form. If you kick this around in your head a bit, I think
you'll see what I'm talking about. Ring gages, in particular, are very
effective at determining many features, although they may not describe the
degree of error that may exist. They actually check all major features,
major diameter, pitch diameter and minor diameter, and by variations in how
they fit, thread form. When a go gage fits well, but the no go does, too,
you know something's amiss. All you have to do is determine what's wrong.
There's nothing like having a comparator to help in working with threads
when it's important that they be right.

Harold


  #27   Report Post  
jim rozen
 
Posts: n/a
Default A different single-point threading question....

In article , Harold & Susan Vordos says...

The harsh reality is that the wires *will* be measuring at the pitch
diameter, it just won't be right because of form error. I think you can
see that. The problem with triangles is they bear anywhere but at the
pitch line if the angle is off, and it makes no difference which way.


I guess for me, the pitch diameter is a specific theoretical size
based on the particular thread - so that if the form is off, the
wires will be measuring at *some* pitch diameter - just the
wrong one.

Actually, thread gages pick up thread form error to some degree.
Considering the no go is generally truncated, if a go gage fits, but the
form is off, the no go is likely to go on as well, depending on the thread
form angle. Other features may be off, so it won't go. Because the gage
checks angle to some degree, when you finally get a thread to fit the gage
that is off form, it is usually off so far in other features that the no go
betrays the bad form. If you kick this around in your head a bit, I think
you'll see what I'm talking about.


Yes. I've seen this when single pointing threads with some
error along the way - having the tool not set 90 deg to the
work comes to mind. Or trying to fit a thread that was
improperly cut to begin with as another example. Say if
an ID thread has too large of a flat on the major diameter,
or if the minor diameter has the threads too pointy (no flat).

Then I've seen where the thread one is trying to single point
to fit the part simply won't go unless it is either cut too
far, but simply kissing the major diameter of the male thread
will allow it to drop in nicely.

Ring gages, in particular, are very
effective at determining many features, although they may not describe the
degree of error that may exist. They actually check all major features,
major diameter, pitch diameter and minor diameter, and by variations in how
they fit, thread form. When a go gage fits well, but the no go does, too,
you know something's amiss. All you have to do is determine what's wrong.
There's nothing like having a comparator to help in working with threads
when it's important that they be right.


For me at home I'm typically trying to fit some existing part with
my single pointed thread. So I simply use the part as the 'gage'
in a rough sense. Of course that leads to the problem that at
some time I wind up trying to fit to another part I've already
made, and I wind up with my own private local NBS for threads. :^)

Anyway I've always found that getting the tool ground to the
correct angle, getting it set perpendicular to the work, turning
the major diameter correctly, and then leaving a bit of the part
undersized (to be removed afterwards) to the minor diameter, are
a few of the best ways to get a decent threading job.

I'll have to see about this wire stuff - sounds like a better
way to go.

Jim

==================================================
please reply to:
JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com
==================================================

  #28   Report Post  
Harold & Susan Vordos
 
Posts: n/a
Default A different single-point threading question....


"jim rozen" wrote in message
...
In article , Harold & Susan Vordos says...

The harsh reality is that the wires *will* be measuring at the pitch
diameter, it just won't be right because of form error. I think you can
see that. The problem with triangles is they bear anywhere but at the
pitch line if the angle is off, and it makes no difference which way.


I guess for me, the pitch diameter is a specific theoretical size
based on the particular thread - so that if the form is off, the
wires will be measuring at *some* pitch diameter - just the
wrong one.


Yeah, I think that's more what I had intended to say. The pitch line is
wire diameter critical, so altering the form would have some minor effect on
the true (desired theoretical) pitch line, although it would still be very
close, certainly closer than a triangle that would bear either at the major
or the minor diameter. The main idea is that the wire will be riding
somewhere near the pitch line, which, obviously, thanks to form error, would
not be proper. Not that it's any better, though. If anything is
wrong, does it really matter which feature? Scrap is scrap. That's the
reason we were never allowed to chase threads without the threading tool
being inspected by QC with a comparator before making the setup. It was not
uncommon to chase threads for a week at a time, and then repeat with a
different part. All threads we generated were single pointed. There were
no die heads in the facility, and that was by choice. Those of us that
chased threads got very adept at doing so. Please keep in mind that this
was years before insert tooling was available. Guys today would read this
and wonder just what the hell I was talking about. In all my years in
the missile industry, I never saw an insert threading tool, ever. What a
far cry from today, where most CNC operators likely have no clue about
sharpening a threading tool. Things change, not necessarily for the
better! :-) I cherish my hand sharpening skills.

Actually, thread gages pick up thread form error to some degree.
Considering the no go is generally truncated, if a go gage fits, but the
form is off, the no go is likely to go on as well, depending on the

thread
form angle. Other features may be off, so it won't go. Because the

gage
checks angle to some degree, when you finally get a thread to fit the

gage
that is off form, it is usually off so far in other features that the no

go
betrays the bad form. If you kick this around in your head a bit, I

think
you'll see what I'm talking about.


Yes. I've seen this when single pointing threads with some
error along the way - having the tool not set 90 deg to the
work comes to mind. Or trying to fit a thread that was
improperly cut to begin with as another example. Say if
an ID thread has too large of a flat on the major diameter,
or if the minor diameter has the threads too pointy (no flat).

Then I've seen where the thread one is trying to single point
to fit the part simply won't go unless it is either cut too
far, but simply kissing the major diameter of the male thread
will allow it to drop in nicely.


Yep, I've seen that, too. These examples point out just how critical
threads are, yet are treated as if they are insignificant by many.
Threads, and gears, are almost an industry unto themselves. There's so
much to learn and know that many never even scratch the surface. I've
had some experience with threads, but know nothing about gears. I shudder
to think now long it would take me to get up to speed with them.

Ring gages, in particular, are very
effective at determining many features, although they may not describe

the
degree of error that may exist. They actually check all major

features,
major diameter, pitch diameter and minor diameter, and by variations in

how
they fit, thread form. When a go gage fits well, but the no go does,

too,
you know something's amiss. All you have to do is determine what's

wrong.
There's nothing like having a comparator to help in working with threads
when it's important that they be right.


For me at home I'm typically trying to fit some existing part with
my single pointed thread. So I simply use the part as the 'gage'
in a rough sense. Of course that leads to the problem that at
some time I wind up trying to fit to another part I've already
made, and I wind up with my own private local NBS for threads. :^)


Chuckle! That's one of the reasons I preach thread wires. If one is
conscientious about grinding and setting the threading tool, you can work to
known standards (P.D. from the charts) and get a good thread every time.
You seldom stray far from interchangeability.

Anyway I've always found that getting the tool ground to the
correct angle, getting it set perpendicular to the work, turning
the major diameter correctly, and then leaving a bit of the part
undersized (to be removed afterwards) to the minor diameter, are
a few of the best ways to get a decent threading job.

I'll have to see about this wire stuff - sounds like a better
way to go.


Funny, I've used them as long as I've known how to thread (47 years now) and
just assume others have had a similar experience in the course of their shop
activities. The beautiful part about wires is that you have a complete
inspection system, especially if you use pre-ground inserts for threading.
Each wire size serves for any diameter thread with a like pitch, so even if
purchasing the premium wires, which are expensive, your investment in
gauging is minimal, yet of the utmost quality. Assuming you have the tool
set up properly, and know about the proper major diameter (not always
nominal), chasing a thread and sizing by wire will yield a proper thread
automatically.

For someone of your caliber, I think you'll enjoy using them, secure in the
knowledge that you are no longer creating the "Jim Rozen" series of threads.
On the other hand, maybe you'll miss the notoriety! g

Give it a go, Jim, and give us your impressions of their use. Read my
instructions of how to apply them. It works great, is very easy to do.

Harold


  #29   Report Post  
Ken Cutt
 
Posts: n/a
Default A different single-point threading question....

jim rozen wrote:


For me at home I'm typically trying to fit some existing part with
my single pointed thread. So I simply use the part as the 'gage'
in a rough sense.




Jim


Yea this is my typical system as well . Not ideal yet still what I fall
back on time and again
Ken Cutt

  #30   Report Post  
John Normile
 
Posts: n/a
Default A different single-point threading question....

Many years ago, right out of school, I worked at a gage shop in
Chicago grinding threaded plug gages. I measured pitch diameter all
day using wires. We took a wire and wrapped sewing thread around one
end and secured it with duco cement. Cut off about a foot of thread.
Then tied all 3 wires together at the end of the foot long threads.

The three wires were suspended over the work from a simple stand. We
would check the gage pd using a supermicrometer. This set up made
handling the wires very convenient.

John Normile


Guess I'm going to have to cut some music wire and make a holder.
Otherwise this could be awkward with only two hands. :-) Any ideas on
this holder?

Ted





  #31   Report Post  
jim rozen
 
Posts: n/a
Default A different single-point threading question....

In article , Harold & Susan Vordos says...

For someone of your caliber, I think you'll enjoy using them, secure in the
knowledge that you are no longer creating the "Jim Rozen" series of threads.
On the other hand, maybe you'll miss the notoriety! g


I was told a story once by a man who worked for Weston, the meter folks.
He said that their operation pre-dated most of the standardized thread
forms, going back before the turn of the century - and that they had
their own in-plant thread standards which they supported with home-made
gages of all sorts. Up until the late 70s they simply used their
own standards and forms on all of the meters they manufactured. Amazing.

Give it a go, Jim, and give us your impressions of their use. Read my
instructions of how to apply them. It works great, is very easy to do.


Hmm, lets see, first step is to get some copper wire of about the
right size.....

Jim

==================================================
please reply to:
JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com
==================================================

  #32   Report Post  
Harold & Susan Vordos
 
Posts: n/a
Default A different single-point threading question....


"jim rozen" wrote in message
...
In article , Harold & Susan Vordos says...

For someone of your caliber, I think you'll enjoy using them, secure in

the
knowledge that you are no longer creating the "Jim Rozen" series of

threads.
On the other hand, maybe you'll miss the notoriety! g


I was told a story once by a man who worked for Weston, the meter folks.
He said that their operation pre-dated most of the standardized thread
forms, going back before the turn of the century - and that they had
their own in-plant thread standards which they supported with home-made
gages of all sorts. Up until the late 70s they simply used their
own standards and forms on all of the meters they manufactured. Amazing.



Amazing, indeed! On the other hand, why not? Seems to me that thread
standards are what they are only because everyone (?) agrees with standards
set forth. Had Weston been aggressive in promoting their standards, maybe
we'd have a completely different system today.



Give it a go, Jim, and give us your impressions of their use. Read

my
instructions of how to apply them. It works great, is very easy to do.


Hmm, lets see, first step is to get some copper wire of about the
right size.....


I've always favored #12 solid and a heavy hand on the mike. :-)

Harold


  #33   Report Post  
Harold & Susan Vordos
 
Posts: n/a
Default A different single-point threading question....


"John Normile" wrote in message
...
Many years ago, right out of school, I worked at a gage shop in
Chicago grinding threaded plug gages. I measured pitch diameter all
day using wires. We took a wire and wrapped sewing thread around one
end and secured it with duco cement. Cut off about a foot of thread.
Then tied all 3 wires together at the end of the foot long threads.

The three wires were suspended over the work from a simple stand. We
would check the gage pd using a supermicrometer. This set up made
handling the wires very convenient.

John Normile


Of all systems I've ever seen or used, this one would be very acceptable.
The thread would not influence the wires in any way, and you'd never lose
them if you dropped them. Excellent suggestion in my opinion.

Harold


  #34   Report Post  
 
Posts: n/a
Default A different single-point threading question....


as a non-machinist I was having a hard time picturing this process. a
quick search got this:

http://www.precisiontwistdrill.com/t...h_diameter.asp

which helped a lot.....
  #35   Report Post  
Tim Williams
 
Posts: n/a
Default A different single-point threading question....

"Harold & Susan Vordos" wrote in message
...
I've always favored #12 solid and a heavy hand on the mike. :-)


So that's how they make thin triangular barstock...

Tim

--
"I have misplaced my pants." - Homer Simpson | Electronics,
- - - - - - - - - - - - - - - - - - - - - - --+ Metalcasting
and Games: http://webpages.charter.net/dawill/tmoranwms




  #36   Report Post  
Harold & Susan Vordos
 
Posts: n/a
Default A different single-point threading question....


"Tim Williams" wrote in message
...
"Harold & Susan Vordos" wrote in message
...
I've always favored #12 solid and a heavy hand on the mike. :-)


So that's how they make thin triangular barstock...

Tim


Yeah, but with notches. :-)

Harold


  #37   Report Post  
Harold & Susan Vordos
 
Posts: n/a
Default A different single-point threading question....


wrote in message
news

as a non-machinist I was having a hard time picturing this process. a
quick search got this:

http://www.precisiontwistdrill.com/t...h_diameter.asp

which helped a lot.....


Very cool site! It should help those that are confused on the issue.
Thanks for the link!

Harold


  #38   Report Post  
Bill Darby
 
Posts: n/a
Default A different single-point threading question....

Been wondering if I could get a fairly accurate depth of thread
measurment with only a single wire and a mic.
*****************************

So I took a new 1/2" 13 bolt and miced it. The measurnent of the major
diameter was .489"

I miced it again with a .040" drill bit inserted in the thread. The
measurnent was .496"

In order to balance that reading I subtracted half the major diameter of
the bolt (.496" - 489"/2) = .2515" and doubled the result .2515"*2 =
..503"

So I now had the equivalent to a 3 wire reading. [IE .503"] So the
sharp depth diameter reading would be 3 times the .040" drill diameter
less or .503"- 3 * .040" = .383"

The pitch diameter would be one pitch height greater or .383" +
1/13*.86603" = .4496"

This .4496" pitch diameter falls nicely into the pitch diameter range
of a class 3A thread.
******************************
Bill

May seem complicated to do but you need no special kit, only two hands,
and once you figure out the mechanics of it, it is easy and I would
guess that the accuracy, while not as good as the proper three wires, it
could serve most quite well.

Bill

(Hoping I didn't foul up my numbers)


  #39   Report Post  
Eric R Snow
 
Posts: n/a
Default A different single-point threading question....

On Wed, 2 Jun 2004 18:53:31 -0400, "Bill Darby"
wrote:

Been wondering if I could get a fairly accurate depth of thread
measurment with only a single wire and a mic.
*****************************

So I took a new 1/2" 13 bolt and miced it. The measurnent of the major
diameter was .489"

I miced it again with a .040" drill bit inserted in the thread. The
measurnent was .496"

In order to balance that reading I subtracted half the major diameter of
the bolt (.496" - 489"/2) = .2515" and doubled the result .2515"*2 =
.503"

So I now had the equivalent to a 3 wire reading. [IE .503"] So the
sharp depth diameter reading would be 3 times the .040" drill diameter
less or .503"- 3 * .040" = .383"

The pitch diameter would be one pitch height greater or .383" +
1/13*.86603" = .4496"

This .4496" pitch diameter falls nicely into the pitch diameter range
of a class 3A thread.
******************************
Bill

May seem complicated to do but you need no special kit, only two hands,
and once you figure out the mechanics of it, it is easy and I would
guess that the accuracy, while not as good as the proper three wires, it
could serve most quite well.

Bill

(Hoping I didn't foul up my numbers)

Of course, your one wire method only works if you first measure the OD
of the part. And if doing several parts you must measure each part on
the OD first. Unless your setup is good enough that the part to part
variance is small enough that you can live with it. I hate thread
wires. They are hard to hold on large diameter parts. And on coarse
threads the wires may be so far apart that you are forced to use only
one wire because the mike spindle is too small to bridge two wires..
And they don't check thread angle or minor diameter. And they are easy
to lose in the chip pan. But I use 'em a lot anyway.
ERS
  #40   Report Post  
Bill Darby
 
Posts: n/a
Default A different single-point threading question....


"Eric R Snow" wrote in message
news
On Wed, 2 Jun 2004 18:53:31 -0400, "Bill Darby"
wrote:

Been wondering if I could get a fairly accurate depth of thread
measurment with only a single wire and a mic.
*****************************

So I took a new 1/2" 13 bolt and miced it. The measurnent of the

major
diameter was .489"

I miced it again with a .040" drill bit inserted in the thread. The
measurnent was .496"

In order to balance that reading I subtracted half the major diameter

of
the bolt (.496" - 489"/2) = .2515" and doubled the result .2515"*2 =
.503"

So I now had the equivalent to a 3 wire reading. [IE .503"] So the
sharp depth diameter reading would be 3 times the .040" drill

diameter
less or .503"- 3 * .040" = .383"

The pitch diameter would be one pitch height greater or .383" +
1/13*.86603" = .4496"

This .4496" pitch diameter falls nicely into the pitch diameter

range
of a class 3A thread.
******************************
Bill

May seem complicated to do but you need no special kit, only two

hands,
and once you figure out the mechanics of it, it is easy and I would
guess that the accuracy, while not as good as the proper three wires,

it
could serve most quite well.

Bill

(Hoping I didn't foul up my numbers)

Of course, your one wire method only works if you first measure the OD
of the part. And if doing several parts you must measure each part on
the OD first. Unless your setup is good enough that the part to part
variance is small enough that you can live with it. I hate thread
wires. They are hard to hold on large diameter parts. And on coarse
threads the wires may be so far apart that you are forced to use only
one wire because the mike spindle is too small to bridge two wires..
And they don't check thread angle or minor diameter. And they are easy
to lose in the chip pan. But I use 'em a lot anyway.
ERS


Yes Eric, this method, as far as I can see, will only work by first
measuring the
major diameter. It may work well if, as you suggest, part to part
variance is
small.

In any case, I wasn't so much thinking of a production set up as I was a
one of a
kind deal where you are single point turning and you want to get a
reading on
how close you are to a specific fit.

I personally have never tried the three wire system (don't have the
wires) and
was just doodling around trying to figure a way to do it with the things
I have in
the shop.

PS I found that both my digital calipers and the mic could be used to
get the
same numbers.

Bill



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