Hello,

I am rehousing a webcam for use in astronomy and I turned down on my
minilathe a simple adapter tube out of aluminum to fit the standard
1.25" diam eyepiece holder.
I now have to turn an inside thread to hold
a standard filter. The filter requires a 1.125" x 40tpi thread. I am
trying to grind my own highspeed steel tool and having some difficulty
getting the threads to look right. They are there but look flattened.
Does someone have a dimension or procedure for grinding such a
tool to work with aluminum? Would the same tool work for delrin? I
have searched the web many times and I can turn up very little on this
subject.

Please advise,

Vince Coppola

In article ,
Vincent Coppola wrote:
Hello,

I am rehousing a webcam for use in astronomy and I turned down on my
minilathe a simple adapter tube out of aluminum to fit the standard
1.25" diam eyepiece holder.
I now have to turn an inside thread to hold
a standard filter. The filter requires a 1.125" x 40tpi thread. I am
trying to grind my own highspeed steel tool and having some difficulty
getting the threads to look right. They are there but look flattened.

Hmm ... at a first guess, you don't have enough relief below the
point. Remember that your workpiece is curving towards the tool, so you
need to grind away enough (a curve) below the point so it stays clear of
the workpiece. The smaller the ID, the more the curve needed to clear.

Personally, I would use laydown insert tooling for this. I find
tooling for that made in Israel (ISCAR is the brand, IIRC) for very
small inside threads. I think almost small enough to handle
single-pointing a 1/4-20 thread, and at least small enough for a 5/16"
thread.

Does someone have a dimension or procedure for grinding such a
tool to work with aluminum? Would the same tool work for delrin? I

What lube are you using for aluminum? The easiest to use is a
spray can of WD-40 -- it makes a nice aluminum cutting lube.

For the Delrin, you should not need any lube (or coolant) unless
you are turning *way* too fast.

have searched the web many times and I can turn up very little on this
subject.

Please advise,

You have my thoughts above.

Good Luck,
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 ---

"Vincent Coppola" wrote in message
om...
Hello,

I am rehousing a webcam for use in astronomy and I turned down on my
minilathe a simple adapter tube out of aluminum to fit the standard
1.25" diam eyepiece holder.
I now have to turn an inside thread to hold
a standard filter. The filter requires a 1.125" x 40tpi thread. I am
trying to grind my own highspeed steel tool and having some difficulty
getting the threads to look right. They are there but look flattened.

DoN has mentioned the necessary amount of clearance on the threading tool,
but there's one thing that you may be missing, and it's easy to do. The way
you describe your thread leads me to believe that you have your compound set
improperly. The markings on compounds are not all the same. What is 30
degrees on one is 60 degrees on another. To set your compound properly,
assuming you are threading a right hand internal thread, cutting from the
outside towards the headstock, you should start with your compound parallel
to the cross slide, with the handle towards you. At that point, you should
turn the handle TOWARDS the headstock until you've gone almost 30 degrees.
I like to use 29, which makes sure you keep cleaning up the back side of the
thread. It may not read 29 degrees, but 61 instead. Don't let that worry
you, it's the way the machine is marked. Setting the compound as I've
suggested is important to a good end result. Don't set the compound the
same way you do for an external right hand thread.

If you're not comfortable with your compound set as I've suggested, the next
best way is to set it exactly 180 degrees opposite, with the handle on the
far side of the bed, and pointed towards the tailstock. That way you always
feed such that you keep the leadscrew loaded by the cut. I tend to harp
on this subject endlessly, but it's a good lesson to learn and remember, and
it ALWAYS applies when threading, regardless of the type of thread.

Hope this helps. If you're still having trouble, feel free to contact me
on the side and I'll try to carry you through the proper threading tool
configuration. There's no real reason to NOT hand grind this tool, it's
quite simple to do.

Harold





Does someone have a dimension or procedure for grinding such a
tool to work with aluminum? Would the same tool work for delrin? I
have searched the web many times and I can turn up very little on this
subject.

Please advise,

Vince Coppola

Vincent Coppola writes:

Does someone have a dimension or procedure for grinding such a
tool to work with aluminum?

I use a band saw (or hack saw) to cut a 1/8" notch across the end of some
1/2" mild steel rod, braze in a length of 1/8" square HSS crosswise, and
grind that to a 60 degree tip with 10 degrees relief. This yields
essentially a boring bar, but with a threading profile. Then I hold that in
a boring bar holder on the toolpost.

"Harold & Susan Vordos" wrote in message ...
"Vincent Coppola" wrote in message
om...
Hello,

I am rehousing a webcam for use in astronomy and I turned down on my
minilathe a simple adapter tube out of aluminum to fit the standard
1.25" diam eyepiece holder.
I now have to turn an inside thread to hold
a standard filter. The filter requires a 1.125" x 40tpi thread. I am
trying to grind my own highspeed steel tool and having some difficulty
getting the threads to look right. They are there but look flattened.

DoN has mentioned the necessary amount of clearance on the threading tool,
but there's one thing that you may be missing, and it's easy to do. The way
you describe your thread leads me to believe that you have your compound set
improperly. The markings on compounds are not all the same. What is 30
degrees on one is 60 degrees on another. To set your compound properly,
assuming you are threading a right hand internal thread, cutting from the
outside towards the headstock, you should start with your compound parallel
to the cross slide, with the handle towards you. At that point, you should
turn the handle TOWARDS the headstock until you've gone almost 30 degrees.
I like to use 29, which makes sure you keep cleaning up the back side of the
thread. It may not read 29 degrees, but 61 instead. Don't let that worry
you, it's the way the machine is marked. Setting the compound as I've
suggested is important to a good end result. Don't set the compound the
same way you do for an external right hand thread.

If you're not comfortable with your compound set as I've suggested, the next
best way is to set it exactly 180 degrees opposite, with the handle on the
far side of the bed, and pointed towards the tailstock. That way you always
feed such that you keep the leadscrew loaded by the cut. I tend to harp
on this subject endlessly, but it's a good lesson to learn and remember, and
it ALWAYS applies when threading, regardless of the type of thread.

Hope this helps. If you're still having trouble, feel free to contact me
on the side and I'll try to carry you through the proper threading tool
configuration. There's no real reason to NOT hand grind this tool, it's
quite simple to do.

Harold





Does someone have a dimension or procedure for grinding such a
tool to work with aluminum? Would the same tool work for delrin? I
have searched the web many times and I can turn up very little on this
subject.

Please advise,

Vince Coppola

When stuck for an internal threading tool, I've used a ground down
cutting tap.
Grind everthing away except for one full tooth on the tap. It's saved
my butt before.

Gerry

In article , Harold & Susan Vordos says...

DoN has mentioned the necessary amount of clearance on the threading tool,
but there's one thing that you may be missing, and it's easy to do. The way
you describe your thread leads me to believe that you have your compound set
improperly. The markings on compounds are not all the same. What is 30
degrees on one is 60 degrees on another. To set your compound properly,
assuming you are threading a right hand internal thread, cutting from the
outside towards the headstock, you should start with your compound parallel
to the cross slide, with the handle towards you. At that point, you should
turn the handle TOWARDS the headstock until you've gone almost 30 degrees.
I like to use 29, which makes sure you keep cleaning up the back side of the
thread. It may not read 29 degrees, but 61 instead. Don't let that worry
you, it's the way the machine is marked. Setting the compound as I've
suggested is important to a good end result. Don't set the compound the
same way you do for an external right hand thread.

If you're not comfortable with your compound set as I've suggested, the next
best way is to set it exactly 180 degrees opposite, with the handle on the
far side of the bed, and pointed towards the tailstock. That way you always
feed such that you keep the leadscrew loaded by the cut. I tend to harp
on this subject endlessly, but it's a good lesson to learn and remember, and
it ALWAYS applies when threading, regardless of the type of thread.

I much prefer the second setup, becuause otherwise the compound
dial and handle tend to interfere with the work on smaller machines.

Has anyone suggested that he double check his thread form with a
simple thread gage to be sure it is correct? I suspect at 40 tpi
his problem is not thread relief on the tool.

Jim

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

(Vincent Coppola) wrote in message . com...
Hello,

I am rehousing a webcam for use in astronomy and I turned down on my
minilathe a simple adapter tube out of aluminum to fit the standard
1.25" diam eyepiece holder.
I now have to turn an inside thread to hold
a standard filter. The filter requires a 1.125" x 40tpi thread. I am
trying to grind my own highspeed steel tool and having some difficulty
getting the threads to look right. They are there but look flattened.
Does someone have a dimension or procedure for grinding such a
tool to work with aluminum? Would the same tool work for delrin? I
have searched the web many times and I can turn up very little on this
subject.

Please advise,

Vince Coppola


For threading holes over an inch, I use a boring bar and make a
threading tip for it. When I say boring bar, I'm not talking about
one of those one-piece jobbies, it's a chunk of round bar with a
square hole in the end at 90 degrees and has a set screw to hold the
bit. I've made one up in about 20 minutes with some spirited filing
to square the hole out. I like to use the Tantung G I've got for
those threading tools, once you get them shaped and stoned, they hold
an edge for a long time. I like to use a bar with just enough
clearance for chips, stiff is good when it comes to threading. For
internal threading you have to watch the top-to-bottom clearance, if
you don't grind enough of an angle, the heel is going to be dragging
in your fresh cut and will mess things up. As another poster
mentioned, the compound has to be kicked opposite the direction it
would be used in when external threading. It also take a little
practice to get to thinking in reverse. Threading stops help a lot,
too. On aluminum, make sure you use some decent cutting fluid made
for the job. Tap-Magic works, Alumi-Cut is good, too. For 40 TPI,
you're going to want to use a thread gauge for both bit grinding and
setup, a magnifying glass will help with stoning to final contour.
You'll have to have a pretty good finish on the tool flanks to get a
good result on your threads. I usually use a black Arkansas stone for
final polish on something that fine. I didn't use to do that when I
first started out, it really does make a difference in final finish on
the threads.

Stan

The tool holder for a small bit is probably the best way to go as you don't
need a large tool tip to do 40tpi threads. You DO need a fair bit of relief
of the tip in order to stay away from the cut surface. If you can't fit
your tip into a properly finished thread at the proper angles, you need to
do more relief of the tip.

--
Bob May
Losing weight is easy! If you ever want to lose weight, eat and drink less.
Works every time it is tried!

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

DoN has mentioned the necessary amount of clearance on the threading tool,
but there's one thing that you may be missing, and it's easy to do. The way
you describe your thread leads me to believe that you have your compound set
improperly. The markings on compounds are not all the same. What is 30
degrees on one is 60 degrees on another. To set your compound properly,
assuming you are threading a right hand internal thread, cutting from the
outside towards the headstock, you should start with your compound parallel
to the cross slide, with the handle towards you. At that point, you should
turn the handle TOWARDS the headstock until you've gone almost 30 degrees.
I like to use 29, which makes sure you keep cleaning up the back side of the
thread. It may not read 29 degrees, but 61 instead. Don't let that worry
you, it's the way the machine is marked. Setting the compound as I've
suggested is important to a good end result. Don't set the compound the
same way you do for an external right hand thread.

If you're not comfortable with your compound set as I've suggested, the next
best way is to set it exactly 180 degrees opposite, with the handle on the
far side of the bed, and pointed towards the tailstock. That way you always
feed such that you keep the leadscrew loaded by the cut. I tend to harp
on this subject endlessly, but it's a good lesson to learn and remember, and
it ALWAYS applies when threading, regardless of the type of thread.

I much prefer the second setup, becuause otherwise the compound
dial and handle tend to interfere with the work on smaller machines.

Has anyone suggested that he double check his thread form with a
simple thread gage to be sure it is correct? I suspect at 40 tpi
his problem is not thread relief on the tool.

Jim

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

Actually I think I had the compound set wrong. To start with, my
threading tool is made from drill rod. I got the idea from the 7x10
minilathe post on yahoo some time ago. Anyway the suggestion was to
get the same size rod as my boring tool holder, in my case 3/8" and
then turn a disk on one end. Make it a 60 degree angle on each
shoulder. Then grind off the top and bottom of the disk to form two
cutting tools. This is what I have been using. Now as far as the
compound angle goes I don't have a handle like you say. Picture it
this way....I shrink myself and stand on the tailstock. I then peer
straight into the headstock. Let's call this 0 degrees. I point the
boring bar in this direction. Now I turn it 30 degrees
counterclockwise. I then feed toward the headstock. I just tried this
and the thread looks much better. Must have done something right. How
does this sound? Of course now I have to bore it to the correct i.d.,
thread it, and finally screw the filter into it. The proof is in the
pudding.

Vince

Richard J Kinch wrote in message ...
Vincent Coppola writes:

Does someone have a dimension or procedure for grinding such a
tool to work with aluminum?

I use a band saw (or hack saw) to cut a 1/8" notch across the end of some
1/2" mild steel rod, braze in a length of 1/8" square HSS crosswise, and
grind that to a 60 degree tip with 10 degrees relief. This yields
essentially a boring bar, but with a threading profile. Then I hold that in
a boring bar holder on the toolpost.

This is a cool idea. One suggestion I heard was to file a square hole
in a rod, grind an HSS tool, insert it and hold it with a set screw.
Your way sounds easier only I don't have any welding equipment. I do
have a propane torch but I don't think that gets hot enough to braze.
What would you suggest I purchase to do a small job like this
repeatably?

Vince

propane gets hot enough for silver solder, that will be strong enough.


This is a cool idea. One suggestion I heard was to file a square hole
in a rod, grind an HSS tool, insert it and hold it with a set screw.
Your way sounds easier only I don't have any welding equipment. I do
have a propane torch but I don't think that gets hot enough to braze.
What would you suggest I purchase to do a small job like this
repeatably?

Vince

"Vincent Coppola" wrote in message
om...
snip------

Actually I think I had the compound set wrong. To start with, my
threading tool is made from drill rod. I got the idea from the 7x10
minilathe post on yahoo some time ago. Anyway the suggestion was to
get the same size rod as my boring tool holder, in my case 3/8" and
then turn a disk on one end. Make it a 60 degree angle on each
shoulder. Then grind off the top and bottom of the disk to form two
cutting tools. This is what I have been using.

There's nothing wrong with that if you know how to properly grind the
necessary relief angles after you've formed the 60 degree sides, and you can
drop the bar such that the top of the tool is on center. Any variation
from center height, or alteration of the top of the tool from dead flat and
parallel to the ways will yield an altered thread form. It's always a very
good idea to never touch the top of a threading tool, no matter what you
hear some of the "experts" say. When you grind a rake angle, the back
side of the tool will generally no longer make contact with the thread, so
the thread doesn't get cleaned up, nor does it conform to the threading
tool, instead taking the angle of the setting of the compound.

Now as far as the
compound angle goes I don't have a handle like you say. Picture it
this way....I shrink myself and stand on the tailstock. I then peer
straight into the headstock. Let's call this 0 degrees. I point the
boring bar in this direction. Now I turn it 30 degrees
counterclockwise. I then feed toward the headstock. I just tried this
and the thread looks much better. Must have done something right. How
does this sound?


Not good! Not if I understand what you're saying, anyway. If you have a
compound, it must have a handle of sorts, and it is that handle that you use
to feed the threading tool on successive passes, after setting the cross
slide to 0. The boring bar itself should parallel the ways of the machine,
assuming the cutting portion is at right angles to the shank of the boring
bar. The way you've described your setup, you have turned the threading
tool 30 degrees. Only the compound should be turned the 30 (actually only
29) degrees, which you'd do before setting up the threading tool. When the
threading tool is properly set, the angle of the thread, 60 degrees, is
equally split on each side of the tool, so the sides of the thread are each
30 degrees as they relate to the cross slide. What's important is that
you feed the tool at slightly less than the half angle of the thread.
Anything more simply cuts away the back side. When you set up your
compound properly, almost all off each pass takes the material off the
forward edge of the material, where the lead screw keeps the tool in
intimate contact with the cut. That not only guarantees the proper lead, but
permits superior chip flow, which can be a serious problem when threading
coarse threads in tough materials. Aluminum is usually pretty forgiving,
as is leaded brass.

If you're still not clear on this, lets keep talking. Threading, in order
to be right, must be approached properly. We'll get you there, just keep
asking questions. If you can post a picture of your setup it would help a
lot! That way we'd get past differences in descriptions.

Harold

In article ,
Harold & Susan Vordos wrote:

"Vincent Coppola" wrote in message
. com...
snip------

Actually I think I had the compound set wrong. To start with, my
threading tool is made from drill rod. I got the idea from the 7x10
minilathe post on yahoo some time ago. Anyway the suggestion was to
get the same size rod as my boring tool holder, in my case 3/8" and
then turn a disk on one end. Make it a 60 degree angle on each
shoulder. Then grind off the top and bottom of the disk to form two
cutting tools. This is what I have been using.

There used to be (and may still be) commercial tools made like
this, with only one ground notch (about 90 degrees to start with), and
as it wears, you rotate the tool a few degrees and grind the top flat
again. You get a large number of re-grinds before there is insufficient
tool left to continue to work.

I seem to remember that the grinding was below the centerline,
so the relief was naturally formed, and the tool was raised to bring the
tip back to center height.

[ ... ]

coarse threads in tough materials. Aluminum is usually pretty forgiving,
as is leaded brass.

The latter is probably the best thing to learn threading on.
Then go to other materials after you get things working right. (And
leaded brass works well for optical threads anyway.) Aluminum can be
very nice to thread, or be very nasty, depending on the alloy and the
hardness. The kind of aluminum you would find in Home Depot would be
very gummy, and difficult to do a clean thread on.

If you're still not clear on this, lets keep talking. Threading, in order
to be right, must be approached properly. We'll get you there, just keep
asking questions. If you can post a picture of your setup it would help a
lot! That way we'd get past differences in descriptions.

Agreed -- with one caveat. *Don't* post the image to the
newsgroup. Some news severs block any binary attachments to discussion
newsgroups (such as this), so not everybody would see it. Instead, send
the image to the dropbox (visit http://www.metalworking.com/ and click
on the [ About the Dropbox ] bar to read how to do it.

Try to avoid spaces and punctuation characters (especially
things like '&', '*', '/', '\' and '?') in the filenames, as they make
problems on different computer systems. Just plain letters, and either
a '-' or a '_' in place of spaces works well.

Once they are there (with a ".txt" file to describe what you
have uploaded), post here with the url for the dropbox

again -- http://www.metalworking.com/

and the names under which the files are stored. (remember that on some
systems the case of the letters matters, so keep that right, too, so
people can find the images.)

Good Luck,
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 ---

(Vincent Coppola) wrote in message
. com...
Hello,

I am rehousing a webcam for use in astronomy and I turned down on my
minilathe a simple adapter tube out of aluminum to fit the standard
1.25" diam eyepiece holder.
I now have to turn an inside thread to hold
a standard filter. The filter requires a 1.125" x 40tpi thread. I am
trying to grind my own highspeed steel tool and having some difficulty
getting the threads to look right. They are there but look flattened.
Does someone have a dimension or procedure for grinding such a
tool to work with aluminum? Would the same tool work for delrin? I
have searched the web many times and I can turn up very little on this
subject.

Please advise,

Vince Coppola


Hi,

I am also into astronomy, and my turning abilities are a bit grim, but I
recently did an internal thread to hold one of these filters by very simply
holding a chaser in a boring bar. Is this approach satisfactory?

Brian Boggenpoel

"Harold & Susan Vordos" wrote in message ...
"Vincent Coppola" wrote in message
om...
snip------

Actually I think I had the compound set wrong. To start with, my
threading tool is made from drill rod. I got the idea from the 7x10
minilathe post on yahoo some time ago. Anyway the suggestion was to
get the same size rod as my boring tool holder, in my case 3/8" and
then turn a disk on one end. Make it a 60 degree angle on each
shoulder. Then grind off the top and bottom of the disk to form two
cutting tools. This is what I have been using.

There's nothing wrong with that if you know how to properly grind the
necessary relief angles after you've formed the 60 degree sides, and you can
drop the bar such that the top of the tool is on center. Any variation
from center height, or alteration of the top of the tool from dead flat and
parallel to the ways will yield an altered thread form. It's always a very
good idea to never touch the top of a threading tool, no matter what you
hear some of the "experts" say. When you grind a rake angle, the back
side of the tool will generally no longer make contact with the thread, so
the thread doesn't get cleaned up, nor does it conform to the threading
tool, instead taking the angle of the setting of the compound.

Now as far as the
compound angle goes I don't have a handle like you say. Picture it
this way....I shrink myself and stand on the tailstock. I then peer
straight into the headstock. Let's call this 0 degrees. I point the
boring bar in this direction. Now I turn it 30 degrees
counterclockwise. I then feed toward the headstock. I just tried this
and the thread looks much better. Must have done something right. How
does this sound?


Not good! Not if I understand what you're saying, anyway. If you have a
compound, it must have a handle of sorts, and it is that handle that you use
to feed the threading tool on successive passes, after setting the cross
slide to 0. The boring bar itself should parallel the ways of the machine,
assuming the cutting portion is at right angles to the shank of the boring
bar. The way you've described your setup, you have turned the threading
tool 30 degrees. Only the compound should be turned the 30 (actually only
29) degrees, which you'd do before setting up the threading tool. When the
threading tool is properly set, the angle of the thread, 60 degrees, is
equally split on each side of the tool, so the sides of the thread are each
30 degrees as they relate to the cross slide. What's important is that
you feed the tool at slightly less than the half angle of the thread.
Anything more simply cuts away the back side. When you set up your
compound properly, almost all off each pass takes the material off the
forward edge of the material, where the lead screw keeps the tool in
intimate contact with the cut. That not only guarantees the proper lead, but
permits superior chip flow, which can be a serious problem when threading
coarse threads in tough materials. Aluminum is usually pretty forgiving,
as is leaded brass.

If you're still not clear on this, lets keep talking. Threading, in order
to be right, must be approached properly. We'll get you there, just keep
asking questions. If you can post a picture of your setup it would help a
lot! That way we'd get past differences in descriptions.

Harold


Harold,
Ok I think I get how to set the compound angle now. Had to look at the
manual. I found the screws to loosen.(Yey) Ok, picture this...a clock
face. The headstock is at 12o'clock, the tailstock is at 6 o'clock, I
am at 9 o'clock. The angle on the dial reads 0 degrees. OK now I
turned the compound counterclockwise until my dial reads 29 degrees,
the compound moved from 12 o'clock to approx. 10 o'clock. I had to
turn the boring bar clockwise to compensate and get it back to 12
o'clock or parallel to the ways. This is probably opposite to what you
told me before.

Wait, now I took another look at it...Now it makes no sense this way
either. If I turn the tool holder to compensate for the angle I turned
the compound, when I engage the leadscrew the tool is moving at the
same speed and in the same direction. The only difference is when I
turn the compound rest crank, the tool moves at an angle and I can see
now how to make a bevel. Still can't see what difference it would make
for making a thread unless there is a force vector against the thread
changing somehow. Can't see how any angle would change on the thread
unless I manually turn the compound rest while the leadscrew is
turning. There that was confusing!
I think the best thing to do is take a picture and email it to you.


Vince

"Vincent Coppola" wrote in message
snip---------
I think the best thing to do is take a picture and email it to you.


Vince

If you can, that would be real good. All of this is real simple once you
understand it. By looking at your setup, I will then be able to tell you
what to change, and why. Feel free to send the pic to me, but make sure
it is well addressed such that I know what it is and from where it comes.
You might put THREADING in the subject line. I get a lot of spam and
delete lots of stuff without looking first.

Harold

DoN. Nichols wrote:

Try to avoid spaces and punctuation characters (especially
things like '&', '*', '/', '\' and '?') in the filenames, as they make
problems on different computer systems. Just plain letters, and either
a '-' or a '_' in place of spaces works well.

Also, please don't use your life history as a file name! I agree that
8.3 is a silly and unreasonable restriction but I recently ran into a
problem with a 157 character file name! No problem on OS/2 but when I
backed up the thing to a CD, it appears that the Jolliet protocall
doesn't handle more than 64 character filenames. Wouldn't be a problem
for anything reasonable.

Ted