Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work.

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Old August 30th 04, 09:08 PM
Jacek Zagaja
 
Posts: n/a
Default High Alloys and turning threads

Gentelman,

Sorry if my writings are little clumsy. Metalworking is new for me
especially in English

I'm trying to achieve plain (smooth) alloy after turning threads. I've
made special knife with carbon plate so that I can cut as near side as
possible. The problems is in surface quality. My alloy is 2H13 (0.2 C
and 13% Cr and maybe small amount of Ni). Is it possible to get good
surface without polishing?

Regards,
__________________________________________________ ____________________

Jack Zagaja - photographer, designer, programmer
free photoshop plugins, photographic assistance
opinions and much more ...

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Old August 31st 04, 06:21 AM
DoN. Nichols
 
Posts: n/a
Default

In article ,
Jacek Zagaja jzagaja-at-poczta.onet.pl wrote:

Gentelman,

Sorry if my writings are little clumsy. Metalworking is new for me
especially in English

I'm trying to achieve plain (smooth) alloy after turning threads. I've
made special knife with carbon plate so that I can cut as near side as
possible. The problems is in surface quality. My alloy is 2H13 (0.2 C
and 13% Cr and maybe small amount of Ni). Is it possible to get good
surface without polishing?


O.K. Let me see whether I understand you properly -- and offer
some terminology in English in the process.

Given the fact that you *can* communicate in my language, and do
a rather good job of it, but I cannot communicate in yours, that shows
that you are *interested* in communicating. I do have at least one
other language, but not yours, unfortunately.

"special knife" -- threading tool?

For most applications, you don't want to use carbon steel for the task,
but rather at a minimum, HSS (High Speed Steel), or for some alloys,
(tungsten-)carbide inserts. Carbon steel can work with care with mild
steel, but I think that your alloy, with 13% Cr would be rather tough,
and would rapidly dull the carbon steel. For that, I would prefer to
use the special carbide inserts in the proper shank (holding tool) for
the threads which you wish to cut.

Note that the size of the lathe, and the rigidity and power will
determine whether you can use carbide tooling to get a better finish.
Your "2H13" appears to be one of the European steel designations, and I
am not familiar with it. But 13% Cr would probably make that a rather
tough steel. Perhaps Ed Huntress could pop up with a close equivalent
in US steel grades?

It may even be that it would be better to grind the threads
instead of to try to cut them -- but this will require a rather
expensive setup.

Are you doing this as a hobby, or are you in a commercial
machine shop? The tools which would be standard in such a commercial
shop are less likely to be found in a home shop for hobby use.

You'll find mostly hobby metalworkers here -- though there are
some who do it as a job. We really need to know some things about the
task and the equipment. How big a lathe? What thread diameter and
pitch? (I would expect them in metric units given your e-mail address.)

As an indication of the sizes of lathes, Mine is an old Clausing
which will swing 12" (300 mm) diameter over the bed, and somewhat
smaller (at least 6" (150 mm) over the carriage. I consider this on the
large end of hobby lathes, though there are others here with larger
machines. Mine is sufficiently rigid to be happy with carbide tooling
and reasonably tough jobs.

Carbide tools can give a smoother surface to the cut, but they
often require higher speeds and more rigidity from the lathe than
equivalent HSS tooling can.

Carbon steel requires *much* slower speeds or the tool overheats
and looses its temper.

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 ---
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Old August 31st 04, 07:09 PM
Jacek Zagaja
 
Posts: n/a
Default

Hi there Don

Yes - terminology through communication is what I need far away. So I
should use cutter not the 'knife' for turning tools right? I'm
studying Materials Engineering and turning is my temporary hobby that
allow me to realize some projects. For example integral spheres for
photometrical measurements.

2H13 is an old Polish label. Now we use European but they are not
intuitive for me so far. Do you know any site that deals with US.
Alloys nomenclature?

The carbide inserts are the only usable. Maybe ceramics can be right
too. There's something weird with turning speed for threads. Let
consider pafana.pl carbide inserts. Average turning speed for
stainless steel is 100 m/min. Now having 42 diameter I should set my
machine to:

n = 1000*Vc/pi*D = (1000*100)/(3.14*42) = 758 [turn/min]

This is some speed! Stopping the machine will cost some time Oh BTW
how you name this small distance (synonym is paddock) where you must
set your cutter and turn on machine. This distance has smaller
diameter than thread.

Note that the size of the lathe, and the rigidity and power will
determine whether you can use carbide tooling to get a better
finish. Your "2H13" appears to be one of the European steel
designations, and I am not familiar with it. But 13% Cr would
probably make that a rather tough steel. Perhaps Ed Huntress could
pop up with a close equivalent in US steel grades?


My lathe is rather powerful enough (1800 turns/min) and my spindle
handle 100 mm rollers. Take a look:

http://tme.szczecin.pl/~jacek/Myslov...alworking.html

2H13 can be toughened so that 60-70 HRC is possible but I don't think
it was toughened. I can check with Vickers hardness test after cutting
my work. The surface is struggled because of hard shavings fall (I
don't know if 'fall' is good here, maybe flow down or something).

It may even be that it would be better to grind the threads instead
of to try to cut them -- but this will require a rather expensive
setup.


Yes however in my city, a common pitch is 1.2 and I need 1.0 with 42
diameter (mm). Also the length of thread is small - max. 5 mm.

Are you doing this as a hobby, or are you in a commercial machine
shop? The tools which would be standard in such a commercial shop
are less likely to be found in a home shop for hobby use.


As I wrote this is a hobby for University purpose. Imagine that we
have Technology Hall. They have digital lathes from Sandvik but they
don't know how to cut thread with good surface for right price. It is
also some relation problem. I did ask first can the chief do it for
me. He told me he doesn't have a time and went away to a tools room. I
did ask another guy. He shook his head. Now all the peoples (it was
vacation time) staying and looking at my work. It looks like (I can't
put drawings on my server for a while):
------------------
| |
| 70mm dia ---- |
|---------- | | |
| | /xxxx | | A |
---------------- |--------------------- ---- |
| ^ | |-
| | -----------------------|-|
- lathe mount | |42mm dia B | |
(spindle) | | ---------------------- |-|
| | | |-
---------------- |--------------------- -----|
| | \xxxx | | A |
|---------- | | |
^ | -----|
| | |
cut it here ------------------

xxxx - is an area of thread (42mm dia and 1 mm pitch). As you see the
diameters is 70 vs. 42 so the side (flange) is a problem for them
The want the thread to be reversed. That is technologically logical. I
told them I didn't have right cutter to perform A notch and what is
important to have absolute match (on axis) of thread with B opening.
The chief who is really nervous threw some insults at me that if I am
wise then I can do it myself and polishing will be to expensive for me
and went away again. As you see I'm trying did as he said

As an indication of the sizes of lathes, Mine is an old Clausing
which will swing 12" (300 mm) diameter over the bed, and somewhat
smaller (at least 6" (150 mm) over the carriage. I consider this on
the large end of hobby lathes, though there are others here with
larger machines. Mine is sufficiently rigid to be happy with carbide
tooling and reasonably tough jobs.


I would say the same instead of threads

Carbide tools can give a smoother surface to the cut, but they often
require higher speeds and more rigidity from the lathe than
equivalent HSS tooling can. Carbon steel requires *much* slower
speeds or the tool overheats and looses its temper.


That is so. I will try to use ready thread cutter (carbide soldered to
the grip) and grind it so that it can be used with that flange.

With Kind Regards,
__________________________________________________ ____________________

Jack Zagaja - photographer, designer, programmer
free photoshop plugins, photographic assistance
opinions and much more ...
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Old August 31st 04, 11:58 PM
Ned Simmons
 
Posts: n/a
Default

In article ,
-you-should-not-spam says...


2H13 is an old Polish label. Now we use European but they are not
intuitive for me so far. Do you know any site that deals with US.
Alloys nomenclature?


According to this page

http://www.demark.com.pl/zastos_a.htm

2H13 is equivalent to AISI 420 stainless steel.

Oh BTW
how you name this small distance (synonym is paddock) where you must
set your cutter and turn on machine. This distance has smaller
diameter than thread.


Thread relief?

Ned Simmons
  #5   Report Post  
Old September 1st 04, 07:29 AM
DoN. Nichols
 
Posts: n/a
Default

In article ,
Jacek Zagaja jzagaja-at-poczta.onet.pl wrote:
Hi there Don

Yes - terminology through communication is what I need far away. So I
should use cutter not the 'knife' for turning tools right?


"Cutter" or "Turning tool" or "lathe tool" all would work.
"Knife" implies a kind of cutting not normally found on a lathe.
Actually, "threading tool" applies specifically to what you are using.

I'm
studying Materials Engineering and turning is my temporary hobby that
allow me to realize some projects. For example integral spheres for
photometrical measurements.


Hmm ... for that, perhaps spinning of thin sheet metal, instead
of machining. Make two pieces (one with an access hole and one without)
joined at the "equator" (if you were talking about the planet instead of
a man-made sphere.)

2H13 is an old Polish label. Now we use European but they are not
intuitive for me so far. Do you know any site that deals with US.
Alloys nomenclature?


I'm sure that such exist, but what I currently use are two
books. One is _Machinery's Handbook_ (pretty much any recent edition),
and one is an older Jorgensen steel catalog. Since both are in English,
they may be hard for you to find. I don't know how available
English-language technical books from outside the country may be.

The carbide inserts are the only usable. Maybe ceramics can be right
too. There's something weird with turning speed for threads. Let
consider pafana.pl carbide inserts. Average turning speed for
stainless steel is 100 m/min. Now having 42 diameter I should set my
machine to:

n = 1000*Vc/pi*D = (1000*100)/(3.14*42) = 758 [turn/min]

This is some speed!


It is rather fast, given your need to cut a short thread, and
the lack of clearance. One thing which might help would be to turn the
tool upside down (adjusting to set the height of the point correctly)
and to cut in reverse, so you cut away from the shoulder. However, I
don't see provisions for a "runout groove" (where the metal is cut away
completely, to provide a space where the tool's motion can be stopped
(or in this case started) without messing up the thread which you are
cutting. Can you introduce such a groove into your design? It will
make the job a *lot* easier.

Stopping the machine will cost some time Oh BTW
how you name this small distance (synonym is paddock) where you must
set your cutter and turn on machine. This distance has smaller
diameter than thread.


I think that this must be the runout groove which I mentioned
before.

Note that you should not need to start and stop the lathe
spindle if you have a runout groove to place the threading tool in to
start, and a threading dial which will allow you to close the half-nuts
at the same reference point each time. (With metric threads, I
understand that the threading dial has a sliding gear with four
different sizes to engage the leadscrew, depending on the particular
thread to be cut. I've not had to work with this style before.

Anyway, with the spindle turning, you crank the point of the
threading tool (the one which you have illustrated would be for
threading towards the shoulder right-side up, you would need a different
one for the upside-down threading, given how little clearance you have.
(Note that I am not accustomed to using the brazed (silver soldered)
tooling, but rather the style with the removable inserts, where a
special pocket exists on the tool shank, and a clamp to hold the insert
in place. These are cheaper to replace inserts on, but what you have is
probably cheaper in initial purchase price.

Anyway -- you move the threading tool into the groove, and set
it to a very shallow first cut, lubricate the workpiece (I would
probably use "Molly-Dee" a molybdimum disulfide based cutting oil for
this, but I don't know what you have available. Once it is in to the
desired depth, wait for a mark to line up with the index on the
threading dial, and note which one you use (probably should just use the
'1' mark -- at the speed and pitch you are working with, the mark will
come around fairly quickly. Then, just as the '1' mark approaches the
index mark, quickly close the half-nut lever. This will start the
thread cutting -- hopefully away from the shoulder if the gear setting
is right, and the spindle is running backwards. Once it clears the end
of the thread, pull back up on the lever to disengage the feed. Then
crank the cross-slide back enough to clear the workpiece, and crank the
tip of the tool back to the runout groove. Then crank the tip back in
to the previous depth, and (just this once) stop there, and re-engage
the half-nuts lever as before. The tip should travel in the same groove
you just cut, without removing much (if any) metal. This is helping you
to be sure that the thread dial is at the right setting.

Once that is proven, crank the tip back out again, and move it
back to the runout groove. Then crank it in and go just a little
deeper. (I won't suggest absolute depths, as you will have to find out
what works with your material and your tool. However, as a starting
point, try 0.10 mm. It is a bit shallower increment than I would use at
the start of the cut, but not much. (I would normally be working in
inches, not mm, though I sometimes work in mm.) As you get deeper, you
need to make the increment a bit less, as you are removing more material
per cut. The final cut, you should repeat at the same depth a couple of
times, which will produce a smoother thread. Then take a file and clean
up the crests of the threads.

Note that US practice while threading usually has the compound
set to feed almost along one flank of the thread, taking most of the cut
off the other side. A common setting is 29.5 degrees, though 29 degrees
will work as well. With this technique, you bring the cross-slide back
in to the same depth and then add a bit more feed using the compound
each time. This means that you will have to correct the compound's feed
for the angle to get the right depth -- but you should also have some
way to measure the thread depth directly -- thread wires and a
micrometer, or if you have access to one, a thread depth micrometer with
the right anvils for you 1.0 mm thread pitch.

Normally, the angle of the compound is to feed it in and a bit
towards the headstock side. With the reversed spindle you would use the
same -- or with no reversal, you would need to shift it to the other
side. Apparently, UK practice is to just feed in square, which would
give you a little less to worry about, but which might not produce as
good a thread. Certainly, cutting towards the shoulder would require a
lot faster reflexes if you want to get the maximum speed out of the
carbide tooling.

Note that the size of the lathe, and the rigidity and power will
determine whether you can use carbide tooling to get a better
finish. Your "2H13" appears to be one of the European steel
designations, and I am not familiar with it. But 13% Cr would
probably make that a rather tough steel. Perhaps Ed Huntress could
pop up with a close equivalent in US steel grades?


My lathe is rather powerful enough (1800 turns/min)


Speed is only one point. There is also the power of the motor.
I am used to it being expressed in HP (horsepower), but European motors
tend to express it in KW instead. My motor is 1-1/2 HP, which should be
somewhere around 1.2 KW or so.

and my spindle
handle 100 mm rollers. Take a look:

http://tme.szczecin.pl/~jacek/Myslov...alworking.html


Hmm ... I see the brazed (silver-soldered) carbide threading
tool. I was sort of expecting the lathe, instead.

Now -- if you really *have* to cut to the shoulder and not have
a runout groove, what I would suggest using for the machine would be a
CNC lathe -- as that can cut and withdraw the tool at precisely the same
point each time, so the end of the thread just lifts out of the groove.

2H13 can be toughened so that 60-70 HRC is possible but I don't think
it was toughened. I can check with Vickers hardness test after cutting
my work. The surface is struggled because of hard shavings fall (I
don't know if 'fall' is good here, maybe flow down or something).


I'm not quite sure what you mean by "fall" above.

However, one consideration, even if the material starts out
annealed (maximum soft state), it may work harden -- and I suspect that
a steel with that much chromium will do so. This may require you to
make deeper threading cuts than I would otherwise like to make.

It may even be that it would be better to grind the threads instead
of to try to cut them -- but this will require a rather expensive
setup.


Yes however in my city, a common pitch is 1.2 and I need 1.0 with 42
diameter (mm). Also the length of thread is small - max. 5 mm.


So -- at most 5 complete threads, and probably less. Certainly
less if you make a runout groove.

Are you doing this as a hobby, or are you in a commercial machine
shop? The tools which would be standard in such a commercial shop
are less likely to be found in a home shop for hobby use.


As I wrote this is a hobby for University purpose. Imagine that we
have Technology Hall. They have digital lathes from Sandvik but they


"digital lathes" are probably what I would call "CNC lathes".
"CNC" stands for "Computer Numerical Control" in English.

don't know how to cut thread with good surface for right price. It is
also some relation problem. I did ask first can the chief do it for
me. He told me he doesn't have a time and went away to a tools room. I
did ask another guy. He shook his head. Now all the peoples (it was
vacation time) staying and looking at my work. It looks like (I can't
put drawings on my server for a while):
------------------
| |
| 70mm dia ---- |
|---------- | | |
| | /xxxx | | A |
---------------- |--------------------- ---- |
| ^ | |-
| | -----------------------|-|
- lathe mount | |42mm dia B | |
(spindle) | | ---------------------- |-|
| | | |-
---------------- |--------------------- -----|
| | \xxxx | | A |
|---------- | | |
^ | -----|
| | |
cut it here ------------------

xxxx - is an area of thread (42mm dia and 1 mm pitch). As you see the
diameters is 70 vs. 42 so the side (flange) is a problem for them
The want the thread to be reversed. That is technologically logical. I
told them I didn't have right cutter to perform A notch and what is
important to have absolute match (on axis) of thread with B opening.
The chief who is really nervous threw some insults at me that if I am
wise then I can do it myself and polishing will be to expensive for me
and went away again. As you see I'm trying did as he said


O.K. Are you using a live center on the tailstock to support
the free end of the workpiece? That would reduce chatter (vibration of
the workpiece as you cut). I *think* that 'B' is supposed to be a hole,
though it appears to stick out a bit. Is the 'A' part a circular
groove? If so, is the inner diameter of that the same as the 42 mm of
the other end? If that is the case, and if the part does not need to
resist lots of twisting force, I would think that it would be easier to
start with a workpiece just big enough to cut the threads on the OD, and
turn the 42 mm parts on each end. Them make the 70 mm diameter piece
with a hole just slightly below 42 mm (perhaps 41.94 or so) and heat the
70mm diameter piece to expand the hole, and slide it onto the other part
after the threading is completed. It will quickly shrink and become
close to immovable -- how much depends on the actual sizes of the shaft
and the hole.

Anyway -- looking at other ways to make something (sometimes of
two or three pieces, instead of just one) might make it easier to make.

As an indication of the sizes of lathes, Mine is an old Clausing
which will swing 12" (300 mm) diameter over the bed, and somewhat
smaller (at least 6" (150 mm) over the carriage. I consider this on
the large end of hobby lathes, though there are others here with
larger machines. Mine is sufficiently rigid to be happy with carbide
tooling and reasonably tough jobs.


I would say the same instead of threads

Carbide tools can give a smoother surface to the cut, but they often
require higher speeds and more rigidity from the lathe than
equivalent HSS tooling can. Carbon steel requires *much* slower
speeds or the tool overheats and looses its temper.


That is so. I will try to use ready thread cutter (carbide soldered to
the grip) and grind it so that it can be used with that flange.


When grinding carbide tooling (you will need something better
than the typical bench grinder), you should wear a breathing mask to
keep the dust out of your lungs. It can be bad after a time.

It is really late now (about 2:30 AM), and I am going off to
bed. I hope to get back to your next message before it is quite this
late -- but I will be at a long meeting tomorrow evening, so I may not
make it back in time.

I hope that this has been some help.

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 ---


  #6   Report Post  
Old September 1st 04, 10:21 PM
Jacek Zagaja
 
Posts: n/a
Default

Don,

The suggestion that reverse tool arranging (upside down) is one of the
most important and can be proven using forces analysis. I've never
tried that way.

I am not sure but in paragraph "Note that US practice while
threading[...]" you describing special cutting technique used in mass
production so that the cutter is worn evenly right? I'm trying to
figure out all that angles in English used in turning. Now I have *two
of 4 (*alfa, *gamma, epsilon, kappa) and a little mess with shoulder
and tailstock. Are they synonyms or shoulder is synonym of headstock?

The link I provided so far extract the Java Console installed on your
system. Then you certainly will able to see panoramic image of the
turning room.

I'm not quite sure what you mean by "fall" above


Fall is used to express what is happening with cut material
(shavings). It should be able to "flow down" Is it correct?

O.K. Are you using a live center on the tailstock to support the
free end of the workpiece?


No I didn't. The material is quite rigid (stiff?) so I gave up this
idea. Maybe this can be such mistake.

Is the 'A' part a circular groove?


Yes.

If so, is the inner diameter of that the same as the 42 mm of the
other end?


No

So in summary we have to check two ways: reverse cutting and extra
small depth of cutting. In next week I will try this. Thank you so
much.

Cheers,
__________________________________________________ ____________________

Jack Zagaja - photographer, designer, programmer
free photoshop plugins, photographic assistance
opinions and much more ...
  #7   Report Post  
Old September 2nd 04, 05:43 AM
Glenn Lyford
 
Posts: n/a
Default

and a little mess with shoulder and tailstock.
Are they synonyms or shoulder is synonym of headstock?


A shoulder is a flat surface perpendicular to the axis,
adjacent to a smaller diameter, or any similar feature where
the part changes diameters. If it is at the end of a part,
it is usually just refered to as a face. In the case of
your part, it is the section adjacent to the diameter where
you are cutting your threads. Threads are much easier to cut
when you don't have to worry about where you stop and start
the cut because of the rest of the part getting in the way.
This is why some were suggesting you make the part in two
pieces.
--Glenn Lyford
  #8   Report Post  
Old September 4th 04, 06:44 AM
DoN. Nichols
 
Posts: n/a
Default

In article ,
Jacek Zagaja jzagaja-at-poczta.onet.pl wrote:
Don,

The suggestion that reverse tool arranging (upside down) is one of the
most important and can be proven using forces analysis. I've never
tried that way.


The major benefit is that it allows you to thread in reverse --
which is normally of benefit when threading up to a shoulder. However,
you would probably be better off to have a runout groove as a starting
point, and thread away from the shoulder in the normal direction. I
think that I got this wrong in the other article, and again, I am typing
at 1:00 AM, so there may be other errors.

I am not sure but in paragraph "Note that US practice while
threading[...]" you describing special cutting technique used in mass
production so that the cutter is worn evenly right?


No -- this is also done in hobby work, and the benefit is that
the chip is mostly formed on only one side of the tool, with the other
side grazing the flank of the thread, and taking very little metal from
it.

Another benefit is that this keeps the forces in one direction,
so it holds the half-nut firmly against the leadscrew -- even if it is
worn badly enough to have significant backlash. As Harold Vrodos would
tell you if he were in this thread, this can lead to "drunken" threads
-- threads which wander a bit to the left or right of where they should
be.

I'm trying to
figure out all that angles in English used in turning. Now I have *two
of 4 (*alfa, *gamma, epsilon, kappa) and a little mess with shoulder
and tailstock. Are they synonyms or shoulder is synonym of headstock?


A shoulder is an artifact of a workpiece. One which prevents
you from having free access to both sides of the area. In this case, as
you have it mounted, based on your ASCII drawing of the workpiece, the
larger diameter gets in the way of your threading to the right of the
area being threaded. It is better there, than to the left for normal
threading, as long as you cut a "runout groove" (a groove as deep as the
thread, and enough wider with a flat bottom so you can either position
the threading tool before starting the cut, or (in the normal direction
of threading), so there is a wider place to give you a bit more
reaction time to pull up the half-nuts lever and stop the feed of the
cutting (threading) tool.

While we're here, let me make clear the meaning of headstock and
tailstock, just in case you need those.

Headstock: The part of the lathe which contains the rotating
spindle, and drives the workpiece by one of a number
of means -- holding it in a collet, holding it in a
chuck, holding it between centers, and driving it with a
lathe dog and a faceplate, clamping the workpiece to a
faceplate.

Carriage: The part of the lathe which carries the cutting tool,
and travels from left to right under hand control or
under power. It also carries the cross-slide, which may
carry a compound which may be adjusted to move at an
angle to the cross-slide, as when threading.

Tailstock: The portion of the lathe which may be moved from right
to left after unclamping it from the bed, and then may
be clamped to the bed to drive a drill bit (in a drill
chuck or with a taper), or to hold a live (or dead)
center to steady the tailstock end of the workpiece to
control flex, or to allow turning between centers.

The link I provided so far extract the Java Console installed on your
system. Then you certainly will able to see panoramic image of the
turning room.


Oh -- I keep Java and JavaScript turned off for security
reasons. Are you sure that was not another URL? I backed up one layer
and found another one called "panorama" (or something like that), but I
could not see the panorama without enabling Java or JavaScript.

I'm not quite sure what you mean by "fall" above


Fall is used to express what is happening with cut material
(shavings). It should be able to "flow down" Is it correct?


O.K. For normal turning, the chips curl up above the tool, and
(depending on the geometry of the tool, the depth of cut, the presence
or absence of a chipbreaker groove (part of the geometry of the tool),
and the characteristics of the metal alloy, the chips will either flow
smoothly in a continuous string, curl, or break into short pieces. The
last is the best and safest, and is the purpose of a chipbreaker groove
in the tooling.

However, with an upside-down tool (either with reversed spindle
with the tool in the normal position, or with the spindle running
forward, with the tool located on the back of the cross slide, as is
sometimes done with a parting tool), the chips fall from the cut more
easily. This is probably most beneficial in the parting, where the
chips tend to build up and jam in the cut, and is one of several reasons
for the upside-down parting tool in the back of the carriage.

O.K. Are you using a live center on the tailstock to support the
free end of the workpiece?


No I didn't. The material is quite rigid (stiff?) so I gave up this
idea. Maybe this can be such mistake.


It can be, indeed. It is amazing how much flex there is in a
workpiece and in the machine tool itself. Anything to minimize that
helps. In this case, the fact that you have a larger diameter towards
the tailstock (which is what forms the shoulder restricting access to
the area to be threaded) tends to create higher forces while turning
that part, and the smaller diameter towards the headstock and the chuck
(or collet -- I don't know which you are using to hold the workpiece)
allows greater flex in the workpiece. So use of a live center in the
tailstock to support the free end will help reduce "chatter" and improve
the finish in your thread -- as well as in other parts of the project.

Is the 'A' part a circular groove?


Yes.

If so, is the inner diameter of that the same as the 42 mm of the
other end?


No


Is it smaller, or larger? If it is smaller, then making the
part as two pieces and heat-shrinking them together will make it easier
for you to turn the threads, as you can eliminate that shoulder to the
right of the area being threaded -- at least until after the threads are
cut and the other piece is heat-shrunk in place.

So in summary we have to check two ways: reverse cutting and extra
small depth of cutting. In next week I will try this. Thank you so
much.


I believe that another followup showed your material as being
similar to 420 stainless steel in the USA.

If so, the description in _Machinery's Handbook_ says;

420 (S42000) Higher carbon modification of type 410. (followed by
a list of typical applications.)

What it does *not* say, and what I would expect, is that it
would be likely to work harden, in which case you need to be careful not
too make *too* shallow a cut. Once it work hardens, you will have a
difficult time getting the cut going again.

I've never used this, but I do use 416 SS, and find it fairly
nice to machine. (Though I don't think that I've tried threading it.

Good Luck,
DoN.

--
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  #9   Report Post  
Old September 4th 04, 08:57 PM
Jacek Zagaja
 
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Don,

Oh -- I keep Java and JavaScript turned off for security reasons.
Are you sure that was not another URL? I backed up one layer and
found another one called "panorama" (or something like that), but I
could not see the panorama without enabling Java or JavaScript.


I'm sure, there is no another URL. This is just an applet. Nothing
more. So all in all I understand you have seen my panorama.

Is it smaller, or larger? If it is smaller, then making the part as
two pieces and heat-shrinking them together will make it easier for
you to turn the threads, as you can eliminate that shoulder to the
right of the area being threaded -- at least until after the threads
are cut and the other piece is heat-shrunk in place.


It is smaller. If the "easy way" is concerned then no problem but the
case is to make the worst way having integrity on axis. Imagine
there's such thing you must do it as I do. The end justifies the means


I believe that another followup showed your material as being
similar to 420 stainless steel in the USA.


The teacher says to student "We have in Poland such a carbon steel
which is weldable, but the same steel in US. isn't meant to be
weldable ". This show the technological level differences in general


Stay tuned for part two of this thread.
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  #10   Report Post  
Old September 7th 04, 05:52 AM
DoN. Nichols
 
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In article ,
Jacek Zagaja jzagaja-at-poczta.onet.pl wrote:
Don,

Oh -- I keep Java and JavaScript turned off for security reasons.
Are you sure that was not another URL? I backed up one layer and
found another one called "panorama" (or something like that), but I
could not see the panorama without enabling Java or JavaScript.


I'm sure, there is no another URL. This is just an applet. Nothing
more. So all in all I understand you have seen my panorama.


The original URL showed me only what appeared a brazed insert
threading cutter.

When I removed the last element of that URL, I backed up to a
page which offered several choices, including one labeled as a panorama.
When I selected that, I saw nothing -- but since I have Java and
JavaScript turned off, I would not expect to see anything, if it is
powered by Java or JavaScript.

Is it smaller, or larger? If it is smaller, then making the part as
two pieces and heat-shrinking them together will make it easier for
you to turn the threads, as you can eliminate that shoulder to the
right of the area being threaded -- at least until after the threads
are cut and the other piece is heat-shrunk in place.


It is smaller. If the "easy way" is concerned then no problem but the
case is to make the worst way having integrity on axis. Imagine
there's such thing you must do it as I do. The end justifies the means


You need the thread to be truly concentric to the ID of the
hole in the large end. How important are the other features of that
end? The ones which come to mind a

1) The OD of the inner part of the groove.

2) The ID of the groove.

3) The depth of the groove.

4) The OD of the major diameter.

If none of those have to be precisely concentric with the
threads and the central hole, it strikes me that the easier way is the
best choice.

I believe that another followup showed your material as being
similar to 420 stainless steel in the USA.


The teacher says to student "We have in Poland such a carbon steel
which is weldable, but the same steel in US. isn't meant to be
weldable ". This show the technological level differences in general


There are variations of alloys some of which are easy to weld
and some are not. I know that 12L14 (a very easy to machine mild steel
alloy) is supposed to be difficult to weld, because of the lead content.
1214 (without the 'L') is a bit more difficult to machine, but is easy
to weld. You have to make choices based on what you need to do.

I believe that some stainless steel alloys also have additives
which make them hard to weld, but easier to machine.

I don't do welding (yet) so I don't know too much about this,
but I do know that there are alloys which are designed to be easy to
weld, and others (almost the same, but for small changes) which are
difficult to weld, but easier to machine.

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 ---


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