|
I recently attempted to make a 3C collet chuck to fit the 3MT taper
in my lathe. This seemed to go OK but the first try was not a good
fit (rear of the collet fit sloppy) so I made another which fit
better. The chuck is based on an article by Exactus, 2984 found here:
As a newbie, I've never seen a collet chuck in action so I don't know
exactly what to expect from it. What I hoped was that it would
provide simple, non-marking gripping of work with zero runout. My
chuck may be poorly made or perhaps I'm overly optimistic on how it
should work.
I bought a 3C South Bend 3/8 brass collet on eBay as a model to judge
fit; my goal was to eventually make steel collets to fit the chuck.
When I put this collet into my chuck I find that the runout varies
each time I tighten the drawbar, typically 2-4 tenths, sometimes up
to 1 mil. When the runout is large it gets larger as I move farther
from the chuck so apparently it is angled somewhere (the work or the
collet itself); if I tap the test piece on the high side with a block
of wood it generally will settle to the more typical 2-4 tenths
anywhere along the length of the 1 inch long test piece (a commercial
3/8 D bit shaft.
Ths narrow part of the SB collet tapers about 6 mils, getting larger
as one goes from the threads toward the steep taper. I made the chuck
so it is an easy fit for the first part of the collet but I have to
press firmly to fully insert it due to the collet's taper. Similarly,
it requires a push with the drawbar to get enough to protrude so it
can be pulled out.
With the above as background, I have a number of newbie questions on
collets and collet chucks:
1. What is the expected runout when using a collet?
2. Is the taper on the narrow part of the collet machined in or does
this happen when they add the slits? Will this also be present on
steel collets or just on brass?
3. What surface(s) are critical in providing the collet centering.
That is, is the fit of the chuck onto the rear of the collet
critical? Does the chuck need to be tapered in the narrow bore to
match the collet? Is there a specification for the steep angle on a
3C?
Any help here would be appreciated. I've put quite a bit of time
into making this chuck and now don't know whether it is useful or
just a fancy doorstop.
John
|
Based on building a 5-C adaptor I believe that the bore should be
straight to align the collet body coaxially with the lathe axis.
Bill in Boulder "Engineering as an Art Form!"
|
See if there's anything here that helps: Roy --- In 7x12minilathe@..., "John" <moran03@e...> wrote: I recently attempted to make a 3C collet chuck to fit the 3MT taper
in my lathe. This seemed to go OK but the first try was not a good
fit (rear of the collet fit sloppy) so I made another which fit
better. The chuck is based on an article by Exactus, 2984 found here:
As a newbie, I've never seen a collet chuck in action so I don't know exactly what to expect from it. What I hoped was that it would
provide simple, non-marking gripping of work with zero runout. My
chuck may be poorly made or perhaps I'm overly optimistic on how it
should work.
I bought a 3C South Bend 3/8 brass collet on eBay as a model to judge fit; my goal was to eventually make steel collets to fit the chuck.
When I put this collet into my chuck I find that the runout varies
each time I tighten the drawbar, typically 2-4 tenths, sometimes up
to 1 mil. When the runout is large it gets larger as I move farther from the chuck so apparently it is angled somewhere (the work or the collet itself); if I tap the test piece on the high side with a block of wood it generally will settle to the more typical 2-4 tenths
anywhere along the length of the 1 inch long test piece (a commercial 3/8 D bit shaft.
Ths narrow part of the SB collet tapers about 6 mils, getting larger as one goes from the threads toward the steep taper. I made the chuck so it is an easy fit for the first part of the collet but I have to
press firmly to fully insert it due to the collet's taper. Similarly, it requires a push with the drawbar to get enough to protrude so it
can be pulled out.
With the above as background, I have a number of newbie questions on collets and collet chucks:
1. What is the expected runout when using a collet?
2. Is the taper on the narrow part of the collet machined in or does this happen when they add the slits? Will this also be present on
steel collets or just on brass?
3. What surface(s) are critical in providing the collet centering.
That is, is the fit of the chuck onto the rear of the collet
critical? Does the chuck need to be tapered in the narrow bore to
match the collet? Is there a specification for the steep angle on a
3C?
Any help here would be appreciated. I've put quite a bit of time
into making this chuck and now don't know whether it is useful or
just a fancy doorstop.
John
|
Hi Roy, Thanks for the link. I looked at the site and wrote to the owner, Dave Audette, who provided a considerable amount of information in a detailed reply. One key bit of data is that his runout is about 4 tenths, similar to mine when the collet settles in the chuck properly. I also found a CNC site which gave collet runout as 5 tenths max so apparently my collet chuck's performance is in the ballpark. However, it is interesting that Dave gets 4 tenths runout with a SB collet holder which I assume is probably concentric to the headstock MT3 socket. Makes me think my headstock may be poorer than most since I find the following when indicating various points on the backplate: Outer rim = 5 tenths Land for chuck registry = 2 Inside of MT3 socket = 6+ Inside of 3C chuck = 2 Piece in collet = 2-4 typical, sometimes 10 (tapping with a block of wood causes it to pop into alignment yielding 2-4) Logically, a perfectly concentric collet chuck's runout could be no better than the socket it is mounted in.I use a witness mark to align my collet chuck to the backplate/MT3 socket so the socket runout should be cancelled because the chuck was machined in that socket and replaced in the same orientation. That is, my collet chuck is slightly eccentric but in a way which compensates for the MT3 socket's runout. The above figures indicate (no pun intended) that the runout of the MT3 socket in my backplate is larger than desirable and that Dave's machine seems to run truer by quite a bit since he gets the same runout without having machined his chuck in place. Based on the above I would guess that during manufacture the backplate is turned to size on a production machine with the chuck land left slightly larger than final size. The backplate is then mounted on the lathe and the chuck land is machined to final size in place to minimize runout. I intend to polish the inside of the collet chuck in an attempt to cause it to register the collet the same way each time so I don't sometimes have to tap the work with a block of wood. John --- In 7x12minilathe@..., "roylowenthal" <roylowenthal@y...> wrote: See if there's anything here that helps:
Roy
--- In 7x12minilathe@..., "John" <moran03@e...> wrote:
I recently attempted to make a 3C collet chuck to fit the 3MT taper in my lathe. This seemed to go OK but the first try was not a
good fit (rear of the collet fit sloppy) so I made another which fit
better. The chuck is based on an article by Exactus, 2984 found here:
As a newbie, I've never seen a collet chuck in action so I don't know
exactly what to expect from it. What I hoped was that it would
provide simple, non-marking gripping of work with zero runout. My
chuck may be poorly made or perhaps I'm overly optimistic on how
it should work.
I bought a 3C South Bend 3/8 brass collet on eBay as a model to judge
fit; my goal was to eventually make steel collets to fit the
chuck. When I put this collet into my chuck I find that the runout
varies each time I tighten the drawbar, typically 2-4 tenths, sometimes
up to 1 mil. When the runout is large it gets larger as I move farther
from the chuck so apparently it is angled somewhere (the work or the
collet itself); if I tap the test piece on the high side with a block
of wood it generally will settle to the more typical 2-4 tenths
anywhere along the length of the 1 inch long test piece (a commercial
3/8 D bit shaft.
Ths narrow part of the SB collet tapers about 6 mils, getting larger
as one goes from the threads toward the steep taper. I made the chuck
so it is an easy fit for the first part of the collet but I have
to press firmly to fully insert it due to the collet's taper. Similarly,
it requires a push with the drawbar to get enough to protrude so
it can be pulled out.
With the above as background, I have a number of newbie questions on
collets and collet chucks:
1. What is the expected runout when using a collet?
2. Is the taper on the narrow part of the collet machined in or does
this happen when they add the slits? Will this also be present on
steel collets or just on brass?
3. What surface(s) are critical in providing the collet
centering. That is, is the fit of the chuck onto the rear of the collet
critical? Does the chuck need to be tapered in the narrow bore to
match the collet? Is there a specification for the steep angle on
a 3C?
Any help here would be appreciated. I've put quite a bit of time
into making this chuck and now don't know whether it is useful or
just a fancy doorstop.
John
|
I wonder if the brass collet is part of the problem. Coming from e-bay, there's no telling what sort of abuse it may have suffered. Steel collets are "spring hard" to avoid distortion during use; they eventually wear eccentric. (Long eventual, except in high volume production.) Trying to work to tenths is sort of frustrating - surface finish of mating parts has a disproportionate effect on readings. Actually, surface finish on the part being indicated can "drag" the indicator to a slightly false reading. Presumably, your measuring technique gives the same reading on return to the same point. There's enough flex in these machines to get a measurable deflection from resting your forearm on the headstock. Except for really critical work, ignoring any runout under .001" or .002" saves a lot of set-up time. Roy --- In 7x12minilathe@..., "John" <moran03@e...> wrote: Hi Roy,
Thanks for the link. I looked at the site and wrote to the owner,
Dave Audette, who provided a considerable amount of information in a detailed reply. One key bit of data is that his runout is about 4
tenths, similar to mine when the collet settles in the chuck
properly. I also found a CNC site which gave collet runout as 5
tenths max so apparently my collet chuck's performance is in the
ballpark.
However, it is interesting that Dave gets 4 tenths runout with a SB
collet holder which I assume is probably concentric to the headstock MT3 socket. Makes me think my headstock may be poorer than most
since I find the following when indicating various points on the
backplate:
Outer rim = 5 tenths
Land for chuck registry = 2
Inside of MT3 socket = 6+
Inside of 3C chuck = 2
Piece in collet = 2-4 typical, sometimes 10 (tapping with a block of wood causes it to pop into alignment yielding 2-4)
Logically, a perfectly concentric collet chuck's runout could be no
better than the socket it is mounted in.I use a witness mark to align my collet chuck to the backplate/MT3 socket so the socket runout
should be cancelled because the chuck was machined in that socket and replaced in the same orientation. That is, my collet chuck is
slightly eccentric but in a way which compensates for the MT3
socket's runout.
The above figures indicate (no pun intended) that the runout of the
MT3 socket in my backplate is larger than desirable and that Dave's
machine seems to run truer by quite a bit since he gets the same
runout without having machined his chuck in place.
Based on the above I would guess that during manufacture the
backplate is turned to size on a production machine with the chuck
land left slightly larger than final size. The backplate is then
mounted on the lathe and the chuck land is machined to final size in place to minimize runout.
I intend to polish the inside of the collet chuck in an attempt to
cause it to register the collet the same way each time so I don't
sometimes have to tap the work with a block of wood.
John
--- In 7x12minilathe@..., "roylowenthal"
<roylowenthal@y...> wrote:
See if there's anything here that helps:
Roy
--- In 7x12minilathe@..., "John" <moran03@e...> wrote:
I recently attempted to make a 3C collet chuck to fit the 3MT taper
in my lathe. This seemed to go OK but the first try was not a
good
fit (rear of the collet fit sloppy) so I made another which fit
better. The chuck is based on an article by Exactus, 2984
found here:
As a newbie, I've never seen a collet chuck in action so I
don't know
exactly what to expect from it. What I hoped was that it would
provide simple, non-marking gripping of work with zero runout.
My chuck may be poorly made or perhaps I'm overly optimistic on
how it
should work.
I bought a 3C South Bend 3/8 brass collet on eBay as a model to judge
fit; my goal was to eventually make steel collets to fit the
chuck.
When I put this collet into my chuck I find that the runout
varies
each time I tighten the drawbar, typically 2-4 tenths,
sometimes up
to 1 mil. When the runout is large it gets larger as I move farther
from the chuck so apparently it is angled somewhere (the work
or the
collet itself); if I tap the test piece on the high side with a block
of wood it generally will settle to the more typical 2-4 tenths
anywhere along the length of the 1 inch long test piece (a commercial
3/8 D bit shaft.
Ths narrow part of the SB collet tapers about 6 mils, getting larger
as one goes from the threads toward the steep taper. I made the chuck
so it is an easy fit for the first part of the collet but I
have to
press firmly to fully insert it due to the collet's taper. Similarly,
it requires a push with the drawbar to get enough to protrude
so it
can be pulled out.
With the above as background, I have a number of newbie
questions on
collets and collet chucks:
1. What is the expected runout when using a collet?
2. Is the taper on the narrow part of the collet machined in or does
this happen when they add the slits? Will this also be present
on steel collets or just on brass?
3. What surface(s) are critical in providing the collet
centering.
That is, is the fit of the chuck onto the rear of the collet
critical? Does the chuck need to be tapered in the narrow bore
to match the collet? Is there a specification for the steep angle
on a
3C?
Any help here would be appreciated. I've put quite a bit of
time into making this chuck and now don't know whether it is useful
or just a fancy doorstop.
John
|
The collet is a new SB, sk-polishing offers these frequently on eBay and I took advantage when one didn't seem to draw many bids. I have accepted it as a standard in testing my collet chuck, at least so far... Your comment on working to tenths is very interesting. Having no experience or training in machining I've been developing my own methods on an ad hoc basis. I've run into the problem you mentioned of "noise" on the DTI due to surface finish; my crude solution has been to use fine carbide paper to polish the surface a bit prior to taking the reading. I then wipe the surface with a paper towel and add a little oil. My measuring technique is to run the lathe at its lowest speed, about 12 rpm, and watch the DTI. The needle is still a little shivery but watching several cycles allows me to get a reading by averaging the maximum and minimum readings. I am open to any improvements in technique since I am very much a beginner at this. Your point on accepting a couple of mils of runout is one I have slowly arrived at in using the 3 jaw. Lately, I try to leave the diameter on the large side if a part will need to be removed and re- installed in the chuck, going to the finish size as the last step when possible. Thanks for the info. John --- In 7x12minilathe@..., "roylowenthal" <roylowenthal@y...> wrote: I wonder if the brass collet is part of the problem. Coming from e-bay, there's no telling what sort of abuse it may have suffered.
Steel collets are "spring hard" to avoid distortion during use; they eventually wear eccentric. (Long eventual, except in high volume
production.)
Trying to work to tenths is sort of frustrating - surface finish
of mating parts has a disproportionate effect on readings. Actually, surface finish on the part being indicated can "drag" the indicator
to a slightly false reading. Presumably, your measuring technique
gives the same reading on return to the same point. There's enough
flex in these machines to get a measurable deflection from resting
your forearm on the headstock.
Except for really critical work, ignoring any runout under .001"
or .002" saves a lot of set-up time.
Roy
--- In 7x12minilathe@..., "John" <moran03@e...> wrote:
Hi Roy,
Thanks for the link. I looked at the site and wrote to the owner, Dave Audette, who provided a considerable amount of information
in a
detailed reply. One key bit of data is that his runout is about 4 tenths, similar to mine when the collet settles in the chuck
properly. I also found a CNC site which gave collet runout as 5
tenths max so apparently my collet chuck's performance is in the
ballpark.
However, it is interesting that Dave gets 4 tenths runout with a
SB collet holder which I assume is probably concentric to the headstock
MT3 socket. Makes me think my headstock may be poorer than most
since I find the following when indicating various points on the
backplate:
Outer rim = 5 tenths
Land for chuck registry = 2
Inside of MT3 socket = 6+
Inside of 3C chuck = 2
Piece in collet = 2-4 typical, sometimes 10 (tapping with a block of
wood causes it to pop into alignment yielding 2-4)
Logically, a perfectly concentric collet chuck's runout could be
no better than the socket it is mounted in.I use a witness mark to align
my collet chuck to the backplate/MT3 socket so the socket runout
should be cancelled because the chuck was machined in that socket and
replaced in the same orientation. That is, my collet chuck is
slightly eccentric but in a way which compensates for the MT3
socket's runout.
The above figures indicate (no pun intended) that the runout of
the MT3 socket in my backplate is larger than desirable and that
Dave's machine seems to run truer by quite a bit since he gets the same
runout without having machined his chuck in place.
Based on the above I would guess that during manufacture the
backplate is turned to size on a production machine with the
chuck land left slightly larger than final size. The backplate is then
mounted on the lathe and the chuck land is machined to final size in
place to minimize runout.
I intend to polish the inside of the collet chuck in an attempt
to cause it to register the collet the same way each time so I don't
sometimes have to tap the work with a block of wood.
John
--- In 7x12minilathe@..., "roylowenthal"
<roylowenthal@y...> wrote:
See if there's anything here that helps:
Roy
|
My choice for a "standard" collet would be a pristine steel one, from one of the suppliers who states accuracy. I'd use it to hold an accurately ground test rod - dowel pins are good. I've had horrible results with drill blanks not being straight! I always use indicators on stationary parts; without the cute little roller point, I don't indicate parts while they're moving. For a runout check, I'd manually rotate the test piece to 4 perpendicular points. If a tiny bit of reverse rotation causes large indicated runout change, it's a symptom of dragging the indicator. Back rotate or not, just be consistent on all measurements. It's also better to keep oil away from indicators - sooner or later, some gets inside. It doesn't take much oil to make an indicator really sticky & unusable (think millidrops!) Leaving things .001" or so oversize allows room for filing/polishing for final finish. When I'm trying to make a new surface concentric with or blended into an existing one, I use the 4- jaw. When I've used collets for that sort of thing, they still needed indicating & gentle persuasion with a small rawhide mallet. Roy --- In 7x12minilathe@..., "John" <moran03@e...> wrote: The collet is a new SB, sk-polishing offers these frequently on eBay and I took advantage when one didn't seem to draw many bids. I have
accepted it as a standard in testing my collet chuck, at least so
far...
Your comment on working to tenths is very interesting. Having no
experience or training in machining I've been developing my own
methods on an ad hoc basis. I've run into the problem you mentioned of "noise" on the DTI due to surface finish; my crude solution has
been to use fine carbide paper to polish the surface a bit prior to
taking the reading. I then wipe the surface with a paper towel and
add a little oil. My measuring technique is to run the lathe at its lowest speed, about 12 rpm, and watch the DTI. The needle is still a little shivery but watching several cycles allows me to get a reading by averaging the maximum and minimum readings. I am open to any
improvements in technique since I am very much a beginner at this.
Your point on accepting a couple of mils of runout is one I have
slowly arrived at in using the 3 jaw. Lately, I try to leave the
diameter on the large side if a part will need to be removed and re-
installed in the chuck, going to the finish size as the last step
when possible.
Thanks for the info.
John
--- In 7x12minilathe@..., "roylowenthal"
<roylowenthal@y...> wrote:
I wonder if the brass collet is part of the problem. Coming from
e-bay, there's no telling what sort of abuse it may have suffered. Steel collets are "spring hard" to avoid distortion during use; they
eventually wear eccentric. (Long eventual, except in high volume
production.)
Trying to work to tenths is sort of frustrating - surface
finish of mating parts has a disproportionate effect on readings. Actually,
surface finish on the part being indicated can "drag" the
indicator to a slightly false reading. Presumably, your measuring
technique gives the same reading on return to the same point. There's
enough flex in these machines to get a measurable deflection from
resting your forearm on the headstock.
Except for really critical work, ignoring any runout
under .001" or .002" saves a lot of set-up time.
Roy
--- In 7x12minilathe@..., "John" <moran03@e...> wrote:
Hi Roy,
Thanks for the link. I looked at the site and wrote to the owner,
Dave Audette, who provided a considerable amount of information
in
a
detailed reply. One key bit of data is that his runout is
about 4
tenths, similar to mine when the collet settles in the chuck
properly. I also found a CNC site which gave collet runout as
5 tenths max so apparently my collet chuck's performance is in
the ballpark.
However, it is interesting that Dave gets 4 tenths runout with
a SB
collet holder which I assume is probably concentric to the headstock
MT3 socket. Makes me think my headstock may be poorer than
most since I find the following when indicating various points on
the backplate:
Outer rim = 5 tenths
Land for chuck registry = 2
Inside of MT3 socket = 6+
Inside of 3C chuck = 2
Piece in collet = 2-4 typical, sometimes 10 (tapping with a
block of
wood causes it to pop into alignment yielding 2-4)
Logically, a perfectly concentric collet chuck's runout could
be no
better than the socket it is mounted in.I use a witness mark to align
my collet chuck to the backplate/MT3 socket so the socket
runout should be cancelled because the chuck was machined in that
socket and
replaced in the same orientation. That is, my collet chuck is
slightly eccentric but in a way which compensates for the MT3
socket's runout.
The above figures indicate (no pun intended) that the runout of the
MT3 socket in my backplate is larger than desirable and that
Dave's
machine seems to run truer by quite a bit since he gets the
same runout without having machined his chuck in place.
Based on the above I would guess that during manufacture the
backplate is turned to size on a production machine with the
chuck
land left slightly larger than final size. The backplate is
then mounted on the lathe and the chuck land is machined to final
size in
place to minimize runout.
I intend to polish the inside of the collet chuck in an attempt to
cause it to register the collet the same way each time so I
don't sometimes have to tap the work with a block of wood.
John
--- In 7x12minilathe@..., "roylowenthal"
<roylowenthal@y...> wrote:
See if there's anything here that helps:
Roy
|
A lot of helpful hints in your post, Roy, thanks. This is the type of info one would pick up as an apprentice in a machine shop, I guess. I'm looking around for a new steel collet for use as my standard. Meanwhile, I'm roughing out blanks for some 3C collets in steel per the Exactus articles. I annealed the steel from the rod in a large shock absorber and can now machine it -- it seemed very hard prior to annealing in my fireplace; there is a good side to the cool spring we're having! Regards, John --- In 7x12minilathe@..., "roylowenthal" <roylowenthal@y...> wrote: My choice for a "standard" collet would be a pristine steel one,
from one of the suppliers who states accuracy. I'd use it to hold an accurately ground test rod - dowel pins are good. I've had horrible results with drill blanks not being straight!
I always use indicators on stationary parts; without the cute
little roller point, I don't indicate parts while they're moving.
For a runout check, I'd manually rotate the test piece to 4
perpendicular points. If a tiny bit of reverse rotation causes large indicated runout change, it's a symptom of dragging the indicator.
Back rotate or not, just be consistent on all measurements.
It's also better to keep oil away from indicators - sooner or
later, some gets inside. It doesn't take much oil to make an
indicator really sticky & unusable (think millidrops!)
Leaving things .001" or so oversize allows room for
filing/polishing for final finish. When I'm trying to make a new
surface concentric with or blended into an existing one, I use the 4- jaw. When I've used collets for that sort of thing, they still
needed indicating & gentle persuasion with a small rawhide mallet.
Roy
--- In 7x12minilathe@..., "John" <moran03@e...> wrote:
The collet is a new SB, sk-polishing offers these frequently on eBay
and I took advantage when one didn't seem to draw many bids. I have accepted it as a standard in testing my collet chuck, at least so
far...
Your comment on working to tenths is very interesting. Having no
experience or training in machining I've been developing my own
methods on an ad hoc basis. I've run into the problem you mentioned
of "noise" on the DTI due to surface finish; my crude solution
has been to use fine carbide paper to polish the surface a bit prior
to taking the reading. I then wipe the surface with a paper towel
and add a little oil. My measuring technique is to run the lathe at its
lowest speed, about 12 rpm, and watch the DTI. The needle is
still a
little shivery but watching several cycles allows me to get a reading
by averaging the maximum and minimum readings. I am open to any
improvements in technique since I am very much a beginner at this.
Your point on accepting a couple of mils of runout is one I have
slowly arrived at in using the 3 jaw. Lately, I try to leave the
diameter on the large side if a part will need to be removed and re- installed in the chuck, going to the finish size as the last step
when possible.
Thanks for the info.
John
|
I am surprised that the strut rod steel is hard to turn as it comes from
the strut! In my experience once you get under the chrome plate it is
very nice turning. Except of course where it has been spot welded! I am a
little surprised that the rod is big enough to make 3-C collets. What is
the maximum diameter of a 3-C? I may need to reevaluate my need for a
set!
Bill in Boulder "Engineering as an Art Form!"
|
Hi Bill, The diameter of the shock absorber rod is 0.865 while the large end OD of the collets is 0.830 so I can't be too sloppy when centering; the body OD is 0.650. This shock was bigger than most, enough material for 4 collets. Messy business draining the oil out of the shock itself. I use a Sawzall for cutting metal and it removed the outer shell of the shock very nicely. The turned down ends of the rod cut easily too. The chrome part seemed very hard; I tried a regular hacksaw to make sure the Sawzall blade was OK and the hacksaw wouldn't cut it either. I was surprised that the ends were notably softer than the rest of the rod. Cooking it in the fireplace for a couple of hours made it much more workable. However, I still have the newbie problem of a rough finish on steel so I use a file to remove the last mil or so, even after using my "finish" tool. The largest diameter 3C collet seems to be 1/2 inch although in the 7x10 group someone said they had a 3C slightly larger (I've not seen anything larger than 1/2 offered in catalogs). Thanks for the info on 5C collet diameter. I don't know why my collet is expanded along the narrow split part. I'm looking for a steel collet for use as a standard in place of the brass collet I'm presently using -- perhaps the steel collet won't have this. John --- In 7x12minilathe@..., William A Williams <bwmsbldr@j...> wrote: I am surprised that the strut rod steel is hard to turn as it comes from the strut! In my experience once you get under the chrome plate it is very nice turning. Except of course where it has been spot welded! I am a little surprised that the rod is big enough to make 3-C collets. What is the maximum diameter of a 3-C? I may need to reevaluate my need for a set!
Bill in Boulder "Engineering as an Art Form!"
|
Thanks for the information. Somewhere I have seen a dimensioned drawing
of a 3-C collet; if I find it I will get it to you. I suspect that you
are "skating" the tool tip on the chrome plate. You have to cut it off
with a shouldering tool or one that actually undercuts the plating.
You do know to make the collets in pairs? I think that I have the
procedure for turning them spelled out in an old English machining book.
Bill in Boulder "Engineering as an Art Form!"
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Collet dimensions: Roy --- In 7x12minilathe@..., William A Williams <bwmsbldr@j...> wrote: Thanks for the information. Somewhere I have seen a dimensioned drawing of a 3-C collet; if I find it I will get it to you. I suspect that you are "skating" the tool tip on the chrome plate. You have to cut it off with a shouldering tool or one that actually undercuts the plating.
You do know to make the collets in pairs? I think that I have the procedure for turning them spelled out in an old English machining book.
Bill in Boulder "Engineering as an Art Form!"
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I'm working from the pdf files of articles written by Exactus: As you suggested, he has you make the collets in pairs and gives the order of most of the machining operations as well as methods (which us newbies wouldn't think of) to improve the accuracy of the result. His articles are general in that they aren't about 3C collets, just collets in general. I would like specs on 3C collets if you can find them, especially the angle of the steep taper. I calculated it as 11 degrees but it didn't seem to fit properly so I used 12 degrees. The expanded nature of my brass collet makes it difficult to evaluate the fit using chalk or machinist blue because once the collet is in the chuck it is hard to rotate it while it is tight against the taper. My conclusion about the hardness of the shock absorber rod is based on my hacksaw/Sawzall test; I couldn't cut it to fit into the lathe until it was annealed. I don't have a steadyrest (yet). Once it is in the lathe I start at the end adjacent to the live center and make a truing cut which takes the chrome (green after annealing) off using a carbide tool. Seems to work OK although it smokes a bit as the cutting oil burns off the chips. John --- In 7x12minilathe@..., William A Williams <bwmsbldr@j...> wrote: Thanks for the information. Somewhere I have seen a dimensioned drawing of a 3-C collet; if I find it I will get it to you. I suspect that you are "skating" the tool tip on the chrome plate. You have to cut it off with a shouldering tool or one that actually undercuts the plating.
You do know to make the collets in pairs? I think that I have the procedure for turning them spelled out in an old English machining book.
Bill in Boulder "Engineering as an Art Form!"
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