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In looking for projects which involve my recently completed taper
fixture, I have decided on a 3C collet chuck to fit the MT3 on the
minilathe -- this based on reading pdf files on the net.

As a newbie I immediately began making chips rather than carefully
planning how the chuck would be used. Now that I've made the taper
and have started working on the chuck itself, a number of questions
have arisen.

The pdf articles assume that the tool can be positioned right up to
the chuck backplate. The minilathe seems to expect the chuck to be
used for all workholding; when positioning more toward the headstock
(as when using the collet chuck) the rear of the carriage contacts
the motor enclosure and the carriage handle contacts the electronics
enclosure, this when the tool is about an inch from the backplate.
Greater overhang of the compound is one possibility for improvment
but I am concerned that this will increase tool chatter.

Should I make the socket so the end of the collet will be an inch or
so from the backplate? My understanding of collets is that they work
well partly because they are closer to the headstock - will this
extended collet chuck make my setup less useful?

For the closer my current plan is to turn and thread a short piece to
fit the thread on the 3C and then thread/loctite this to a piece of
pipe and add a collar and handle to allow tightening. (The reason I
don't plan to thread the pipe itself is that I get a poor finish on
some steel so I plan to use steel which takes a good finish for
contact with the collets.) Is this a reasonable plan? Will the
loctite stand up to this use?

John

Which taper attachment did you make?
The motor enclosure can be modified to clear the carriage & an
extension shaft made for the handwheel to allow the carriage to
travel closer to the HS. When I made a chuck mounting plate from a
barbell weight, I bolted it directly to the spindle & used tool
protrusion & the compound to reach. Chatter was less of a problem
than I'd expected.
For both rigidity & work length, I'd keep collet protrusion as
short as possible. The Loctite should work fine, degrease the
threads thoroughly first; brake cleaner works well. Even if it comes
loose, it'll be annoying, not catastrophic.

Roy
--- In 7x12minilathe@..., "John" <moran03@e...> wrote:

In looking for projects which involve my recently completed taper
fixture, I have decided on a 3C collet chuck to fit the MT3 on the
minilathe -- this based on reading pdf files on the net.

As a newbie I immediately began making chips rather than carefully
planning how the chuck would be used. Now that I've made the taper
and have started working on the chuck itself, a number of questions
have arisen.

The pdf articles assume that the tool can be positioned right up to
the chuck backplate. The minilathe seems to expect the chuck to be
used for all workholding; when positioning more toward the

headstock

(as when using the collet chuck) the rear of the carriage contacts
the motor enclosure and the carriage handle contacts the

electronics

enclosure, this when the tool is about an inch from the backplate.
Greater overhang of the compound is one possibility for improvment
but I am concerned that this will increase tool chatter.

Should I make the socket so the end of the collet will be an inch

or

so from the backplate? My understanding of collets is that they

work

well partly because they are closer to the headstock - will this
extended collet chuck make my setup less useful?

For the closer my current plan is to turn and thread a short piece

to

fit the thread on the 3C and then thread/loctite this to a piece of
pipe and add a collar and handle to allow tightening. (The reason

I

don't plan to thread the pipe itself is that I get a poor finish on
some steel so I plan to use steel which takes a good finish for
contact with the collets.) Is this a reasonable plan? Will the
loctite stand up to this use?

John

Hi Roy,

Thanks for the input. Glad to hear you were able to reach near the
backplate using overhang without too much chatter. After thinking
about it some more I made the chuck with about 1 inch protruding. My
thought is that if it doesn't work out this way I'll make the mods
you suggested and re-work the chuck to make it shorter -- I found
making the steep taper was fairly easy and shortening the chuck just
requires more passes with the boring bar.

I thought your use of a barbell weight for a backplate was very
interesting. I tend to make most things from "found" material and
interestingly the collet chuck is made from the bar of a barbell; it
had a raised part to which I added a thread with the idea of making a
large nut to fit this thread for collet chuck extraction. I used 16
threads per inch which, now that I look at it, seems like it may be a
finer thread than would normally be used for this application. (This
was my first try at threading and it went surprisingly well.) If it
doesn't work out I'll turn it down a bit and use a coarser thread.

The taper attachment is from a pdf file at mlprojects: LongTaper.pdf.
I added some pictures and notes about my minilathe adaptation of it
on my site:

The taper attachment remains a work in progress. I'm watching the
landfill for a better piece of angle iron; once I find that I'll move
the arms toward the chuck a bit and add braces from the arms to the
lathe legs to make it more rigid. It works but the taper it produces
isn't perfect because of flexing in the mount so I end up finishing
the tapers with a file to get them to fit properly. This isn't a
fault in the taper fixture design, rather a fault in my
implementation and the materials I used.

John


--- In 7x12minilathe@..., "roylowenthal"
<roylowenthal@y...> wrote:

Which taper attachment did you make?
The motor enclosure can be modified to clear the carriage & an
extension shaft made for the handwheel to allow the carriage to
travel closer to the HS. When I made a chuck mounting plate from a
barbell weight, I bolted it directly to the spindle & used tool
protrusion & the compound to reach. Chatter was less of a problem
than I'd expected.
For both rigidity & work length, I'd keep collet protrusion as
short as possible. The Loctite should work fine, degrease the
threads thoroughly first; brake cleaner works well. Even if it

comes

loose, it'll be annoying, not catastrophic.

Roy

The barbell weight wasn't an original idea! I used a 2 1/2# one
from Walmart; it was cheap & had the least amount of detail cast in.
I'd expected it to warp when the "skin" was machined off, it did, but
not when both sides were faced; turning the outside to finished
diameter was the stress unlocker. Next time, I'll rough machine all
the surfaces before finishing any of them.
The other nuisance was from bolting it directly to the spindle.
Without a face plate to act as a dust shield, the illuminated power
switch collected enough fine, conductive swarf to not turn off! The
lathe would keep running at minimum speed, increasing the speed would
draw enough more current to let it turn off.

Roy
--- In 7x12minilathe@..., "John" <moran03@e...> wrote:

Hi Roy,

Thanks for the input. Glad to hear you were able to reach near

the

backplate using overhang without too much chatter. After thinking
about it some more I made the chuck with about 1 inch protruding.

My

thought is that if it doesn't work out this way I'll make the mods
you suggested and re-work the chuck to make it shorter -- I found
making the steep taper was fairly easy and shortening the chuck

just

requires more passes with the boring bar.

I thought your use of a barbell weight for a backplate was very
interesting. I tend to make most things from "found" material and
interestingly the collet chuck is made from the bar of a barbell;

it

had a raised part to which I added a thread with the idea of making

a

large nut to fit this thread for collet chuck extraction. I used

16

threads per inch which, now that I look at it, seems like it may be

a

finer thread than would normally be used for this application.

(This

was my first try at threading and it went surprisingly well.) If it
doesn't work out I'll turn it down a bit and use a coarser thread.

The taper attachment is from a pdf file at mlprojects:

LongTaper.pdf.

I added some pictures and notes about my minilathe adaptation of

it

on my site:

The taper attachment remains a work in progress. I'm watching the
landfill for a better piece of angle iron; once I find that I'll

move

the arms toward the chuck a bit and add braces from the arms to the
lathe legs to make it more rigid. It works but the taper it

produces

isn't perfect because of flexing in the mount so I end up finishing
the tapers with a file to get them to fit properly. This isn't a
fault in the taper fixture design, rather a fault in my
implementation and the materials I used.

John


--- In 7x12minilathe@..., "roylowenthal"
<roylowenthal@y...> wrote:

Which taper attachment did you make?
The motor enclosure can be modified to clear the carriage & an
extension shaft made for the handwheel to allow the carriage to
travel closer to the HS. When I made a chuck mounting plate from

a

barbell weight, I bolted it directly to the spindle & used tool
protrusion & the compound to reach. Chatter was less of a

problem

than I'd expected.
For both rigidity & work length, I'd keep collet protrusion as
short as possible. The Loctite should work fine, degrease the
threads thoroughly first; brake cleaner works well. Even if it

comes

loose, it'll be annoying, not catastrophic.

Roy