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How I made dead length collet out of a 5c extended length emergency collet.

jims

Hot Rolled
Joined
Sep 12, 2004
Location
Sonora , Calif
This will work for a lot of small parts. Where the length of part is critical and the stock od varies causing lengths to change. I bored a Hardinge emergency 5c collet to size needed , then drilled a cross hole thru side of collet. Drilled the hole with enough slop that when I slipped a 1/4 inch bolt thru hole and across face of fixed end of spindle the collet gripped stock but no pull back because bolt was free floating in hole . The bolt then became a stop when pushed against fixed against fixed end of machine. The bolt was free floating in hole but held in place by bolt head on one end and a nut on other end. So the collet grips the part and the bolt stops collet pull back.
Jimsehr

I also found a company that makes 5c emenercy extended length collets named Exact tool and supply that makes these collets to hold larger size parts.
 

thermite

Diamond
This will work for a lot of small parts. Where the length of part is critical and the stock od varies causing lengths to change. I bored a Hardinge emergency 5c collet to size needed , then drilled a cross hole thru side of collet. Drilled the hole with enough slop that when I slipped a 1/4 inch bolt thru hole and across face of fixed end of spindle the collet gripped stock but no pull back because bolt was free floating in hole . The bolt then became a stop when pushed against fixed against fixed end of machine. The bolt was free floating in hole but held in place by bolt head on one end and a nut on other end. So the collet grips the part and the bolt stops collet pull back.
Jimsehr

I also found a company that makes 5c emenercy extended length collets named Exact tool and supply that makes these collets to hold larger size parts.
You may have an "improved repeatability" collet. But it isn't "dead length" any more than use of the common 5C rear-mount depth stop would be.

Pullback is now (more) predictable.

But pullback still "has to happen" for THAT sort of single-acting forcing-taper ... 5C and dozens of cousins - to grip.

There are whole clans and tribes of OTHER closure-style collets that come right out of the box meant to do what you seek. Some do it better than others.

5C's primary claim to fame is that it is CHEAP.

Secondary claim "common".

I remain to be convinced it has a third virtue?

But if you needed "true" dead-length from a 5C or "cousin"?

The collet has to be threaded into a FIXED relationship to the spindle.

Closer that acts on the taper must then be moved forward, not the collet moved to the rear. Power nose-mount closers have been engineered to do this - preserving the full through-bore, too.. if need be.

More often, one simply uses a different collet system. There are PLENTY - around a hundred, is it?.

I'm just a retiree. Not sure I have even a full dozen different collet systems.

Yet.

:)
 
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EPAIII

Diamond
Joined
Nov 23, 2003
Location
Beaumont, TX, USA
Jims, you should post a photo. I think Thermite did not understand your post. If I read it properly one side of the 1/4" bolt rests against the front of the spindle and then the part rests against the other side of the bolt. That should provide positive positioning. But just how that happens is not clear. Do your 5C collets fit inside the spindle? Or do you have a separate, collet chuck that mounts on the spindle and the collets are in it. But then, how does the bolt rest against the spindle? Is it the ends of the bolt (head and nut)? Or does the center of the bolt rest against the spindle?

More explanation is needed and one or more photos would be nice.

Once i noticed the draw back problem, I wanted a really fixed stop for my SB lathe so I built this:

P1010024crop.JPG

The handwheel (at the left in the photo), with a roller thrust bearing rests against the outboard end of the spindle. The collet draw bar is attached to the handwheel. The threaded rod passes through a brass nut which is threaded onto the end of the draw bar and can be adjusted by turning it in that nut. There is a steel lock nut to prevent it from changing position. The threaded rod passes all the way through the draw bar and it's right end passes into the collet. This provides true positive positioning for all the collets I have for the SB, not just one. It completely solves the draw back problem.

Note: The brass nut was made from a brass pipe cap. The original, inside threads are what attaches it to the draw bar. A hole drilled in the center was tapped for the threaded rod.
 

jims

Hot Rolled
Joined
Sep 12, 2004
Location
Sonora , Calif
Jims, you should post a photo. I think Thermite did not understand your post. If I read it properly one side of the 1/4" bolt rests against the front of the spindle and then the part rests against the other side of the bolt. That should provide positive positioning. But just how that happens is not clear. Do your 5C collets fit inside the spindle? Or do you have a separate, collet chuck that mounts on the spindle and the collets are in it. But then, how does the bolt rest against the spindle? Is it the ends of the bolt (head and nut)? Or does the center of the bolt rest against the spindle?

More explanation is needed and one or more photos would be nice.

Once i noticed the draw back problem, I wanted a really fixed stop for my SB lathe so I built this:

View attachment 366087

The handwheel (at the left in the photo), with a roller thrust bearing rests against the outboard end of the spindle. The collet draw bar is attached to the handwheel. The threaded rod passes through a brass nut which is threaded onto the end of the draw bar and can be adjusted by turning it in that nut. There is a steel lock nut to prevent it from changing position. The threaded rod passes all the way through the draw bar and it's right end passes into the collet. This provides true positive positioning for all the collets I have for the SB, not just one. It completely solves the draw back problem.

Note: The brass nut was made from a brass pipe cap. The original, inside threads are what attaches it to the draw bar. A hole drilled in the center was tapped for the threaded rod.
Paul
yes , you read it right the collet pulls back but the bolt stops against end of spindle and part stops against other side of bolt. Collet pulls back but bolt can not because it is against end of spindle. Reason to do this is extended 5c collets are much cheaper than dead length collet set ups. I have and use Hardinge dead length collets and use them but this is another dead length way to hold parts.
To do this you have to use an extended length collet. These collets extend out of spindle about an inch. Hardinge sells them and as I said company called Exact Tool makes them with a larger size.

Jimsehr
I tried to post video of set up but can not get it to post.
 

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thermite

Diamond
Once i noticed the draw back problem, I wanted a really fixed stop for my SB lathe so I built this:

View attachment 366087

^^^ THIS ^^^

And many variations on it, has been the "traditional" way of solving the problem for as long as spring collets have been in use. Over a hundred years, IOW.

- Upside ONE is that with a thread-in tip, one rod or tube can work for all collet sizes.

- Upside TWO is that it can work with 'standard' collets ...or any of many speciality ones. Read "also more economical" as it can utilize - but is not dependent on - 'extended' collets.

- Upside THREE is that a form of it can even be applied for use with front-closer (no drawtube) collet systems. The ONLY kind I use.. because my lathes are already starved for free-bore and they are faster to swap (D1-3).

- Downside is that it shares the same limitation as the cross-bolt stop. Yah hafta work with pre-cuts, or as second-op. Yah cannot feed 'continuous' lengths of bar or rod. EITHER sort of "stop" is in the way.

That last one is a show-stopper for many folks, "CNC" world especially.

Hence the availability of so many OTHER collet - or non-collet workholding systems, such as power chucks with bespoke top-jaw.

Only a fractional subset of those are 'dead length', even so.
It isn't always a pressing need.

"Old Day Job" had been sorting and storing incoming steel, brass, coin silver, and Alpaca metal rod by diameter since the early 1920's. When a production run used-up one diameter, the setup was changed to suit the next diameter in inventory. Rare for the dif to be even two thou, so repeatability was good enough.

Faster and cheaper that way, too.
 
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jims

Hot Rolled
Joined
Sep 12, 2004
Location
Sonora , Calif
I guess I failed to notice the use of oversized or extended length collets in this tip. It was there, just not super obvious.
The reason to use the extended 5c collets. Is that the Hardinge dead length set up costs over $250 .
 








 
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