ON-topic --Soft collets

I need to increase production on a job here...
It is a second-op end-work operation ( cnc milling ) on a small turned piece
and I need to chuck onto it off of the threaded end which is @ 4mm.
Currently I am using a 5/64 5c collet in a lever operated hardinge type indexer which works great but this only allows one part at a time to be machined and we do these things by the thousands and the cycle time is only a minute or so meaning this job currently requires full time labor input...
So I been thinking--why not use a soft collet and bore it out 3 places?( near to where the pins go )
--allows holding 3 parts per cycle now now instead of only one...
In fact, I could probably even use a brass collet and machine some extra slots in it, which would allow holding 6 parts, perhaps 9 even
--so long as every hole is centered on a collet slot AND they are all at the same radial distance from centerline I can't forsee any problems.
So I guess my question then would be does anybody else see a problem with doing this ?
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On Thu, 17 Mar 2011 12:10:06 -0700, "PrecisionmachinisT"

It sounds as it would be doable, but why not use separate fixtures? Easier to handle, you are not limited by the collet size and you can fill one while the machine is doing it's thing. Perhaps a scaled-up version of the collet with the parts in a circular pattern and a tapered plug in the center to apply pressure.
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wrote:

Yup the plan is already to use at least two fixtures.
Initially, I had planned to screw the threaded end into a simple fixture but had problems with the parts randomly coming unscrewed as they are knurled and so without any wrench flats for securely tightening.

A "pot-chuck" would allow for a higher part density---at any rate there definately needs to be a separate slot for each workpiece...
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wrote:

Ah Clem, That is a fascinating idea to hold multiple parts in one collet. Thanks! But why are you posting it in a Political discussion group?
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Thx.
Ended up I made a batch of beer that evening, mostly kegging these days so be sure and stop by if you get down this way.
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drill and tap a bunch of holes, say ten or so, screw the parts in and load in a vise. Have a secondary fixture to swap out so the operator can be loading parts into new fixture while machine is runnin and swap of fixtures should take less than 30 seconds
On Thu, 17 Mar 2011 15:10:06 -0400, PrecisionmachinisT

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Thk but I tried exactly that already
--they come loose randomly which messes up the endmill, and no way to reliably torque because there's no wrench flats....and if I use vise grips etc it damages the knurled syrface
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STRAP wrench ?
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Largest diameter on the part is .236 and is knurled.
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wrote:

What about a sprague clutch? I had a part that was smooth, with no flats, etc. A sprague clutch was able to torque it to the breaking point without leaving any marks.
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On Thu, 17 Mar 2011 15:58:25 -0700, "PrecisionmachinisT"

=======Unless you need to have a circular fixture, for example to mount on a rotary table, consider a linear fixture. Easy to make by simply taking two pieces of tooling plate, squaring up, drilling for dowel locator pins, put a 5 or 10 thousandths shim in between, and drill/tap as many holes as you like to the correct depth. Remove the shim stock, thread the parts into the holding fixture and clamp in the mill vise. Another possibility is to make the fixture in one piece, but drill holes at right angles to the threaded holes and insert short pieces of urethane etc. that stand slightly proud. Again easy to thread parts in/out, but holds well when squeezed in the mill vise. Sort of an inside out nylock.
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PrecisionmachinisT wrote:

How about lining the visegrip jaws with delrin?
Best, Steve
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Straight knurl or diamind? If straight, then you could use a pc of soy, O1 and make the same knurl, say .001.-.002 over the part knurl dia, torch heat treat it, surface grind the end, then use it as a broach. In other words, make a socket to fit your part. If it is a diamond knurl, then,,,,,,,,,,, sorry! The delrin jaws on a pair of pliers sound good, if the part is steel, brass would be a good call, I have a pair of interchangeable jaw pliers that I make brass inserts for that have been used on thousands of kovar parts with a 3mm thread, kovar is a very soft iron nickel alloy, I tapped the jaws and as long as the operator didnt get "brick hands", everything ran fine.
"D"
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wrote:

I have used elastomers (buzz word for rubber) like FibroFlex or similar for multi-parts holding jobs. They last practically forever and even out the clamping force over all the parts - as a bonus it sucks up vibrations.
http://fibro.com/produktseite.asp?area=hauptmenue&site=gelastomere&cls &uakt=normalien
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http://fibro.com/produktseite.asp?area=hauptmenue&site=gelastomere&cls &uakt=normalien
All good ideas but I would rather not have to screw anything.....hence the collet chuck, which takes only single lever action motion to clamp and can easily be converted to air or hydraulic and even be actuated by program m coding if desired. ( I've been turning screws to earn a living for quite some time now and so I commonly experience moderate bouts of tendonitus in both of my wrists as it is )
FWIW, I've also messed around with a vise for these having aluminum solid jaw and delrin strip on the movable jaw, bored for 8 parts with with a shim then removed the shim--this works fine on a series of 1/4 in dia smooth parts we do but the delrin got chewed up rathe quickly on the knurled ones.
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On Mar 19, 1:01pm, "PrecisionmachinisT"

5C collets suck. :-) I mean they suck in if the parts are a tiny bit smaller. This is what I would do... Make two thin steel plates with a bunch of holes the size of the thread major. Get a bag of 4mm nuts and a lightweight cordless screwdriver and a nutdriver bit for it. The nuts are to hold the part from the bottom of each plate. So, the parts are secured tightly with consistent torque to the plate and do enough of them that the cycle time is more than the time to load parts to the plates. All that's left is to make a foolproof way to hold the steel plate, like an aluminum block with a pocket for clearance and a couple of locating dowels and screws to lock it in.
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On 3/17/2011 11:10 AM, PrecisionmachinisT wrote:

I make some SS rectangular buttons for a high end audio company, these have a 3/4" radius on the face. I CNC milled 3 pockets that straddle the slots, and turn this radius 3 at a time.
So long as the slot is narrow enough to leave sufficient material to grip the part, no reason that I can think of it won't work for you.
Jon
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wrote:

I would be more inclined to buy or make a fixture similar to Hydramax:
http://hydramax.com /
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