Slippery Collet Adaper ??? (little long)

[uute]

Looking for input on another silly idea, or a better alternative from this wealthy knowedge base. : )

Problem: Want to grip bolt threads in 5C collets. Always seem to be .010 under nominal -- just outside safe range of collet -- bad for collet and poor holding power.

Best Solution I Know: bore emergency collets undersize to fit - some expense for 5 or more of them.

Half Baked, Friday After 3 Beers Workaround Idea: Bore 3/4" bar for undersize grip, relieve rear section like collet, chuck as an adapter in 3/4" 5C collet.

How bad will it slip?

Better to thread hole? - be inconvienient to mount work.

Better to make #2MT collet - use in #5MT / #2MT Sleeve?

Thanks
uute

[ERBenoit]

I think the problem with trying to grip a threaded part in a 5C collet, other than the fact the part is usually too small in diameter for a collet to grip with enough holding power, is a lack of surface area to grip. The emergency collet bored to the needed o.d. would probably be the best bet. What is it that you are tring to accomplish or make? Might get some other ideas.

[SGW]

Maybe try using aluminum for your adapter sleeve, so the threads aren't riding on a polished, hardened surface.

Make the sleeve as thin as decently practical, slit one side of it so it will close up...is that the idea? What the hey, give it a try! Won't take too long to try it out. I think I lot depends on how much of a grip you need for what you're trying to do. If you're doing "light cuts" on the bolt, it ought to be fine.

[coles-webb]

With 5C collets for undersized I simply make split bushings out of aluminum, mild steel or nylon(Nylon used for threaded parts so threads will not be damaged. I just drill, ream or bore to size(ensuring I have 1/8 inch will minimum) and split with a hacksaw or use a slitting saw if I want to be fancy. You will be amazed at how often you will use the adaptors afterwards. You can etch the size on the end or just try the part to see if it fits. sure the unside is a good smooth finish to help it have more surface contact for gripping.

Mike

[DR]

We hold threaded parts in 5C's all the time. Even using the nominal collet size, like a 1/2" collet for 1/2-13 or 1/2-20 threads. And this is done with a power collet closer on the CNC's.

[rockrat]

Granted that the following is for a 3jaw chuck, but it might help with an idea.

I keep a set of nuts around that I cut special to hold bolts. I took a standard nut, cut it axially (spelling?) and then use a 3 jaw chuck to hold it. The cut is stationed between 2 of the 3 jaws. Thread the bolt in and tighten the chuck up. Works great for drilling a hole down the middle or cutting the bolt down. I have also used them on all thread. They sit in my box more than I use them, but when needed, what a time saver.
rock

http://img.photobucket.com/albums/v1...oject2/nut.jpg

[Bill Cook]

For holding bolts by the threads, I keep an assortment of ~1 3/4 x ~1/2" turned, faced, drilled, and tapped disks near the lathe. (Plus some blanks).

The "backs" are c'bored on the smaller sizes.

Jamb nuts back or front hold tight enough to get the job done.

Another handy spud has a pilot that centers 1 1/4" flat washers and a 1/2 - 20 hole for clamping. This allows the washers to be turned for use as custom bearing and seal drivers. It also has a shoulder that bottoms against the tops of the chuck jaws.

bc

[uute]

Thanks all,

The aluminium sleeve adapters are the refined/simplified version of what I was thinking. Like the other ideas too (split nut and threaded fixture).

Last time I needed to make a stud 3/8-24, but w/ 1/2" of 3/8-16 on one end. Chucked up 3/8-24 bolt (1 1/2 or 2" long), cut head off untreaded portion of shank, tryed to cut a thread on it. Slipped -- lost registration on thread -- had to use a die, and collet still slipped.

now have better ideas for next time! these will go in my tips/tricks files.

TA
uute

[This message has been edited by uute (edited 11-19-2004).]