5C collet closing range

adamsgt

adamsgt

Jerry Adams
First off in deference to Asa Yam, I did do a search on this topic and received zero results.

I have a Bison 5C chuck but have not mounted it on the adapter yet. I had turned some 1" round aluminum to make a choke tube remover using my 3 jaw chuck and thought if I were to make more of these it might be better to use the collet chuck. So I tried to fit the round stock into a loose 1" collet and found that it wouldn't fit. The stock measured slightly over 1", can't remember exactly how much. Anyway, did a little search on the web for info on the closing range for 5C collets and didn't have much success. I did notice that collet sets are sold in increments of 1/8, 1/16. 1/32, 1/64 and generally top out at a 1 1/16 opening.

Finally to the question. Can I assume that if a piece of metal doesn't fit into a collet of given dimension that I can go to the next larger collet and it will close down sufficiently to grip the stock? In other words, in a collet set of specified increments, 1/8 to 1/64, will there be complete overlap in the closing range from one increment to the next?

Obviously I could solve this problem by mounting the 5C chuck and will do so shortly but I'm curious about this and also the advantages or disadvantages of collet sets with different increments. Would 1/64 increments be a lot better than 1/16 and why?
 
Every shop

I've been into has had 5C collets in 1/64" increments. That way you can cover bastard sizes and metric stock. For specialty jobs you can buy "emergency" collets which are soft and can be bored for special applications. From my experience collets wil accept stock only thats aprox .002" over their stated size.
 
AJ300MAG said:
From my experience collets wil accept stock only thats aprox .002" over their stated size.
Click to expand...

Just trying to make sure I'm understanding the functional design of the collets. Based on what you said, that means to me that a collet of a given size will accept stock slightly larger than it's specified size and will close down just enough to grip tightly. In other words, there is no overlap between collets of a given increment. So, if I have a piece of stock that is .2185 in diameter for some reason and my collet set is in 1/16 increments, it will be too large to fit in the 3/16 (.1875) collet and will be too small to be held in the 1/4 (.250) collet. Have I got that right? :confused:
 
Yes,

You've got it right. you'd need a 7/32" collet. They have aprox .015" of travel. A steady diet of undersized stock will eventually deform a collet also.
 
5C collets are really made for holding on size stock. They work well with maybe +.002" to -.005 of nominal. You can get a bit more but you would be pushing it trying to overlap sizes even if you have collets in 1/64 increments. It's just not optimal trying to use 5C's for a full range collet system. The ER collets or better yet Pratt and Burnerd multi-size collets are the way to go for full coverage collets for holding odd size material.
 
Thanks guys, that's exactly the info I was looking for. So today isn't wasted, I learned something.

I've seen ER collets mentioned quite a bit on machining forums but know next to nothing about them. Could you educate me a little more :eek:
 
You must log in or register to reply here.
Back
Top