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Making a square peg fit a round hole

DPittman

DPittman

Ultra Member
I have an odd ball (oz25) collet set for my little lathe. I have never seen square or hexagonal collets for it. Harold Hall has plans for jaws that fit into a round collet that allows them to clamp onto these other shapes.

I made an attempt at making a set to fit a 1" round collet that would hold a .375" square stock. While they didn't turn out quite as nice as I had hoped, I think they will be usable. The jaws looks terribly aligned in the collet but that didn't seem to matter as much to how it centered the sqaure stock. The square stock centered to with .05mm (<.002") , not great in the world of collets but probably good enough for most of my work. I think I could do better on the next set.
Because they are loose, individual jaws they are a bit fiddly to get set but I
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guess they are better than nothing.
 
I only seen square collets for the 5C hex too and You can make your own shape as well. Most collets are not "work holding" but tool holding - such as ER32 are end mills not actual stock you work on hence why no square ER32 AFAIK.
 
Tom Kitta said:
I only seen square collets for the 5C hex too and You can make your own shape as well. Most collets are not "work holding" but tool holding - such as ER32 are end mills not actual stock you work on hence why no square ER32 AFAIK.
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Tom

Did you happen to listen to the Home Shop Machinist's Podcast episode with Robin Renzetti by chance?

Wayne
 
Tom Kitta said:
I only seen square collets for the 5C hex too and You can make your own shape as well. Most collets are not "work holding" but tool holding - such as ER32 are end mills not actual stock you work on hence why no square ER32 AFAIK.
Click to expand...
Yes I know tool holding is the primary use my collets were designed for but what I think make them suitable for work holding to some degree is that they are long (2" good grip) and they had an available morse taper holder for them, AND they were affordable.
 
No I do not recall any video by Robin Renzetti

Nothing wrong with using Er32 or similar to hold work - they just have some drawbacks for such use (mainly what you can pull through them size wise) Many people including me use Er40 chucks on their lathe.
 
Nice work! I think I have the same book by Harold that he shows making those. It is on the list. What type of metal did you use? Harold seems to call almost everything up as 12L14 or the European equivalent.
 
Hruul said:
Nice work! I think I have the same book by Harold that he shows making those. It is on the list. What type of metal did you use? Harold seems to call almost everything up as 12L14 or the European equivalent.
Click to expand...
I just used 1/2" key stock. I figured for for what I am holding with it ( mostly brass) it didn't have to be anything special.
 
YotaBota said:
Is there enough material to add a groove and O-ring to hold the pieces together?
Click to expand...
No that's a smart idea! Yes I think on these particular jaws there would be enough room for a thin o ring. I will have to keep that in mind for next set.
 
For those like me that do not have and will never have itunes on their PC, a directly downloadable, copyright free mp3 of this podcast is here: (the interviewers' website)...
 
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The collet setup looks like it certainly works, and if you're inside a couple thou that should be effective for a lot of work. Nice job!
 
Take 2...
Well after @YotaBota most excellent idea of using an oring to hold things together, I figured I should try another set incorporating that idea.

I did a better job of centering the beginning
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square stock in the four jaw to begin with and used less thickness of card stock in between the pieces than I did the first time.
I milled the jaws all individually to account for the small differences among the 4 pieces.
The oring was definitely worth doing as it makes them much easier to use. All of the cuts were interrupted cuts and I took it easy. The most unnerving was the parting off of the jaws.
Just like the first go around, I forgot to account for the loss of material with the parting operation so I have 2 sets of jaws with slightly different length (doesn't matter a lick).
Here's a couple of pictures.
I have some slow-mo vids of the turning I think are kind of cool, but I have never figured out how to post video here other than YouTube links.
 
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