Silly Collet question

[tmuir]

I know that ER32 collets are sold with their the compressed diameter and then uncompressed diameter so a 5-6 is 6mm uncompressed and 5mm compressed. Now lets say I have a 6mm diameter item I want to hold in the collect do I need to buy a 6-7 or a 5-6 collet?

Pretty simple question I know but which one would be the correct collet?

Thanks

 

[GailInNM]

In most cases either collet will work fine. However, I have had one experience with an ER16 collet that led me to rethink that statement.
I was clamping a tool with a shank diameter the same size as the small end of the collet range. It felt tight and all that sort of thing, but I was getting a poor finish and the depth of cut varied. The collet had closed up as far as it could until the slots were closed up and was not gripping the tool with full force. I had several other collets the same size and manufacture that worked fine. I retired that collet to a bag with a note not to use the small end of the range. Since then I have made it a practice to always use the smaller range when faced with a situation like you propose, that is use the 5-6 collet. This makes sure that the collet is gripping with full force and not bottoming out on it's slots making me think that everything is OK. It might never happen again, but this way I know for sure.
Gail in NM,USA

Edit. After the second pot of coffee, I corrected the text to show what I actually do. I typed it backwards which would lead to the incorrect result. Sorry. Gail.

 

[JMe]

Hi
i have a lot of collets (ER25)
Bison : no capacity marked
Interstate (read Chinese) : printed 12-11
Vertex : printed 4-3 and on the other side 1/4"
all the time, the largest capacity then the smallest.
If you want to grip somethings 6mm, use 6-5 collet.
Regards
Jacques

 

[rake60]

That's a very good question.

It's already been well answered here.
You always want to use a collet that tool will slide into without springing it open
and will tightly on the tool without totally collapsing the collet.

At work our ER32 collet sets are almost all metric and we use them quite effectively
for holding Imperial size tooling. With a full 1mm range they work fine for us.

At home my ER32 collets are all Imperial sizes.
We've always considered them to have a + 0 / - 1/32" range.
This thread got me to asking what that range truly is.
A 5/8" collet has a listed range of .625 to .586" that's .039" (1mm)
A 7/16" collet will hold .437 to .398" That's also 1mm.

Another integration of the two systems...

Rick

 

[tmuir]

Thanks,

I figured that would be the best way but just wanted to check as the last thing I want is an endmill flying at me

 

[rake60]

End mills rarely fly out.

#1 If they suck out of a collet slightly they cut too deep.
#2 If they suck out moderately they will chip an edge and start hammering.
#3 If they suck out to an extream they shatter like an ice sickle dropped
on the concrete.

Those conditions relate to:
#1 You make a new part.
#2 You buy a new end mill then make a new part.
#3 Go change your pants then buy a new end mill and make a new part.

Rick

 

[tmuir]

:big: