MT3 Round Collet Questions

[ShagDog]

I have some questions on MT3 round collets and use in a lathe. My lathe has an MT3 spindle, and I have a drawbar for it. I am interested in your opinions on the capabilities and limitations of this type collet (as opposed to ER type collets) for work holding purposes. Questions are various, such as the work holding ability, range of size of round object that can be used in a specific size collet, and other questions. I know for Er collets, there is a size range for each size collet. Does this apply to a 3mt round collet as well?

Input on any issues is appreciated.

 

[BROCKWOOD]

All collets have a size range - though I believe the ER style has a better range for each collet than the MT style.

 

[Jim F]

MT3 collets will not let you have pass through.
I use 3C collets in my SB 9.

 

[Tozguy]

My MT3 and R8 collets only get used for exactly the nominal size of the collet.
An ER collet has a range but there again it is best not to stray too far from the nominal capacity.
It is in the nature of collets to be size specific and to have small jumps in size from one to the next.

 

[ShagDog]

Thanks for the responses so far. Looks like the size is not as versatile as ER. More specifically on this issue, will an 11/16" (.6875") 3mt collet properly hold a 17mm (.669") shank?

As to the other issue, how about work holding qualities?

 

[Tozguy]

A .0185'' difference is too much for the MT3 collet to handle properly,
for both work holding or tool holding.