ER collet size choice for mill

[martik777]

I'm trying to decide which size to get for my 'new' MT3 benchtop mill. The ER20 collet chuck and full set of collets is less than 1/2 the cost of an ER32 set and I cannot foresee needing any tooling over a 1/2" shaft diameter, so is there any reason to go larger than ER20? Would the ER32 be more rigid? The ER32 is a little deeper at 1.57" vs. 1.22" for the ER20

 

[12bolts]

Martik,
I know you area asking about using it for tool holding in your mill, and for that, I would probably say 1/2" yes that is sufficient for most home hobby use. But have you considered the other uses for collets? Workholding, especially in your lathe, comes to mind. Pretty sure your SB9 will have MT3 up the spindle. Consistent rechucking is always handy. Dont forget to think outside the box

Cheers Phil

 

[martik777]

Thanks, I did think of that but I wouldn't want to keep switching the collet chuck between machines and the inability to insert stock thru the spindle without an expensive ER 'thru-chuck' or fixture limits lathe use.

However, now that you mentioned it, I will take another look around for a way to secure the ER collets on the lathe with some thru spindle capability.

 

[PurpLev]

Thanks, I did think of that but I wouldn't want to keep switching the collet chuck between machines and the inability to insert stock thru the spindle without an expensive ER 'thru-chuck' or fixture limits lathe use.

However, now that you mentioned it, I will take another look around for a way to secure the ER collets on the lathe with some thru spindle capability.

I went with the ER32 system because I was planning to use it on both lathe and mill - wish I had gone with the ER40 :/ for even larger through hole capacity, but oh well... I'll just stay limited at 3/4"

I got a chuck for the lathe and mounted it with a back plate for a through spindle capability here:
http://www.hobby-machinist.com/entry.php/20-ER32-Chuck-Mounted

fairly straight forward, not expensive and works very well.

Cheers