"Robert Swinney" wrote in message
...
A rule of thumb that has served me well is: Ok to use collets for holding
endmills under 3/4 inch. Above that, endmill holders are required.

Thanks, that helps. I also found a note from Forest Addy on
www.practicalmachinist.com describing how toolholders wear.

I ended up buying a collet holder so I'll use that for the smaller size
tools.

Thanks,
Pete