milling collets

[nickk]

need to cut two 12mm wide keyways 50 long each, tomorrow ,only have an imperial collet holder, whats the chance of gripping my 12mm slot drill in a 1/2" collet by wrapping shim strip around the shank, anyone successfully achieved this?

 

[Pete.]

Better than if you tried it without.

If you have a lathe, make a split collar. Drill/ream/bore the ID first to 12mm, turn the OD down to 1/2", part off, slit, deburr. Otherwise 14 thou shim or even so many turns of bacofoil.

 

[gaz1]

you might be able to get it from a piece of copper pipe 15mm or 1/2" if you have some this will reduce it down enough

 

[addjunkie]

Id go down in size and do more passes. Espescially if the 12 mm width is really critical. Any minor wear on the milling head and your keyway will be 12 and a bit.

 

[gordon stephenson]

The slot drill wrapped with a piece of 0.010" decent shim should be OK,

 

[scott0031]

Personally, i would never recommend shimming out a cutter it is a bad practice, full stop. Breaking a cutter/ damaging the job will normally cost you more than getting the right collet in this day and age, lots of cheap adequate tooling out there. If you have to do it i would uses Pete's suggestion. You also don't mention the type of collect i'm assuming its spring collet? 10 thou shim no go you create a taper in a spring collet, asking for trouble.

Also you should not really be using a 12m cutter for a 12mm slot or key, you should be using a cutter under that size and offset to get the 'correct size to suit the actual piece of key to be used.

Edit: Just to add. If by any chance you are using a Clarkson collet chuck then it's total no go. Don't even attempt it. Sorry to state the obvious but better safe than sorry.

Its only advice.

 

[nickk]

Fair comment about U/S cutter.
It’s a BSA collet chuck.
I’ll look for a 7/16 slotted.