Carbide drill bits and using them

[mirage100]

I am very new to drilling hard material with Carbide drill bits. I think I got the speed and travel down . The problem is when I use a 3/16 carbide drill bit in my 1/2 inch drill bit chuck I brake them. I have broken two new ones. Now when I use my 1/4 inch drill bit in a 1/4 collet I have no problem. So I am guess the vibration is what is doing it. I think someone must make a drill bit collet set for a milling machine. Is this correct? My machine take the R8 collet. Any info on a drill bit collet set would be GREAT.This is a manual mill. My guess is a collet set is rather large money. Mirage

 

[Aukai]

Could it be the runout on the drill chuck?

 

[brino]

Could it be the runout on the drill chuck?

Agreed. That's the first thing to check.
Get a piece of 3/16"drill rod or something you know is straight; roll it on a surface plate to check.
Chuck that into your drill chuck and put an indicator on it.

My guess is that your chuck is slightly off centre so that the end-mill is actually tracing a small circle.
Carbide is brittle.

A single 3/16 collet should not be that expensive.

-brino