Are 6mm endmills ok to use?

Looking to purchase a new endmill set and I keep seeing 6mm shanks being automatically used instead of 1/4" shank when I do web searches etc at various places. I’m Canadian and understand mm, however, I also know often they are very much different when converted to inches as they are often “close” but not bang on.

Basically I’m asking, can u get away with a 6mm set instead of finding a 1/4" set?

@Chyren I would get a 6mm collet cone, or find 1/4" mills. Are you looking for something special in mills, Gary? I’ve had no trouble finding lots of variety in both 1/8" and 1/4" shaft.

6mm or metric bits are often used outside of North America, but if you are using a 1/4" (6.35mm) collet, most collets won’t be able to securely clamp down on smaller shank bits. I have tried mounting a 6mm end mill into a Makita RT0700 collet which works, but you run the risk of damaging the collet.

Typical rule of thumb I personally use is to use a collet up to 0.1mm larger than your shank.


Any plans to stock the European Makita 6mm collets?


Thanks guys. I will stick to the 1/4 shanks.

I use both 6mm and 1/4" in my Makita and have for years, no problems to date (touch wood). My Makita is a European model so that might explain it, you could pick up a 6mil collet like gwilki suggested they are readily available. I picked up a set of collet adapters on amazon 1/8", 6mm, and 8mm for peanuts and as of yet haven’t used them.

Well it is something I looked into but not a high priority at the moment.