Metric Drill Bit Sizes

[Randy Lucius]

Looking at some 6mm and 8mm pins. 6mm=.236 a #73 bit is .240
8mm is .314 a #67 is .320. The #73 looks like it will be fine not sure about the #67.
What do you guys use or recommend?

 

[KenH]

It depends on the use. Most folks recommend a drill bit 3 or 4 thousandths over the pin side for handle scale pins.

 

[tkroenlein]

I like at least .003" clearance but not over .007" clearance. I think those you picked would be perfect.

 

[Contender Machine]

A #67 drill is .032 and a #73 is .024 might be a little snug

A letter O drill is .316 and a letter B is .238

 

[52 Ford]

You can always ream after drilling.

It's worth noting that twist drills are not super precise. If you have a drill that measures, for example, 0.500", it may drill a little under or over sized. This can be due to a lot of things, like how it's sharpened (uneven flutes can cause an oversize hole), chuck runout, etc. Heck, even things like what kind of cutting oil you use effect bore diameter. If I'm not mistaken, thick cutting oil can cause a slightly oversized hole (compared to something thin like IPA or water-based cutting fluid).

If you're concerned with consistency, I'd pick up some readers. You can get them in pretty much any size imaginable.

Sent from my Champion Forge using Tapatalk

 

[tkroenlein]

A #67 drill is .032 and a #73 is .024 might be a little snug

A letter O drill is .316 and a letter B is .238

^ That is correct. I didn't even pay no mind to the numbers. Those number bits are eensy weensy.

 

[Randy Lucius]

You can always ream after drilling.

It's worth noting that twist drills are not super precise. If you have a drill that measures, for example, 0.500", it may drill a little under or over sized. This can be due to a lot of things, like how it's sharpened (uneven flutes can cause an oversize hole), chuck runout, etc. Heck, even things like what kind of cutting oil you use effect bore diameter. If I'm not mistaken, thick cutting oil can cause a slightly oversized hole (compared to something thin like IPA or water-based cutting fluid).

If you're concerned with consistency, I'd pick up some readers. You can get them in pretty much any size imaginable.

Sent from my Champion Forge using Tapatalk

Thanks. Really good information! I use a #30 on 1/8 pins and a "F" on 1/4 pins and they fit great. Just trying to get the same fit with metric pins. Out of curiosity I just measured a 6mm pin. Should be .236 and it measures .232. That's an .008 difference with a #73 bit. Might just need to get a few bits on either side and see which works the best. Thanks for the response everybody!