Originally Posted by Cap Erict3
Don't let the bit get hot.
Looking for another pretty place to work on the boat.
Even more importantly, don't let the work piece get hot!
The following might not be best practice as I'm self taught but after drilling perhaps hundreds of holes in 316 by hand in sizes ranging from 1/8 to 3/4 " allow me to suggest the following.
HEAT is your enemy. It will work harden the drilling surface in a flash and it can almost make it impossible to continue in that hole.
Drill rpm should be as slow as you can make it.
Feed pressure as high as you can make it.
IMO, you can't too slow or too hard.
Lube is your friend and I'm sure machinists use all sorts of special brews but I find ordinary dishwashing detergent to be excellent - fairy or joy etc. Use heaps and it is easy to wash your hands afterwards
If for any reason, the drill stops biting, STOP and find out why. Even if you continue for say another 10 seconds, the hole will overheat,
Usual reason is the drill bit is blunt.
A sharp bit is essential. I just use normal HSS bits and sharpen regularly - usually on 400 or 600 grit linisng(sp?) belt. Others perfer cobalt or other hard bits.
IMO, a slow speed fast feed works because the bit is continually cutting into cooler metal remembering that 316 is a poor conductor of heat so the heat transfer from the cutting surface is moving into the material below, slower than the bit is feeding into the hole.
As I say, there may be better ways but these methods have worked for me.