which drill bit for hardened steel?

[Teranchelope]

Drill using a masonry drill. Tungsten carbide. Can improve lips on green grinding wheel. Have tested on armour plate and used many tines. Centre pop the stud first.

[Teranchelope]

Or hsw3 greaee with molibdinum disulphide mixed

[macafee2]

Originally Posted by Rich in Vancouver

"Cobalt" It is the bit of choice for titanium and hardened steels. A lubricant is a must to keep the temp down in order to prevent bit breakage and extend bit life. (The work should not be glowing red!) I use a cutting lubricant the consistency of honey as it tends to stay where you put it rather than flow away like lubricants designed for drilling/milling/CNC machines which are very thin.

I realised when I drilled using the lathe what the mark was on the painted osb board at the back of the bench, lubricant. I'd not seen it spray the board before but did this time . Cutting agent really did seem to make drilling easier

macafee2