[gangzilla]

Looking for any info on hard drilling and tapping I have some new tooling I'm about to try when I ran into a couple of questions.
1- When I use a carbide drill do I or do I not use a center drill
2- can I drill a hole intersecting another hole with a carbide drill
and does anybody have any good rules for this operation things to and not to do

[HorridHenry]

1- When I use a carbide drill do I or do I not use a center drill

It is wise to drill a pilot hole first so that the required size drilled hole does not waver off true.
The harder the steel the slower the drilling other wise if you go too fast it will wear out the drill/tool faster.

[DareBee]

I know guys that thread mill hardened steel.
I usually EDM tap

[SirDenisNayland]

It is wise to drill a pilot hole first so that the required size drilled hole does not waver off true.
The harder the steel the slower the drilling other wise if you go too fast it will wear out the drill/tool faster.

Not true with carbide drills, youll bust the tips of them off when the drill engages the material.

[DareBee]

I agree with SDN.
Use a spot drill to make a small spot. Just enough to hold the tip of the carbide drill.
Drill virgin hole only. If your hole is big dia, interpolate it in a CNC with end mill.

I find a custom sharpened cement drill to be most effective. Maybe I am doing something wrong, but a $7 cement drill usually survives where I break the $120 specialty drill.