Any advice for drilling ?

[5030]

Some strange ways to test hardness...

The accepted machine shop practice is to use a file. If a file cuts the metal, it's workable. If not, it's hardened and won't drill with high speed drills. Simple and effective.

Cobalt drills are nothing more than high speed steel with with cobalt added for toughness. I prefer M42 Cobalt, Titaninum Nitride coated for chip flow, however a 'Cobalt' drill isn't any harder than high speed, it's just more resistant to to edge breakdown (dulling), which, in my case is moot because I sharpen every drill I use everytime I use them.

If you want to drill hardened steels reliabily, the only accurate method is to use a 'High Rock' die reclaim drill. Hi-Rock's can drill glass, tool steel, hardened die plate or anything with a Rockwell above 58. 'Coolant' is water flooded at the point of cutting and they need to be run in a drill press. Hand drills wil break them as they won't tolerate off angle drilling or wobbling in the hole.

 

[SPYDERLK]

Dont like to dull my files either. I assume the Hi Rock die drill is Carbide? ... probably straight flute.
larry

 

[BHD]

unless on looses the carbide off the masonry bit, one can easly sharpen them, using a Green Silicon Carbide wheel, made for the carbide tipped tools, CGW Abrasives 34655 Green Silicon Carbide Surface Grinding Wheels 7X1X

 

[Renze]

Most cutting edges arent heat treated: they are just hard as is. Tempering doesnt help.
You can drill Hardox 400 with high quality drills and lots of pressure on the drill, but torching is easier.

 

[MikeD74T]

Would appreciate any advice for drilling snow plow cutting edge. The Plant Manager (bless her warm heart) brought a 7' piece back from the dump for me. I don't know what kind of steel it is or if HSS drills are good enough. Been procrastinating getting Cobalt, but is this stuff going to be real tough? Thanks in advance,
Jim

A woman that brings good stuff back from the dump - there's hope for this world yet !!!!! MikeD74T

 

[Baby Grand]

Most cutting edges arent heat treated: they are just hard as is. Tempering doesnt help.
You can drill Hardox 400 with high quality drills and lots of pressure on the drill, but torching is easier.

That's what I was afraid of - so I have to keep making chips at a good rate so I don't overheat the bit. And use lots of coolant.

A woman that brings good stuff back from the dump - there's hope for this world yet !!!!! MikeD74T

Yes - I got very lucky finding her!