Solid Carbide Drill Bit Questions

[RLYoung]

First off, I have a few of the following that are used and need sharpening (some are chipped.

http://www.am-ind.com/garr-tool-stu...3xd-135-point-15-helix-series-1510h-gtl-19726

I know these are used for drilling hard materials, but how exactly would the everyday garage man use them? My experience involves only mild steel, alu, and a little bit of stainless. Is a specialty tool and/or cutting fluid needed to turn them? Drill speed?

How are they sharpened?

If I wanted to offload a couple what would be their worth considering their dull/chipped condition?

 

[Deadhead]

takes a special grinder to sharpen those bits
Do not attempt it yourself.


If they are chipped, they can be cut off below the chip, re-ground and put back in service. Just shorter of course.

Been decades since I programmed a CNC lathe running one of those bits, but I do remember it was a 3/4" drill and it seems like we were pushing it .018 to .021 per rev if that means anything to you. Made for fast acurate drilling and high production. You dont see them ran in a manual lathe very often as you will burn them up. They dont break like normal HSS drills, they explode most of the time.

 

[yaidunno]

Carbide's real quality is heat resistance. Because of this, it can be run at much higher speeds/feeds as compared to HSS. It's also brittle and unforgiving, so its best suited for a milling machine, or other rigid setup. Its overkill for anything the "everyday garage man" will drill, with the exception of a broken tap or other very hard material. As for drill speeds, its determined by the proper calculation based on drill size, material, and work piece material. Long story short, about 3-4 times the RPM of HSS, but you must have a machine that is rigid enough, i.e. a mill or very heavy drill press with auto feed.

They certainly can be re ground, but in a chipped or dull condition, id venture a guess of $10-15 ea.