How To Grind a Drill Bit For Brass?

[EdK]

Thanks for the video Tom. A couple of drill indexes are on my shopping list. One for plastic/brass drills and one for flat bottom drills.

Ed

[Mayhem]

Just buy a cheap import set of drills Ed, they will be sufficiently blunt to drill plastic, brass, wet paper bags etc

[EdK]

(09-02-2013, 10:18 AM)Mayhem Wrote: Just buy a cheap import set of drills Ed, they will be sufficiently blunt to drill plastic, brass, wet paper bags etc

[oldgoaly]

Tom
Thanks for sharing your knowledge with the group! I've been grinding about an hour a day on drill bits. Now I got a question, I have some bits that are old been ground upon years ago and damn near 60* point they are less than 90???? a couple are #2 jt all are about 1/2" I've spent a bit of time just getting the close to 120* As not to over heat the bits, coolant and swapping them around has prevented that. I just dawned on me maybe these were ground to drill..... gold? platinum? beer cans? I didn't just regrind special bit back to normal? These bits are from boxes from yard sales, auctions, swap meets (can't throw good steel away!)
One thing I did to help in this regrinds is I marked the tool rest on the grinder at 60* from perpendicular to the stone, sure gives e a better target, I tend to be thinking of other projects when doing something repetitive or in other words I don't pay all that much attention to what the heck I'm doing.

[Mayhem]

Aren't standard drills either 118* or 135* included angle? I'm unsure if an additional 2* makes all that much difference though but I could be very wrong!

I find that the point angle isn't the bit I struggle with, the lip angle is what gives me grief.

[EdK]

(09-02-2013, 10:25 AM)Mayhem Wrote: Aren't standard drills either 118* or 135* included angle?...

Yes, most are either one of those angles.

Ed

[oldgoaly]

the line is to get me close! it doesn't seem like they over heated the bits grinding the to a point, so it has me wondering???
to do the finial "grind" I'm cheating using the lisle bit sharpener. Haven't even tried to do some 135* or s/m drills that Tom made.

[TomG]

Generally, the softer the material smaller the included angle on the point. In other words the 60º points you describe would work well on wood, but would suck on steel. Drills for steel should indeed be in the 118º to 135º range so there is a lot of steel behind the cutting edge to conduct heat away.

By the way, it's an old wives tale (not mine) that overheating drills and tool bits hurts them. High speed steel has what's called good hot hardness and can withstand much higher temperatures than carbon steel. Most grades are good to over 1000ºF before they start to lose their hardness. That means you can get them red without hurting them, of course your fingers might not agree!

Tom

[oldgoaly]

Just prove I'm not seeing things....

   

   

not well organized, just box in a drawer, and another drawer, plus the sets of drill we use, plus a box in drawer in the barn.
   

[oldgoaly]

Hmmmmm googled it and spotting drills came up, note to self don't grind anymore 90* bits also need to sort bits......