Sharpening large drill bits?

[slow-poke]

I use a Drill Doctor for small bits. For larger bits I need to hone my drill sharpening skills. I only have one grinder at the moment and the wheel has a very coarse grit. Seems like I should start with a smaller grit wheel. I actually have an older but good white much finer grit wheel so I think that is probably a good wheel to try? Comments?

I just watched a sharpening video at it seemed like the grinder was turning at a much slower speed, total guess but looked like < 1000 RPM vs. my 3600RPM, since I need to get or make a grinder for this white wheel is there an ideal RPM for sharpening?

What about fixtures to maintain the correct angle, unnecessary or a good idea?

I definitely need some pointers. Thanks in advance.

 

[Tom Kitta]

How big do you go?

Speed is determined by the diameter of the wheel for optimal SFM. So 3600 rpm is great for 6" and 1800 rpm is a bit slow for 10" - 1800 rpm is SLOW for 8"

For drill bit sharpening you need soft wheel - i.e. it needs to fall apart easily to expose sharp pieces.

I frequently sharpen by hand larger drill bits on a belt grinder.

Up to about 3/4 or so I use 6" grinder. Touchup up to 3" is on belt. I have no experience above that size.

I also have home build device to sharpen drill bits on a TC&G.

 

[slow-poke]

How big do you go?

Largest bit is ~1". I use annular cutters above that. So mostly S&D 9/16 to 1"

Anyone using a fixture to keep on track angle wise?

 

[terry_g]

I have a gauge to make sure the angle is correct and it is important that both cutting edges are the same length.
I find big drill bits are easier to sharpen than small ones.
I have a 8" grinder with a white medium wheel for sharpening high speed steel and a 6" grinder with a fine white wheel for finishing the grind. Both run at 3450 rpm.
I use a stone and a diamond file on smaller bits.

 

[MrWhoopee]

The size range you are talking about is perfect for hand grinding. Not too big, not too small. Get a drill point gage for checking angle and width of cutting edges. It's a skill definitely worth learning. It teaches you the basics of cutting edge and drill point geometry in a way you will never learn with specialized grinders and jigs. I've recently been thinning the web of #27 drills free-hand on the corner of a grinding wheel with surprisingly good results.