Thread: Sharpening drill bits on a belt grinder?

I don't mean freehand. Been there, done that, but I was thinking about setting up a Blue Point drill sharpening rig to use with a 2" x 48" vertical belt grinder, I inherited both and about 4 dozen 80 grit belts. I imagine there will be some belt drift if the cut's too deep, but I was thinking more along the lines of cutting the belts. See any problems?

I think a belt would be OK for roughly sorting out a broken drill, but I doubt if the belt remains flat enough to get a good profile to a drill. 80 grit sounds a coarse to me and I suspect its surface speed is too low. Its for grinding off welds, free hand radiusing, de burring, not for putting precision cutting edges on tools.
Frank

What type of abrasive?

I sharpen freehand on my 12" disc, but I have used belts in a pinch, and find that for more than one use, they are pretty worthless unless its a blue, alumina/zirconia abrasive.

If your free belts are blue, it should work- but if they are softer, other types, you are going to be just wearing thru them so fast it will be a waste of time.

I've worked in two shops where the only thing we had to sharpen drills was a 6X48 belt sander. They work OK on drills over 1/2" and quite well over 1". It sure beats spending $60 on a premium wheel and having someone wreck it grinding aluminum, weld slag, or worse.

It has been my experience that a freely accessible tooling grinder is useless after three days.

I sharpen drills all the time on the belt sander.
You need a good belt and a maximum of 100 grit (or heavier)
It cuts cool !
I sharpen dowwn to .060 this way.

here is a photo of a Broach I was making on the sander.
note the marker line on the table.
And for aggressive cooling, I hold a ice cube behind the work.

Rich

The one hassle with a BG is that the belt will deflect a bit, and has a tendency to make a slightly "relieved" edge due to the slight angle where they deflect....... That can happen even if you use the backed area.

Otherwise they DO work well for bigger drills. I went thru a bunch of large drills a while back, freehand (with an edge scale) on a 1" BG. That was an interesting education......... I actually got them done to where I got two curls from all the ones I have used so far.....

What type of abrasive?

Mostly A/O. About a dozen are called Norton Ceramic Hoggers. #SGR981Y. The others are mostly 3M and Hermes. I would only use them for 3/4" and larger. My Drill Doctor handles any smaller. Generally, it is for the drill bits my 'mechanical' friends bring to me. You know mechanics, they'll try to do it themselves until they have ground them beyond all semblance of a drill bit, THEN they call up their 'machinist' buddy to fix them! Typical. I find it faster to bring the cutting edges back in sync on one of these drill bit jigs.

JST is about right. Not the best thing. For drills under 1/2" may be OK but use minimum pressure. If you do not have a wheel - a qualified maybe yes. I would not recommend a belt
for drill sharpening.

I find a belt is easier to judge the angles of the drill's end with. However,as mentioned,a belt does round off the cutting edge a bit,where a wheel doesn't.I recommend touching up the cutting edges with an India stone after grinding. This will eliminate the rounded edge,and also produce a much sharper,finer edge. For smaller drills,if you are fortunate to have one of the horizontal/vertical diamond wheel grinders,they are very nice in the vertical position. They are expensive,but run slowly so the diamond carbon doesn't get into the HSS. I paid big bucks for one for my shop at work,and a few months ago,lo and behold,got a Sunnen on a stand,with one wheel for $150.00 for my home shop. It is the same grinder as the other one. Takes the same wheels.

I have to respectfully disagree about rounding edges.
I have made broaches down to .030, by .100, and .04 x .040
and not had rounded edges.
Look at the photo and you will see nice square corners on that broach .
Rounded corners are caused by a dull belt, when you PUSH the work into the belt,
and the belt 'loops" up just above the work piece, and that rounds the edge when you start to back off. It is also caused by a backing plate which is behind the belt path
The answer is to use sharp (new) belts and make sure the
backing plate is slightly forward of the belt track ,especially on the drive ( bottom ) wheel.
And last is the "touch". don't slow the belt down, if you do, you will burn or round.

Rich

Depends upon what your perception of square edges is.I think it is inherrently impossible for a belt to grind a square edge as sharp as a wheel will. The wheel is not made of fabric,and is hard all the way through. I can't tell anything about the broach from the small picture.
I am talking about a very small rounded edge,be aware,I do not refer to any significant rounding. For a drill,though,this very small rounding will not make the edge as sharp.I prefer to at least stone afterward,or use a wheel.