[jules]

Over the years I've accumulated a huge pile of blunt drill bits. Yes, I know it's possible to sharpen them using a grinder and good judgment but I can never get quite satisfactory precision from hand sharpening so I'm wondering what's available locally [Australia] to revive more than a hundred blunt drill bits.

At the expensive end of the scale there's something called "drill doctor" which looks good but costs $500. At the cheap end of the scale there's gadgets you attach to the end of your power drill. I tried one of these but for various reasons, it was a total failure. A jig for use with a grinder would seem to be a good idea. Do these exist? Any other suggestions? Does anyone have a device they swear by?

jules 

[rabbitz]

Carba-Tec have a jig in their catalogue that is used with a bench grinder but can't find it online.

Cat DBJ-1 at $19.00

I've haven't seen one of those cheaper gadgets that does a good job and seem to get the clearance wrong behind the cutting edge or no clearance. By hand is better and takes a bit of practice.

You just have to have the correct included angle of around 118° (use a hex nut as a template at 120°), equal cutting edge on each side (measure with a ruler) and the hardest part is to get the right clearance behind the cutting edge, around 5° for most materials (check with a straight edge at right angles to the shank and should see clearance. The key is to keep the cutting face parallel with the wheel as you move the drill upward and you do a little clockwise twist of the drill at the end. This last motion is essential to give clearance on the trailing edge before the flute. When done correctly, you end up with a line between the cutting edges and not a point.

Any drills below 3mm are better off with new ones.... I have trouble seeing them, let alone sharpening them.

[jules]

Great descriptive work rabbitz ... I'm inspired to work on improving my skills.

The point you make about clearance does seem to be the key and I can't actually see how any simple device is going to do this for you, so in the end it's going to require judgement.

I might still chase up something like the Carba tec jig to see if it's good for the basic preparation.

Pity about the <3mm bits. I'll bet my eyesight is worse than yours 


jules 

[2wo]

I have a drill Dr. It works very well. I got mine an Sears Here in the USA for About $50 US. I don't know if there is a gold plated one. Might look into buying one on line from the USA even with shipping Might do better...John

[RAW]

Not sure how the drill sharpeners work but I will say that if you want to learn the tricks not hard to sharpen at all on the bench grinder.

One of the first things you have to learn in a machine shop as a apprentice I spent a few hrs burning my fingers and throwing away a few bits.
But once you get the hang of it you never loose it.

Then also you can sharpen bits for wood and steel a little differently

All the best of luck with which ever unit you pick.

[mgalusha]

I've got a Drill Doctor as well and it was about $75 US I believe. While I know how to sharpen bits with a grinder I'll never do so again willingly.