Sharpening Drill Bits

[Darren]

How do you guys go about sharpening drills bits?

And I don't want to hear, I just throw them away and use a new one, larger drill bits are not cheap these days.

I have one of these, but I find it very inconsistent, next to useless and I'm better off grinding freehand..

[Bernd]

Darren,

I have one of those and have to agree with you. I bought myself the "Drill Doctor" model 750. It will do drills up to .750". Great tool, easy to use and very accurate.

You can check it out at www.DrillDoctor.com

Wouldn't be without one now.

Bernd

[Stilldrillin]

Never used a grinding jig, I have always done it freehand. 

I have taught several friends over the years........ It is quite easy to learn the skill. 

David D

[usn ret]

Ditto Drill Doctor 750.
Cliff

[John Hill]

Freehand.

[sbwhart]

I've got one of those but found I can do it better freehand, my Dad taught me how to do it many years ago, once learn't never forgotten. As an experiment showed my own son how to do it, he's never shown any interest in machining, but after 10 min he was making a reasonable job of it. Is it an heredity skill thing 

Stew

[Darren]

I have to admit as said before I do mine freehand most of the time, I was just wondering if a proper setup would be better 

Seems it's swings and rounabouts, as in it depends who you ask 

[DavesWimshurst]

For years have done it freehand.  Then built a Potts drill jig but it didn't work right.  Tried other methods such as "four facet' jigs with better luck.  Eventually took another look at the Potts jig and found some construction errors.  When corrected it gives very good results for a standard grind.  Some jigs won't give the correct amount of relief behind the cutting edge unless the drill extends the right amount away from the pivot axis of the jig.

The four facet drill seems to work better but I don't have a jig for larger than 1/4 inch drills. That said I will hand grind drills, its not that hard to get a drill that works well but it will probably drill oversize due to small errors between the two cutting edges.

Dave

[Bernd]

Dave,

Any chance of a pic of the Potts drill jig?

Bernd

[bogstandard]

That said I will hand grind drills, its not that hard to get a drill that works well but it will probably drill oversize due to small errors between the two cutting edges.

It is for that very reason that I discard all my old drills.

Unless you can get them machine ground, they are not worth size for size the metal they are made out of. 'Somewhere close to the size I am after' is not a saying that is in my vocabulary.

Four facet is definitely the way to go. Designed to start true and drill true without the use of a centre drill, and much lower cutting forces.
I will buy those before any other.

John

[Darren]

I knew you would say that John.....

[bogstandard]

That is why I let everyone else get their say in first.

But I do have a Martek drill sharpener that does an almost acceptable job.


John

[Darren]

Darren,

I have one of those and have to agree with you. I bought myself the "Drill Doctor" model 750. It will do drills up to .750". Great tool, easy to use and very accurate.

You can check it out at www.DrillDoctor.com

Wouldn't be without one now.

Bernd

Thanks Bernd, and others that suggested this unit....

I bought one and although I can and have been grinding drill bits freehand for years with quite acceptable results this does it quicker and better than I can.

I got the 750 model and although not cheap, in one afternoon it has easily paid for itself (I have a lot of drills bits  , never thrown any way over the years, unless I bent one, so the box was quite full.....)

I've had cheap powered drill grinders before, with a stone wheel, but the wheel gets out of shape rather quickly from what I've found.
The diamond wheel in the DD should last a long time.....

[John Stevenson]

It is for that very reason that I discard all my old drills.

John

Philistine.........

I know I'm going to get flack over this but I grind brand new drills.

People say buy good and throw them away but I have quite a unique experience in small drills, last place I was employed at, current job don't count as Gert reckons I'm playing, we used to drill precision holes in wood, by precision I mean 50 thou to a 1/2 thou tolerance and before you skoff, yes it can be done and has been for a 100 years.
But there are no 50 thou drills so we used to have to make them. The result was you learned a lot about what cut best and how to hold tolerances.

Fast forward to today and one of my jobs is making dividing plates, all specials and some have 3,300 holes in them, a normal run will be just less than 2,000 holes 2.5mm, 3 mm and 1/8" are popular sizes.

If I buy good quality Guhring drills I can get 4 plates, about 2,000 to 3,000 holes before the web deteriorates and I get run off or worst a  broken drill which is unacceptable, one for quality and two for lost time.

Now if I take a that same drill after one use and grind it 4 facet on a small German Meteor drill grinder I can get 8,000 holes before changing.
This might sound like bullshit but the Meteor and Christian drill grinders are still made today, small enough to fit in a shoe box but a new Christian will set you back 14 grand, yup 14 grand, no misprint. So there has to be a use and demand for them.

Because of lost time, the drill is £1.50, the plate is about the same but some of these plates are on the machine for close to 2 hours, that's 2 hours at commercial rates lost when a drill breaks I now grind every drill straight out of the packet and change them every 4 sets regardless.

.

[Darren]

Interesting John,

In my last lot of free gifts I was given some drill bits, all good makes, Presto, Dorma, Guhring and some Italian ones I can't remember the name of right now.

Most were new and if you look very carefully one or two were not ground equally on both sides. With cheap drills I find this is quite common, but don't expect it with the more expensive types.

So I popped a couple in the Derex and sure enough one side ground before the other. On the ones that looked good both sides started grinding equally as far as I could tell.

Apart from that they are deff sharper than new. I will have to see how I get on with them.

I suppose when drill bits are made they are ground by the 1,000's or even 10.000's at a time before the machine is re-calibrated thus a chance for tolerances to drift.

[bogstandard]

That is the main problem John.

It would be wonderful to be able to afford a decent drill grinder as you have, and because I can't, I have to rely on the drill manufacturers to get it right for me.

As and when I can afford, or make a tool and cutter grinder, or a jig I can use on my surface grinder, then I will start to regrind my own.

I said that I do have a small commercial drill grinder (Martek), but I wouldn't trust it as far as I could throw it to get small drills spot on. As you said, when you have tolerances to hold, it has to be right. With larger drills it isn't usually so critical, as I use them for quick removal of metal, and the holes are usually bored or reamed afterwards, or if drilling a tapping hole, you normally have a little leeway on tolerance, and if you can creep up on size, you can get them fairly close to the required size anyway.

Anything of 3mm and below, I keep a stock of normally used sizes in bulk packets, and dull ones are just thrown away, to me they are just not worth the trouble to try to regrind. Maybe that would change if I had a reliable sharpening method.

John

[Stilldrillin]

I always used to grind new hs drills before use.

Dormer, mostly, up to 2" dia.
Most would rub just behind the cutting edge, due to incorrect manufacture.

David D