# Drill bit sharpening jig.



## th62 (Nov 19, 2017)

I've made a number of drill sharpening jigs, this is my final effort. I used a piece of 25mm square bar, linished it, milled a V for the drill, cut a 2mm slot down the centre for 110mm, drilled a stepped hole through: 5mm for 30mm and then 11.5 mm for the remaining 110mm. I had to extend an old 11.5mm drill and grind flat on the end so I could machine the end of the hole flat for a stepped bush to run on. I also drilled a couple of debris drain holes and tapped a few 5mm holes for mounting the slide plate, the end plate and the drill clamp. As you can see from the pics there are quite a few bits inside.

The 5mm advance rod was turned down to 3.5 on the end and a 5mm bush with collar was shrunk in place for the end bushing. I turned a bit of stock to 7mm, threaded the inside to 5mm x .8, fashioned a single wing and tacked it to the nut. The bush on the advance end was machined to 7mm with a collar, machined down to fit a 9mm spanner, and threaded inside the same as the advance screw. When screwed into place it’s locked off with a locknut. The plate on the end has a backlash adjuster and locknut and also acts as the outer bearing for the advance screw bush. The end plate is fixed by two 5mm allen heads which I had to turn down to accommodate the backlash adjuster locknut. To the rear of that are the thumb lock nut and the thumb adjuster.

The drill clamp U piece is attached via two 5mm allen heads. I machined a stepped 5mm nut and shrunk it into the top of the U piece. The adjuster screw has a thumb nut attached at the top and the adjuster screw pushes an H shaped plate down onto the drill flutes.

It will accommodate drills from 25mm down to 2mm, but in reality larger bits are probably better ground using a simple conical grinding jig attached to a linisher. Anything under 4 or 5mm would be difficult to grind accurately on this jig, so next project will probably be a jig with a drill chuck for smaller bits.

In use: The drill is secured in place by the adjuster and H plate. To advance the drill onto the grindstone, the advance thumbnut is turned and the single winged nut moves along the advance screw, guided by the slot in the bed, and acts on the rear of drill pushing it forward and onto the grindstone...

I also made a nice wooden box for a housing and included the Chinese words for drill sharpener (a joke). At least I hope that is what it says!

Over complicated? Sure is, but it works well; and, it was an excellent project to design and make.


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## British Steel (Nov 19, 2017)

Very posh, and does 4-facet! Can it do different point angles for e.g. spotting drills, or would it need alternative baseplates?

Dave H. (the other one)


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## EmilioG (Nov 19, 2017)

Nice jig.  I don't use them myself.  I'd like to perfect my hand grinding technique first.
That V cut is very important, how did you get it so precise? I've seen videos where machinists would
have to surface grind the V, after milling it, to get it right. Cool. Thanks for sharing.
PS: I'd ask the same question as British Steel above, what about other inc. angles, 135°, 140°, etc...?
I suppose a different plate and tilting the table?


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## th62 (Nov 19, 2017)

EmilioG said:


> Nice jig.  I don't use them myself.  I'd like to perfect my hand grinding technique first.
> That V cut is very important, how did you get it so precise? I've seen videos where machinists would
> have to surface grind the V, after milling it, to get it right. Cool. Thanks for sharing.
> PS: I'd ask the same question as British Steel above, what about other inc. angles, 135°, 140°, etc...?
> I suppose a different plate and tilting the table?



Just requires a different base plate.   I don't bother, 118 is fine for anything I do.   Sharpening by hand is fine for everyday bits and the way I normally sharpen, but if you want a precise hole, the shoulders need to be exactly the same length.   You can only get that using a jig.


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## EmilioG (Nov 19, 2017)

I know seasoned machinists that can hand grind a drill using a bench grinder and a 59° drill gage. Spot on.
I agree that making a 4 facet drill is not easy, so I just buy them when dull. I'm not good enough at hand grinding yet,
so I may get a Drill Rx...maybe..., if I start going through drill bits.  If I see one of my drills getting dull, I touch it up before it gets really dull.  Drills don't really produce precise, round holes, they're not precision tools., so Drill Rx's and jigs have never been high on my list.  If I need a precise hole, I use my Criterion boring head.

Nice jig. I'm sure you'll get many years of use
out of it.


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## th62 (Nov 20, 2017)

Not really possible to hand grind a bit 'spot on', the human eye is incapable of discrimination in thousands of an inch, that is why we use jigs o to sharpen bits used on lathes and mills.   I learnt to sharpen bits when I first started work as a welder, some 50 years ago.   Over the years I've obviously got better and can sharpen a drill bit very well, but certainly not within thousands of an inch.   I never conical grind, except on large bits, changed to facet grinding simply because facet ground bits work better.


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## ericc (Nov 20, 2017)

Does this sharpener do both facets or only the primary one?  It is hard to tell from the text.


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## th62 (Nov 21, 2017)

ericc said:


> Does this sharpener do both facets or only the primary one?  It is hard to tell from the text.


Of course it does, it can do 20 facets if you want, simply by changing the angle of the table???


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## ericc (Nov 21, 2017)

th62 said:


> Of course it does, it can do 20 facets if you want, simply by changing the angle of the table???



Ahhh.  I got it.  So the primary facets are cut, then the angle of the table is changed, then the secondary ones are cut.  Thanks!


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## th62 (Nov 21, 2017)

ericc said:


> Ahhh.  I got it.  So the primary facets are cut, then the angle of the table is changed, then the secondary ones are cut.  Thanks!


I do it the other way around, but it's not going to make much difference I guess.   Of course you can do just the one facet each side, cuts just as well.


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