Drill sharpening jig.
#1
This is a drill sharpening jig I made some time ago.  It's used for precission sharpening of a drill bit so both shoulders and cutting edge are the same length and angle.  In use it Imeans you get a more accurate hole.
For this drill sharpening jig 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...
Over complicated? Sure is, but it works well; and, it was an excellent project to design and make.


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#2
That's precisely how I sharpen my drills (and take a ton of flak for it on YT). It's called multi-faceted drill point geometry, and it works great. The traditionalists want to see conical relief on the secondary because they claim it can tolerate more heat, which is true, but the way I (we) sharpen them actually produces less heat, so there is less to tolerate.

Nice job on the fixture.

Tom
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#3
(07-09-2020, 08:24 AM)TomG Wrote: That's precisely how I sharpen my drills (and take a ton of flak for it on YT). It's called multi-faceted drill point geometry, and it works great.
Me too. I also use 142 degrees instead of 118 and wow, does that make a difference! the drill cuts far easier, and that split-point means no pilot hole is necessary. I tested my first attempt which was a 1.25" drill on some hardware store steel without any sort of starting treatment just to see if it was true. My jaw was hanging out. :)
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