More tool projects.. (Potts drill grinding jig)

[Bjorn_B]

Hello Vince, it is not all that bad, but there are no instructions as there usually is in kits from Hemingway. Only some short notes, the plans are good thou. Most headscratching comes from thinking over how to set thinks up. A tilting vice or an adjustable angle plate would help a lot in my view.

Thanks for checking in, premiere grind on the worden soon?

[Bjorn_B]

Drill platform is allmost done now, just the lip rest to do, but that will not be done until it is finished. Next part is not very exciting, a casting with two holes drilled and reamed at an odd angle, 59 degrees if I remember correct..

Edit, 72 degrees, pivot should be set 18 degrees from vertical

[vcutajar]

It will be interesting to see how it will be fixed to the grinder.  It think the Worden has the facility to use it.  What drill sizes does it take?

Vince

[Bjorn_B]

It will be interesting to see how it will be fixed to the grinder.  It think the Worden has the facility to use it.  What drill sizes does it take?

Vince

Hello Vince! It is nothing very fancy, a couple of cast  bits bolts it to the bench next to a ordinary bench-top grinder setup to grind on the side face of the wheel, a cup wheel would be best here I guess.

I'm pretty shure it is possible to grind four facet or split point gemetry twist drills on the worden, it would in most cases be superior to the "cone back off" geometry that this jig will produce. I have done split points on my quorn, but is somewhat of a hassle to set up, thus most of my drills are a bit dull...

[Bjorn_B]

Done!

There is two settings to be done fore every diameter of drill to be ground:

First picture, setting the platform offset (shank of drill is used for this)

Second setting is jig to wheel clearance (done by eye), this has to be done for every drill diameter because the first setting advances the platform in relation to the pivot. I have a hex bolt for this right now, but I found a ball handle that I must have made when I did the quorn, I will adapt that so there is no other tool needed to use this.

Thinking about raising the grinder on some sort of platform in relation to the grinding jig so that the direction of grind is more favourable, it is now more or less parallel to the cutting edge. I believe it would be better to grind allmost at the 6 o clock position on the wheel.


Drill range seems to be from about 3mm to 13mm

[Holt]

Thinking about raising the grinder on some sort of platform in relation to the grinding jig so that the direction of grind is more favourable, it is now more or less parallel to the cutting edge. I believe it would be better to grind allmost at the 6 o clock position on the wheel.

Quietly following along, I have used commercial versions of this type of grinders, and all used the nine'o clock position of the wheel, maybe your idea would make the wear of the wheel more even, as it seems there is quickly forming a groove in the wheel when used in the traditionel way.


Holt

[Bjorn_B]

Thanks for commenting Holt, my concern for wheel wear is quite the opposite with this jig. The working space on the wheel can be set anywhere when the second setting is done. The pivot does not have to be vertical, only the angle towards the wheel is of importance and thus a new position can be set everytime the horizontal bar is adjusted for platform to wheel clearance. If I use a position nearer to the bottom of the wheel, things will become more static.

I have never seen a jig of this type ether that is not using this position. Even the big KEF drill grinding jig at work uses the same posision. Can't understand the geometry of that jig thou, it's a very odd one, the pivot tilts away from the grinder, a lot...

[Bjorn_B]

And this is what it has done to my drill inventory...

20160214_135530 by Bjorn Pettersson, on Flickr

I'm happy!

[Doc]

Looks like it's doing a good job! 

[Bjorn_B]

Looks like it's doing a good job! 

It really does! Can sharpen up a drill in a minute or two now, can't compare to a four-facet job, but better a sharp traditional drill than a boxfull of dullies..