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View Full Version : Need help with Potts drill grinding jig



gregl
01-27-2010, 07:22 PM
Well, I made a Potts drill grinding jig but I can't seem to get consistent results with it. I've followed the inadequate directions that came with it, as well as trying a variety of other settings, and getting the correct clearance is always a problem.

When set according to directions, clearance is not enough and seems to decrease as the size of the drill decreases to the point where I get negative clearance at sizes 1/4 inch and under. If I spend an hour fiddling with it, I can get a nice point, but repeating the feat with another size drill requires another hour of fiddling.

I'm positive I'm following the directions correctly.

Anyone out there have one and if so, how do you set it?

Thanks!

SGW
01-27-2010, 07:57 PM
Not much help, but a friend of mine made one and liked it and was able to sharpen tiny drills accurately. Unfortunately, he died suddenly, his shop got sold off, and I can't tell you anything about how he did it, just that it IS possible to get the thing to work.

J Harp
01-28-2010, 11:12 PM
Take a look at this.
http://www.homepages.mcb.net/howe/MinorWorkshopTools.html#drill

There was an article in either Home Shop Machinist, or Machinist's Workshop, which had quite a bit of discussion of different methods for grinding the proper angle and relief on a drill point. I did a quick shuffle through some of my stack of HSM and MW, but didn't find the article. I'll take a better look when I get a chance, or maybe someone else will know which issue it is.

gregl
01-29-2010, 11:40 AM
Thanks, J Harp. I fabricated my jig rather than use the castings, so I think I need to check to see that all the angles called for are actually built into it. From what was said on the website you referred me to, perhaps there is an error in my build.