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Import Tool & Cutter Grinder

s_vanhoveln

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I do use it, and the documentation is near non-existent. Actually, it works very well. There is a (poor quality) video on youtube under "U3" as the search term that makes it more clear. The part that I had to figure out is what the ideal clocking of the drill should be. I set it up to look like an hourglass as it enters the grinding wheel from the normal direction. Then you need to set a stop at the end of the bit, grind one side, then roll the bit 180 degrees and grind the other side. Once set up, it is faster than using my drill doctor and more versatile. The fixture makes a good grind profile and you can get good grinds on small drill bits (less than 1/8 is possible) up to fairly large S&D bits. Oh, you want to grind at a 59 degree angle with the fixture for a 118 degree included angle. Sorry for the weak instructions, but once you see it done on youtube and grind a bit or two, the concept will lock in and you will be rolling. Alternatively, you can grind the four facet pattern. Definitely read the Workshop Practice series tool grinding book (#38) by Harold Hall under downloads on this site if you don't have it already. It explains a lot in a very short space about sharpening drills, including angles, web thinning, split and chisel points, and so on. Hall uses a bench grinder adapter (like the Craftsman) for his main example, which works on the same principle as the drill fixture we have.

Thanks for the reply. I've watched that "U3" video you mentioned, and I've been trying to make sense of his written charts and instruction. It seems that my attachment has a couple minor differences than his, and consistency is eluding me. I understand what you're saying about clocking the bit. I've read #38 a while back, but I believe I still have a fair grasp of the geometry...I just can't replicate it. My issues lie with the amount of stickout of the bit beyond the face of the tool, as well as the stickout of the tool itself. The U3 video documentation implies very little stickout of the bit, but implies tool extension that isn't possible without modification. Any clues you could provide would be very appreciated.
 

pontiac428

Mo-Max
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Harold Hall explains the effect of bit protrusion from the fixture in the #38 book. It does not affect the quality of the grind or cutting performance, but it changes the flatness of the facet based on the arc drawn by the tip as the fixture pivots. Longer radius, flatter arc.

If I get a chance this weekend, I'll find a dull bit and post pics.
 

s_vanhoveln

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Sep 18, 2017
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Harold Hall explains the effect of bit protrusion from the fixture in the #38 book. It does not affect the quality of the grind or cutting performance, but it changes the flatness of the facet based on the arc drawn by the tip as the fixture pivots. Longer radius, flatter arc.

If I get a chance this weekend, I'll find a dull bit and post pics.
I understand that too...that is what was really annoying. I found the problem today and I've made it work. One of the setting scales on the head had slipped or wasn't set correctly and it was adding about 8 degrees to the natural relief angle built into the tool. My bits were getting a very aggressive relief angle no matter what I did. I reset that axis to zero and I've fixed my initial practice bits and given them pretty four-facet grinds. After two full days of making dust it's shocking how easy that fixture is to use once the initial machine settings are correct.

Thanks for offering so much help. If I hadn't found someone who was having success I would probably have given up and put that drill grinding fixture on eBay.
 

C-Bag

Ned Ludd's bro
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Harold Hall explains the effect of bit protrusion from the fixture in the #38 book. It does not affect the quality of the grind or cutting performance, but it changes the flatness of the facet based on the arc drawn by the tip as the fixture pivots. Longer radius, flatter arc.

If I get a chance this weekend, I'll find a dull bit and post pics.
This is the one attachment I've not gotten to with mine. Like you said the instructions are lame and I've not found the U3 YouTube yet. But for whatever reason it seems it has to do with style of presentation what sinks in for me. Compound this with I picked up a Starrett drill bit gage and I had been doing my bits freehand for years. Wish I'd had one of those gages years ago as our Ozzie bro's say it works a treat.
 

pontiac428

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This video is horrible in quality, but you can clearly see how the attachment works. Luc Wybo's first video is good, he gets into geometry and does a good job of explaining it even though he is hard to hear.
 

C-Bag

Ned Ludd's bro
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It is really tough to see around the grinders when operating much less trying to video. But both of these give a much better idea of how it works than the silly booklet that came with the grinder.
 
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