Oh my bad! I think I was looking at the 7" ceramic/carbide grinding wheels in the cup style. But may be this 60 grit is all I need?
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Building Harold Hall's Simple Grinding Rest
- Thread starter stioc
- Start date
Oh my bad! I think I was looking at the 7" ceramic/carbide grinding wheels in the cup style. But may be this 60 grit is all I need?
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The white 38A compound in 60 grit leaves a very fine finish on HSS. I find any finer grit than that is too slow, but that's my opinion. Judging by what that hardware store grinding wheel did to your screwdriver, I'd say you are in for a treat once you get a proper wheel.
This evening I decided to make an endmill holder. The reason being that the 5c blocks are way too big for this small rest. The endmill holders I will need are probably just the 1/4", 3/8" and 1/2". I mostly just use 1/4" and 3/8" endmills but some have 1/2" shanks. Besides, anything less than 1/4" will be hard to regrind. So I made the 3/8" one which came out good, but something went wrong with the 1/2" one where the hole went off center, wasted 40 mins making it 
Anyway, I decided to put the 3/8" holder to test real quick before calling it a night. I dug this old endmill up from my garage sale pile, Dykem'd it. The ends had some damage, wish I took a before pic but I was tired. All I can say is that this holder worked so much better than the 5c block. This is only my second time trying to sharpen the endmill's end. I think I hit the primary angle and the concave angle pretty close to what they should be. The only thing I see now I did wrong was I over did it by grinding it a bit too much so the land is a bit wider. This can be corrected by grinding the secondary relief angle which I haven't done yet. I'm pretty stoked
Anyway, I decided to put the 3/8" holder to test real quick before calling it a night. I dug this old endmill up from my garage sale pile, Dykem'd it. The ends had some damage, wish I took a before pic but I was tired. All I can say is that this holder worked so much better than the 5c block. This is only my second time trying to sharpen the endmill's end. I think I hit the primary angle and the concave angle pretty close to what they should be. The only thing I see now I did wrong was I over did it by grinding it a bit too much so the land is a bit wider. This can be corrected by grinding the secondary relief angle which I haven't done yet. I'm pretty stoked
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Nice job on the end mill and holders. Remember, as you grind an end mill you cut deeper into the helix and the angle of the dangle changes- just like a drill bit ground off-axis with the flutes. If you are doing a heavy grind, remember to re-set the mill in the holder before doing your final finish. Also, I cut my back cut and relief angles first, then the gash cuts, then do the cutting edge last. That helps me get the right amount of removal for the cutting edges and preserves the delicate edge from the rest of the process in case I nick one while grinding a gash cut, etc. Also, interestingly enough, I find it more of a challenge to grind a perfect 2-flute EM than a 4-flute. I guess 4 flutes are easier to "see", and the 2-flute has more "field" are on it's face to be relieved. And the right grinding wheel will make those edges look more like mirrors than curtains. All in all, you've really expanded your tool sharpening capabilities with this project! I love grinding, and judging by the variety of tools you've tried out so far, you will too.
@pontiac428 thanks so much for your continued support and suggestions. Coming from you, someone who has a real tool grinder, it means a lot to hear that I've expanded my tool sharpening capabilities because I'm still unsure of how well this will work. BTW you're spot on in your assessment that despite a few frustrating moments I'm finding this tool regrinding thing a whole lot of fun
Would love to see you and others post pics of what you're grinding even if on a different type of equipment.
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I've got dozens of boring pics of lathe bits an such. Most are hard to see the geometry and edges in once captured in 2D, but if you don't mind the clutter I can post. 
Grinding is a lot of fun, and saves me a lot of money each year. I'm always imagining ways I can grind - and often ways I can't accomplish a grind - with my equipment. Right now I have a fixture block that's almost done to allow me to hold fluted countersinks at a 90 degree angle to the wheel to cut and sharpen countersink flutes. We'll see how that works out.
Grinding is a lot of fun, and saves me a lot of money each year. I'm always imagining ways I can grind - and often ways I can't accomplish a grind - with my equipment. Right now I have a fixture block that's almost done to allow me to hold fluted countersinks at a 90 degree angle to the wheel to cut and sharpen countersink flutes. We'll see how that works out.
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- Apr 23, 2018
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Here's some.
First, a single flute drill bit for spotting and precise-diameter drilling.
Some re-ground cemented carbide lathe bits, because they suck out of the box:
A RH finishing bit:
Grinder. Made a few mods since, this is stock with Kipp levers and China wheel. To the right you can see the lathe bit attachment and the spin fixture for flutes.
Heavy duty RH facing tool. Did a LH of the same grind on the other end of the blank.
Top is a 60 degree threading tool, bottom is a general purpose tool.
First, a single flute drill bit for spotting and precise-diameter drilling.
Some re-ground cemented carbide lathe bits, because they suck out of the box:
A RH finishing bit:
Grinder. Made a few mods since, this is stock with Kipp levers and China wheel. To the right you can see the lathe bit attachment and the spin fixture for flutes.
Heavy duty RH facing tool. Did a LH of the same grind on the other end of the blank.
Top is a 60 degree threading tool, bottom is a general purpose tool.