sharpening end mills

I've got a bunch that have chipped tips on the flutes , and I guess it's time I learned to sharpen them instead of tossing them and buying more .I've poked around a little and found a design for a fixture using 5C collets that I can build with tooling I have on hand . I do have a question about using my mill to grind these . It doesn't spin as fast a a real grinder , about 1800 RPM tops IIRC . I'm looking for suggestions what type of wheel I need . Probably a cup wheel since the end mill will mount with the tip up .

Reply to
Snag
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I've got a bunch that have chipped tips on the flutes , and I guess it's time I learned to sharpen them instead of tossing them and buying more .I've poked around a little and found a design for a fixture using 5C collets that I can build with tooling I have on hand . I do have a question about using my mill to grind these . It doesn't spin as fast a a real grinder , about 1800 RPM tops IIRC . I'm looking for suggestions what type of wheel I need . Probably a cup wheel since the end mill will mount with the tip up . Snag

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This type of fixture works well enough for me, on my ancient $100 surface grinder.

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have the Enco version with 24 click stops, no dial or lock screw. The base was cut square and the relief angle is in the mounting hole for the ring that retains the collet holder. If I'd tried to make it I might have had trouble matching the collet taper, the rest is pretty simple and the tilt angles shouldn't need to be exact, eyeball alignment in the collet and on the grinder mag chuck is good enough to make an endmill cut well. I did machine another collet closer nut that accepts flanged bushings to center an S&D drill bit, etc.

It isn't obvious that the end cutting edges angle in slightly toward the center. If you are set on making your own I can measure the collet holder's lengthwise and sideways tilt angles on mine.

In addition to sharpening the ends normally it can grind worn tips into a 30 degree bevel to cut sideways without dulling the spiral edges. I have one old 1/2" 4-flute that I grind that way and use for roughing, to save the other endmills for finishing. Another scheme to preserve the spiral edges is to rough with plunge cuts which dull only the end edges that I can easily regrind.

I also have a fixture like this to sharpen the spiral edges:

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's quite fussy to set up and use, and it reduces the diameter which can be useful to cut a slot to 0.500" (with multiple passes or another new endmill) instead of slightly larger from deflection, but is otherwise a nuisance since they look the same. I made it more rigid by removing the tilt mechanism that would swing the endmill into or away from a cup wheel, since I grind on the top with a normal 6" wheel.

Reply to
Jim Wilkins

The Griz unit is the one I plan to try to duplicate . The shars unit is discontinued but I seldom dull the sides . Knowing the angles involved would be a big help ... I'm still wondering what type of grinding wheel I need for the RPM's my mill has .

Reply to
Snag

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If that isn't clear, the fixture is tilted onto the 25 degree (I measured it) angled face and the chipped end mill tip is ground back at that angle like the cutting edge of a drill bit. It will cut as long as the least chipped corner has been sharpened, and eventually regrinding may restore others. You can grind a badly chipped one back to square with a bench or angle grinder and restore the cutting edge geometry with the fixture. 4 flute endmills can be salvaged although they are unlikely to remain center cutting, 2 flute ones are easier.

Based on my mill's somewhat limited rigidity I grind the dull point back about 0.025" or less lengthwise, leaving at least half the diameter cutting flat, and alternate between regrinding it square or beveled. Both edge faces wear from roughing by plunge cuts. The beveled cutting edges seem much less vulnerable to chipping in mystery metal with hard spots.

I would be extremely careful to keep grit off the exposed ways of a mill. The ways of a surface grinder are shielded.

Reply to
Jim Wilkins

That's what old sheets are for ... OK , so after watching some Joe Py video I went ahead and ordered a 6" bonded grit saw blade sharpening wheel . It should work well as long as I don't get too frisky with feed rates . This project will go on the back burner for now , got other stuff that's more pressing - like getting the new gears installed in my truck axle . I can't finish carb/timing/etc tuning until that's done . And I can't do that until I get my neighbor's 4X4 UTV finished . Maybe today on that one , almost finished reassembly after replacing a set of bevel gears deep inside the guts . Had to split the cases to get to the damaged gears .

Reply to
Snag

Since I do mostly CNC its not worth it to me generally, but I do have a diamond cut off wheel for the TC grinder so I can lop off the chowdered tips of a carbide mill and use it strictly for side milling. I don't have much in the way of HSS mills. Most of them are still on the floor where I threw that harbor Freight box six months ago.

That being said I have purchased resharpened a couple times when I needed a particular geometry for a single job and didn't want to spend a lot on it. There is a sharpening outfit in Phoenix that used to have tons of resharpened mills on Ebay pretty cheap.

Reply to
Bob La Londe

Projects, projects, ...

AFAICT with limited equipment the collet tilt angles are 5 degrees toward the beveled end and 2 degrees to the left with the bevel toward you (or me). At least those angle blocks visually match it to a square. I confirmed that the bevel is 25 degrees from the base.

Reply to
Jim Wilkins

I'm still wondering what type of grinding wheel I need for the RPM's my mill has .

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I doubt that it matters all that much if you aren't in production, grinding works down to hand honing speed.

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The normal speed of my surface grinder burns carbon steel jointer blades unless I take -very- light passes.

Reply to
Jim Wilkins

Thanks , those are pretty close to the numbers I expected . One more good day on the neighbor's machine should see it back in running shape , the motor's ready to drop in now . I originally told the neighbor that I would do his after I finished the truck ... I relented and moved it up because his wife was making him miserable over it . She's one of those "corporate movers and shakers" . I'm sure glad I married a "simple country girl" !

Reply to
Snag

Thanks , those are pretty close to the numbers I expected . One more good day on the neighbor's machine should see it back in running shape , the motor's ready to drop in now . I originally told the neighbor that I would do his after I finished the truck ... I relented and moved it up because his wife was making him miserable over it . She's one of those "corporate movers and shakers" . I'm sure glad I married a "simple country girl" ! Snag

------------------- My day's project was lost to helping an elderly neighbor too. Everything went wrong, and it's reassuring that in my mid 70's I can still diagnose and fix problems quickly.

Reply to
Jim Wilkins

Kids now days , if they can't read the problem off a computer screen they're totally lost . Remember Gus from Popular Mechanics (IIRC) back in the 50's-60's ? His column taught me to diagnose a burned exhaust valve by sticking a strip of paper to the end of the exhaust pipe with bubblegum ...

Reply to
Snag

Speaking of off the computer screen. There is a YouTuber who uses his mill fairly often as a grinder you might find interesting. Its not typically a "grinding" video, but instead one part of a project. He did a fair amount of grinding in a video about making a grinder vise (screwless vise). In a more recent video he touched on mill grinding when making a case hardened gear. He also does a bit of case hardening.

Artisan Makes

Aside: I currently use modified grinder vises as my primary fixturing attachment on 4 mills because they take up less space for their range than a mill vise, and they are more flexible than a fixture plate. (I Use fixture plates too. Some mount in the vises as needed.)

Back on topic: I suppose I should have put this out there sooner. There are two answers that come to mind for me about your concerns for speed. (1) A larger wheel gives more surface speed. (2) Grinding slower works fine. Its just slower. For example a Tormec knife grinder is an order of magnitude slower than a bench grinder or most other machine shop grinding machines.

Reply to
Bob La Londe

I chose the 6" saw grinder wheel partly because it has 1 1/2 times the surface speed of a 4" cup . And partly because it was fairly cheap , and partly because of the profile . With the right setup I can gash with it too . I've been pondering the base for the fixture to mount the end mills . I think I'll make the bottom angles and have the sides and ends square with them . Then put the 2° bevel on top with the thru hole perpendicular to the top . Just seems like the easiest way to me .

Reply to
Snag

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I set the end mill fixture on my mill with the collet upright, 1/2" rod in the fixture and spindle collets, raised the table to contact with the back right corner, then pushed a 1/4" thick bar into the wedge space underneath from the front (bevel) side. The bar intersects the left side 2.05" from the back and the right side 2.95" from the back. A squared rectangular base block could be clamped to a mill table or lathe faceplate this way and bored straight in to get both 2 and 5 degree angles easily.

I might attach the 1/4" angled spacer with countersunk screws to reduce fumbling and let the setup be accurately repeated later. jsw

Reply to
Jim Wilkins

I'm going to have to take a minute to digest that ... OK , if I'm understanding this correctly I'll only have to cut one angle on the bottom , the other two will be produced by the way the hole for the collet is bored in the block - 2° tilt to the rear , 5° to the right . If I put a couple of degree angle on the left end I can set the fixture up to do the gash with the end mill horizontal/angled slightly down . It's been a long day , and I do enjoy a few shots of sour mash in the evening . It's been a gloomy day here , fine drizzle most of the day . The dog and I both hate being cooped up inside all day .

Reply to
Snag

I'm going to have to take a minute to digest that ... OK , if I'm understanding this correctly I'll only have to cut one angle on the bottom , the other two will be produced by the way the hole for the collet is bored in the block - 2° tilt to the rear , 5° to the right . If I put a couple of degree angle on the left end I can set the fixture up to do the gash with the end mill horizontal/angled slightly down . It's been a long day , and I do enjoy a few shots of sour mash in the evening . It's been a gloomy day here , fine drizzle most of the day . The dog and I both hate being cooped up inside all day . Snag

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Yes, the angled 1/4" spacer tilts the base block to the 2 degree sideways and 5 degree lengthwise angles, or at least it will duplicate the angles of mine with only simple length measurements. If you fit it to the base block before milling the 25 degree bevel you can screw it down in the area that will be removed.

However it won't allow very secure clamping, so if you want to go that way I'll have to find out how far you can rough drill and bore the collet holder recess with the base block clamped squarely and solidly in a milling vise. Then you'll have to re-locate the center in the rough hole when it's clamped at the angle, perhaps with a sheet metal template of the base with the center punched. You could clamp stuff around it to help keep it from twisting out of place from the cutting force.

You only have to mill the 25° (degree) bevel which can be done with the base block clamped solidly in the vise. Do you have an angle block set? Mine is a much cheaper Enco version of this:

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Before MSC bought them, Enco had a retail store in southern NH (no sales tax) so I stocked up on everything I might need. jsw

Reply to
Jim Wilkins

I'm going to have to take a minute to digest that ... OK , if I'm understanding this correctly I'll only have to cut one angle on the bottom , the other two will be produced by the way the hole for the collet is bored in the block - 2° tilt to the rear , 5° to the right . If I put a couple of degree angle on the left end I can set the fixture up to do the gash with the end mill horizontal/angled slightly down . Snag

------------- I don't understand the last sentence.

Facing the base bevel, the collet tilts 5 degrees toward you and 2 degrees to the left. Conversely the way I have it in the mill with the collet vertical, the base tilts up toward me and on the left side, which is why the

1/4" parallel jammed under it is at an angle. The easy way to copy that angle is to duplicate the distances from the bar to the back of the base block on both sides, assuming you make the block the same width as mine, 2.5053".

The 5 degree tilt provides back relief to the cutting edge, the 2 degree dishes the edges inward slightly so only the tips cut, even as they dull. I don't think either angle is critical, recommendations I've seen for back relief are a range that almost always includes 5 degrees. Likewise grinding while on the 25 degree base bevel merely removes the bulk of flute material behind the cutting edge, or balances it if you ground most away faster on a bench grinder. Surface grinder wheels can explode if you try to force too heavy a cut, I've been nearby on another machine when a kid did that.

I think you can make all cuts with the end mill or boring head vertical, and do most of the machining on the base with it square or single-angled in the vise. On my mill the head can be tilted and swiveled to bore the angled collet recess directly, with the base in the milling vise, though squaring (tramming) it up again afterwards is a lot of trouble since the round ram shifts when the clamps are tightened.

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Reply to
Jim Wilkins

I took my endmill fixture apart to measure the stock size you'd need to copy it. This is the same design:

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The base is 1" thick by 2.5" wide by 4.5" long. The collet holder is rod stock at least 1.85" diameter by 2.75" long. Its retaining ring is 2.375" diameter by 12mm thick (plate stock?). It fits into the angled bore in the base block. The collet closer nut is a little under 1.5" diameter. The 3 indexing balls are .187" diameter, with similar sized compression springs.

The collet holder has a circle of 24 indexing dimples in the flanged lower end.

The holes for the index balls and springs were drilled while the block was tilted, so you may have to center it on a rotary index table with the 1/4" spacer in place. Likewise the 3 screws that attach the collet retaining ring were angled through the base, thus square into the ring, and countersunk at the angle from the bottom side, which may be tricky.

The Grizzly G9887 is on sale for $61.15.

Reply to
Jim Wilkins

I was talking about cutting the end gash with the end mill held horizontal and using the edge of the grinding wheel . I've got this figured out now . I planned on making this with a screw lock and 12 dimples in the collet sleeve to lock the setting . For now though it's on the back burner .

Reply to
Snag

I was talking about cutting the end gash with the end mill held horizontal and using the edge of the grinding wheel . I've got this figured out now . I planned on making this with a screw lock and 12 dimples in the collet sleeve to lock the setting . For now though it's on the back burner . Snag

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The screw lock style should be less demanding to machine, on mine the three spring-loaded balls have to all engage the dimples equally, but I can turn it with one hand that is on the far side of the fixture from the spinning wheel, and count the clicks. With the single screw lock a slight indexing error won't matter.

Actually you need only as many dimples as you have flutes to sharpen, which for me is 8 on shell mills.

Reply to
Jim Wilkins

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