Sharpening End Mills on a Junked Disk Sander

[vtsteam]

Because of interest elsewhere in the forum, here is a brief description of an end mill sharpener I've been using for several years, built from an old broken tag-sale belt/disk sander.

The start:

[vtsteam]

The belt casting was broken but the disk was still good. I cleaned it up and added a new 80 grit disk to try it out (first photo).

I tried it initially for grinding lathe tool bits with a different jig than I ended up with. But then it occurred to me that I could use the existing table slot with a slide to possibly grind end mills. To make that slide I hunted up some small pieces of 1/8" flat bar -- one to fit the slot, and the other (2" wide) to serve as the sliding table. (second photo)

[vtsteam]

I have a spot welder that I got a couple years ago from Harbor Freight. After cleaning off the two pieces of metal, I welded them together, and milled the narrow strip to fit the slot in the sander's table. It was a little oversize to start with -- 0.5" while the slot was 0.460". If you were building one like this you could also silver solder them -- or even probably soft solder. There is very little stress on the parts. Or you could mill it out of the solid -- a piece of 1/4" plate.

[vtsteam]

I needed some cross pieces to serve as guides on the sliding table. So I spot welded one on at 90 degrees. But the angle needed for end mills isn't 90 degrees so it needed a little modifying.

First step was to blue the slide piece, and mark a line 1-1/2 degrees off square. I decided to do this using a little math since that's a pretty small angle to mark with a protractor.

The cross piece measured 2.10" long, and I wanted to know how far out to make a mark at one end to yield a 1-1/2 degree angle. I figured the tangent function would do it.

With the pocket calculator TAN of 1.5 degrees x 2.1 = .055. So I needed to make a mark .055" in from one end, and then connect it to the other end. This is what it looked like:

[vtsteam]

Then I started filing to the line. I could have milled it, but I didn't have a rotary table. And by the time I set up the mill and got that heavy vise over to 1-1/2 degrees, set the cutter height and did edge finding, etc.....well it was a lot quicker and easier to just file it  to the line. I might have spent 5 minutes total.

[vtsteam]

I decided to use some 1" square aluminum bar stock I had -- cutoffs I bought in a barrel at auction once, as end mill holders for the sharpener.  I took one of the aluminum blocks and another strip of 1/8" by 1/2" steel, and positioned them to get the exact space needed from the one I just filed. I clamped the steel strip down with a welder's clamp. (first photo)

Then I removed the spacer block and spot welded the new strip in place:

[vtsteam]

Then I took three of the aluminum cutoffs and faced, drilled, and reamed 3/8", 1/2" and 3/4" to fit some end mills.

[vtsteam]

It turned out that for shorter mills the slide can be on the close side of the sander's table slot:



And for longer mills, I can turn the slide around so it is on the other side of the sander's table slot. The 1-1/2 degree relief angle stays in the same orientation, either way. The blocks can be rotated 90 degrees and replaced in their slide to sharpen each of 2 or 4 flutes.

[crueby]

Not seeing amy pictures...   

[vtsteam]

Sorry Chris, looks like the problem is that the images are old http hosted, and some new browsers now insist that they be https. I guess I'll have to re-do all of the images to make them work. But they will no longer be in-line, which sucks.

This will take me a little while to do.

[crueby]

Can see them now as the attachments,  thanks!!

[vtsteam]

Okay, fixed..... where was I...?

Oh yes, besides the small angle added to the slide, there is also the disk sander's tilting table. That sets the axial relief angle (I believe it's called) for the end mill. I don't remember what it is set at, I'll measure it in the shop tomorrow, but you can also get that from an existing end mill by just eyeballing it next to the disk. I think they vary a little anyway.

Note that to grind a mill you are just setting it at the edge of the disk with one lip on the disk.

Okay, at first I decided to give myself a big challenge off the bat using the grinder..... I figured I should pick a bad mill from my donor stash -- this was a rusty victim of my tiny shop's humidity, and spring flooding, plus about ten years of neglect.

[vtsteam]

First, to remove the rust, I put it in a cup of water and washing soda, and electrolyzed it during lunch break.then rinsed dried and set it in one of the holders.

[vtsteam]

I used two different size dull, abused, but freshly sharpened mills (using the sander) for this piece of chewey hard to mill steel. The smaller one milled the slot, the larger and rusty one mentioned above bored the hole.

Not bad for a broken tag sale disk sander used as a cutter grinder!

Now does this replace a Quorn? Uhhhh, no. It only grinds the ends of a mill. But is it useful? Absolutely. I was given a big box of HSS endmills thrown out as salvage, and 90% of them are totally usable for my purposes, with this grinder.

BTW if milling a slot, one way of preserving the edge sharpness of an end mill is to chain plunge cut the slot first, overlapping plunges less than half the cutter diameter. THEN doing the final milling of the slot to clean it up. This puts most of the wear on the end, rather than the sides.