How to round corners on end mill

Yes, of course. They are called radiused, or rounded-corner, or bull end mills. Look in any of the tool catalogs, like MSC, J&L, KBC, Travers, Quad City, etc.

Without a tool and cutter grinder, it would be pretty hard to make one.

Jon

I know how I do it...try to cut something really hard.

We all knew that one was coming, didn't we...

To do an accurate job you need a tool and cutter grinder with a radiusing attachment. It is a big help if you want the radius accurate and even on all flutes.

If you can live with not so perfect results, a little carefull grinding on a bench grinder, and frequent checks against a radius gauge of the correct size can get you through. I have done this on 2 flute cutters a couple times and it worked well enough, but I was not exactly making parts for NASA either.

Garr Tools and lots of others sell bullnosed endmills with a wide selection of diameters and radii. For a price. Not unnaffordable, but not excatly bargain stuff either.

You may be able to get radius grinds put on an end mill that you already have, if you can find a tool and cutter grinding shop near you.

Cheers Trevor Jones

============= What you are looking for are called "bull nose" end mills. Used extensively in the aircraft industry to avoid sharp corners/stress risers. IMNSHO these should be *MUCH* more widely used. The rounded corners last longer and give a better finish and sharp inside corners break on things other than aerospace.

see:

Unka' George (George McDuffee) .............................. Only in Britain could it be thought a defect to be "too clever by half." The probability is that too many people are too stupid by three-quarters.

John Major (b. 1943), British Conservative politician, prime minister. Quoted in: Observer (London, 7 July 1991).

I think it's my turn...

Nonsense!

I've hand ground end mill corners with radii countless times. Even full balls, which are better purchased than hand ground. Use a radius gage and go slowly, running an aluminum oxide wheel, well hand dressed (not with a diamond). Keep clearance in mind as you grind. With careful work, you can achieve .005" precision easily. Do a final stoning to blend any irregularities. Remember, only the highs will cut, so try to keep the multiple lips ground evenly so the finish is good and you can use a reasonable feed rate.

Harold

On Thu, 07 Dec 2006 03:43:59 GMT, with neither quill nor qualm, "Tom Gardner" quickly quoth:

OK, roll up your sleeve and bend over. Do you want regular or ethyl?

- Press HERE to arm. (Release to detonate.) -----------

Or have motor spinning the wrong way ;)

With a large radius like that, an alternative would be to leave a step and finish with a 1/4" ballend mill.

Fred