End mill regrinding

I wonder if I could get your thoughts on sharpening and mills / slot mills.

I have a Clarkson tool and cutter grinder. I have been learning to sharpen my blunt end mills.

Some people say sharpen the end only (which is reasonably easy ...now).

But I notice my mills will normally be cutting in a horizontal plane. This suggests the bulk of the cutting is made by that small part of the fluted side next to the end.

If my observation holds water then any sharpening would need to be both end and flutes.

What do others think please?

Also can anyone advise the best angle to relieve the end cutters, not the 5 degree angle but the one the raises the cutters outside edge over the centre. I have been using 2.5 degrees, but not sure this is enough.

Many thanks

John

I think it depends on how deep cuts you take and so how much of the flute is worn. If you just grind the end teeth then you need to cut back to where the flute is sharp - normally I think it's the corners that get rounded so you don't need to take off a lot. However you may need to re-gullet the cutter at some stage. As for the "dish" angle, I'd have though that 2.5 degrees is too much! The greater the angle the harder the corners have to work. I normally use 1 degree.

I've been using a Stevenson's sharpening fixture of late and this uses an angle of 2°. If it was good enough for him, it's good enough for me and gives perfectly acceptable results.

Have a look here

John

I rang Dormer tools Ltd and they sent me a free handbook with lots of information on sharpening cutters taps and drills. I just rang and asked for customer services 0870 850 4466 they are at Chesterfield.

David

Or alternatively if you are only concerned with creating flat surfaces you can with ease grind 2 45degree cutting surfaces on the tips of the cutter. This is even easier with end mills. This will give you a very robust cutting edge of 135 degrees which lasts much longer than the usual tip cutting cutters (if that makes) sense, and does not require the sharpening of the flutes or much removal of metal. I find this gives a super finish and can at a pinch be done by hand and eye in the same way one would sharpen a drill.

regards Martin

Don't understand that Martin, please can you do a drawing or photo.

In my experience its the corner that wears out first and the edge of the flutes stays sharp for much longer. I usually sharpen just the ends but periodically give the edge of the flutes a very light grind. This does of course change the diameter of the cutter slightly.

I recently purchased a Chinese copy of the Deckel SO tool and cutter grinder which can grind both ends and flutes of cutters with ease. Best thing I've bought for the shop in years...

David, would you please let us know the name of the booklet when it arrives, so we can search for a downloadable version, rather than troubling Dormer.
Thanks

Bill

Like this

Chamfer end mill

Ifoggy is correct it's the corners that go. With a chamfer the cutting tip has more metal around it so is more robust and will stay cooler and in consequence last longer. Finishing end mills have a slight radius on the tips so this is a sort of half way house.

regards Martin

How often do you use the full length of the cutter, not very often, so total waste of time sharpening the diameter, all you are doing is resharpening a fairly sharp cutter. Most model engineers only take silly little cuts so it is the corners that wear therefore a good resharpening of the end will do the job. The cutter end should be hollow ground by 2 degrees to ensure only the tips cut. If you have a spare cutter sharpen the end and then sharpen a five degree angle up the flute for a length of about 5mm, every time you resharpen do the end and side and you have the best of both worlds, sharp end and side, it is also a very economical way of sharpening a cutter, it will not give square corners so rough out with it and change to your best cutter for finishing.

Lots of really helpful advice here - thanks.

2° angle to centre seems to be popular.

I have both a small Emco mill and a big beast. The beast (AEW Viceroy) can cut 1/4 inch with a 20 mm mill.

But for the Emco size I can see it just makes sense to return the face back to the sharp flutes - no more than 30 thou in my case.

Martin - I like the idea you suggest. Basically making a sort of fly cutter but with more cutters. I will give that a try.

Interesting link from John Hinkley - I had no idea these existed - thank you.

John