End Mill Sharpening

[Clive Brown 1Participant @clivebrown1]

[Clive Brown 1Participant @clivebrown1]

In the olden days, most of the end mills that I acquired had a centre-hole which enabled easy sharpening of the end-teeth on my Quorn.

Recent 4 flute end-mills now seem to have a pair of end-teeth that run fully across the diameter, making sharpening as I did it before impossible, without leaving a pip in the centre.

The only way round that I can think of is to grind that one pair of teeth out of the way with, say, a saucer wheel, thus rather spoiling the cutter.

Is there a better solution? Or are all end mills now "throw-away".

Perhaps I should say that I'm referring to cutters of 1/2" dia. or less.

[JasonBModerator @jasonb]

They are not throw away, just need sharpening with something that can sharpen "center cutting " milling cutters or you need to rethink your Quorn set up.

[RichardNParticipant @richardn]

I think a pair is gashes at 45 degrees to the cutting edges through the centre is the quick and easy solution with a saucer wheel if you have one- the centre portion has virtually no cutting effect anyway… while this may affect the aesthetic of the cutter, does it have a negative effect on the cutting action?

I find that once 'gashed' the cutter can be touched up several times before needing hashing again..

[mechman48Participant @mechman48]

How about gashing a gap in the middle with the edge of your saucer wheel? Then you'll still be left with a 4 flute cutter

George.

[Thor 🇳🇴Participant @thor]

Hi Clive,

You have, of course, checked Harold's website? I don't know if these may be of some help: link1 , link2. They are not using the Quorn, but should give some guidance. When I sharpen the centre cutting edges of end mills I do that much the same way as slot drills.

Thor

[michael howarth 1Participant @michaelhowarth1]

A few weeks ago after an episode of cackhandedness involving breaking a tap inside the workpiece I tried "drilling" it out with a small carbide endmill and was astonished at the ease with which it cut through the HSS. Could a hole be milled/drilled into your endmill in a similar way?

Mick

[KWILParticipant @kwil]

RichardN,

Purpose of the over centre teeth is to permit plunge cutting (normally done with a slot drill), You cannot do that with a normal end mill.

Horses for courses.

[Jon GibbsParticipant @jongibbs59756]

To save changing to a saucer wheel on the Quorn you can also produce the gashes with a cut-off wheel in a Dremel.

Jon

[Stewart HartParticipant @stewarthart90345]

Hi

Don't get mixed up with slot drills and end mills:- slot drills you can plunge cut and usually have two or three flutes, end mills are for cutting horizontally, the four flute jobs that cut across centre are a bit of a mix between the two personally I wouldn't use them as a slot drill

I've reground all these cutters the two on the left are slot drills the four flute on the right is milling cutter, the two slot drill I re-cut the gash with a hand held dremell I gashed the end mill on my home brew cutter grinder you can see I've reground it quite a few times and the original centre hole has gone.

This is how I gashed it

And sharpended the face

And proof of the pudding EN8 milled on my X3

Stew

[BazyleParticipant @bazyle]

I think this type has been introduced for CNC to give the features of a 4 flute but also the plunge capability so save swapping to a drill or slot drill to start a pocket. I've not found a decent picture on the web equivalent to Stew's above showing what this configuration looks like. But given that a Quorn can do anything and the mfr had to make them it's got to be possible with a bit more thought.

[JasonBModerator @jasonb]

The sharpeners such as the EMG-12 that ARC sell do the gash cuts as part of the sharpening process but leave one flute long so you can still plunge or ramp in with the cutter.

[Dave HalfordParticipant @davehalford22513]

I have several 2 flute cutters sharpened 'off' centre, they plunge just fine

[Anonymous]

Posted by Bazyle on 04/09/2017 20:16:54:

I think this type has been introduced for CNC to give the features of a 4 flute but also the plunge capability so save swapping to a drill or slot drill to start a pocket.

Correct, but it's normal to ramp or follow a helix instead of plunging. That way the centre isn't trying to cut at zero feedrate. When using a ramp or helix I normally reduce the feedrate to about half to account for the fact that only some of the teeth are cutting at the centre, and for the full length of cut on the bottom edges. Something that doesn't happen in normal constant depth milling.

Andrew

[Stewart HartParticipant @stewarthart90345]

Posted by Andrew Johnston on 04/09/2017 21:23:55:

Posted by Bazyle on 04/09/2017 20:16:54:

I think this type has been introduced for CNC to give the features of a 4 flute but also the plunge capability so save swapping to a drill or slot drill to start a pocket.

Correct, but it's normal to ramp or follow a helix instead of plunging. That way the centre isn't trying to cut at zero feedrate. When using a ramp or helix I normally reduce the feedrate to about half to account for the fact that only some of the teeth are cutting at the centre, and for the full length of cut on the bottom edges. Something that doesn't happen in normal constant depth milling.

Andrew

That makes sense.

I have a few TC centre cutting 4 flute cutters in my box picked up from the factory scrap bin that I intended to sharpen one day but never got round to, I'll see if I can take a picture of them later, when I'm shaved and dressed.

Cheers

Stew

[Stewart HartParticipant @stewarthart90345]

Ok

Her's the picture you can see that the cutter has been well used with the edges chipped but you can see the centre cutting configuration.

Stew

[Danny M2ZParticipant @dannym2z]

After using my 'Harold Hall' simple grinding table (with square block attachment) to re-sharpen the bottom edges of a few end milling cutters I noticed that the center gash/hole was getting a bit small so I used a small conical stone in my tool-post mounted Dremel to restore the hole. It worked.

(I was always trying to figure out a practical use for some of the stones).

* Danny M *

[Anonymous]

Stew: I'd hazard a guess that the cutter shown is keenly priced far eastern? It's not clear how the edges meet in the centre. This is what I would expect from professional cutters:

Of course, when all is said and done the cutters are intended to cut mostly on the sides, not on the ends.

Andrew

[JasonBModerator @jasonb]

Similar to this Rougher

And a not very good photo of a sharpened cutter retaining the two longer end cutting flutes

[Clive Brown 1Participant @clivebrown1]

Thanks for all the interesting comments. My cutters look like the one pictured by Stewart Hart, they could well be "keenly priced far eastern". They're just labelled "Clarkson"

I take aboard the comment that they won't cut well at their centre, so I think that a gash across the middle might be the best way. I haven't got a Dremel, so I might try mounting a 1 mm thick abrasive disc in the Quorn.

I'm sure Prof. Chaddock would have devised a method of restoring the full edge, but the set-up would be a very precise one, so I'll opt for the easy way!

[petro1headParticipant @petro1head]

Sorry to bring this back up but I found this that may be usefull

Edited By petro1head on 22/10/2018 12:03:01

[Pete RimmerParticipant @peterimmer30576]

I sharpen those end mills on my Clarkson grinder by holding them in a R8 collet and using a simple index wheel on the back. It works very well indeed.

[not done it yetParticipant @notdoneityet]

Yes, better to keep as much grinding well away from the lathe as possible, or at least protecting the ways from errant grinder dust.

[petro1headParticipant @petro1head]

There is always one that has to state the bleeding obvious

[Howard LewisParticipant @howardlewis46836]

The late, and lamented, John Stevenson used to sharpen End Mills and Slot Drills on the EMG12 and EMG 20.

Does anyone else offer that service now? I lack the courage to try regrinding on my Worden!

Howard

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