Sharpening Milling cutters

Just wondered how many of you chaps sharpen your milling cutters, i made the Harold Hall grinding rest a while ago and today I made the simple oblong block and sharpened some end mills the result was ok but I do see a difference compared to a new cutter, but it's the first time I've done it so will improve over time hopefully, how many sharpen there cutter's opposed to buying new ones.

Alan.

I do, with reasonable success, but so far only on the ends. I want to make an adaptor for 1mm angle grinder discs, for cutting gullets across the end of cutters.

Neil.

I sharpen my milling cutters (end mills and slitting saws) using the HH grinding rest and am very happy with the results. Below 1/4 inch though I just throw them away and buy new.

Russell.

Hello Alan - At the moment I do not have any facility for cutter grinding, or the room. Apart from that, I spent some years in a tool & cutter department and I think I would rather be doing something else these days.

I have collected hundreds of HSS cutters over the years from car boots and the like and being only a light user expect them to last me out. In order to eke them out I use a small selection of good quality carbide cutters whenever I can.

That is not to say that the ability to tiddle up the ends of the HSS tools would be quite handy - it would, but there is a cutter grinder business not far from me that will touch up my cutters for not a lot and if I ever feel the need I will head their way.

Rik

PS Saw a lovely example of a STENT tool & cutter grinder at the Midlands Model show last week..

I hone slightly worn slot drills with a diamond hone. The worn ones I try to grind to get them sharper, as Russell I don't sharpen the small cutters. They can be used to make round HSS toolbits for tu rning or flycutting. The slot drills I sharpen is used for roughing cuts, a new one for the final.

Thor

Edited By Trevor Drabble on 20/10/2013 19:45:24

I completed a Worden T&C grinder from Hemingway. (Completed? Is anything *ever* complete?)

Use it for lathe tools, but have not yet sharpened an end mill. I'm collecting dull ones, and this snowy upcoming Winter I expect to sit down and get proficient at it.

I really enjoyed the Worden build - although it was tough to get motivated to build a part (say, radius grinding attachment) after completion, the sense of accomplishment was really nice!

Does that help?

Another JohnS.

Couple of snaps above from the Midlands Show. The Stent as refered to by Rik plus something a little different. Sorry, did not know how to add text to the pics.

Trevor

Thanks guys, when i sharpened the end mills i went with the 5 degree Harold talks about in his book but i didn't put on the second edge at 12 degrees (didn't read that bit just started grinding, pillock i know) but they seam to cut well is this ok or do i need to do it next time.

Al.

On a side note, I'm about to modify my Stevenson Hex ER32 collet holder to put a clamp groove about 6mm/0.25" up from the base so it can be clamped with the axis vertically up on a milling bed.

I need this to allow cnc thread milling inside & outside circular objects while permitting easy zeroing of the machine - will zero the spindle in the X & Y axes then clamp the tooling around a bar in the spindle, and then clamp the holder to the bed. This is quicker & more likely to be exactly vertical than putting the Stevenson Hex collet in a vice, and it means I don't loose throat height from the depth of a vice either.

Should be a useful mod to an already useful little tool.

Regards,

Richard.

John' yes, AL & I have a surface grinder, have you made a jig to fit the cutter into, so you can sharpen them on the surface grinder? If so would you post pic's. We do have a jig to sharpen punches & chisels for it.

rob

Sorry john just seen the link on your post, didn't see it when I read it, silly me, that explains how you hold then.

> I'm about to modify my Stevenson Hex ER32 collet

Good idea Richard, but as they are hardened, let me/us know how you get on before I trash mine

Neil

Neil' why are you modifying the Stevenson Hex ER 32 collet? & what into bit small to become a space rocket! Have I mist something. Properly mist something, I live in the sticks, it's pigeon shooting season so no mail again.

rob

just read Richards post, all clear now. ( I think)

Edited By Robonthemoor on 22/10/2013 14:50:15

Hmm. Wasn't aware of that. Anyway, we shall see. If it's too bad, maybe I'll be forced to make the adaptor I dreamt up in a mad moment - a fixture to allow a 4.5" angle grinder to pivot vertically on the toolpost (after putting rather a lot of 'something' over the lathe to protect it from grit).

As for the reason why I need to modify it.

Well, I have a little cnc engraver/very light mill (as well as my Warco WMT300 combi lathe). The cnc machine has a fairly low gantry and I want to thread pen barrels, caps and sections by using thread milling (I need an M7.4x0.55, M12.5x.8 four start, M9.5x.5 and a couple of other fun sizes unavailable as taps & dies or as thread pitches on the lathe) . That means they have to be machined upright in the collet chuck. However, the pen barrel alone is 80mm long & the gantry has a clearance of 100mm. That really isn't enough if the Stevenson collet is clamped in a vice, and the collet nut prevents clamping down on the shoulders of the collet. So, I need to machine in a groove about 6mm up, width about 4mm by enough depth for a clamp to get a grip, say 2mm. Then I'll be able to clamp it down after zeroing the cnc machine for the thread milling.

My hope is to make this:

The pen is intentionally difficult to make with a lathe - it's intended to help me learn as much as possible about cnc as quickly as possible.

Regards,

Richard.

Does anyone sharpen horizontal milling cutters at home ? I have picked up a few lately, and while most were usable some could do with a grind.

Thanks john, i'll look into that fixture. As for slitting saws , i bought a job lot at an auto jumble a couple of weeks ago, i only wanted one or two for the occassional job, but the seller wanted rid of them and gave me the lot (about 70) for 40 euro and chucked in a few horizontal milling cutters too.

You didn't specify the difference but I suspect the cutting edges are not the same depth because if you are applying any force at all the rest, being quite high, will flex. We are talking tenths here. I suggest you make sure the end stop is very positive and the reference edge in each position has the same relationship to the cutting edge in each position. This means a very good concentric cutter holder. Then you need to make sure movement is silky smooth so no force is needed.

You might get some ideas off here and other articles on the Stent grinder. Since the Stent is a mini Clarkson the workholders follow a similar pattern to what was once used for actual production of new cutters not just resharpening.

Edited By Bazyle on 24/10/2013 10:03:55

Stub Mandrel:

I machined my Stevenson Hex ER32 collet holder last night. You were correct, it is hardened. I started off with an HSS parting tool, which had the edge knocked off in short order. Then I used carbide inserts for left & right shoulders to make a 6mm wide slot. The machine was working so hard that I stopped before cutting completely though the flats of the hex. The material was surprisingly ductile despite the hardness & formed big burrs on the downcut side of the hex. Finally, I used a file to clean up the 2mm deep notches I'd made in the corners of the hex, and found the cutting rate was much higher than I obtained with the lathe!

Anyway, the collet holder doesn't look pretty (in fact it looks as if it has been assaulted by an incompetent maniac with a file fetish), but it can now be clamped on the bed of my CNC without a vice underneath it or any other fixture. With a collet in situ, the top of the fixture is 67mm above the bed of the machine. Perfect. My experiments on thread milling start this weekend...

Regards,

Richard

Sharpening milling cutters in my Arduino controlled screwcutting lathe...trial run.

I made the Harold Hall cutter grinder which sharpens the end of the cutter quite well, however trying to sharpen the flute edges did not produce the clean edge you see on new cutters, so I decided to use the screwcutting facility of my Arduino lathe which can be programmed for virtually any thread.

Pic below shows an end mill I sharpened on H.H's grinder with cutter set up in lathe ready for a trial grind of the edges, you can see that the finish is a bit rough and unsteady due probably to not feeding the cutter against the grinding wheel with a smooth linear motion in H.H's fixture.

I used a Dremel fixed to the toolpost with a small grinding wheel, the pitch of the cutter is about 80mm and this was loaded into the Arduino's Spindle and Leadscrew program with the spindle rotating at 1 rev every 8 seconds.

I found that the secondary grind angle could be set up by starting the spindle rotating a little earlier relative to the Leadscrew motion startup, this was achieved by putting the grinding fixture a small distance from the initial start point of the primary grind set up so that the wheel hit the rotating cutter at a later time., ie no special measuring device needed.

I intend to make a jig which uses the H.H collet holding jig in order to re-set the cutter for each flute edge, however the results of the initial grind were quite pleasing with clean sharp edges and a nice finish.

I was surprised that the small resin bonded Dremel grinding wheel produced such a nice finish, I inclined the wheel at about 45 deg to the cutter axis, I finished the ends the normal way in the H.H grinder.

..Bob -.- -.- -.-