Sharpening carbide end mills?

[kevin.decelles]

Well, add one of those to my wish list


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[RobinHood]

You can make your own using a spindexer as a starting point.

Check out this Darex Air Bearing:

 

[Mcgyver]

So If I'm following this, the air supply does not 'rotate' the spindle, simply enables the smooth manual turning (rotational) and lateral (left/right) movement?

The air bearing literally is a bearing of air. The spindle floats on air (the gap between housing and shaft is precise and small, such that the shaft floats. It consums a surprisingly small amount of air) and has almost no friction. The great advantage of this is that you get sensitive, smooth operation pulling the flute over the tooth rest....which of course is how the helical path is determined.

A few tool grinding thoughts. I've done my share of endmill and milling cutters and think a T&CG is a great shop addition. You can sharpen carbide, but of course you need diamond wheel. I'm not crazy about doing so because of the cobalt it puts in the air (bad for you, its a binding agent in the carbide). Frankly I see little reason for using carbide endmills in the home shop - few of us would have a vertical mill capable of taking advantage of them. So mostly I use and sharpen HSS.

imo you don't need to worry about coated carbide EM's. I believe most sold are not coated. Coating can give improved removal rates and wear, but so what? So does coated HSS but you still regrind them. It performs after grinding just like a new (non coated) carbide end mill

I've never tracked how many regrinds you can get, it'll depend on the diameter of the cutter, but for a larger EM 10-20 wouldn't surprise me. You're not taking very much off. Because its easy to end up acquiring large quantities of dull but never ground endmills for next to nothing, I'll never find out (how many grinds you get). Dull un-ground EM's are just too plentiful. Between ones I've dulled and ones that came in door as part of acquisitions, there's probably 200 in the pile now. I let them pile up then batch 'em. I almost have to relearn how each time but when batching in bulk this way you get fast, Who knows when I'll get to them - the sharpened pile is still a lot bigger!

The time consuming part is the end, which mostly, I don't worry about. Unless you are plunging you're always cutting on the side not the end of the EM. I keep a good stock of ones with the ends done so have them when plunging is necessary, but its not 5% of time and not futzing about grinding the end makes regrinding endmills really fast.

You need an air bearing to sharpen end mills. Some will argue against that, and I suppose they are technically right but I'm not grinding one without an air bearing so in my shop I'm right . It just makes a miserable task so easy. Mine takes 5C collets as to all the Harigs I've seen which is what I'd suggest - they have to be the cheapest and most plentiful collet there is

I've got a two T&CG grinders. The floor model I did a ground up scraping job on and its perfect. I do a lot of cylindrical grinding on it and can fairly confidently work to a tenth (that accuracy isn't so much need for tool grinding, but its nice having an accurate machine). The bench model (Chevelair (Taiwan, ok quality) knock of of the post model cuttermaster) I would say is the best all around format for the home shop. Compact and with a range of tooling, it can do most of what a bigger one will do. I've got a Deckel but hardly use it. The home shop man is ingenious and you can figure out how to grind an endmill on one, but its a bit a square peg in a round hole in my view. A grinder for endmills really needs that horizontal longish air bearing to do a great job, at least imo

A few T&CG photos to make it more interesting

 

[Janger]

Great post McGyver! Nice pictures. For your Chevelair I note the castings are maroon and cream coloured - is this a machine made from two machines? Also it's a little hard to tell but it appears the table & airspindle are not attached to the column holding the wheel - do you have to align the two parts?

 

[Mcgyver]

thanks.....not a frankengrinder.....just the Chevalier two toned paint job. Fairly common for that brand afaik.

The table, er I guess really the saddle, rides on the same base casting the post is mounted to. You can rotate the post, as in the second photo where I'm gouging a rotabroach. If you want it dead on, just dress from the table, buts often (usually?) an advantage to have it a bit off. i.e. of you dressed from the table, you rotate the head a degree or two...leads to less rubbing and heat. I mostly just dress with a norbid stick by hand and put some relief on the wheel behind the cut.

I've since added a home brew mist coolant system to this machine and with that you can really hog on it. Almost like plunge grinding when you are saying doing the roughing cuts on a lathe bit

 

[PeterT]

Very interesting stuff Mcgyver. What kind of line pressure does your air bearing require? Anything special like needs to be run through a dryer medium?

 

[Janger]

In the last picture Mcgyver are you making a ground collet?

 

[Mcgyver]

Last photo is regrinding a spindle for a Schaublin 70, a current reconditioning project (A project I did in my head in an evening....in reality 4 months later of every moment of spare time I'm maybe 1/2 way there...penance for something no doubt). Tonight am grinding gibs.

Those plane bearing double taper bearings are imo the most difficult things to get right, there's a 45 and 3 degree section on the inboard side and they've got to mate perfectly with the bearing. The goal is Swiss precision instrument lathe quality. Its really really nasty getting two axial tapers to mate! Did the last by scraping and a final fit with non embedding lapping compound. Didn't like doing that, with lapping compound, as you are never suppose to lap tapers, but it was super fine grit and basically just took the burrs off

Air is just shop pressure, I think around 115 which iirc is about right for them. No special dryer, it would be nice to have one but it hasn't proved neccessary. No rust and it works beautifully.

 

[Janger]

I got the EMs back from Taylor tool works. Sharpened and recoated. $160 including pick up and delivery. 3/4 EM diameter now measures 0.7358”. I’ll try it out and give my impressions.