APT High speed, high hardness end mills - anyone used them?

I have a little emergency project on the go - re-creating the locking wheel nut key I unknowingly lost a few weeks back and now need!. I've sorted out the design OK, but the only suitable material I have knocking around is some 25mm 304 stainless round bar, which is likely 50HRC absolute tops, probably less as I cut a billet off the rod with a hand hacksaw no probs. Now I have a couple of the above mentioned cutters which might do the job, but has anyone ever tried them on stainless, and if so what sort of DOC and feed worked best please?

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Originally Posted by Voicecoil

Now I have a couple of the above mentioned cutters which might do the job, but has anyone ever tried them on stainless, and if so what sort of DOC and feed worked best please?

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Nobody can answer that,.! You haven't said the tool size for starters and APT makes lots of different cutters in various grades of materials and with different coatings.
However, even if you had given that information every machine is different and they don't know anything about your machine so at best it could only be a ball-park figure. Stainless can be bare to cut at best of times so trying to advise someone without any of this info is impossible.!

Have you tried taking the locknuts off with a gator grip? Attachment 27801

What style of locking wheel nut?

The biggest issue with stainless, is you need to be continually cutting. The moment your cutter rubs, it'll work harden, and then you need a lot more power and DOC to get through the hardened bit.
You can machine 304 with HSS, it's just carbide and coatings last longer.

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Originally Posted by JAZZCNC

Nobody can answer that,.! You haven't said the tool size for starters and APT makes lots of different cutters in various grades of materials and with different coatings.
However, even if you had given that information every machine is different and they don't know anything about your machine so at best it could only be a ball-park figure. Stainless can be bare to cut at best of times so trying to advise someone without any of this info is impossible.!

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I have 6mm and 4mm High Speed, High Hardness cutters (as per the thread title) which APT recommend 16K and 20K RPM for which should work OK with my spindle which gives constant power between 12K and 24K.

They're the 4 pin style, like the cursed Peugot things, with a centre boss that's designed to shear off if you try welding anything onto it :thumbdown: Thanks for reminding me about the quirk of stainless, I learned that a few years ago when making an underwater camera mount for one of the Springwatch guys: yeah once you start you just have to keep going 'til you're through, no job for the fainthearted ... which was one reason I want to get a decent strategy planned before I press CYCLE START.

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Originally Posted by cropwell

Have you tried taking the locknuts off with a gator grip? Attachment 27801

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No, I'm not sure how well they'd work on this type - it will depend on the size and spacing of the pins: there's basically 4 off 4.4mm holes on a 60 degree, 90 degree and 75 degree interval on 19.0 diameter, and a centre locating boss: but thanks for the suggestion anyway, if I can find one locally I might give it a try.
Attachment 27805
If you could get 3 or 4 pins in each I guess it would likely work, if it's just 1 or 2, I suspect not, the local garage have done them up well tight.

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Originally Posted by Voicecoil

I have 6mm and 4mm High Speed, High Hardness cutters (as per the thread title) which APT recommend 16K and 20K RPM for which should work OK with my spindle which gives constant power between 12K and 24K.

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Not being funny here but you can't ask questions about feeds n speeds and expect any sensible reply if you don't give all the details. You say 4 and 6mm but no mention of # flutes. Then you still have the machine to factor into the mix.? Is this a router with 2.2Kw spindle.? or is it a mill.? These make a big difference to how you would tackle this job and esp this material.! . . For instance, I wouldn't even attempt to try to cut Stainless with a router unless it was built like a brick shit house.!

Perhaps I'm missing something but it looks to me more like a job for the lathe (to make the fundamentally cylindrical body), followed by the mill (to position and drill 4 holes), then bang some pins in the holes. How were you planning to use the end mills?

304 isn't actually very hard (typically HRB 70 ie it doesn't even make the bottom of the HRC scale) - and being stainless you can't through harden it either. Machineability is different to hardness. Some form of carbon steel would be a better, allowing you to machine it easily and then harden it with a torch and a bucket of water. Then you'll get something nearer HRC60.

If it's an emergency and you are short of carbon steel, how about using an old cold chisel, crowbar etc as a donor. Cut a bit off with an angle grinder, heat it up to a cherry red and let it cool. Then you should find it easy to machine. It's easy enough to harden up again using the bucket of water etc. You can get tools like this at Aldi etc for peanuts if you don't have any.

While you are figuring this out, you could be letting some penetrating oil slowly do its business....

+1 regarding Muzzer solution/ turning first op (don't machine the counterbore yet)then setup for dividing and drilling the four holes (drill right through so you can fuse the ends of the pins to the body) return to lathe and do the counterbore, make and fit pins.