[How do I?] Mill Hardened Steel

maker of things

maker of things

Hermit
Registered
Joined
Jul 23, 2014
Messages
347
I have a 3/8 micrograin carbide 4 flute endmill, a bridgeport and a import lathe qc tool holder. I want to use the first two to modify the third to allow a larger size tool. What is the recommended process? i.e low rpm + deep d.o.c or fast rpm and light d.o.c? I would prefer not to wreck the endmill, which is what would undoubtedly happen if left to my own devices.
 
Run at about 375 RPM at full depth and full cut, rather its .093" or .125". Feed rate is as fast as you can push it. And lots of cutting oil or spray mist preferred. Don't baby it! Don't take light cuts! You got to get under the harden skin on those import tool holders.
 
4gsr said:
Run at about 375 RPM at full depth and full cut, rather its .093" or .125". Feed rate is as fast as you can push it. And lots of cutting oil or spray mist preferred. Don't baby it! Don't take light cuts! You got to get under the harden skin on those import tool holders.
Click to expand...

I would suggest on the first cut follow his suggestion on feed and depth but hand feed as fast was you can crank the handle. If you feel comfortable how it cutting then next cut use the power feed on the rest.

Good luck with your project, post some photos when finished.
 
I didn't know those import tool holders were actually hardened!:) ARE YOU sure they are actually hardened?

But I find "hand crank as fast as you can" pretty questionable. My genuine Hardinge tool holders are blacked,but not at all hard. Maybe they left them that way so we could mod them. They wanted $275.00 PER HOLDER back in the 90's,so they MUST be good!:)

I said to heck with that and made up 20. 10 for my HLVH and 10 for my partner's HLV.

I'm thinking you mean you want to remove material from the slot to hold larger cutters? How much?
 
Last edited:
george wilson said:
I didn't know those import tool holders were actually hardened!:) ARE YOU sure they are actually hardened?

But I find "hand crank as fast as you can" pretty questionable. My genuine Hardinge tool holders are blacked,but not at all hard. Maybe they left them that way so we could mod them. They wanted $275.00 PER HOLDER back in the 90's,so they MUST be good!:)

I said to heck with that and made up 20. 10 for my HLVH and 10 for my partner's HLV.

I'm thinking you mean you want to remove material from the slot to hold larger cutters? How much?
Click to expand...
Well, they are harder than a chinese hss end mill.o_O Seems to be case hardened. Yes, just need to open it up about .100"
 
Chinese HSS end mills are generally HARDER than USA ones! And,more brittle,too. Some pros I heard liked them as they's mill some harder metals that USA mills would not cut.

So ,the holders must be hard! I hope you don't break your carbide end mill. How about heating the holders up enough to anneal them? Sand a surface clean so you can see the color of the metal. Remove the set screws FIRST!

Then,with a Mapp gas torch,nestle the holder in a corner that you make out of 3 or 4 bricks(DRY BRICKS!) Heat the tool holder till it goes up to blue,then up to a gray color. Let it cool slowly in the air. It should be annealed. After it is cooled off to ROOM temp.,test it again with a fine cut file. It should be soft enough to file easily.

Really,those holders do not need to be hardened. I have been using my non hardened Hardinge copies for 15 years,along with the ONE real Hardinge tool holder I was lucky enough to get,along with the tool post. They are fine. Indeed,years later I did mill one of them larger to hold a special knurling tool. I don't carelessly clamp cutters down over small chips,etc. and,they are as good as when I made them.
 
Maybe not glass hard, but the file does skate easier than on 1018. Maybe they just work hardened the material by grinding too aggressively or the coolant pump broke LOL. I only need to do one so it's not too big a deal.
 
Use a very sharp new milling cutter slow speed with a flow of cutting oil NOT a Pump can Do not use a slow feed
If is very hard you need more than one cutter
If can hand grind the spot you planning milling first to remove any case hardening

Dave
 
I agree about hand grinding to remove the case. A good idea,as Asian case hardening is usually not very deep. You can't get all the way down into the bottom corner,though. But,that might be enough to keep from breaking your cutter.

If it were me,however,I'd just anneal it. Easier on your expensive cutter,and hardening not really necessary for a nom high production holder where different guys might be using(or abusing it) in a factory.
 
You must log in or register to reply here.
Back
Top