Anyone here know about machining HSS?

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Engineeringtech

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Wondering if anyone here has done any machining and hardening of HSS like M2 or M4. I've never worked with the stuff. It's expensive, so I'd rather not invest the money, if it's going to be impossible with my equipment. I have an idea for a circle cutter (similar to a trepanning tool) that would proably be more successful with a HSS blade. I'd need to cut some .140" wide slots, 1" long in 1/8" thick flat stock. I don't have a furnace, but have been very successful hardening and tempering tool steels like O-1, A2, W-1 with a torch. McMaster sells unhardened M4 flat s with a hardness of B95, and yield strength of 60,000 PSI. I have carbide end mills and an old tired Bridgeport to work with. No grinding equipment here except for a bench grinder. Would the M2 destroy the end mills in short order? Think I could control the heat treat?

I suppose I could also try something like D2, which is known for wear resistance, but I have never cut and heat treated that either.
 

WOB

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Look up the procedure for hardening HSS and I think you can answer your own question.

WOB
 

Hopper

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+1 on what WOB said. Not really feasible for the home shop. It is more usual to make the body of your special tool out of mild steel, machine slots in it where you want the cutting edges to be, and silver-solder (or silver-braze as the pedant squad likes to call it these days) pieces of HSS lathe toolbit blanks into the slots. The HSS can be ground to shape on the bench grinder before being silver soldered into position.

Another alternative is to make the tool out of gauge plate (carbon steel) and then harden and temper it with a torch, but it is not as hard or durable as HSS. Okay for low volume jobs in the home shop though, at slow cutting speeds.
 

Engineeringtech

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Look up the procedure for hardening HSS and I think you can answer your own question.

WOB
Pull the datasheet on most any tool steel, and the accepted "procedure" calls for a furnace, special quenchants like salt baths or cyanide, very controlled timing, etc. I have to work with what I have available, and that's a propane torch. I experiment. I've been very successful through hardening O1, W1, A2, 4140, and case hardening other steels, as long as the parts are small. I just hoped someone here had tried working with HSS (with or without the furnace) and would let me have the benefit of their experience.

Still waiting for someone to tell me if the UNHARDENED M4 that McMaster carries can be drilled, milled. The Rockwell rating would seem to indicate so, but I also know the material is very tough. I guess I will have to buy some to try.
 

Engineeringtech

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....... It is more usual to make the body of your special tool out of mild steel, machine slots in it where you want the cutting edges to be, and silver-solder (or silver-braze ....HSS lathe toolbit blanks into the slots.......
Thanks. That was a fallback position for me. Problem is, I have never mastered silver soldering with a propane torch. I did some silver soldering working for a job shop 28 years ago. They used something they called "Easy Flow". I bought some a couple years back. Silvery wire about 1/16" in diameter. I played with it for a few days until the boss discovered it had cadmium in it, and took it away from me. (OSHA is very strict about ventilation requirements for cadmium.) I bought some other brazing rod that was about 5/32" diameter, brass colored rod, coated with an orange colored flux. No matter what I tried, I was never able to get it to flow or adhere to anything. I couldn't get the work piece hot enough to get the rod to melt, and if I got too close to the rod with the torch, it just melted back and beaded up. So no, I'm not a brazing expert!
 

WOB

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=Still waiting for someone to tell me if the UNHARDENED M4 that McMaster carries can be drilled, milled. The Rockwell rating would seem to indicate so, but I also know the material is very tough. I guess I will have to buy some to try.
Annealed HSS machines easily with carbide inserts. I have never tried it with HSS cutters, but I suspect it can be done as I have cut it on a band saw with bi-metal blade.

WOB
 

Hopper

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I reckon it would be easier to teach yourself to silver braze with modern rods than to harden and temper HSS without a temp controlled furnace. From what I remember in the very distant past, HSS has a very narrow range of temps so the old heat her up until she glows xxx color in the dark trick does not really work. But you dunno till you try...
 

TonyM

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They used something they called "Easy Flow". I bought some a couple years back. Silvery wire about 1/16" in diameter. I played with it for a few days until the boss discovered it had cadmium in it, and took it away from me. (OSHA is very strict about ventilation requirements for cadmium.)
Cadmium in silver solder, or any other similar products, has been illegal in the EU since 2011. I am surprised OSHA still allow it in the USA. Unfortunately for us the price has risen substantially because more silver is used these days and the flow temp is a bit higher.
 

nautilus29

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You shouldn't have any issues machining the material unhardened.
 

lohring

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I once worked for McCrosky Tool Company. Machining high speed steels and carbides was their business. It takes special grinding wheels to machine them in the hardened state. That included grinding precision serrations in milling cutter blades. They used a variety of temperature controlled salt baths to carefully harden and temper the steels. In the unhardened state normal cutting tools work fine.

Lohring Miller
 

Wizard69

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Cadmium in silver solder, or any other similar products, has been illegal in the EU since 2011. I am surprised OSHA still allow it in the USA. Unfortunately for us the price has risen substantially because more silver is used these days and the flow temp is a bit higher.

The EU makes a lot if things illegal without justification. The trick with all hazardous materials is in the handling. That being said home shops probably should avoid the more dangerous materials.

To look at it another way the EU went off its rocket over lead but leaded steel is pretty popular in home shops. I seldom see indications of lead poisoning in home shop machinists.
 

Engineeringtech

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I was away from this thread for a long time due to family issues. My apologies for abandoning the thread without thanking everyone. Thank you.
 
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