Jackhammer bit heat treating....for a rental yard | Page 2 | Heat Treating | Forum

I took some tubing to a machinist pal of mine to be squared up and he asked me about this very thing.

He needs to sharpen and heat treat a large breaker bit. This thing is like 3-4" diameter round and 36" long. His plan was to heat the tip and then using a trackhoe to hammer the tip into a large V swage.

I relayed some information I read on one of these blacksmithing websites. 😉

He's just gotta figure out those pesky little details, now :p

His process won't work. First, most machinists have no idea what a forging heat is, they usually think they can heat it with a rose-bud to a dull red and then it's easy. Second, when you forge a point you are making the part longer. Driving it into a "V" swage will not do that. A 15 degree saw fixture, M-42 blade and 100SFPM does the best job. I have done tens of thousands that way. Even did it that way making new ones.

They are already heat-treated to about 50 Rc and are a deep hardening steel like 4340 or EN30-B.

We normally use a 400 ton forge press, manipulator, and quench in oil, no temper, have not had any problems, but then I have been doing these for about 30 years, so I may have picked up some tips along the way.
It would be like you going to a machinist mate and saying I need to cut a 1/2" wide double helix acme thread on a piece of 4" bar for a marine winch application, I am thinking of using an old pushbike frame to drive it and a sharpened screwdriver to cut the thread, do you think it can work.

Grant;10384 wrote: Always appreciate your input Phil! But I still can't figure out how you oil quench down there when you're upside-down and all.:giggle::giggle:

I've hammered and pressed a fair number of them. Gotta watch out when someone like Phil says "oil quenched, no temper". From similar experience making tools for the shop from low-alloy steels "no temper" rarely meant quenching down to dead cold. While I did a fair amount of "no temper" quenching, it often meant bringing the part out of the oil at anywhere from wispy smoking to really smoking or even at the point where the oil would flash.

Pretty standard stuff in the shop, but the description can be deceiving.

OK Grant I'll use a disclaimer,
Now kiddies Old uncle phil here's a professional at this, so don't you go trying it at home
now will you!

We quench at about 800 deg C right down to hand warm, but we are quenching moils from 65mm dia up to 170mm dia in this manner, and we know it can be hard to get enough hardness in oil at the best of times in these sizes, so a straight quench seems to work OK, for the smaller moils we will burn the oil off the moil with the oxy torch after quenching to temper them.

And its not us thats upside down it's you guys, and anyway theres no such thing as gravity, the earth sucks,

Phil

Moil is what guys in new jersey put in there Buick... Hey Jimmy! We needs some moil ova heer!

Sorry. A moil is a point

Rob F;10525 wrote: Same as a Gat?

Lots of different terms used "Gat" comes from "Gad" point. A hundred years ago a gad-point meant a steel that was sharpened just on one side, just like it had been sawed off at a 20 degree angle.