Un workable steel

This raises a somewhat off topic issue of motor ratings.

The motor plate will have the hp or Kw output on it and right next door it should have the rating as CONT or INT.

CONT gives you continuous output at that power output all day. INT gives you intermittent power output for something like an hour or less. Then it needs a cool down period like a welder does and so must be run lightly loaded for a while.

Some machines with electric speed controllers will blow the electronics instead when you stray outside the duty cycle. Trouble is it's difficult to tell how hard we are driving our motors.

Same result though. Ouch, my wallet hurts.

Dave.

Equivalent to EN8?

Neil

Just out of interest, AISI 4140 is closer to EN19 (or 709m40) in composition. It has a Chromium and Molybdenum composition which EN8 does not have.

Looking at the hardness, HRC35 roughly equates to a V condition, 65 ton. It's a bit in the "Hmmn" region for me, but still machinable with a good machine and tooling.

Neil

Some time ago I sawed a piece of 4140 from 4" x 1/2" flat bar stock then bored, faced and turned it to make the camshaft for my 9 cylinder radial. On my Boxford LOO I had no trouble with this steel and obtained a very good finish using quality carbide tips in 16mm tools and using Lubysil flood, so this relatively small machine can handle it okay.

Once my mill has been rebuilt and tested for accuracy, this cam blank will be set up on a rotary table to cut the lobes. As this machine is only a tiddly Emco FB2, a bit more thought and care might be needed.

Trevor.

If you are near Shropshire, come stick it in my forge for half an hour and then come back the next day, it should anneal reasonably well (although I've never done anything this thick in it before).

If you're unable to machine it, I'd make the assumption that it cannot be any grade of mild steel and must be a medium carbon or high carbon steel that has for whatever reason hardened to some degree. If carbide won't cut it - I think this must have been fully hardened. I've work hardened tool steel bad technique/blunt HSS tooling before but carbide just eats through it.

I have seen ceramic tooling cut hardened steel on youtube - make sure you have your fire extinguisher at the ready!

The idea of sticking it in a fire is a good one, if it's a big enough fire with enough coal around it it should reach critical temperature without the need for any air input, then you can just leave it there overnight.

Most people don't like mystery steels because of this but I can't deny the appeal of picking up things for next to nothing! My dad had an 8x8x2 inch block of steel from years ago that he just found - it's now a nice bench anvil. Not sure what it is but it's certainly higher than mild steel.

Why not get it cut into strips about 10mm square and 100 long, and sell them on e-bay as indestructible tool bits?

Oh, I don't know how you would get it cut, though ...

tim