Steel Spec.

[ozzie34231]

I'm looking at some old plans published in England that call for EN8 steel.
I've tried to research it and I find it was a WWII designation meaning Emergency Number 8. That doesn't help much.
Can anyone help with a designation for a steel available in the US.
There are two parts involved, running on each other, an eccentric and its mate. Speed is low about 500 rpm.
O-1 is readily available in flat and rod which are the profiles needed and I have a little heat treating oven. I know nothing about steel designations. I have a little experience with O-1 drill rod, heat treating.
This is a home shop project, not commercial. Any thoughts?
Ozzie

[Geof]

You say; are two parts involved, running on each other, an eccentric and its mate.

Having the same material for two parts running together is not really good design unless the parts are hardened and ground or otherwise finished very smooth; similar materials sliding together can gall up and seize (unless the material is brass which is the only exception I know about).

A hardenable material such as O1 could be suitable if you can correctly heat treat it.

Alternatively if you can incorporate a bushing or wear pad made out of brass or bronze for the sliding elements it may be possible to use C1018 which is a low carbon mild steel which cannot be hardened without carburizing.

[ozzie34231]

Thanks Geof,
That occurred to me, same metals, but the designer was Dr. Caddock, of Quorn fame and he says that both parts need to be able to take quite a bit of strain and nothing less than EN8 should be used, so it seems he was more concerned with strength than similar metals running together. He says that the EN8 has a yield strength of 18 tons per square inch. He recommends as a lube MoS2. Note that the strain is not at the point of the running mates, but at other points of the same parts.
I can grind the parts, I think, though I haven't done internal grinding before; I should learn.
Regarding hardening, my little oven is digitally controlled but only as to temperature, not timing. I have hardened before by going to the correct temp. quenching and doing the drawing down in the same oven at about 600 degrees, and air cooling. I have a chart of tempering temperatures but I'd need to know what hardness I'm shooting for.
So, the questions are:
Does O-1 exceed the yield strength of the EN8?
Do you or anyone have a wild guess as to how hard it should be?

Ozzie

[Geof]

........Do you or anyone have a wild guess as to how hard it should be?

Ozzie

You want wild guesses now? You have come to the correct place.

18 tons per square inch is only around 40,000 psi which is within the range of C1018, O1 hardened is above that.

Another choice could be 4340 or 4140 both of which are easier to machine than O1 and they can be hardened.

How hard should it be?

Somewhat similar to a hardened gear in an automobile transmission or a solid cam follower in an engine; Rc 35 to 40??? Is that a wild enough guess?

Harden and then temper to a medium straw.

[ozzie34231]

Super, Super, Super.
Exactly what I need, you are the man Geof!

Ozzie

[Nzoldun]

I have some technical data on EN8 (circa 1962). Can you wait 'till Monday so I can retrieve the book from my office at work?

Grant Notley
grant.notley@xtra.co.nz

[gridley51]

Ozzie,EN8 is only a 0.4% carbon steel,nothing special.I buy it by the tonne every month.Here`s a link to the specification for it.This is for EN8DM.The D means it`s at the top of the spec for carbon content and the M means free cutting.
http://www.niagaralasalle.co.uk/dist...aspead40m.html

Mark.