What steel to Order

I want to make a few tools. Grinding rest being one. I have worked out what steel and quantities involved.

When I emailed various supiers to quote for the steel I'm being asked Bright or Black. ? I can find no refernce for this probably most obvious question.

Is there a price diffence would you think ?

I could skim dark in a Mill to make Black into Bright but it stikes me as a bit boring.

Any advice appreciated.

Chris

Edited By chris j on 17/09/2012 21:20:37

What spec have you quoted them for the steel you have requested, as I thought black steel would have a different spec to bright. Typically, M-Machine do not quote a spec for their black steel, at least on the pages I have looked at.

If you do not quote a spec you can end up with any spec, maybe one that machines poorly,

In any case, what is the purpose for such items as a grinding rest to purchase black and then have to machine it to get to a bright finish. Even if the black is offered at a knock down price.

Harold

Hi Chris, IMHO, as a general rule, I would use black steel where the surface finish is of no real consequence, i.e. locomotive frames and any other general fabrication jobs. Black steel doesn't always machine to a good finish. Bright steel is much more suitable for the likes of the grinding rest and other tools of a simalar nature, but as Harold says, if a spec number is given, then that should be sought after.

Some tools may require steels such as gauge plate or silver steel, black or bright steel will not be an alternative for these.

Regards Nick.

I would suggest asking (what was McReadys) Acenta steel as they are the gospel in steels?

the 230m07 you mention is bulk standard EN1A mild steel, not sure about the 080a15 though (080m15 is EN32)

If the parts to be made will require a lot of stressful pressures then something a bit better than en1a would be required but should be ok for a grinding rest.

Edited By M0BND on 17/09/2012 22:33:24

Thanks Chris for that.

I would not expect 230M07 to be available in black, but I could be wrong, as it is a free cutting steel largely for turning. However, 080A15, mostly in a wide range of flats, I see from the Macreadys catalogue is available in bright and black. We learn somthing every day

This is the first time I have come across the question being asked. Probably due to the smaller suppliers to the home workshop only stocking bright material.

The simple answer to your questions is though, to go for bright steel if for no other reason than to minimise the work involved. There is another consideration, that is size. Once surfaced the material is going to be smaller than I quote on the drawings, in some cases this could impact on the design as other parts may need changing due to the thinner/narrow material being used.

I have myself only once surfaced a piece of black steel and found it easy to machines, something I have recolections of the same being stated on the forum. Perhaps, someone with more experience with the material can tell us more about using it., but not for my projects.

Harold

Bright steel is usually BDMS (Bright Drawn Mild Steel). This means that it has been sized by drawing it cold through a die. This results in a stressed surface. Black steel is as it left the rolling mill when hot and has cooled slowly, retaining its oxide coating. Bright steel tends to have residual stresses in it and black steel does not. Practically, if you were to mill one side off a piece of bright steel then it is likely to bend. This would not normally be a problem for something constructed from sawn pieces but might be an issue if some intricate milling were involved. BDMS can be annealed by heating to red and then allowed to cool slowly.

HTH

Rod

Thanks Guys

Plenty of food for thought there.

Thanks Rod, brief but very precise. Just how I like it.

I often, so as to use existing stock. take a piece of bright steel and cut a narrow strip from its width, finally skimming it on the mill to bring it to size. The strip cut off is frequently, but not always, very bent.

I made George Thomas's retractable tool holder which has some very complex shaped parts and had considerable problems with distortion. Surely a case for black steel, though I was provided with bright in the kit provided.

For anyone interested, I provided an article for it in issue 117 of MEW, in which I referred to the problem.

One last question. How accurate, size wise, is black steel?

Harold

Edited By Harold Hall 1 on 18/09/2012 09:52:09

Harold, H R steel accuracy, near enough for structural work, and things like loco frames, but if you want accurate, go a size bigger, and machine to size. Flat strip tends to be "dog bone" ie thicker down the edges, thinner in the middle (mybe only a thou or two), if you want flat, cut it from plate. If you don't want the mill scale, you can pickle it in citric acid (or what ever).

Afraid I use rebar, and all sort of junk! Ian S C

Ian I would hardly call rebar junk.. probally hitensile and close spec.. material..

But I know what you mean..on our home machines it turns how it turns..and tables of machinability and feeds 'n' speeds are a guide only ( 10 000 rpm /diameter still works for me as starting point)..

I know the steels OK, but turning the bumps off is a right B****r. Ian S C

bumps? uk stuff has pattern that takes a kind of "loose" nut for pretestioning if required...even found some stainless re enforcing bar..as I heard once "hard as woodpecker lips"...

Heating BMS to a dull red colour and cooling slowly will remove a lot of the internal stress and minimise distotion. Anyone with an open fire will find it an ideal medium for this "stress relieving process"

Tony

> stainless re enforcing bar

Interesting, my understanding is that rebar has to be rusty before it is used to ensure it doesn't react with the concrete.

Can someone remind me of the name of teh flats that collapsed with 'concrete disease' in the 70s - something Point?

Neil

Ronan Point but I think the gas explosion had a lot to do with it.

I think the rust On rebar reacts with the concrete, preventing further rust, I must do a bit of research on that. Ian S C

re stainless rebar Wellll... Its non magnetic, shiney, not monel.. not ali ...hard.... grinds with white sparks ( never quite got the hang of hss /carbon steel/ ms id from gringing sparks... ) being used in a retaining "pier"/ "pile" in concrete.. with ss ( again I have checked) wire lacing...

have to say I have always seen "rusty" rebar before ( yes something to do with concrete chemistry) but this was shiney so I scrounged some ends ( 18" bits) " might come in for some thing"..

NASTY TO TURN "nobbles" are awfully tough...

Thanks Andy,

Yes it was Ronan Point. I was thinking of - I was only 6 at teh time, so I must have heard about it later in the 70s. the article linked below mentions three roof collapses that led to the banning of high alumina cement in the mid 70s - I think I was confusing these to issues. I think I saw a documentary on the subject as a kid.

Jason

It appears stainless steel is used in certain, demanding, conditions **LINK**

Neil

The Ronan Point gas explosion was thought to have been caused by a broken gas adaptor, the drawing was re-dimensioned, but not re-drawn. This made the thru' hole very close to the thread root, result a crack. All the remaining buildings to that design had steel angle ( 4x 4 ?) fastened round the perimeter walls.