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Key steel vs BMS sq bar

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DaveH:
John,

No - you haven't misread anything, it was just that as an apprentice "2000 years ago" I was told "Use key steel for square and rectangular stock" it is a much better "quality" steel than "bright mild steel". Also I was told it had less of a tendency to warp after machining.

It is something that has stuck with me - I forgot everything else.  :lol:  :lol:  :lol:

Maybe it was in 1960, I also thought it may have been heat treated but I don't think it is.

If it is just from it's shear strength, I would sooner use a free cutting steel.
 
:beer:
DaveH

Pete.:
If it's an important part that mustn't fail I'd go for proper keystock but if it was just some pulley on a polishing machine shaft etc I would just use whatever I could machine to fit the keyslot.

Anzaniste:
Key steel is a medium carbon steel supplied cold drawn and would have a tensile of 35/45 ton/sq in in old money.
I always remember the rule of thumb that  Mild Steel  had a tensile strength of approximately 30/32 tons/sq in.
Steel below 0.40% carbon, i.e. mild steel will not harden by quenching. Key steel has 0.50% carbon therefore will harden by quenching although not much.

There is a hell of a lot more to it than that but not being that clever I can't remember all I was taught in the olden days!! :palm:

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