Key steel

[Garry ColesParticipant @garrycoles69390]

[Garry ColesParticipant @garrycoles69390]

Hi, I would like to know if key steel is any different to BMS. The reason I ask is I'm cutting some 3/16 keyways in a axle and I have got some 3/16 x 3/16 BMS in stock.

Thanks.

Garry in sunny Jersey.

[Nicholas FarrParticipant @nicholasfarr14254]

Hi Garry, good quality key steel is usually EN8, but I guess it all depends on what loading you are expecting, if it is fairly low I would imagine your mild steel will suffice.

Regards Nick.

[Garry ColesParticipant @garrycoles69390]

Thanks for that info Nick. The keyways are in the axle for the my 2in scale D & NY traction engine. I would have thought the load would not be that great.

[Nicholas FarrParticipant @nicholasfarr14254]

Hi Garry, I'm not familiar with traction engines, but there are a few on here who are and can probably advise you better.

Regards Nick.

[Phil PParticipant @philp]

Hi Garry

Personally I would opt for buying a foot of proper key steel, it only costs a few quid a length.

Mild steel is always going to be a bit undersize on the square dimensions, and that assumes it is actually square as well. Key steel is made to much tighter tolerances as well as being a tougher grade of steel.

I have seen the results of using mild steel keys at work and it is not pretty, the keyway in the shaft gets chewed up as well as the key failing, so it will mean a lot of work to rectify it when it fails.

Just my 2p worth

Phil

[Brian HParticipant @brianh50089]

I came across this company in Sheffield who supply silver steel, key steel and shim in quantities suitable for model engineers.

No connection but I saved there website for future use.

**LINK**

Brian

[not done it yetParticipant @notdoneityet]

+1 for Phil P reply.

It is just not worth “spoiling the ship for a ha’porth of tar”.

It would not show up until much later but would likely need some considerable remedial detail, if it did…

Likely less than a ‘few quid’ if the individual keys are bought from, say, an agricultural mender.

[Phil PParticipant @philp]

Depending on what you are doing you might be better off using a Woodruff key rather than a Feather key.
I usually make my own by parting off a slice of Silver Steel bar and cutting in half to make a couple of keys.

It does mean you also need a woodruff key cutter to produce the keyway in the shaft, but the woodruff key seems to be a lot more stable than a feather key as it goes much deeper into the shaft.

Some people make the mistake of using an endmill or slot drill of the same size as the key to produce a feather keyway in a shaft, but you will find if you try to do this the slot will often end up oversize due to the action of the cutting forces. You are better off using a smaller cutter and taking multiple passes to get the exact width you want.

I wont go on about how to cut the keyways in the mating part with the hole, suffice to say if you ever get the chance of some Marlco keyway broaches grab them while you can

Phil

Edited By Phil P on 11/10/2020 19:57:29

[Colin HeseltineParticipant @colinheseltine48622]

BearingBoys also sell keysteel off their website at what I thought were very good prices (no connection just a satisfied customer).

I think I only paid £4.50 (post free) for two lengths of 18mmx11mmx180mm. They do shorter lengths and lots of other sizes.

Colin

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