Crankshaft steel specification

[Mike Ginn]

I will soon need to machine a single throw (9/16") crank about 5" long for the Kiwi. I would really welcome suggestions re the steel spec which I would need to purchase in the UK. Ideally it should be easy to machine, give a good surface finish and not warp due to stresses.
Thanks in advance.
Mike

 

[stevehuckss396]

In the US that would be 1144SP. I'm sure with a little digging you can find it's metric equivalent.

 

[Mike Ginn]

Umm 1144 is available in the UK but only as round bar which is a real pain! It is quite difficult to find equivalents to the US steel codes.
Thanks
Mike

 

[stevehuckss396]

It's only round here also. Other than that it meets all of your requirements. I have made 3 or 4 cranks using it and I would do it again.

 

[gbritnell]

For a single throw crank I would just fabricate it. Get a piece of drill rod (silver steel) make the webs and silver solder (braze) It together. I have made many cranks this way with good success.

 

[Jasonb]

Westbury only specified mild steel for the crankshaft so no need to go for anything exotic.

I tend to use EN8 (090M40) for these type of engine cranks and don't have problems with movement though I do usually rough them out and then let stand for a week or so. Easy enough to machine if a little harder than EN1A

This one is very similar
https://www.modelenginemaker.com/index.php/topic,6471.msg134411.html#msg134411

 

[TonyM]

If you really want good crankshaft steel then EN9 should be readily available in the UK as flat round or hex. I personally use mild steel as it's easier to get for me.

 

[ajoeiam]

Umm 1144 is available in the UK but only as round bar which is a real pain! It is quite difficult to find equivalents to the US steel codes.
Thanks
Mike

I have a book, unfortunately NOT handy, where comparisons between ANSI (IIRC), DIN, can't remember the Japanese code abbreviation.
The book does not promise to cover every grade of everything but its only about 400 pages.
Machinerys Handbook is no help either (just checked!!)

 

[rhitee93]

Umm 1144 is available in the UK but only as round bar which is a real pain!

This is a bit of a crazy idea, but one of my other hobbies is blacksmithing and bladesmithing. There are quite a few top-notch bladesmiths in the UK who could take your round bar and forge it flat in a press to whatever thickness you desired. Any good bladesmith could also thermal cycle it to remove stress and reset the grain structure to preserve the qualities of the steel. You might look around to see if there is someone near you.

 

[Jasonb]

I simply mill the round bar flat, bit off one side then flip it over and a bit off the other and so on. Just written one up here and over the page

https://www.modelenginemaker.com/index.php/topic,10778.msg249899.html#msg249899