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Material for crankshaft

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michelko:
Hi Guys,
i am working on a holt 75 engine and i am not sure what material to use for the crankshaft.
It will be machined from an solid piece.
I thought about etg100 it is a free turning high strength steel, but that piece of metall will cost some money and it is only available as a round stock.
c45 is availale as flat material, but whats about distortion after or while machining?
Has anybody made cranks from freeturning steeel like 11SMn30+C (1.0715) or something compareable?

Would be nice to heare your thoughts and wisdom.

Thanks in advance

Roger B:
I have used C45k flat bar for single cylinder crankshafts. These were roughed out, left for a few weeks and then finished. I think this may be a problem with multi cylinder shafts unless you make some fixtures for finishing the big end journals.

john mills:
Hi
I  have machined mainly alloy steels  i have made a few crank shafts from solid i have used m200
it is aplastic die steel supplied in a heat treated condition so it will machine well ,after machining it can be used as is or heat treaded again and or nitrided.the biggest was for a 6" stroke with 3" dia journals  it was for a testing machine at work the boss liked  m200  after machining it was nitrided.i have used the same material for several steam engines since. I have used machining grade of 4140   which is M709 for other things these alloy steels can move while machining care must be taken not to have any loads on the material while machining that may tend to bend while holding for machining. i  watch what is happening and proceed as i see what is happening .i may rough
then semi finish before finally finish specialy the main journals between centres with just enough pressure to support  enough for machining much pressure will bend but with good feel you machine it straight and it will be straight because you have finally machined it straight.the material numbers you mention i do not know but it depend on your local suppliers .these steels are often supplied in a heat treated condition  hardened  and tempered  if it is in an annealed  state it will be awful and it will only rip and tear and you won't get a reasonable finish.i worked wear there was plenty of 8620 which was in an annealed state  it needed to be hardened and temperd to do much with it it was for bending so was supplied annealed .
 John   

gbritnell:
HI Michelko,
Over here a lot of us use 1144 steel. The proprietary name is 'stressproof'. I don't know what it compares to in Europe. It also only comes as round stock so for a planar type crank a lot of metal has to be removed. Tool steel such as 4140 can be used but this grade is quite a bit harder to machine than 1144. At the bottom of the ladder is 1018 steel, common name 'cold rolled'. The big problem with this steel is it warps really bad initially. If the excess is removed in steps most of the warpage can be controlled.
I would think that the builders in Europe would be the best ones to answer your question.

dieselpilot:
ETG100 = SAE1144

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