Author Topic: Material for crankshaft  (Read 1051 times)

Offline michelko

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Material for crankshaft
« on: January 22, 2021, 01:15:03 PM »
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

Offline Roger B

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Re: Material for crankshaft
« Reply #1 on: January 22, 2021, 02:27:51 PM »
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.
Best regards

Roger

Offline john mills

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Re: Material for crankshaft
« Reply #2 on: January 23, 2021, 05:16:29 AM »
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   

Offline gbritnell

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Re: Material for crankshaft
« Reply #3 on: January 23, 2021, 12:21:42 PM »
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.
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Offline dieselpilot

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Re: Material for crankshaft
« Reply #4 on: January 23, 2021, 04:02:58 PM »
ETG100 = SAE1144

Offline crueby

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Re: Material for crankshaft
« Reply #5 on: January 23, 2021, 04:17:51 PM »
I really like the 1144, have done a few crankshafts with it and had no noticeable movement when cutting away one side or the other. After tips from George and others I learned to saw away the bulk of the material to reduce the interrupted cuts.
latest one with 1144, worked out great:


Offline john mills

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Re: Material for crankshaft
« Reply #6 on: January 23, 2021, 08:32:58 PM »
For these sort of parts the the cold rolled versions should be avoided  this can have stresses  which cause the distortion as metal is cut   black bar  hot rolled is much more stable  it can be quite rough  but  it does not move like hot rolled can.the local suppliers often supply cut to size from big blocks so that can be good it does not have the sometimes thick black scale an be closer to the sizes required not limited by stock sizes and grain structure that direction grain does  not need to be considered  .just care needs to be taken when holding when starting machining not to tending to bend the steel if clamping in a vice or clamping however you hold the material as you start cutting .
       John
               

Offline michelko

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Re: Material for crankshaft
« Reply #7 on: January 24, 2021, 09:04:10 AM »
Thanks for your replies.
I found another source for the etg100 stuff where i pay ca.100 euro per meter instead of 290.
I think i will purchase this material.
Unfortunately still have to remove big amount because of the round form

Online fumopuc

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Re: Material for crankshaft
« Reply #8 on: January 24, 2021, 02:32:21 PM »
Hi Michael, my last source for ETG 100.
https://www.zahnradbude.de/etg100/
Kind Regards
Achim

Offline steamer

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Re: Material for crankshaft
« Reply #9 on: January 24, 2021, 04:20:56 PM »
Plus 1 for 1144SP.    I buy three steels typically     303ss,  0-1 oil hardening and 1144sp.    It machines very nice and has relly good material properties....
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Offline fidlstyks

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Re: Material for crankshaft
« Reply #10 on: April 10, 2021, 03:51:04 AM »
The crankshafts I make have diameters of 5/16 and 3/8". I cut coldrolled 1 3/8" x 1/2" for a 7/8" throw and a 5/16" crank diameter.

The 3/8" crank a little larger. What I did was cut out the cold rolled and let it set for 6 months before turning. I also cut them from hot rolled steel. I think the hot rolled balls up and does not machine as well, but when being careful it worked, and I machined them the same day. But I also put the blank in the surface grinder first. The scale makes the blank not flat.
     I also silver solder cold rolled in a 5 piece link. That is easy, but silver soldering like this takes practice. I have known people who said the press fit cranks like silver soldering and pinned them. I never liked that.

    The reason I am bringing this up is that I am wanting to forge some crankshafts and am wondering what steel to use. I do not think there is any point in having the best made steel. I am planning for now to use hot rolled steel. I also am using a die so that I can make cranks in a uniform appearance.
I have tried loading pictures from Practical Blacksmithing on how to forge a crankshaft, but it won't load.
Any thoughts on this would be apprciated.
« Last Edit: April 10, 2021, 04:07:51 AM by fidlstyks »

Offline steamer

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Re: Material for crankshaft
« Reply #11 on: April 10, 2021, 05:52:06 PM »
For crankshafts with plain bearings, some carbon content is desirable.   It improves the durability of the bearing surface.   The problem I have is I've never specified a forging before.    That said, I think the basics of bearings must be the same regardless.    So a medium carbon steel would be a good starting point.

The forging portion of this is something that I think you will know far better than I.  I would look into the hot working ability of a 1144SP...It's a readily available, but I'm sure some experimentation would be required.

Dave


"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!