4140 steel as a one piece crankshaft

[Parksy]

Gday all

I was wondering how well this type of steel machines. I will mill out the majority of material for the crank throw and finish it up on a four jaw on the lathe.

My understanding with different steels is that a stress proof steel is desired with making crankshafts. Please correct me if I'm wrong, but is the reason for this because if steels with internal stressors are used, the machining process can cause the part to distort?
How does the 4140 perform with regards to this? What does the term peeled and polished actually refer to with regards to 4140 rod?

Thank you all

Andy

 

[gbritnell]

Hi Andy,
I have never used 4140 for a crankshaft although I have used it for other parts. I suspect that most of the machining would go ok you would just have to be careful with the offset turning because it's tougher than most steels we normally use. I generally use 1144 stressproof in most of my engines and it has worked out well. The terminology that you're referring to probably means that it is usually supplied in a rolled condition like most steels and polished would mean a ground finish. 1144 can also be purchased this way. What peeled means I'm not quite sure.
gbritnell

 

[kvom]

I made the conrods for my Joy engine from stressproof (1144) rod, and it machined beautifully; best steel I've ever used.

 

[Parksy]

Thank you gbritnell and Kvom. I have tried sourcing some 1144 stress proof here in Australia but without success. If anyone down in this part of the world knows where to source this stuff I'll be happy to know.

I have just realised that I have some old Nissan patrol axles in the shed. Does anyone know what kind of material these could possibly be?

Cheers

Andy

 

[Mark Rand]

Peeled steel is steel that's been through a machine that cuts off the decaurburized/cruddy/damaged layer on the outside. It's not as smooth as ground steel but it's smoother than cold rolled.

The machines are rather impressive from what I remember from seeing a video a few years back. they have cutting heads that rotate around the steel as it is pushed through them after going through straightening rollers etc.

Hope that makes some sort of sense

 

[goldstar31]

I have just realised that I have some old Nissan patrol axles in the shed. Does anyone know what kind of material these could possibly be?

Cheers

Andy

'Sparey' in Amateurs Lathe or the one that I bought as a young airman suggested lorry half shafts as a source for -------wait for it----COLLETS.

Norman

 

[Cogsy]

If anyone down in this part of the world knows where to source this stuff I'll be happy to know.

I couldn't locate any in Australia when I wanted some, and most US suppliers wanted both my legs for postage, but Amazon ended up being a good source. From memory I paid about $16 for a 1" x 24" rod and about $25 shipping - USD though so the current exchange rate will hurt. Definitely the best steel I've machined, and I carved a 1 piece V4 crank out of it with no stress/warp problems at all.

 

[michael-au]

Amazon is your best bet for 1144, I don't think its available here in Australia

Amazon has fast postage to here as well, I have got this steel from them a few times

Michael

 

[Steve J]

If you are looking for aluminum the best price I have found is at aluminumyard.com. depending on the shape it is $3.00 a pound or less. Call and ask for Darrell. they are in Wichita Kansas and will ship ups or usps. Just bought two 3 foot pieces of 1/2" aluminum rod and it was $12.00 including shipping. More for shipping than material. They have a very very large selection.

 

[jayville]

Parksy..check out the thread headed..bright mild steel supplies au...west gippy got me on to this supplier...by the look of there list if they haven't got it nobody has...they may have an equivalent.....clem

 

[goldstar31]

Just an aside for both Parksy and Bazmak!

In happier days, I used to watch afternoon French TV. One bit that I recall was a Froggy blacksmith making knives out of broken coil springs. Tres Interessant?

Again, one of my old 'oppos' a tin coffin engineer made lots of his tooling from things like motor cycle spokes and Allen keys.

Another guy writing in Model Engineer described using broken ball race cages for cutting tools.

Just in case you've forgotten, old files are pretty good too

Cheers

Norman

 

[gadabout]

Try here for 1144

http://www.ian-stansfield-smith.com.au

cheers
Mark
Hobart, Tasmania

 

[Fluffy]

G'Day Andy,
I use 4140 for all the crankshafts that I have turned for the last 5 to 6 years & I have not had any problems. It will turn very well with sharp HSS & I used neat cutting oil (Rocol RTD). For my experience does not stress relieve for the diameters (Ø50 mm) that I have been using. I hope that this helps.
Regards,
Don.
Attached are images of the latest crank.

 

[jayville]

fluffy...I wish I had the skill to do that....clem

 

[Parksy]

Thank you all for your posts. Very informative and helpful. I will attempt to machine some 4140 and will try and get some 1144 from the various suppliers that have been suggested.

Cheers

Andy

 

[Parksy]

Had a go at turning some 4140 on the mini lathe and to my surprise it wasn't that bad. I turned each sides down first to required dimension, then used some round aluminium stock and used the mill to find center, then across 14mm, drilled and reamed a 10mm hole. Then super glued the crank into the offset hole and used the mill to remove the majority of material, then transfered it to the lathe to finish the final dimension for the throw.

Worked well. I will machine the round sections into counter weights and mill some keyways into each end to mount flywheels/gears.

 

[Parksy]

I forgot to ask,

Fluffy, what did you use to machine the crank throw in the centre to achieve that shape? I have a vague idea but would like to know for certain.

Cheers

 

[Fluffy]

Andy,
I roughed the crank pin down to 1.0 mm oversize with a parting blade to relieve the following cuts & then used two ground HSS tools similar to a parting tool to bring the crankpin to 0.05 mm oversize. The HSS tool with the shortest ground length was used when the material was at maximum diameter & the longer tool was used to bring the crank pin to size. Then I used a modified boring bar to relieve the inner faces of each web. The crank pin was bought to final size by using a piece of abrasive stick held on a piece of 8 mm square bar. To turn the main journals & threaded sections a piece of aluminium was filled to a slight interference fit between the inner web faces & held in pace with loctite & a cable tie.
When turning a one piece crankshaft I prefer to mark out & centre drill the centre holes for the crankshaft & crank pin axes rather than use a type of jig to turn the crank pin. Just a personal preference.
Good luck with the rest of your build.
Regards,
Don.

 

[Parksy]

Thanks Don, I appreciate it. Does the aluminium between the webs help stop chatter? Or stop deformation when supporting with the live centre?

Cheers

 

[Parksy]

Machined the round sections into a counter weight kind of shape. There is nothing calculated here, it's purely for aesthetics and I haven't taken into any accounts the weight of piston/rod.
One thing I need is a new mill. I've got my practice in on the little sx2 mill but now I need something bigger. The lack of rigidity is a pain, and creates some rough milling finishes. At least that's what I think it is.
Anyway, in the process of filing and sanding the marks out. Slow process.