Using automotive crankshafts as a source of cast iron

[digiex-chris]

I have 400 lbs of aluminum sitting on my garage floor in the form of an old Ford Ranger engine. I'm building a furnace to melt that down. I realized that there's a huge chunk of cast iron sitting inside! The crank ought to be real nice stuff to make cylinders and pistons out of. I havn't gone looking to see the extent at which it's been hardened, I'm hoping it's just the journals. I know I can deal with the hardness issue once I have my furnace built, but I wouldn't mind getting a head start on a cylinder while I'm buying parts for the furnace. Anyone use car parts like this? Any guidance?

 

[Chazz]

Are you sure the crank shaft is 'Cast Iron'? ??? Most cranks are Built-up, billet or cast steel (I think?)
Having said that, engine blocks and their components are an excellent source of material.

Cheers,
Chazz

 

[digiex-chris]

You're right, probably cast steel. There's a parting line at least, so I think it's cast. Still usable? I figure it's pretty good quality stuff.

 

[Florian]

I Think there are also forged crankshafts...?

 

[Ken I]

Normally cast from a high tensile material like EN30B - high performance cranks are often forged.
Heat treated to "toughen" - journals typically hollow milled, induction hardened, roller burnished in the fillets and superfinished.

Typically good quality inclusion controlled steel - but tough to machine.

Some cranks (BMW M3) have a wierd (I think) nitriding process that turns them a vivid blue/green colour - the whole crank.

If you are going to chop into chunks I would suggest you anneal them in a furnace prior to use.

WTH just try a piece.

Automotive cranks are definately not cast iron.

Ken

 

[Blogwitch]

Crankshafts, half shafts etc off autos are a real bummer if you don't have fairly heavyweight machinery and tooling.

Trying to cut the stuff using normal small machinery and tooling available in a home workshop, you will usually be on the road to a hiding.

The stuff is as tough as old boots, and you need the power to get your cutting tools through it, plus a good supply of tips if you are using tipped tooling.

Normal cast steel is bad enough, but compared to trying to machine what has been mentioned, it is easy.

Look elsewhere for your materials and leave that stuff alone if you want an easy life.

How do I know?

Over many years, I have tried to source most of my materials for free, and have tried to cut and use almost everything that is out there, some materials cause a lot of heartache and expense, and an old crankshaft is one of them.


John

 

[digiex-chris]

bummer. annealing doesn't help?

 

[Ken I]

Annealing will help but as John said it is still "tough as old boots".

Ken

 

[Blogwitch]

What else that has to be taken into consideration is the grain structure of the steel.

If it is a forging, and a great many are, the grain structure actually follows the outside shape of the part, up and down, side to side, it is this which gives it it's major strength.

So it doesn't react and machine in the same way as 'normal' straight grained materials, that is why, if any areas need to be machined on it, it is usually done by grinding, which is basically immune to the grain structure direction, unlike normal machining methods.


John

 

[digiex-chris]

ah, makes sense now, thanks. I'll only waste a little time on it, instead of a lot of time. ;D

 

[Tredder]

Over many years, I have tried to source most of my materials for free, and have tried to cut and use almost everything that is out there, some materials cause a lot of heartache and expense, and an old crankshaft is one of them.


John

John,

Spill the beans on some of your favourite sources of recovered material......

Simon

 

[firebird]

Hi Chris

I built this beam engine http://www.homemodelenginemachinist.com/index.php?topic=10002.0 from old car parts. The con rods are cast and machine beautifully. Aluminium pistons also machine easily as did the cylinder which I made from a brake cylinder. The flywheel is a cam shaft timing gear. The valves which I used as the columns however would not machine even after annealing. You can see though that if you let your imagination run there are plenty of parts that can be used.

Cheers

Rich

 

[Blogwitch]

Simon,

I am very lucky in that I have a major recycling yard fairly close to me, and getting to know a few people that work there has been invaluable over the years. I only needed to tell them that I wanted something, and when it came in they would put it to one side for me. Sash weights are a good example. Here in the UK, they seem to be made of better material than elsewhere, from an average sash weight, I can get 13" of 1 3/16" diameter, 100 year old, very well seasoned and close grained cast iron out of each one, at a cost of 30pence each. It is perfect for the sorts of things we make.

Friends and relations are always a good source of materials, when you ask them if they have any materials in their garages or sheds, all of a sudden things start to appear. I have many hundredweight of brass bar from such sources. They know not what they have until you remind them. Some of it is many years old, say when they cleaned out their old relatives sheds and thought something would come in handy, but never did. It really is amazing what people keep for years and never throw away.

Friends and relations, if they are still working, will get throw outs from where they work, usually, you just have to ask. One friend brings me scrap steel bars and rods from when he does his job of fitting new garage doors, usually hot rolled, but also a fair amount of cold rolled bright bar, up to about 4ft long. I cut it up into manageable lengths, say 12" long, and share it out amongst other model engineering friends, again, I have cwts of the stuff in stock, all for free.

Very rarely do I buy materials, except when a customer required a special material, would I purchase it.

I have forgotten the last time I bought anything for one of my projects, unless it came as barstock with a casting kit that I have bought.

If you don't ask, you will never get.


John

 

[Entropy455]

My two cents:

Most modern crankshafts are either forged steel, or cast steel. Large ones are case-hardened, smaller ones are through-hardened with a temper. Unless you have an industrial oven to properly anneal the steel, you'll have an extremely difficult time machining them.

Crankshafts from 70s automobiles are typically a nodular cast iron. This material is also heat treatable, and is quite hard in the as-removed state from the engine. Again, you’d want to anneal it before you machine parts.

If you require large solid chunks of cast iron, contact your local recycler, and inquire about obtaining an old lathe bed, or machine foundation (you’ll want to avoid machining anything from ways, as they are hardened). You can also obtain decent quality cast iron from large marine type gate valves. Make sure it’s a water valve, as steam valves are typically cast chrome steel. The hard part is cutting the pieces down to shop-size starting material. A plasma cutter works well. However unless you’ve got a large 3-phase machine, you’ll have difficulty cutting thick chunks of cast iron. . .

 

[ShedBoy]

Easiest way to tell if it is cast or forged is to look at the part line. A forged crank will have a thick chunky part line where the flashis trimmed off and the cast ccrank will have a nice thin line. Most production cranks are forged as it is a quicker process.

Brock

 

[steamer]

Guys really
get some 1144 stress proof

Great stock Machines well and great properties

Dave

 

[Maryak]

A plasma cutter works well. However unless you’ve got a large 3-phase machine, you’ll have difficulty cutting thick chunks of cast iron. . .

AND a bloody great big air compressor to go with it. ;D

Best Regards
Bob

 

[Entropy455]

http://www.mcmaster.com/

McMaster-Carr sells high quality cast iron, in the annealed state. Look in their website under "Raw Materials" / "Metals" / "Iron"

They have several grades available.

You're going to pay $$$, however the material is high quality stuff. . . .

 

[rleete]

I gave up trying to find a decent cast iron window weight without lots of very hard scale, inclusions, voids and the like. I bought from McMaster-Carr, and the stuff cuts so well it's almost scary. In making a Poppin, the fins cut easily with a parting tool. No mess, no drama.

Do yourself a favor and stop fighting with mystery metal. Buy some decent cast bars, and marvel at how well it machines. What's more valuable? 20 bucks, or hours of time wasted in frustration?

 

[digiex-chris]

It's a little different here in central Canada. My local shop doesn't carry it, but the same chain can order it for me from their Ontario locations. That $20 bar comes with a $50 shipping charge. I'd glady pay $20, but $70 is a little harder.