Sourcing Cast Iron

[t3kboi]

I am going to need a few fairly chunky bits of cast Iron for a project.

I have found a lot of big CI dumbbells and kettle bells on Craigslist (far cheaper than metal shops).

Has anyone here ever tried machining these?

Also - weightlifting plates, and theatrical stage weights - both are CI and have large-ish dimensions.

 

[C-Bag]

This has been discussed here on H-M several times but admittedly might be hard to find in a search. While you might get lucky and find something not too bad, most of those items are not cast with machinability in mind. The best stuff is Dura Bar, or grey iron or I think called CL 40. Non grey iron can be so hard as to be a challenge to carbide. Also those junk iron things can have voids and not be very pure. Depending on your project this might not be a problem but if you are wanting to make something machine grade you’d be better off finding a piece of an old junked machine to work with. I got a nice piece of Dura Bar off eBay. The machinability especially compared to some of the Chinese cast iron I’ve machined is night and day. Nice finish that doesn’t kill my carbide with no voids.

 

[t3kboi]

Thanks!

 

[JimDawson]

I bought some from McMaster -Carr a few weeks ago. https://www.mcmaster.com/cast-iron

 

[t3kboi]

I can buy from anywhere - but the question is, are the cheap/almost-free sources useable....

I can literally buy 100# of dumbbells for $20.

So - since I know what I can buy, but don't know about the answer to my question - I guess I will get a couple of them, see how they machine, and report back...

 

[Nogoingback]

I have no experience with dumbbells, but a number of folks here have reported they machine badly: the material is the
cheapest garbage that can be poured into a mold. If you have casting your own material in mind, I think a trip to the
wrecking yard would be better: lots of cylinder head etc. available and almost certainly better than dumbbells. Another
possibility is a scrap metal place that lets you pick and choose. If you want to buy material, an alternative to iron is
1144 stress proof. It machines very nicely. I've bought drops off eBay at reasonable prices.

 

[benmychree]

Dura bar is a bit hard on the surface, but is quite fine grained and nice to machine once you get through the hard skin.

 

[C-Bag]

There are a couple guys on YouTube that home cast their own iron and where it’s sourced and the additives along with technique are important. There’s a reason fine machine tools are made from high grade cast iron. And it’s tough to do. We see so much junk iron like in weights and old window sash weights etc where it’s not crucial because it’s not going to be machined into precision shapes where it’s porosity and super hard nature is going eat up tooling.

I’m all about cheap and repurposing but in this case you get what you pay for. I made these dogs for my shaper out of Dura Bar.

 

[Mitch Alsup]

There are four basic types of cast iron

white iron
gray iron
ductile iron
malleable iron

White Cast Iron
Characterized by the prevalence of carbides, impacting
high compressive strength
hardness
good resistance to wear

Gray Cast Iron
Characterized with graphite in the microstructure, giving
good machinability
good resistance to wear and galling

Ductile Cast Iron
Gray iron with small amounts of magnesium and cesium which nodulates the graphite, resulting
high strength
high ductility

Malleable Cast Iron
White cast iron heat-treated to improve ductility

The question is what kind do you want ?

 

[Lo-Fi]

Meehanite is another trade name of cast iron manufactured with machinability in mind. No voids, hard spots or even surface hardness to speak of. It's a joy to work, mess aside.