Cast iron bar stock- what & where

Machining down a commercial TP grinder post the other day, I realized how much I like cast iron. Sure it's dirty, but for some applications like laps and machine parts, it can't be beat. It would be nice to keep some bar stock on hand, say 1 or 2" diameter lengths of a foot or three, and maybe some rectangle or plate. Problem is, I have no idea what grade would be considered general purpose, nor where to buy small (hobbyist) quantities. What's a fair price? Can anyone share some wisdom?

Thanks,
Conrad

If you found it nice to machine it was almost certainly ductile cast iron; you have to be careful just saying 'cast iron' because it comes in several types.

I Googled 'ductile cast iron' and came up with this:

http://www.okfoundrycompany.com/grayductileironplatestock.htm

Bought a 2" (actually big enough to clean up at 2") X 3 foot from McMaster-Carr. They offer Cast Gray and Ductile. Any of it "machines nicely" and has for hundreds of years. My piece was $53 and change plus shipping. Is that "fair"? Is to me. These folks have what I want and don't waste any time at all getting it here.

John Oder

Thanks- I never thought of McMaster. They tend to be on the high side for pricing, but not so bad, and the convenience of getting almost everything imaginable from one source makes up for it.

As an aside, I have a few bars of what I think is cast steel lying on the floor somewhere, and it's the worst thing to machine I've ever come across.

I recall visiting an old metallurgist friend of mine. Over his desk he has a shelf where he kept his most used references. In of these was a boc encyclopedia sized obb entitled simply "Casr Ieon" and in it was a jillion pages of discussin analysis, and specs for the many different grades of castiorn, their usesm and foundry data. At a guess there's aeveral hundred different specs for cast iron so you have to be a little specific.

Several different grades of cast iron have proven themselves for castings and parts for machine tools. Thanks fo developements like continuous casting, cast ieon can be furnished in bar form convenient for parts manufacture. Powerful band saws are used to "resaw" large section cast iron bar to smaller, near net shapes to suit customer need. While this is a boon for someone needing to replace a gib the material can still be expensive. The basic weight charge may bea fraction of the delivered material price.

Here's a link for grade comparason http://www.dura-bar.com/products/index.cfm.

Your local supplier may not have the bar suze or the cutting resources to serve your needs. You mey beed to go out of state ro a major supplier. Shop around. Prices and cutting service can vary considerably. Weight is also a factor as cast iron is dense. I live in the Seattle Area and the last time I bougrh about 380 Lb of cast iron from a Minisota supplier for my scraping class project pieces, it was almost $700 by the time it was delivered to my door.

Dura-Bar is a continuous cast product, and about as nice to machine as you could ask. There is no hard skin, as often found on sand cast parts. Rectangular bars I have bought were band sawed slightly oversize so they would clean up to the size ordered. There are never any hard spots or porosity. There may be brands or sources for the product than Dura-Bar.

But be aware that you can also find cast iron bars that are not continuous cast, at least I got some some years ago. I got some round bar that turned out to be sand cast, with a parting line and a slightly hard skin, but otherwise OK. I got a rectangular bar that was open loam cast. That is where the iron is poured into an open-top hole in a dirt floor at the foundry. That one was so badly porous and non-homogeneous I got an apology from the dealer, who then sent a piece of good continuous cast iron.

Larry

+1 on the Durabar products. Great stuff, easy machining.

Old window weights are cast iron,though probably not of the best quality. They may have little pores in them.

Old sash weights may also be harder than carbide where they aren't porous.

Conrad

I'm with you -I find machining cast iron immensely satisfying (provided it hasn't been chilled, unintentionally or intentionally, on solidifying)

I have some round sticks of Ni-resist (high Nickel, heat resisting spheroidal graphitic cast iron) I had a local foundry cast for me as a teenager

I had conceived a project to design and build a steam engine (to install in my Fiat Bambina!), a refinement of the elbow engine along Volvo Flygmotor hydraulic motor lines, but my aspirations soared far above my ability to carry through.

I found the sticks, with their sandcast surface, impossible to machine with the resources then at my disposal: I couldn't chuck them firmly enough and I couldn't get through the skin with my puny Myford ML7.

Here's the point in my post: with the exact same lathe I was recently able to put one of these sticks (yes, I've never thrown anything out, ever) to good use, and look forward to doing the same with the rest in due course.

And I used the same lathe, despite having much better options.

The secret is this: toolpost grinder improvised from a flex-shaft die grinder (shown here doing a different job)

By this means it's simple matter to create a chucking 'handle' at one end and a steady patch at the other.

The 'key enabling concept' here is this: when cylindrically grinding, (especially with such a woosy setup) the push-off forces are tiny by comparison with trying to take a hard foundry skin off with a carbide tooltip.
Furthermore you're only turning the spindle by hand, so little is at stake if things come loose.
Consequently the rough stick can (if you're fussy) be wrapped in soft (eg alu MIG) wire and gripped in any chuck you happen to have fitted, or (if not) simply gripped lightly in a 4 -jaw, perhaps with a shim or wedge or 2 (even cardboard would do) to stop rocking.

The grinding operation has the further advantage that it is supremely indifferent to the sand content of the surface skin.
The abrasive effect on the 'cutting' tool is immaterial, and the machine will already need to be shrouded for grinding grit so there's no extra effort required here.

Once these patches are cleaned up, the item can readily be machined by turning, even in a floppy Myford ML7. My ML7 has be relegated to such dirty jobs (toolpost grinding, machining cast iron, turning hardened parts)

Once the nasty part is accomplished (if the accuracy is needed) I move the whole setup, without loosening the chuck jaws, into the "kept for best" refurbished Super 7, or go to a new setup in a bigger lathe if horsepower and rigidity are required.

The reason I'm going into this detail is that there are attributes of the Myford (which you asked about in another post) not shared by other modern lathes which make it unusually versatile.
For instance, the photo shows the compound slide moved further back on the cross slide than the usual position, to allow grinding a chamfer which a conventional cross slide would not travel inwards far enough to reach.
The flat bed is also somewhat easier to shroud for grinding, and for machining abrasive materials.

Because the basic Myford was designed with a view to turning, milling, line boring, grinding, and tackling work too big for it (albeit adopting a 'sneaking up' approach to material removal), it does have a number of virtues which will not immediately be apparent to people to whom a lathe is 'just a lathe'.

I find that continuous cast iron bar is similar in price to CRS bar. I only buy complete lengths, even though I'm a hobbyist. That makes quite a difference on the price. If you end up resawing bar to get a smaller section, be aware that below about 6" section, it will distort in the same way that CRS does. Not always to the same degree, but enough to cause bad language. If I need to resaw a piece I normalize it first. Then you only get a few thou of distortion.

Troup said:

Once this is done, the item can readily be machined, even in a floppy Myford ML7. My ML7 has be relegated to such dirty jobs (toolpost grinding, machining cast iron, turning hardened parts).

Click to expand...

To my Jaundiced eye, it looks as if it would have been quite difficult to do that job on the S7 at the time

• I deal with Lokey Iron & Alloy out of Ft Worth, TX. They don't care if you want 1" piece of something or a truck load. Prices are seem reasonable to me. They also have a wharehouse in northwest Houston, not too far John O. for those of you in the Houston area.

Ken S.

Dura bar should be able to help you out.

When ways on a grinder I bought were trashed we used dura bar to machine new ones.

They have alot of sizes, ect. in stock.

There's also Speedy Metals for small quantities. They sell by the inch I think.

http://www.speedymetals.com/c-8386-.aspx

Mike

Also try Team Tube and Castle Metals. I've ordered some 4" dia ductile for a estimated price of $50 per foot through a local machine shop, but haven't seen the material yet. It's to be piggybacked on a stock order to save on shipping costs. There seems to be a big markup on the stuff; if you have any leverage at all, use it. For example, Graingers will knock off $20 and ship for free to commercial accounts -- personal credit cards accepted and they will ship to your home address.

I found some very nice "stage curtain weights" at a scrapyard a few years back. Beautiful stuff to work with, but you never know. All gone now.

The durabar website doesn't use the term meehanite, but would any of their products be considered equivalent? They show a range from ferritic to pearlitic and options of either flake or nodular, but not being a metalurgist, those terms only evoke ancient memories of physical chemistry class lectures on phase diagrams/transitions.

In case it is of any help to you:

http://en.wikipedia.org/wiki/Meehanite

and the original US patent can be seen here


cheers,
Michael

I just ordered and used a 6" x 12" chunk of High-Strength Cast Ductile Iron and it's quite nice to work with.