The continuously cast iron bar is a joy to machine, no hard skin and you should get chips with very little dust.

As Emgee says Pistons, piston rings, cylinders on IC engines. On steam engines again cylinders, eccentric straps, bearings can all be cut from solid be it round, square or rectangular bar.

A few examples, slices of 80-mm bar

Become eccentric straps

Block about 3" long

Into a cylinder

Piston rings

Small IC piston

Chips not dust

Edited By JasonB on 01/12/2015 18:43:47

Cast iron is valued for its ease of machining without distortion, and the way it copes with (intended) sliding. It is not particularly strong, and its resistance to shock loading is only moderate, but many sliding and rotating parts rely on it, particularly where sliding is relatively slow and lubrication is intermittent or neglected.

Mild steel, on the other hand, is (as you have found) cheaper and more readily available. As well as being almost as easy to machine, it can be bent and forged (which cast iron can't). Other benefits are in its ease of joining by soldering, brazing and welding, the fact that it can be case hardened, and it is tougher than CI.

For pistons in full size internal combustion engines, neither is used as better characteristics are available in light alloys, particularly for heat conductivity. Model engines can still use cast iron as the parts are much smaller, (the clue is in the term 'model&#39 and they produce only low power, and do not run for long at a time. For petrol or diesel road vehicles, cast iron pistons were obsolete by about 1924, for aircraft they did not last through WW1.

Hope this helps with some background

Regards, Tim

Cast iron is a joy to machine, a dust mask is a good idea.unless you don't mind having black snot afterwards…

Neil

I have used cast iron pistons in cast iron cylinder liners and steel liners with very few problems.

They have run at 15000rpm and higher on an experimental static test.

The steel liner has been blue with the heat and under competition done nearly 2 Kilometres on a tethered line.

Modern silicon aluminium piston material might do the same job but think it would require a ceramic coating because of the very high temperature steam involved.

Paul

College Engineering?

Neil

I have very little to do to the cylinder after careful machining I use a glaze buster making sure the cross hatching is there to retain the graphite lubricating paste and make piston to cylinder clearance 0.003" to 0.004" it has a Dykes piston ring.

Over many years of high speed running 113mph to 129.33mph I have had no seizures only problem contamination from carbon? or over heating of the stainless steam generator causing particles of scale to mark the cylinder.

The piston is a slipper type with a series of grooves in the thrust faces to retain lubricant.

Edited By Windy on 02/12/2015 01:01:19

Edited By Windy on 02/12/2015 01:05:38

There is cast iron and there is cast iron so properties vary according to what's in it.

**LINK**

And there are variations within the types too eg

**LINK**

I'd guess that the continuously cast iron bar that is most likely to be supplied in the UK is this one

**LINK**

There are several other types in the index on that page. SG iron for instance can go up to 700n/mm^2. I notice that Arc offer an sg iron milling vice. The sort of thing it's used for.

John

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I use cast iron pistons without rings in either steel or cast iron cylinders, the cylinder lapped to a fine finish for my hot air engines, and use them with minimal or no lubrication. Each piston has 3 or 4 fine grooves(labyrinth grooves), these assist in sealing the piston.

Ian S C

Picture shows the inside of a cast iron piston made for an ETWestbury designed engine that was fitted to a field charger used for charging radio transmitters in the field during WW2. The engine/charger assembly was parachuted in to the agent/resistance.

The original piston was made from a casting and had 2 top compression rings and an oil scraper ring close to the skirt, the small lip below the bottom ring failed and a large part of the piston broke away. The new piston was some 20% heavier than the original.

Emgee

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