Piston Ring Castings

I have been in the automotive repair business since 1967. I am not familiar with that term. I do know that cast iron piston rings are very common. That is the best I can offer. good luck.

Most piston rings are made from high grade (fine grain, high strength) pearlitic cast iron. The only way to get this stuff is by casting from molten metal using pretty exacting foundry techniques to control the metallurgy.

Piston ring castings are cast as oversized closed rings on a sprue of upwards of 100 rings and then machined conventionally, albiet with fairly specialized lathes and mills, to their final configuration. Coatings like chrome and moly are added later.

I have a book published around 80 years ago by a piston ring manufacturer. It's full of good illustrations. Soon as I can find it and scan some more pics of the Dynastar engine for Peugeot man I'll post a scan or two from the piston ring book.

Ed Weldon

Yes piston rings are casted in oil casting and latter on preciously machined. They have some flexibility for fitting on the pistons.

Suresh -- Thanks for the bit of information about the use of "oil casting". While writing my answer last night I briefly thought about the process of building a mold for the "tree" of castings and realized the traditional foundry method of packing "green" sand around a pattern in a cope and drag was not the way to make any more than a single layer mold of a few ring castings.

Looking back to my youth and year of maintenance engineering work in an iron foundry I see how the process of oil casting would work. I visualize a core box that creates a single layer of ring cavities along with short portions of the sprues and risers (or at least vents of some kind?). Once cured in the core oven these "cores" are stacked and aligned vertically in a flask for pouring.

Oil sand casting sounds like an interesting process. It was never very common in the USA and is even less so these days with the advent of modern foundry methods. At one time we had an oil sand foundry in San Jose which specialized in casting aluminum.

I remember having them quote on some of our work when I worked for the disc drive company in the 1980's. This was a time of 14 inch disk drives, machines the size of large refrigerators. I think the oil sand foundry prospered in those years because a lot of local engineering talent did not have time to design machine components for casting due to shortened product development cycles. A common order from a customer was based on a quote for a fully machined single part that had been a composite structure of a number of machined aluminum parts bolted together. Typically the casting drawing would be prepared as an afterthought often without any mention of such things as draft angles or parting lines.

I'm still looking for that 80 year old book on piston rings......

Ed Weldon

I had always been of the opinion that casting methods left cast pieces with poor finish qualities. I later learned from an uncle that worked for an instrument company, that most of the finely made parts were cast in very precise molds because it was better for constancy, and cheaper than having them machined. That was way back in the 60s though.

Hi Ed,

I am not a foundry man but I spent one year as trainee in different depts.of foundry, in the year 1961-62. I was on shop floor in one of the leading steel foundry in India. We also had grey iron casting div where I learnt about oil castings. Now a days you can also get much better finish in Investment Casting but it is more expensive. As foundries are labour intensive units hence they have moved out of metro cities like Mumbai.Also there are pollution problems.

Suresh Sharma.