New Pistons for compressor

[quadrod]

I have been in the process off and on of rebuilding my older Quincy compressor. I am now considering making my own pistons. My question has to do with material choice. The original pistons are made out of cast steel. Could anyone recommend a steel to use, such as 12l14 or 1144 stressproof. Thanks

[nickel-city-fab]

Hrm,,, the 12L14 will certainly take a better finish (and maybe easier to hold tolerances on) but the 1144 is well, stress proof as it says. That's a tough call, but I think you would be OK with either one. Depends how hard you use the compressor. I know the 12L14 is good for 50ksi, and the stress proof is double that, but do you really need it in a compressor? Consider that a lot of compressors use aluminum pistons and get away with it.

[epicfail48]

Im voting for the stress-proof. Id imagine that compressor pistons see some pretty considerable forces, especially around the... pin? The bits that hold the pistons to the crankshaft. Seems like stress-proof would be more likely to hold up over time

[quadrod]

I was thinking of the 12L14 or stressproff for the wear not just the strength. I am using steel instead of aluminum to try and keep the weight as close as I can. It only turns may be a 1000 rpm probably less but there is a balance factor to consider. I was just wondering if there might be a better material for the wear characteristics.

[Mcostello]

7075 aluminum closer weight match, decent strength.

[nickel-city-fab]

I was thinking of the 12L14 or stressproff for the wear not just the strength. I am using steel instead of aluminum to try and keep the weight as close as I can. It only turns may be a 1000 rpm probably less but there is a balance factor to consider. I was just wondering if there might be a better material for the wear characteristics.

Pretty sure that any kind of steel is going to have the same wear characteristics unless you use hardened and ground tool steel, like D2 or A2. So basically it's a toss-up for the steels you listed.

[JoeLee]

Pretty sure that any kind of steel is going to have the same wear characteristics unless you use hardened and ground tool steel, like D2 or A2. So basically it's a toss-up for the steels you listed.

I have to agree completely on this. Matching the weight is going to be the most important factor involved. Since the original pistons were cast how are you going to duplicate the interior shape with all it's curves around the pin hole etc. which can't be machined. All that adds to the proper weight of each piston.

The OD, length and distance from pin center to top are all critical dimensions. Cut your ring grooves to size and position and then start hollowing out the inside until the weight is matched to the original. Sound like a chore to me.

JL................

[old mart]

Pistons are commonly turned oval below the rings, I dont know if the cooler working conditions with compressors requires that. The bores would certainly have to be refurbished before making the new pistons or it would be a waste of time. New rings with a ridge dodger top ring would be the easiest way to give the compressor a new lease of life.

[quadrod]

Yes it will be a learning experience on how to machine the interior of the piston. The pistons are flat top, no cir-clip groves and round not oval like a hi-performance automotive piston. New over size pistons are available but very expensive. Last night I priced 12L14 and 1144 from online metals and speedymetals and was shocked at the price.

[nickel-city-fab]

Last night I priced 12L14 and 1144 from online metals and speedymetals and was shocked at the price.

You too? Seriously, try eBay -- I've been getting better deals on "drop" bar ends from major steel shops there. Usually the shipping costs more than the metal, so watch for that --

[JoeLee]

Yes it will be a learning experience on how to machine the interior of the piston. The pistons are flat top, no cir-clip groves and round not oval like a hi-performance automotive piston. New over size pistons are available but very expensive. Last night I priced 12L14 and 1144 from online metals and speedymetals and was shocked at the price.

The cost of enough to make a couple pistons may exceed the cost of buying them not to mention the time involved. Speedy Metals has some good prices but the shipping will kill you.

Sometimes you better off buying the painting rather than trying to copy it !!

JL.............

[quadrod]

I have been and will continue to watch ebay, so far nothing large enough, I need one piece 2 5/8 x 6" and one piece 3 5/8 x 6''. The bores of the compressor are 2 1/2 and 3 1/2". At some point it may be cheaper just to buy an inexpressive compressor to stick on my tank.

[J Tiers]

A foot of 1144 3 5/8" is about $213 from McMaster, which is admittedly not the cheapest source. But unlikely that you will take a LOT off that regardless of source, aside from drops..