Question for you CNC experts

[12 point]

Could these antique aluminum tractor pistons be duplicated with a CNC machine? Or are they something that has to be cast? If they could be machined, what type aluminum would be needed and what would you estimate the total bill to be for one pair?

They are Liquid Propane Pistons and are a tad bit longer than the gasoline version for a John Deere 2 cylinder farm tractor aka Poppin Johnny.

Approximate width is 5 7/8" and the length is close to 8".

[Goldeneagle]

Yes they can be made. It would take either a multi axis lathe or a lathe operation and a milling operation. No idea on the cost cause I work for a large company and don't do quotes. Also not sure on what type of aluminum to use, but that could be researched. Can you find any replacements? Because having them made will probably be costly.

[12 point]

Thanks for responding. New LPG pistons are NLA unless I can find a set of NOS. The used pistons I've bought off EBay have been disappointing. I can buy brand new pistons for gasoline JD's but they are shorter. They'll work, it's just that the engine will have less compression and I'd have to make adjustments to compensate.

I've been searching for well over three years. There are some salvage yards that have some but it's a gamble since they're in the engines. Another source has some that look like they've been beed blasted and I'm hesitant to purchase them.

[offroadodge]

if you have to go with shorter piston can you get a longer rod to comp the difference? It can be made.

[DirtyDave]

You are looking at about a full days worth of work to make 2 parts. Shops charge an average of $100/hr.

Reverse Engineering time + Programming + 4 setups + Run time.

I'm seeing 2 lathe operations and 2 mill operations to make these.

[CSF45]

Would not be real difficult to machine, would be at least a full day's work though. I would think they would be forged

[Graysonhogs]

Easily a days work, like DD said. I bet someone on an antique tractor forum could steer you in the right direction.

[12 point]

Guess I'll just keep searching for some. Thamks for the input.

The problem with trying to buy from a salvage yard is that the odds are high of finding pistons in good shape that aren't stuck in the cylinders. It took a lot of work to get the stuck pistons out of the tractor I'm working on. The tractor sat unused in a barn for about two decades. It still ran when last parked in the barn.

[Goldeneagle]

Can they just be cleaned up good? They really don't look that bad. I've seen worse.

[12 point]

The photo was before they were shipped to me. They got damaged by USPS. When they arrived there were broken rings and some of the grooves got distorted.
The pistons banged against each other while in the box.

[Goldeneagle]

If the rest of the piston looks OK, the ring grooves can be cleaned up.

[Graysonhogs]

If the rest of the piston looks OK, the ring grooves can be cleaned up.

What he said ^^

[12 point]

Oops, I forgot to mention an important detail. Didn't have the pistons in front of me,. Since they were damaged, I waited on attempting to clean them up until after things were settled with the USPS claim. Of course they didn't reimburse me 100% of what I paid. Only got about 50% back. While cleaning them with a soft, brass bristle brush I soon learned what were advertised as Standard size pistons were actually +.125 oversize.

I had two different machine shops check and measure the cylinders and they have not been bored out, so the oversized pistons are of no use. Planned on shipping the pistons back to the seller for a partial refund of what I originally paid plus shipping., since as was already mentioned, USPS refunded half the purchase price.

If they just weren't oversized I was leaning towards just going ahead and using them.

[12 point]

A friend of mine has a machine shop. All the work is manually done. No CNC. Since LPG pistons are no longer manufactured, it makes me wonder about having these oversized pistons turned down. Would it be doable? I've never heard of it, so I thought I should ask on here before I ship the pistons back to the seller.

[Goldeneagle]

I would think they could be turned. This would also let the ring grooves be cleaned due to having to be re-grooved for standard size rings. I'd give it a shot. If your friend can't do it, I could if you send them to me. I just need to know what the diameter of stock piston is and diameter of the bottom of the ring grooves for stock.