serviceable piston

[MrCrowley]

Draw a perfect circle line around your piston, piss easy....

Stick it in your vice, grab a file and file down the line to make a groove. Open vice, roll the piston over to see more line, close vice and continue.

USE YOUR HEAD.

[no-limit]

If only I had a vice, think i'll go buy a lathe instead. I don't like half-assed.

[MrCrowley]

Okay go buy a lathe for a couple of hundred, if you have the money I don't see why not.

[ammosmoke]

I wouldn't say that using a vice is half assed, as a lot of the members on here do not have access to a lathe, and have made perfectly respectable cannons.

[Rob Thornton]

Regarding not having a lathe, I have had huge success by hooking the piston up to a drill/drill press. It's much more ghetto, and probably not as safe as possible, but it works a treat. But even if you do have cash for a lathe - what else are you going to use it for? My guess would be not much... seems a waste of resources.

Oh yeah, I want to use a 1" sprinkler valve to pilot it.

As you can see in the pictures of biged's tennis ball cannon above, he's using a QEV (quick exhaust valve) as his pilot.
I'm a huge fan of QEV's:
They're about the same price as a sprinkler valve.
They look much neater.
They require no modding whatsoever.
You can fill your chamber through the QEV - so you drill less holes (less chance of leaks)
Oh, and did i mention they're very efficient. That QEV will dump the pilot chamber air faster than you can say 'cat in a hat'.

Good Times

Rob

[Biopyro]

No, you just have to do it by eye. put the piston on a flat surface and use a pencil or chalk at a set height, then turn the piston. This will give you an even line all the way.

An abra file is a notched wire which works as a file. They are very handy for all sorts of jobs. Abra file

Edit: I didn't see there was a second page, but yeah, a good lathe is a lot of money. Unless you plan to use it a lot, you're much better getting a vice. If you don't have one already then, well, you should!

[no-limit]

Looks like I will be getting a vice. I have a drill press but it has to be perfectly centered or you will only hit one side of whatever you are trying to work on.