You will need some brass tubing (YOU pick the size), Aluminium rod to fit inside the brass, 440 pushrod, and "O" rings slightly larger (.005) than the aluminium rod.

Use your lathe to cut a groove in the aluminium rod for the "O" ring. (This is your piston) cut it off at about 1/4 in, with the groove in the center.

Drill and tap the center of the rod for the 440 pushrod.

Cut and groove another piece of the aluminium rod, 3/8" long with the groove 1/16" or less from both ends. Make one groove for an "O" ring and the other end to crimp the brass tube into.

Drill one of these (centered) for the end that the pushrod exits, and off to the side for the air line. ( be sure and leave enough room for the hose!)

Use 1/16" brass tube for the airline and loctight in the hole. (Clippard makes a nifty barbed fitting that is even better, if your cylinder is big enough.)

Cut and groove another rod for the anchor end of the cylinder, make it long enough so you can drill and tap both sides for an "L" bracket. Drill and install 1/16" air tube in the center.

Install and loctight the 440 pushrod in the "Piston", put on an "O" ring, and lube it with some "White" grease.

Insert in the brass cylinder.

install another "O" ring and put the Aluminium rod over the pushrod and insert in one end of the brass tube.

Using your tubing cutter, crimp the brass into the smaller groove of the aluminium tube.

Repeat for the anchor end.

You can make them any length and dia you need.

Hook it up to an air supply and enjoy.