Tuesday, July 20, 2010

Making a Bulk-Fill Cap for a Crosman 160 Part--2

The slow saga continues.

Didn't think that there was enough material in the plug made in part 1 for 1/8" NPT female thread to fit my bulk-fill adapter. Rather than start again from scratch (and buy another specialty tap to match the gas tube threading) I thought that a larger diameter head added to the front of the plug seemed to be the easiest way to salvage the project. So, another piece of 0.750" dia. drill rod is cut.

Reduced just less than half the OAL to 0.379" dia.

...and threaded to 3/8"-24.

The new head for the plug. Why 3/8"-24? Well, it looked like the largest thread size I could comfortably cut into the plug and I had both the required tap and thread cutting die--so no additional capital outlay was necessary.

Need to seal the two pieces together so the CO2 won't leak. A small, home ground parting tool made a relief cut at the base of the male threads for a small o-ring. Wrapping several turns of teflon tape around the threads would have probably worked, too, but I'm a glutton for punishment.

The front of the plug was initially left long to provide a holding surface to cut the o-ring grooves. Shortened it up a bit with the parting tool.

Again, lots of cutting fluid and slow turning speeds saves the blade.

Through drilled the plug with a 1/8" bit.

Then, drilled partially through the front third of the plug with a 21/64" bit and counter bored. This left a stepped hole of two sizes. No pictures for some reason? Not shown: Tapped the hole 3/8"-24 followed with a bottoming tap. A bottoming tap typically leaves about three threads only partially formed at the bottom of the hole. So, I ground off the taper on a spare tap and put full-size threads right to the bottom.

Used a tiny boring bar to cut a seat for the o-ring into the front of the plug to seal the threads.

The small o-ring to seal the halves together is a P7. The two larger o-rings that seal the gas tube are 112's.

O-rings on...

and pieces screwed together with the locking ring in the middle.

Installed, again, with one live CO2 cartridge and one dummy to check pressure retention. No leaks to report three days later.

Just need to tap for the 1/8" NPT fitting and make a check valve that seals the gun as the paintball tank is removed after filling.

More to come...

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