Experiments because I haven't done this before and I don't have a "milling machine", but I do have a very rigid drill press and a lathe. But I wouldn't recommend doing it this way because it was a PITA, but I managed to make it work.
I'm talking about buttoning the piston and compression tube on my 97K, which I've been contemplating doing for some time.
I started out by truing up the runout between the piston head and the piston body on the lathe which wasn't much .003" radial and .002" axial, probably doesn't matter, but I did it anyway. Then drilled the blind holes on the drill press 140rpm using a 3/16 carbide, 4-flute center cutting end mill
.This was set up as rigid as possible, being as close to the stubbed up end mill as I could, only having to feed the quill down less than a 1/2", and my drill press will go down to 140 rpm's, which I used. Only drilling about .025" deep, I have a indicator rigged up for a depth stop.
Two buttons on top and four on the bottom.
Next I made the buttons on the lathe for a snug fit and super glued them in place. Then dialed the piston in with the 4 jaw chuck and turned them for a slip fit in the compression tube.
Piston came out good with a nice sliding fit in the compression tube, now the piston will stay centered in the tube.
Now for the compression tube. I had heard that it was case hardened, but it wasn't as hard as I had thought it might be, and no match for the carbide end mill. I did go slow with it though. Before I started, I machined a delrin plug for a snug fit inside the compression tube, and this I think, helped with the rigidity when buttoning and when chucking in the lathe to turn the buttons.
I put four buttons on the top and four buttons on the bottom, machined them for a slip fit in the receiver. These next pictures are where I have already applied the Krytox lube GPL223 on the piston and compression tube, so you can see how little I use on them. This is the bottom....
And this is the top. I have blued the front portion that will "show" when it's in the receiver as well as the face of the compression tube.
I also machined a new oring piston cap with the trued up piston so it's all concentric less than .0005" and installed a new Viton oring.
I'm still using the old JM QX4600 spring with my guide kit that's spaced up to max, it has thousands of shots on it and still going. Assembled it all back together for testing.
Initial impressions, I like it. Cocking is smooth with no play, a lot more solid when closing. Just seems more solid all around. Of course it will break in over time. I assume the oring piston will also break in over time and speed up some. I only shot a 100 pellets today before it started raining again.
These are the first shots at 40 yards benched, all 10 shot groups, shot in order 1 thru 5.
After the 4th group it started to settle in and group. These were shot with QYS 8.48 pellets.
I chronied with the Garmin Xcero.
Next I tried the AA 8.4's top row, then two more groups with the QYS bottom row, it started raining so I stopped shooting. But the chrony numbers sped up a little by the last two groups, so oring is settling in.
I think after some more shooting it will be good. Very solid shot cycle, and pleased with the effort. I don't want to do it again no time soon..lol. I forgot to check the piston latch rod runout, but I've done this in the past several times. I also need to touch up some bluing and wanted to make screw cups. And ultimately get a walnut stock of some sort.
I'm talking about buttoning the piston and compression tube on my 97K, which I've been contemplating doing for some time.
I started out by truing up the runout between the piston head and the piston body on the lathe which wasn't much .003" radial and .002" axial, probably doesn't matter, but I did it anyway. Then drilled the blind holes on the drill press 140rpm using a 3/16 carbide, 4-flute center cutting end mill
Two buttons on top and four on the bottom.
Next I made the buttons on the lathe for a snug fit and super glued them in place. Then dialed the piston in with the 4 jaw chuck and turned them for a slip fit in the compression tube.
Piston came out good with a nice sliding fit in the compression tube, now the piston will stay centered in the tube.
Now for the compression tube. I had heard that it was case hardened, but it wasn't as hard as I had thought it might be, and no match for the carbide end mill. I did go slow with it though. Before I started, I machined a delrin plug for a snug fit inside the compression tube, and this I think, helped with the rigidity when buttoning and when chucking in the lathe to turn the buttons.
I put four buttons on the top and four buttons on the bottom, machined them for a slip fit in the receiver. These next pictures are where I have already applied the Krytox lube GPL223 on the piston and compression tube, so you can see how little I use on them. This is the bottom....
And this is the top. I have blued the front portion that will "show" when it's in the receiver as well as the face of the compression tube.
I also machined a new oring piston cap with the trued up piston so it's all concentric less than .0005" and installed a new Viton oring.
I'm still using the old JM QX4600 spring with my guide kit that's spaced up to max, it has thousands of shots on it and still going. Assembled it all back together for testing.
Initial impressions, I like it. Cocking is smooth with no play, a lot more solid when closing. Just seems more solid all around. Of course it will break in over time. I assume the oring piston will also break in over time and speed up some. I only shot a 100 pellets today before it started raining again.
These are the first shots at 40 yards benched, all 10 shot groups, shot in order 1 thru 5.
After the 4th group it started to settle in and group. These were shot with QYS 8.48 pellets.
I chronied with the Garmin Xcero.
Next I tried the AA 8.4's top row, then two more groups with the QYS bottom row, it started raining so I stopped shooting. But the chrony numbers sped up a little by the last two groups, so oring is settling in.
I think after some more shooting it will be good. Very solid shot cycle, and pleased with the effort. I don't want to do it again no time soon..lol. I forgot to check the piston latch rod runout, but I've done this in the past several times. I also need to touch up some bluing and wanted to make screw cups. And ultimately get a walnut stock of some sort.
. Have a temporary shop or really hobby room where my bedroom is supposed to be. I need an outbuilding built for various typical homesteading purposes. That outbuilding will have my work benches and some basic machinery. IE drill press, small metal lathe and milling machine. It and an upstairs guest room will be climate controlled. This has been planned for two years but needed home improvements and continual rotation of terrible contractors has prolonged it's completion. I'm waiting to buy the machinery because my current work space is small and temporary. Eventually everything should come together. Thanks to the lack of available good contractors it's just taking much much longer than I thought.
