Wednesday, January 12, 2011
Bolted a couple 1-2-3 blocks together and placed the original mag against the soon-to-be. This arrangement kept things relatively square while I marked the angle across the corner. The angle appears to be for ease of insertion into the mag carrier on the gun. Not shown: milled and finished the angle.
I set up the original mag in the milling vise and used it to set up the quarter round cut. The depth of this cut indicates the mag in the carrier. I used a depth micrometer set against the lower fixed jaw on the vise to position the work in the same location.
Used a 4mm end mill then test fit the mag in the gun. It was a good fit in the carrier. A bit tighter than the original.
Not exactly an epiphany, but I've been thinking a lot about how to mark off the pellet hole spacing on the mag. It occurred to me that I could simply remove the barrel...
and just use a transfer punch to mark directly though the breech.
Put some layout fluid on the face of the mag, then slid it home.
Lucked out and had a punch that fit the breech like it was made for it.
Tap, cycle the carrier manually. Tap, cycle the carrier...
Testing: Drilled some aluminum with various sizes of bits then tested .177 cal wadcutters in the holes. No real surprises here, but I settled on a #16 bit for final size.
A pointed indicator is used to locate the center of the hole...
then it's replaced with a bit and through drilled.
Then back to the indicator for the next hole. Slow, but it worked.
Opened the holes up to #16 (0.1770").
Used a #15 bit in a pin vise to chamfer the breech side of the mag to allow the pellet skirt to seat flush.
A small groove cut with a 1/4" ball mill marks the side to load.
Front view. Test firing was surprisingly uneventful. The darn thing functions and the pellets go into a little tiny single hole on the target--??? I am utterly astonished that this even cycles--let alone works. Oh, the bottom mag is the new one. I'm absolute proof as to the old saying about blind pigs and acorns.
With the valve apart it’s time to make some changes.
The internal valve body threads are 27 tpi, as best I can figure. I was hoping I’d have a tap to clean the threads out but it was an odd diameter…
So I used a pipe tap as a scraping tool, following the wall around to clean off all the schmutz.
The plug was cleaned up with a thread file.
Now it screws together easily.
Whatever the old seal is, it has to go.
I made an arbor to hold the plug on the lathe. A rubber washer protects the inlet valve seat.
Parting tool set up to make an o-ring groove.
Turning the groove.
Test fitting an o-ring
Doesn’t screw quite all the way on, but that will be addressed…
Cleaned up the face of the plug while I was at it.
I needed to bore a recess for the o-ring in the valve body.
Just enough to get down to the thread root.
Seems to go together snugly.
The solder filled a groove at the end of the threads on the valve body. I turned away the solder until I just hit the brass.
Test fitting it to the tube. Aligned, the gap is too large, but I suspected the threads in the tube needed more cleaning.
You can see that the slot and the setscrew hole need to be aligned.
After cleaning out the tube threads a bit more the gap is acceptable and similar to the assembled versions…
I also made two seals for the inlet and exhaust valves. They may be too thick (.125”) although the old ones are so deformed it’s hard to tell how proud they should be. I’ll try them like this and modify as necessary.
Next up is the pump plunger, then figuring out how to keep the tube aligned and sealed to the valve body without resorting to solder. Then reassembly…