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PostPosted: Sun Aug 16, 2015 12:33 pm 
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Joined: Tue Oct 18, 2011 12:21 pm
Posts: 431
Location: Ontario
My cousin gave me his old Walther PPK which had recently developped a severe leak.

He didn't want to tinker with it and was ready to let it go. I normally leave my airguns alone unless it is absolutely necessary to open them up and this was a good example of "it cannot get worse".

An internet research didn't bring any in-depth disassembly tutorial. The only ones I found were showing how to remove the slide which is fairly basic.

After printing the diagram, I started to study it.

Image

Basically, I just needed to reach the valve unit and it seems that it would fairly easy to acces it. The slide lock needs to be removed from the left side and from the right, the grip, the safety and the trigger must come out.

Image


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After that, two pins are driven out and the valve unit is free. Visual inspection showed that the cartridge seal seemed OK but the brass nozzle that pushes the BB in the barrel was sticking out a lot (probably the reason why the magazine couldn't be inserted).

I used a thin steel plate to unscrew the valve cover and the internals popped out.

Here they appear in the order they came out. A green o-ring was still in the valve body and is not shown in the picture. After comparing with the diagram, I realized that the stacking was incorrect and the reason why the nozzle was sticking out farther than it should have.

Image

It seems that my cousin didn't tell me that he went inside the valve.

After inspecting the components which all looked OK, I reassembled the valve in the correct order and put the pistol back together to test it.

When the cartridge of CO2 was pierced, there was a loud bang and the gas was all exhausted through the barrel. After removing the slide, I saw that the valve cover had popped open which brought me to suspect that the threads in the valve body were stripped.

Using only the valve body and cover, I discovered that there was a thread engagement of only 1/4 of a turn. I should have thought a bit more before doing it but I decided to sand down the end of the valve body to give a bit more engagement to the cover threads. I shaved enough material to end up with a full turn of engagement.

That was a mistake. By doing that, I reduced the internal cavity and after stacking all the components, the cover didn't reach the point where it coud be screwed in.

To gain some space, I sanded the valve seat to reduce the thickness and changed the O-ring for a smaller one that was thinner. The cross-section being smaller it didn't closely fit the inside wall of the valve body. A bit of teflon tape in the groove of the cover solved the problem.

After fighting with the valve assembly, I finally was able to screw in the cover. Only to have it popped open a minute later. The last portion of thread in the body had given up and it was all stripped out. Basically, there was no way to fix it.

This is until I had the idea of pinning the cover in place. This was the last option to salvage the repair. The area where the thread is located is a neutral zone that doesn't affect the operation of the valve.

I found a finishing nail that had a diameter of .0625 inch. So after compressing the valve assembly in a vise to bring the cover in contact with the body, I used a .0625 inch (1/16") drill bit to drill a hole deep enough to go through the wall of the valve body and partially in the valve cover threaded section. It is important to not reach the center hole where the piston is.

The pin was a sliding fit with the hole and I was thinking that it could slide off when I would drill the other side but when the pressure of the vise was released it was jammed in place. Just to make sure, a piece of masking tape was placed over it and the valve turned over in the vise for the second side. The top of the pins were filed flush with the valve body as shown in the picture.

Image

Since the geometry of the valve was slightly modified, I was not sure what would happen when the pistol is pressurized.

After piercing the cartridge, everything worked fine and the Walther PPK is now operational. An hopeless situation was salvaged.

In conclusion, if you come across stripped threads, this is a viable option. If the internal components look fine, just repack them and pin the cover, it might save the day.

R-Gun Pete


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PostPosted: Sun Aug 16, 2015 7:37 pm 
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Joined: Wed May 12, 2010 12:21 pm
Posts: 1099
Nice Save Pete!!


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PostPosted: Sun Aug 16, 2015 8:24 pm 
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Joined: Sat Mar 16, 2013 5:15 am
Posts: 3580
Location: Edmonton
... and a great report on same. Thanks for sharing.


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