Jeffrey Corton’s Diana Seal Tool

As you can probably tell, I’m in the midst of Holiday craft selling insanity and haven’t had time to play with the Rochesters or any other airguns lately.

A while ago I received the following pictures from Jeffrey Corton showing his extremely simple (as in, "why didn't I think of that?"), no machining required version of the seal tool I made for the Diana pistol piston seals. Also scroll down to the bottom for a nice solution to the Crosman model 38 valve tool as well…

All pictures and text by Jeffrey Corton, thanks a bunch Jeff!

1. Parts: seal, electrical end cap (large end diameter slightly larger than piston crown), O-ring, 2" socket extension and socket (slightly wider than the electrical end cap).

2. Work seal over small end of cap.

3. Set end cap inside O-Ring. Press seal using extension/socket down to O-Ring. O-ring is simply present to prevent seal from sliding off the end cap.

4. Final position of seal and end cap.

5. Place end cap over piston crown.

6. Using extension and socket, press seal over end cap and onto piston. Picture has seal already installed and one set to go.

7. Seal pressed in place.

8. Remove extension/socket and end cap should be free.

9. Tada, mission complete.

As promised, a bonus for the Crosman Model 38 valve:

"Don't have a cool lathe like you, so I had to figure out another way to unscrew the Crosman 38T Valve. So: snap ring pliers. See attached pic. I just used the 90-degree attachment, didn't even attach the ends to the plier handles. Just set them in place and twisto-presto. Easy peasy lemon squeezy."

Thanks again Jeff!

Fixing a Stripped Powerlet Screw Thread on the Crosman 38T

So I had a few minutes of free time and decided to do some plinking in the back yard. Went to charge my .22 38T with gas and somewhat terrifying "whoosh!" all the gas shot out between the cartridge and the sealing unit. After calming down a bit I checked the pistol and found the powerlet screw thread in the frame was stripped. It allowed just enough pressure to pierce the cartridge but then would move from the back pressure. Darn.

You can see the aluminum in the threads of the powerlet screw (#38C-045).

I carefully pried off the cup (#38-131).

You can see how the internal threads are stripped.

Lots of aluminum wrapped around the screw.

So I drilled out the hole to a letter "Q" drill.

And tapped it 3/8"-24 (fine thread)

I turned down a piece of steel to 3/8", drilled and tapped for the 1/4"-28 thread of the powerlet screw.

Then tapped it 3/8"-24

Threads...

I put a very shallow screw driver slot in the end.

And parted it off to length.

Looks good? I then deburred it all over.

I used red loctite to make sure it stayed in place and screwed it flush with the frame.

Inside the frame.

I pressed the cup back on.

Looking at this I wish I'd refinished the end of the screw...that the slot is so abused can only mean someone reefed down on it with some force, which is probably why the threads ended up stripping. Well, I'm the one who only buys used guns...so it's par for the course. You only need a tiny bit of force to seal and pierce the CO2 cartridge, which is why the manual (.pdf) says to use a coin, not a screwdriver to pierce the CO2 cartridge!

The repair seems to have worked well, although I'll check it nervously every time I charge the pistol. I am happy that I was able to resume plinking, this pistol is great for knocking over tin cans.

Crosman 38C, I Spoke Too Soon...

I guess I spoke too soon as I found the 38C had leaked out all of its gas on Sunday morning. So I took it apart again and decided the 38-094 Valve Seal was the likely offender, as it looked a tad discolored and possibly had some cracks.

So I turned up a replacement seal from 95 durometer urethane rubber. It'a bit softer than the seal in the pistol but it should seal well.

I took the time to sand the faces flat and smooth. I replaced it in the gun and it sealed fine. As of this morning it's still holding gas with no evidence of leaking. Teflon, Nylon or Delrin might have worked as well, if it develops a leak again that's what I'll try. But for now it's all fine.

I ordered the 38A027 (piercing pin) and 38-128 (End Seal) from Crosman this morning, 6 of each for about $21.00 w/ shipping. You know, just in case...

Oh, I thought I'd mention that Derrick has a winning entry up in the Crosman "Summer House". I can't hardly wait to hear what he won. It's a great story especially if you like old Crosman guns.

Next project for the blog? I'm working up the nerve to take apart my BSA Superstar with Theoben gas ram. We'll see what happens.

Two New Crosman 38's

Well, bargain hunter that I am, I bought a lot of airgun parts off of Gunbroker.

This was the first picture in the auction, it's an impressive bunch of parts including a complete trigger assembly from a Crosman 160/180/400, a slew of other Crosman parts and some other odd stuff.
(picture copyright David Banker, 2008)

But this is what got my attention, a .177 Crosman 38T and a 38C, complete! The price for the lot was $65.00 w/shipping, which seemed a bargain. There is almost a 3rd 38T in pieces, just a few parts are missing.
(picture copyright David Banker, 2008)

The 38's seemed to function fine, but as is typical, they leaked.

The CO2 cartridge seal on the 38C seemed fine, and indeed it was.

The o-ring 140-058 was replaced with a viton #011 o-ring. All part numbers refer to the valve schematic on the Crosman site.

The 38-130 o-ring was replaced with a #009 o-ring.

38-065 square seal was replaced with a #004 o-ring. It deforms and seals fine when stuffed into the CO2 seal assembly. Indeed I tested the previous 38T I'd resealed using these o-rings and it is still holding gas. All other seals were reused.

The 38T CO2 cartridge seal and 38-130 o-ring weren't in good shape, luckily I had one old CO2 cartridge seal in my box of spare parts. So I was able to reseal it. I will order a bunch of CO2 cartridge seals and piercing pins soon, just in case I run across any more of these lovely old pistols.
The parts are 38A027 (piercing pin) and 38-128 (End Seal), and they are used in the current model Crosman 357-6W and should be available from Crosman directly.

So now my collection includes a .22 38T, a good condition .177 38T in box, two more .177 .38Ts and a .177 38C. I'll be getting rid of one of the 38Ts and looking for a .22 38C (have one in rough shape? I'd love to have it!), because sometimes you set out to collect and other times collection is thrust upon you...