Holding Air Pistol Cylinders for Rebuild?

[Gwhite]

I have a Hammerli AP40 cylinder that still has 3 years of official life, but the valve leaks. I have a couple expired cylinders I can cannibalize for parts if it needs more than cleaning & grease.

I've got an adjustable pin spanner for the valve end, but they are put together pretty tight. Using a non-slip glove to hang onto the cylinder doesn't cut it. I can rig up Vee blocks for a vise, but I don't want to risk any damage to the cylinder. I also have a selection of small (and not so small) strap wrenches, but that will require some juggling to hold the strap wrench, cylinder AND the spanner at the same time.

Any favorite tricks I should know about? I was thinking about 3D printing vise jaws, but I need some sort of non-slip material to line them with. The team I help coach has about 30 of these cylinders, so investing time in a secure & safe solution is worthwhile for the future.

Thanks!

[crrmeyer]

I usually used old bicycle inner tubes for this type of application. The bike stores are nice and give me bad ones for free.

[fhorrigan]

With the caveat that the following applies to CO2 cylinders, here are some tips:

I had the same problem with an old CO2 cylinder for a Walther CP2 a few years ago. I was ultimately able to unscrew the valve and get it working again (it just needed cleaning), but it took took a lot of torque to unscrew the valve and several failed attempts at clamping the cylinder. I tried making wooden Vee blocks for a vice to clamp the entire length of the cylinder, but it wouldn't hold tight enough to prevent the cylinder from spinning. Maybe a non-slip material or stronger vice would have helped. After much swearing I eventually succeeded by wrapping the cylinder in a rubber sheet and holding it with it with a pair of curved jaw vice grips. But I don't recommend this approach since I scratched the cylinder; and this was a very heavy duty steel CO2 cylinder, not an aluminum air cylinder.

I later contacted a former dealer/repairer of the CP2 for his advice. He said I could share his tips, so they are posted below with his illustrations. I believe the device he used is called a split-block clamp. I don't know if it can be purchased in the correct size, or has to be made by a machinist. But, given the difficulty I had, it might be worth having one made, especially if you have many cylinders to work on.

"Being in the business I was required to do a lot of cylinder repair. I worked only on the CO2 cylinders, air was just starting to get popular, I did not work on the air cylinders. For the CO2 cylinders I had a machinist make up a steel clamp for me which worked very well. It looked something like this…It would be easier to make it simply in two halves and clamp it in a big vice.
Yes, It does take a lot of clamping pressure!! " - Ray McDougall

image001.png (26.5 KiB) Viewed 2553 times

[marky-d]

I use a wood block. I was fortunate enough to have a drill bit approximately the right size (although not exact), so I drilled a hole in a block of 2x4, then cut it in half, just like the image on the right. Because my drill bit was too small, I left the edges fairly thin, so it could spring out enough to fit the cylinder.

I did have trouble with it slipping in the blocks (possibly because my blocks were not exactly the right size), and I didn't have any inner tubes to cut up, so I lined the blocks with some strips of electrical tape. That provided enough grip on the cylinders I was working on, but it was borderline -- the tape got twisted around and had to be replaced after each cylinder, but it did the job.

FWIW, I cheaped-out on the pin wrench too, although I wouldn't recommend it. I just drilled a couple holes the appropriate distance apart in a scrap of aluminum, then put some pins in the holes to make a wrench. But I was only doing one cylinder with that type of interface.

marky-d

[David M]

4 in. Vee blocks made from polypropylene or thick leather held in a vice.

[High Left]

I'd go with split aluminum blocks, but I've got machines ... back in CA anyway.

The wood block option could work as well, and you can get a good fit by 'glass bedding'. Shouldn't be hard to rough something out, even with a pocket knife if you're Jed Clampett. Wax a cylinder and bed it in with some Devcon plastic steel. Even the hardware store variety in a syringe will do the job. JB as well. DO NOT clamp right where the threads are. You can compress it to a pointt they'll bind, and aluminum galls (welds to itself) quite readily.

My personal concern, which appears by the previous posts to be unwarranted, would be there's a thread sealant (Loctite) applied. Attempting to unscrew an aluminum assy with Loctite involved quite often also results in galled threads. Torqued in, they're bearing on one face and the Loctite fills the void on the other. So when you unscrew it, the previous bearing faces rub against each other *ALL* the way out. Just something to keep in mind for other adventures in 'repairs'.

[spektr]

Before you open it up..... Try to lube the valve and exercise it with a wooden q tip or something like it..... My P44 tank had a slow leak because it got lightly corroded /dirty.....Synthetic oil and a wooden q tip to exercise the valve washed away the corrosion/dirt/whathatever and it was back to working normally

[6string]

Here's some suggestions, assuming the cylinder is completely empty and will be thoroughly cleaned before reassembly.
Try using applied heat and cold alternately to the outside of the cylinder/valve area. Use a heat gun (not hair dryer) to get it hot and a compressed air aerosol can (sprayed upside down to use the coolant) to get it cold. A very fine penetrating oil such as Kroil can be applied to the thread juncture (be sure to really clean it later!) as you go.
This will help loosen things up, and perhaps break down any thread sealant to prevent galling.
Also, consider making a dedicated, fixed spanner wrench. The adjustable ones can be kinda light duty. Plus, if you make your own you can make an extra long handle (or cheater bar) to really lean into it.

These approaches, along with the nice clamping block plan posted earlier, are good enough to get rusty barrels off of old military bolt action rifles.

[David M]

My personal concern, which appears by the previous posts to be unwarranted, would be there's a thread sealant (Loctite) applied. Attempting to unscrew an aluminum assy with Loctite involved quite often also results in galled threads. Torqued in, they're bearing on one face and the Loctite fills the void on the other. So when you unscrew it, the previous bearing faces rub against each other *ALL* the way out. Just something to keep in mind for other adventures in 'repairs'.

The air tanks are NOT loctited, they are sealed by "O ring" and just nipped up.
A fair force is needed with a good fitting pin spanner.
You need something that will grip the tank to prevent slipping.
Having done many tanks I found that 1/4 thick leather (underside to tank) held in a vice works well, holds well and does not mark alloy tank if it slips.
re-install with new seals and a little lube on seals and threads.

[Gwhite]

Thanks for all the suggestions. Given that I have other cylinders of different diameters (Morini, Steyr, Benelli) that I may need to work on at some point, Vee blocks are appealing. The problem I've had in the past is that when torque is applied, they want to shift in the vise. One will try to go up & the other down.

I can 3D print blocks that have lips that match the vise jaws to prevent that. I've got leather, rubber sheeting & rosin to prevent slipping & cushion things a bit. I'm still torn between printing blocks custom sized for each cylinder diameter vs the Vee block. A cylindrical grip should be much more secure and put less strain on the cylinders, so I think I'll go that route.

I'll keep folks posted on how it goes.

[thirdwheel]

Whatever vice you use make sure it is in good condition and the jaws do not droop or are out of parallel in any way and the smallest jaws I would use are 5", 1/4" tan leather as soft jaws works, not sure about the plastic used in 3D printing as it is slippery as hell and may give up under the pressure. The split blocks work the best but I do have a lathe to bore them out then drill them for the fixing location, cut it lengthwise and tap the holes for the fixings. The custom pin wrench is a good idea too if you are having to do a lot of the same as the Y shape shifting ones can compromise themselves. There is nothing like having the right stuff to hand to do a task. Good luck!

[porkchop]

How about putting wrench in vise and using nonslip gloves to grip cylinder and turn it. Of all the grippiest gloves I've used, my wife's dish washing gloves are the best.

[Gwhite]

The 2.5 mm spanner I have is this one:



It's not very conducive to clamping in a vise.

I've got the start of a 3D printed set of vise blocks, but I need to decide what sort of gripping/cushioning material I want to use so I can enlarge the ID appropriately.

[brent375hh]

When I changed rifle barrels, I used two wood blocks. It would always turn in the wood until I used powdered rosin. After that, no problems. I don't know if the anodized finish could get marred by rosin though. I would think if you could get one burly man to hold the cylinder with a strap wrench, and you had the spanner, it would break free.

[Gwhite]

I've used rosin for things like this in the past, and I've got plenty on hand. I doubt it would damage the finish, but when it does its thing, it sort of melts and sticks. It's pretty easy to clean off with alcohol.

I have some silicone rubber sheet that is very high friction. I'm going to try that for lining the jaws. I suspect the problem may be slippage between the linings and the 3D printed jaws, in which case I can use a LOT of rosin to stop that.

[Gwhite]

I'll have to take some photos, but it works just fine. Two 3D printed vise jaws, and a sheet of red silicone D90 rubber:

https://www.mcmaster.com/5773T22/

were all I needed. No rosin required.

The bad news is that the Hammerli AP40 cylinder valve appears to be held in place by a pressed-in thick aluminum ring. It is clearly NOT designed to be serviced. That said, I can try to flush out the leaking one and get some lube into it. If that doesn't work, I can replace the entire valve end from an expired cylinder.

Update: I've attached a PDF with a description & photos of the final vise setup. I'm also printing jaws for other brands/sizes of cylinders so I have a full set. Before I go any further on the actual repair, I want to make sure the valve is the problem, and not the cylinder seal or gauge.