HW35 leather piston seal

[Garden Guns]

Hello all.

Does anybody know where to get a replacement leather piston sea? Mine is not in great shape.

I have tried Knibbs, Chambers and protek.

I really don’t want to have to go down the synthetic route and sleeve the transfer port.

Many thanks

Neil

[coburn]

Hello all.

Does anybody know where to get a replacement leather piston sea? Mine is not in great shape.

I have tried Knibbs, Chambers and protek.

I really don’t want to have to go down the synthetic route and sleeve the transfer port.

Many thanks

Neil

Hi Neil, I imagine there are plenty of good used ones belonging to members on here who gladly sell you one, try a wanted add.

Is your one totally shot?, Have you tried soaking it in neatsfoot oil?

[Garden Guns]

Thanks for replying Coburn,

It has got a nick in it that soaking hasn’t sorted out unfortunately.

Will try and add!

[DCL_dave]

Hi Neil,

I may have something in my box of odds and sods so...

What size is a HW35 leather piston seal? ...and is it just the cup washer part itself that you need?

[T 20]

What size is a HW35 leather piston seal?

From memory they're 30mm OD X about 10mm deep.

[stevegv8]

Mine is on the bench right now so had a quick check, it's still fitted to the piston so don't know the cup depth but yes it's 30mm OD, 11mm deep and wall thickness is 3mm so opening for the cup is 24mm, that should suggest the cup is 8mm deep.

[Phil Russell]

If you are feeling brave (?) they are really not too difficult to make if you can find leather the correct thickness ... old belt? Old handbag from that ancient trip to Greece or Majorca? Plenty of instructions on google.Or:
Adapted from an article that appears on the Airgun BBS by Rob M

Material: off-cuts of sole leather from a cobbler's shop or hide from a bag maker, leather cycle saddles, leather belts, handbags. Car boot sales are good sources.

It's good to make your own washers, with a few scraps of sole-leather you have all you need to keep an old-fashioned springer working for a lifetime! It's also satisfying to make the bits you need to keep your old guns alive. These methods can help with the manufacture of leather breech seals too if you should need them.

The ways that leather washers are affixed to the piston vary from manufacturer to manufacturer. Some are held on by bolts, hex bolts or machine screws, others are riveted on.

To make the washer, measure the diameter of the old washer (or the piston) then add twice the height of the washer to the diameter. Cut out a disc this size (approximately) from your leather This can be done by:
1. Use a holesaw designed to cut holes in wood. Clamp the leather between two sheets of ply or hardboard and cut the disc. This is easy to do and gives you a centre hole from the start.
2. Cut the disc out with a sharp knife or fretsaw or similar. Find the centre of the leather disc, and drill a small hole there.

To size the disc, with a nut and washers, fasten the leather disc to a bolt that you can hold in the chuck of an electric drill. Now you can use the drill as a lathe, and use some clean files and wet and dry abrasive paper to round the disc off perfectly and also make the leather thinner if necessary. It has to be "Wet and Dry" type abrasive, as sandpaper or glasspaper will shed bits of abrasive that might end up embedded in the leather, this doesn't happen with "wet and dry". If using a drill or lathe wear eye protection. Depending on how much reshaping you need to do, a dust mask might also be necessary. You can shape leather like this easily by hand if you don't have power tools, but it will take a little longer.

If the leather has a shiny side, remove the shine with Wet and Dry, as it is sometimes a paint-like finish applied to the leather and could have adverse effects on the efficiency of the finished washer. Some say that the shiny side should go on the outside of the washer where it contacts the cylinder wall, but washers made of raw unshiny leather soon develop a shine after a few dozen shots anyway.

Most leather washers are actually a pair of washers; a large rear washer that is formed into a cup shape, then a smaller front washer that fits inside the cup to minimise lost volume, so you will probably end up making two discs, one smaller than the other. Sometimes the ‘inner washer’ is a countersunk steel or brass one.

Fit the washer(s) to the piston, then fasten a jubilee clip loosely around the washer to shape it into the necessary 'cup' shape. I spray the washer liberally with a little aerosol of stuff I got from a cobbler's shop called 'Leather Stretcher', which actually just softens leather enabling it to be formed into shape more easily. Tighten the clip gradually over a period of a few hours to get the correct shape. It's worth taking your time. This stuff really helps, and makes the job much, much easier. Tighten up the jubilee clip until the washer fits easily into the cylinder. Spray it, retighten the jubilee clip until you are happy with the fit and shape, then leave it to dry and set overnight or for a day or two if you can. If necessary, any bits of leather that you feel need removing can be carefully trimmed off now with a sharp knife.

Don't worry if, at the moment, it does not look anything like the old washer: The last step in the procedure will shape it precisely to fit the piston and the cylinder. At this point, the washer might appear much thicker than the original, and have a large gap between the back of the washer and the piston, especially around the outside, but don't worry. The important thing now is that the piston can be refitted into the cylinder without the leather washer getting damaged on threads, cocking slots, etc.

Before refitting it, let some "Bisley Gun Lubricant", or "SM50" soak into it for a few hours, or overnight, this is a silicone oil that will not cause the leather to disintegrate over time, plus it contains molybdenum which will lubricate the leather in use. Let the Bisley Gun Lubricant soak well in, but before refitting it, you might need to dab it with a clean cloth or tissue if there is much silicone lube on the outside of the leather. Silicone lube is good for the leather, but no good where metals will be in contact with each other, so you don't want it dripping off the washer into the cylinder or smearing the cylinder wall, for instance.

Obviously, if you are going to put GN paste or moly grease on the piston, do that now. When you have finished reassembling the gun, let the gun stand for a few days with the piston at the end of the cylinder under spring pressure (as if it has been fired), so that the spring pressure can slowly form the washer to fit the cylinder perfectly. Avoid the temptation to fire it straight away! This last step shouldn't be rushed, as allowing the leather to gradually conform exactly to the shape of the cylinder, rather than slamming it suddenly into shape by firing the gun straight away, will increase its life and help to stop it disintegrating when it gets old.

If you do all this, and haven't made the washer too big or too small, you should have an efficient and long-lasting piston head washer... It may take a short while to bed in, but it shouldn't require any more lubricant for thousands of shots now. If you should ever want to relube it I recommend taking it out of the gun to do it, rather than putting silicone oil down the transfer port which could end up damaging the piston and the cylinder.


Over the years I have adapted this approach: No need to cut a circle to start. You can produce the circle at a late stage when the washer is sizing in the jubilee clip, but cut it oversize still as when in the cylinder and compressed, the sides will be pushed down to fill the void and produce a nice consistent seal. Leather stretcher is IPA .. not the beer but isopropyl alcohol.

It really is not that difficult ....
Cheers, Phil

[stevegv8]

Material: off-cuts of sole leather from a cobbler's shop or hide from a bag maker, leather cycle saddles, leather belts, handbags. Car boot sales are good sources.

Interesting, I have got off cuts from cobblers too before in various thickness so I can make my own breech seals, I've never tried the piston leather though due to needing to shape it and your method is worth giving a go.

[deejayuu]

Looking tomorrow.

[Cinimod]

https://www.freewebstore.org/puctum-..._17936423.aspx

Possibly try here.....dom

[Garden Guns]

Thanks for the replies and the advice.

I am shooting today at a comp and won’t have ‘tinternet.

Hopefully I will be able to source one from here if not I guess I will have to try to make my own with the help of the rather good guide! Hope it doesn’t come to that. If you have seen my attempts at DIY you would understand. Hamfisted is a kind way of describing the efforts!

Have a good weekend.

Neil

[evert]

Several people on here have converted leather sealed HW35's to modern seals, some should have them left in the spares box!

[WebleyWombler]

A friend of mine told me ages ago that he had used a leather cup seal from an Italian cycle air pump. Don't know any more about it and unfortunately he passed away last year. I carry a stock of leather pump washers to use in my old Brits but have nothing at 30mm.

[DCL_dave]

Hi Neil,

Sorry for delay, and also because I do not have a seal in that size...I can make you one to 30mm though if you give me a few days to sort it out - I wet cast them into moulds and it can take a few days for them to dry out naturally...no charge.

Or you can get a 1 1/4" leather cup washer/pump seal for a few quid off the bay that should fit ok with a little persuasion - item No. 324686903414 for instance (two for £7.25 inc delivery)

HTH,
Dave

p.s. if you want to have a go at making your own I can let you have some veg tanned leather in a few different thicknesses, ideal for the purpose...

[Garden Guns]

Hi Dave,

Thank you so much.

Sorry for not getting back to you. I have come down with man flu, at least I hope that is what it is. Had to go for a covid test today.

I would trust your ability to make a suitable seal over mine! I would be happy to pay or if you would rather I’ll make a donation to a charity of your choice if that is ok? I am in no rush.

Once again thank you very much.

All the best


Neil