Sizing seals in springers

[Vernal]

Could I please ask the experienced tuners for advice on which abrasive to use for sizing seals in springers?
New seals are almost invariably a very tight fit in the cylinder, and I know from experience how much this reduces energy, so I do like to get them to a better fit. I am reluctant to use wet and dry, as I worry about grit particles becoming embedded in the seal and working on the cylinder, diamond plates just do not seem to remove anything, and I worry again that maintaining pressure to try and get more action raises the temperature too much. Files seem a bit drastic, and might leave a poor finish, so what should I use please?

[Phil Russell]

I am surprised there have not been more replies .... I do not class myself as a tuner when compared with recognised masters of the art but I have sized a few seals in the past, although mostly home made leather ones.
For a modern synthetic I have rarely needed to ... but that does not mean it is not needed at times. When I have done it I have used maybe 600 grade wet and dry, used dry ... engineers can weep at this point. I think it important to have a means of turning the seal e.g. mounting the piston in a lathe or a 'mounted' electric drill and going very carefully. Mounting the piston plus seal in a hand held electric drill and bringing the seal into contact with the grit paper could work but is somewhat imprecise as it is not as controllable as if the drill is mounted. Check for size often, remembering that the seal will invariably bed in after a short time and you do not want to remove too much and preferably none from the outer lip of a 'parachute' seal. While doing this I take care to wipe the seal after each 'treatment' and, when satisfied I have the size right, clean the cylinder, seal and piston thoroughly before final reassembly. I have never used a file on a synthetic seal.
Leather is different as my home made ones invariably need resizing. Depending on what needs to be removed I have used a lathe with a sharp cutter or even a file before finishing with dry 600. It is possible to size leather by hand as well provided you go slowly. Leather is more forgiving in this regard.
Good luck.
Cheers, Phil

[Hsing-ee]

Maccari has advice on this, less it more ...

https://www.airrifleheadquarters.com...age/251485.htm

[Shed tuner]

bear in mind a freshly sized seal will wear in very quickly, so do not size to prefection, or it will be too small with a few dozen shots. Size to be too tight, but so you can get it and and move it with a good shove. then shoot 30-40 and it'll probably be fine..

[Vernal]

I am surprised there have not been more replies .... I do not class myself as a tuner when compared with recognised masters of the art but I have sized a few seals in the past, although mostly home made leather ones.
For a modern synthetic I have rarely needed to ... but that does not mean it is not needed at times. When I have done it I have used maybe 600 grade wet and dry, used dry ... engineers can weep at this point. I think it important to have a means of turning the seal e.g. mounting the piston in a lathe or a 'mounted' electric drill and going very carefully. Mounting the piston plus seal in a hand held electric drill and bringing the seal into contact with the grit paper could work but is somewhat imprecise as it is not as controllable as if the drill is mounted. Check for size often, remembering that the seal will invariably bed in after a short time and you do not want to remove too much and preferably none from the outer lip of a 'parachute' seal. While doing this I take care to wipe the seal after each 'treatment' and, when satisfied I have the size right, clean the cylinder, seal and piston thoroughly before final reassembly. I have never used a file on a synthetic seal.
Leather is different as my home made ones invariably need resizing. Depending on what needs to be removed I have used a lathe with a sharp cutter or even a file before finishing with dry 600. It is possible to size leather by hand as well provided you go slowly. Leather is more forgiving in this regard.
Good luck.
Cheers, Phil

Thank you Phil, I have been running it in my woodworking lathe, which has a four jaw chuck, but only using a diamond plate. If you have never had problems with 600 wet and dry I will give it a go, but it may not need much more now that I have read Jon's comments - I may have been aiming for too loose a fit.

[Vernal]

Maccari has advice on this, less it more ...

https://www.airrifleheadquarters.com...age/251485.htm

Very helpful thank you. Confirms that I should put it in with a tightish fit then keep a careful eye on the chrono for the first few hundred shots.

[Shed tuner]

also depends what kind of firing cycle you want.. generally, a somewhat tight fit will give a softer cycle, at the expense of some efficiency...

[Vernal]

While I like a soft cycle Jon, what I am looking for is greatest accuracy off the bench, which probably means a faster cycle, so I am just fitting a Mk 2 latch rod in my Mk 3 TX, as recommended by you and Nick at the Norfolk Bash. Back together and off to the range for testing on Tuesday.

[Shed tuner]

While I like a soft cycle Jon, what I am looking for is greatest accuracy off the bench, which probably means a faster cycle, so I am just fitting a Mk 2 latch rod in my Mk 3 TX, as recommended by you and Nick at the Norfolk Bash. Back together and off to the range for testing on Tuesday.

yeah, that'll shoot pretty sweet, so you can size optimally without relying on a tight seal to calm it down.

When fitting the rod in the piston, there is a quite a bit of slop in the thread, so make up a snug bush (electrical tape can be used to fine tune fitment if needed) to temporarily place in the rear of the piston, to hold the rod centrally whilst the Loctite goes off.

[TonyL]

Maccari has advice on this, less it more ...

https://www.airrifleheadquarters.com...age/251485.htm

Very helpful thank you. Confirms that I should put it in with a tightish fit then keep a careful eye on the chrono for the first few hundred shots.

Yep, useful indeed.

[TonyL]

Graham Henderson, one of the lovely chaps of notable fame from the springers-in-FT days, told me that many of the top shots wth sliding comp tube guns would boil the cylinder and piston & seal assembly to conform the seal to the cylinder without the use of abrasives etc.

.......But also that a sloppier fit would follow quicker than that of an unsized seal.

So you could try this method on the TX?

Maybe this could also be used on rifles that don't have a sliding comp tube by obtaining a short piece of tube with the correct ID and boiling the seal in that?

Personally I haven't ever felt the need to size, just allowing them to run-in naturally whilst keeping my eye on the power. But then I've not had one that I considered far too tight........

However, when I worked on the Mercury S a few months ago I did go for the Meteor 'O' ring for a far less tight fit.......

Mike, NickG has done some pretty awesome work with 'O' rings and 'X' rings. With the ease of strip-down on the TX I ponder whether it might be worth experimenting with home made carriers and the rings for sealing if you have plentiful playtime? Er.......I seem to remember him playing with a different material also recently?

Hope this provides a little more food for thought.

[hmangphilly]

why muck about with a random finish to a random size on a synthetic seal ?

Plenty of places will professionally ,accurately hone your comp tube to a perfect fit .

If your seals are made to any kind of quality , you should be able to buy a handful of the same batch and youve got enough to last a lifetime . .

Kills 2 birds with one stone .

Betcha your comp tube is not round, parallel ,correctly sized , blah blah .

If it's tx dont be fooled by the cross hatch pattern and try to pretend it's been properly honed . Cross hatching means nothing .

All those i've measured have been all over the place .

[Shed tuner]

If it's tx dont be fooled by the cross hatch pattern and try to pretend it's been properly honed . Cross hatching means nothing .

All those i've measured have been all over the place .

yeah, we've noticed that too.. also the distortions caused by the ABT slots are pretty significant - they must mill that lot out with about 10 ton of force in 1 second flat.

[Phil Russell]

why muck about with a random finish to a random size on a synthetic seal ?

Plenty of places will professionally ,accurately hone your comp tube to a perfect fit .



All those i've measured have been all over the place .

What sort of variance did you find? Given the number of successful TX on the competition circuit I can only surmise that a slight (undefined) variation in dimension is of no importance ... presumably once the seal has 'bedded in'. Surely AA work to a tolerance level and as long as the cylinder is within tolerance then performance is assured. But what is the tolerance? I ask out of sheer ignorance as I have no equipment capable of measuring the variability in id of cylinders. Are we talking about 1 or 2 thou? ... or is that a pipe dream (no pun intended).
Cheers, Phil

[Vernal]

I seem to have learned a lot about TX cylinders from this thread, as well as about sizing seals. I certainly was fooled by the cross hatching into assuming it had ben properly honed, but I noticed the tube has clearly been rubbing oppsite the shoe recess. I have no internal mike to check with, but the gun was running with only a few fps variation with the old piston and seal, so any variation in diameter shouldn't be a problem. It is now back together with a tight (but not ridiculously tight, as it was out of the box) seal, but only giving me 9.5 with 42mm preload, I suspect due to the tight seal. I'll put some pellets through it in the garden tomorrow, then see if that improves things.
I don't think I am brave enough to try Tony's idea of boiling the whole assembly - has anyone tried it?