Tuning Novel method for sizing piston seals

That’s interesting. Thanks for sharing. No idea how well it would work. I suppose it’s dependant on getting the seal to just the right temperature so it’s able to conform to the tube. 
Ofter read about how important it is the seal is a perfectly fit. 

i thought the seal was dynamic and pressure forced it against the tube anyway, doubtful unless it was really tight sizing it would make a hill of beans difference .. more important the seal and tube surface is just in excellent shape ..of course ive never cooked a gun before, maybe theres a benefit i cant see lol ...

Piston seals are relatively cheap, it would be worth some experimenting !! I suppose it makes a difference what material the seal is made of. Interesting idea though !!

I've softened seals in water to help get them installed onto tight piston dovetails. But they never "confirmed" under the heat and went back to their shape once cooled. 

So my guess is it's not going to work the way you think. And also, it may still not end up sized right. 

That's a whole lot of work to get around just doing it right. You could size one properly by the time you get the water boiling. 

Yes indeed polyurethane has memory and while POLY with take a set over time somewhat yielding to the shape it is forced to take .... hot water and a temporary shape shift while hot don't see doing much ? 

Then again ... may be worth trying for those who can't properly mechanically size a seal.

I've softened seals in water to help get them installed onto tight piston dovetails. But they never "confirmed" under the heat and went back to their shape once cooled. 

So my guess is it's not going to work the way you think. And also, it may still not end up sized right. 

That's a whole lot of work to get around just doing it right. You could size one properly by the time you get the water boiling. 

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Yes indeed polyurethane has memory and while POLY with take a set over time somewhat yielding to the shape it is forced to take .... hot water and a temporary shape shift while hot don't see doing much ? 

Then again ... may be worth trying for those who can't properly mechanically size a seal.

Click to expand...

I apologize if I appear to be hijacking the thread. But I have a vey direct question about piston seal sizing. I love tinkering and working on my springers to improve over all accuracy and performance. But this is one area in which I have not delved into and should. I agree with both Thumper and Motorhead that this boiling water process will not really accomplish much. I just don't see how it would. But.......what is the "correct" way to properly size a seal? I've read about and heard of this so often, but I will have to plead ignorance. 

How is it done???............Thumper and Motorhead, you two may have a different way or opinion on this and thats ok. But I would love to hear from both of you.

Thanks in advance......TR

I turn seals on a Lathe with seal snapped onto a holding nub/fixture. Sanding down the diameter at a controlled angle gradually. Placed back onto piston and trial fitted. Repeat until fit is correct / what wanted.

I turn seals on a Lathe with seal snapped onto a holding nub/fixture. Sanding down the diameter at a controlled angle gradually. Placed back onto piston and trial fitted. Repeat until fit is correct / what wanted.

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" Repeat until fit is correct / what wanted."

Which in your case is what kind of force ? I've heard members describe just enough resistance where one finger could slide it into the bore.

I do mine in a lathe too, with the seal held onto a "button" that's made to hold the seal tightly. The material gets removed from the seal with a grinding stone that's held in the tool post on the lathe. 

But to be honest, a drill and some Emory cloth glued to a flat stone is plenty sufficient enough. 

The snugness is pretty much a feel thing. You can get away with less snug if the seal has a deep floppy lip, and a little more snug if it's a rigid cup type seal. 

Generally I err on the loose side if the tube is good. If it's too tight, they tend to be more temp sensitive and can rob power. 

Lubed up and fitted, I like mine to move with a small push of the finger. If you have to lean on it, it's too tight. Just no real good way to quantify it as far as I can manage anyway. 

But if you're not sure, go too tight. That's better than too loose for sure.

I turn seals on a Lathe with seal snapped onto a holding nub/fixture. Sanding down the diameter at a controlled angle gradually. Placed back onto piston and trial fitted. Repeat until fit is correct / what wanted.

Click to expand...

" Repeat until fit is correct / what wanted."

Which in your case is what kind of force ? I've heard members describe just enough resistance where one finger could slide it into the bore.

Click to expand...

Pending seal TYPE, Hardness of seal, Roundness of Tube, Target or Field gun / magnum and Caliber all matter to some degree.