Making piston seals, help please.

[Geoff555]

Hello and a Happy New Year to all.
I have tried more than once to make piston seals for a springer and failed. Would someone please be kind enough to give me an idea of what to use/do etc. I have tried some polyureathane (spelling most probably wrong, sorry.) and find that it squashes in the chuck and as soon as touched by a tool comes out of the chuck.
So what should I be useing?
Also the type/shape of tool and speed.
I bought a seal (green) from Australia and found that it was just too tight and tried to size it and to be honest made a muck of it.
I cant measure the cylinder because it is wider at the trigger end and is smaller at the front, tap, end. The piston is quite a loose fit so its not much good measuring that.
I have modified the piston to take a synthetic seal, it is an Osprey.
Sorry chaps I am really struggling to spell and get my head to work as I have been hit by 'man flu' , in truth a really bad cold but man flu sounds better!!
Thank you.
Cheers.
Geoff.

[T 20]

On the Hawks and Ospreys I just machine the nose of the piston to take a 25mm Weihrauch seal.

[ggggr]

I found this. How Lawrie makes them.
http://anotherairgunblog.blogspot.com/search?q=lawrie

[johnbaz]

A cheap way to make them is to get a bit of plywood 8 or 10mm thick (Depending upon the depth of the seal needed) and use a hole saw to make a hole equal to the diameter of the cylinder, Make a dowel 6mm smaller in dia then soak a piece of 3mm leather in warm water, Lay it over the hole and knock the dowel in so that it pushes the leather in to the hole, Trim it to the top of the wood and remove the dowel, That's the form, It just needs a hole in the centre now


John

[Geoff555]

Hello T20 many thanks, this I have done, it seemed fine to start with but I didn't use it for a month or so and found that it was notably hard to cock and it seemed down on power, about 6 ft-lbs. decided to have a look at the piston and had a hell of a job to pull it out. It ,the seal, seemed to have squashed?? expanded?? or something, it seems to me to be soft as I can easilly squash it with my fingers and I am not that strong. Hence needing to make a seal to size. ( and I see it as a challenge).
It did slide in as easy as it seemed reasonable when first fitted.
Thank you.
Cheers.
Geoff.

[Peter Dunkley]

Hi John.
I use a very similar method except I find a socket the right size " I have dozens" and squeeze the leather into the hole with it in a vice. Leave it a couple of days to dry out.

[johnbaz]

Hi John.
I use a very similar method except I find a socket the right size " I have dozens" and squeeze the leather into the hole with it in a vice. Leave it a couple of days to dry out.

Hi Pete

Hope you're well mate

I only ever used this method once, It was about twenty five or so years ago, Can't even remember what gun it was for!!

That's a great idea using sockets, Like you i've loads but i'm too thick to have thought about using them!!


Happy new year


John

[thisisdonald]

Maybe try freezing the PE and quickly turning it? Or you can get cans of freeze spray at plumb centre

[Peter Dunkley]

Hi Pete

Hope you're well mate

I only ever used this method once, It was about twenty five or so years ago, Can't even remember what gun it was for!!

That's a great idea using sockets, Like you i've loads but i'm too thick to have thought about using them!!


Happy new year


John

Yep still here John.

Love to claim the "socket idea" as an original thought. But no. I read it somewhere.


Happy "collecting" new year to you too!

[scorpiont10]

Try using nylon - machines easily in a lathe and readily available.

[bezzer]

Try using nylon - machines easily in a lathe and readily available.

Nylons no good not stable enough, swelling and shrinking in varying degrees of moisture/dryness. PE is definitely too soft if that's what is being used I wouldn't even bother with HDPE as that isn't exactly hard either.
Acetal is better be it Delrin or other trade name, you do need to be using a very sharp knife lathe tool, med to high speed and not too big depth of cut to avoid overheating

[Benelli B76]

To hold the polyurethane rod in the lathe you need to hold it in a metal collet to spread the grip of the jaws, a piece of sheet steel or bass will do. I run mine at 950 rpm, and use very sharp tools of different shapes. The best way of parting off is to use a scalpel. Pics of an early one did.

Baz

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[leetrenchard]

I have an osprey and was considering a similar mod.

I believe the Webley tracker piston and seal are a direct fit to osprey mechanism.

[Geoff555]

Hi all. Many thanks, I did not consider Delrin or nylon as I read that they were not too good as regards standing up to impact. Benelli B76 pictures worth a thousand words etc. thank you.
Thanks for the tip regards sheet as I have some Crosman seals to do.
Rod and sheet ordered and old lathe tools that I can grind to various shapes.
Thanks again, I will have fun.
Cheers.
Geoff.

[Benelli B76]

Hi all. Many thanks, I did not consider Delrin or nylon as I read that they were not too good as regards standing up to impact. Benelli B76 pictures worth a thousand words etc. thank you.
Thanks for the tip regards sheet as I have some Crosman seals to do.
Rod and sheet ordered and old lathe tools that I can grind to various shapes.
Thanks again, I will have fun.
Cheers.
Geoff.

Geoff, did you notice the shallow hole to take the revolving tailstock centre ? Gives you more support to keep the polyurethane steady and central.


Baz