Buttoning a Piston

[Thegreg]

Is this a worthwhile improvement to go to the bother of doing?

Obviously if I did it it'd be done right with little spot-faces machined to hold the buttons in place.

Most of the buttons I've seen have a domed top, which as I see it would give only point-contact and wear out pretty quickly?

Interested on hearing your opinions

Cheers
Greg

[p.sharp]

They tend to wear out pretty quickly. A lot effort for virtually zero benefit 🙂

[ora8i]

Try Macarri tuning (USA) Old Fashioned Buttons they stick on and they Do Last a long time.

Ora

[Telephonepete]

Is this a worthwhile improvement to go to the bother of doing?

Obviously if I did it it'd be done right with little spot-faces machined to hold the buttons in place.

Most of the buttons I've seen have a domed top, which as I see it would give only point-contact and wear out pretty quickly?

Interested on hearing your opinions

Cheers
Greg

i have a v glide by steve pope one of the very best tuners in the country (v mach). i also have a sandwell stage 2 tune no buttoning just polishing and tuning. it was half the price and is evey bit as good. i should not bother.

[hotversion]

Are they just glued on? they look like they are,if so with what? superglue or araldite ?

[ora8i]

They are small 4mm round dots of some sort of plastic after a very thorough de-greasing they are glued on with quality super glue.

Once stuck on they stay on and can even be sanded if the overall piston diameter is too great, I found then very effective and so much less trouble than drilling the piston to fit delrin buttons.


ora

[Thegreg]

Thanks for the replies chaps

Your responses have reinforced my suspicion that they're not really worth doing!

Is the "done thing" (according to the tuning experts) to turn down the back of the piston before fitting these, so there's no chance of any metal contact?

Cheers
Greg

[Telephonepete]

Thanks for the replies chaps

Your responses have reinforced my suspicion that they're not really worth doing!

Is the "done thing" (according to the tuning experts) to turn down the back of the piston before fitting these, so there's no chance of any metal contact?

Cheers
Greg

never heard of that. i dont know what that means.

[Thegreg]

never heard of that. i dont know what that means.

Having the rear portion of the piston reduced in diameter prior to fitting the buttons. Presumably so when they wear down the metal won't come back into contact with the cylinder. Just want to know out of interest really, think it's very unlikely I'll bother doing it.

Cheers
Greg

[Hsing-ee]

Having the rear portion of the piston reduced in diameter prior to fitting the buttons. Presumably so when they wear down the metal won't come back into contact with the cylinder. Just want to know out of interest really, think it's very unlikely I'll bother doing it.

Cheers
Greg

Venom & V-Mach button pistons and compression cylinders in sliding breech rifles. Air Arms runs its springer pistons on circular plastic bearings, as does the Czech maker Slavia on some of its rifles, and the newish Walther LGV and LGU both sport rear piston bearings and make a big fuss about them.

As far as I know, if the buttons are made well from delrin or similar they do not wear down, they are super-slippery bearing on polished metal so there is very little friction. They can centre the piston and reduce vibration and make cocking the rifle super smooth (if that is important to you). The Feinwerkbau Sport rifle has very fine tolerances and doesn't need buttoning, but many rifles are improved by them if only to make the firing cycle slightly sweeter. I think also it depends on the interior finish of the rear of the cylinder, sometimes this is quite rough, and will need to be smoothed even if no buttons are fitted. Buttoning will also keep the piston central and stop the top rear edge from galling the rear of the cylinder.

It's up to you to not fit them, but if you don't you will never know will you ....

[lensman57]

Thanks for the replies chaps

Your responses have reinforced my suspicion that they're not really worth doing!

Is the "done thing" (according to the tuning experts) to turn down the back of the piston before fitting these, so there's no chance of any metal contact?

Cheers,
Greg

It is not so simple my friend. It dependson how well they were sized to the comp tube and what sort of plastic was used. In general I'd say that if you are not familiar with engineering or model engineering works then leave it alone. Some people are quite happy with metal running on metal and genrally if they are correctly lubricated then it is fine.

A.G

[pelletcaster]

I found quite a lot of free play between piston and sys tube nearly all the time.
So generally I DELRIN plug the shirts of my pistons at 4, 6 and 12 o'clock. Edit: 12, 4 and 8 o'clock.
And yes - it makes a difference.

If case hardening is preventing drill I warm the skirt up with a small gas burner until it starts to get redish then let it cool down slowly.
Drill the three holes and thread them 5mm. De-burr in and outside. Dont worry about some grinding marks at the outside as there will be no more metal-to-metal contact.
I cut three pieces of DELRIN plugs - 6 x abt. 20 mm and thread them too on on side. Threads must be absolutely clean of shaves.

After that I do a real proper degreasing on all the parts with break cleaner.
Metal and DELRIN threads get cured/primed with some acid.
Common superglue (cyanacrylat) is put on the threads of the DELRIN plugs and they are screwed into the piston. Let it cure over night.

Excess on the inside gets cut to a max and carefully grinded flat following the shape of inside of piston.
Excess on the outside gets cut leaving about one millimeter proud. This excess is gradually grinded/sanded down (near the completion of the process in miniscule amounts) until the piston fits the sys tube to its best.
Finally polish the piston.


The whole process irrespective of curing time takes me not more than 1 to 1,5 hours.
Material cost - nearly nothing.
After thousands of shots in different break barrels and underlevers - mainly HWs - all the plugs are still fine, no wear at all.

Here some pictures of different executed projects.

[pelletcaster]

???

I had more links but only three pics showing up.
Is there a limit or its on my side?
Thanks

[Hsing-ee]

I found quite a lot of free play between piston and sys tube nearly all the time.
So generally I DELRIN plug the shirts of my pistons at 4, 6 and 12 o'clock.

You do mean 12, 4 and 8 o'clock don't you?

Ah, I can see in the picture that is what you do. Typo.

[p.sharp]

The button at 12oclock is the one that takes the most punishment on a breakbarrel, I had mine quite snug & set the power to mid 10’s when I first put them on. 500 shots later, I was up to 16ftlb as the buttons wore in. When I stripped the gun & sold off the parts, the 12oclock button was doing zero to prevent metal on metal, has it had worn flush with the surrounding piston body material. This was delrin rod btw, drilled into the piston skirt.