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Thread: Air rifle piston polishing

  1. #1
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    Air rifle piston polishing

    Why when trying to improve the performance of a spring piston air rifle do people feel the need to polish the piston.
    Is it not true that the only part of the piston that is in contact with the Cylinder is the seal.

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    Not sure if it happens on all airguns but the rear of the piston in my HW99S scored the cylinder on cocking. . I suspect other HW models do it.

    Piston in a drill and polished with emery paper.

    Bumslide or other moly grease on the rear of the piston.

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    Quote Originally Posted by bighit View Post
    Not sure if it happens on all airguns but the rear of the piston in my HW99S scored the cylinder on cocking. . I suspect other HW models do it.

    Piston in a drill and polished with emery paper.

    Bumslide or other moly grease on the rear of the piston.
    in that case would it not be better to coat the rear of the piston with ptfe spray.

    Thanks for the reply.

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    Air rifle piston polishing

    Quote Originally Posted by Fudgeisbest View Post
    in that case would it not be better to coat the rear of the piston with ptfe spray.

    Thanks for the reply.
    no
    i've tried it moly grease or dryslide preferably for me everytime.

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    Quote Originally Posted by Fudgeisbest View Post
    in that case would it not be better to coat the rear of the piston with ptfe spray.

    Thanks for the reply.
    Not tried PTFE spray on mine

    Moly or bumslide only . As Junglie said above.

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    Piston Polishing

    The end of the piston was also polished back in the day as under cocking this may well come in to contact with the cylinder. There is no need to polish the entire piston. Mach 1.5

  7. #7
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    Welcome to the forum, Mr Fudge.

    I always polish the piston (by hand, with rag and Solvol) just because it seems the nice thing to do and looks much prettier. Then a small dab of moly paste around the tail / bearing surface and the tiniest trace around the edge of the seal. Then, once the piston is pushed home, a more liberal application of moly grease around the circumference of the cylinder, behind the piston.
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    Quote Originally Posted by Fudgeisbest View Post
    Is it not true that the only part of the piston that is in contact with the Cylinder is the seal.
    Usually not. The piston skirt is in contact with the cylinder in most guns, and on some guns you will see wear marks on other parts of the piston too, indicating metal-to-metal contact between the piston and the compression area of the tube.

    Howewer, polishing is usually not a good solution, creating bearing points of other materials than steel is the way to solve the issue.
    Good lubrication helps, but cant really replace good bearing materials.
    Too many airguns!

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    yup, resr skirt also in contact, during both firing and cocking strokes.. this is why some guns, and some aftermarket tunes, have a rear synthetic bearing on the rear skirt, or synthetic buttons.

    As said, no point polishing anything other than the rear section of the piston, unless it's out of true, in which case sort it in a lathe...
    Always looking for any cheap, interesting, knackered "project" guns. Thanks, JB.

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    [QUOTE=TonyL;8086229]Welcome to the forum, Mr Fudge.

    I always polish the piston (by hand, with rag and Solvol) just because it seems the nice thing to do and looks much prettier.

    Definitely, even when there is a rear bearing to support the piston. There is a lovely warm glow from knowing how nice your piston looks, even when no one can see it.

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    Quote Originally Posted by TonyL View Post
    Welcome to the forum, Mr Fudge.

    I always polish the piston (by hand, with rag and Solvol) just because it seems the nice thing to do and looks much prettier.

    Definitely, even when there is a rear bearing to support the piston. There is a lovely warm glow from knowing how nice your piston looks, even when no one can see it.
    Is this a euphemism Tony?

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    harvey_s is offline Lost love child of David Niven and Victoria Beckham
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    A high polish probably does more harm than good, too shiny and the lubricant will simply be wiped away.
    As long as it's not a rough surface and correctly lubricated that's probably as effective as anything else IMHO.

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    Quote Originally Posted by gtfreight View Post
    Is this a euphemism Tony?
    Absolutely not, Gary.

    It's that devil Vernal up to his tricks.
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    Quote Originally Posted by harvey_s View Post
    A high polish probably does more harm than good, too shiny and the lubricant will simply be wiped away.
    As long as it's not a rough surface and correctly lubricated that's probably as effective as anything else IMHO.
    I know where you're coming from.. I do tend to do the piston, but not to "too high" a polish but I never polish the cylinder. Just degrease and clean. Between the two there should be enough "peaks and troughs" to hold any lube. On pistons where the steel tail is a bearing surface (especially taking cocking into account) I tend to burnish a little moly in, too, either in the form of a tiny amount of dry powder, moly paste or moly-in-carrier, like Dri-Slide.
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    harvey_s's Avatar
    harvey_s is offline Lost love child of David Niven and Victoria Beckham
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    I have been using Tungsten Disulfide assembly paste for some time now with excellent long term results.
    Worked into the metal it's supposed to form a chemical bond with the substrate with a much higher load capacity than moly.
    It's commonly used for lubrication on deep space probes and very aggressive environments where moly based lubes are more prone to be washed off.

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