Springer Piston Polishing...Bad move?

Over the years I have seen posters show pics of 'mirror like' polished pistons. Is this really a good idea? In my mind (tragic story LOL), it seems like it would be beneficial to leave the minor surface imperfections be, to allow lube to be retained on the surface and to fill those in. The compression tubes are honed for the purpose of 'lube loading' I believe. With that said, does anything I'm saying make sense?

BTW, reason for posting more lately is that I had a recent medical event that has put me on short term disability (no, not STD LOL) from work. I simply have too much time on my hands ? Now if I could just receive the piston seal ordered in Sep. for my P1 project from Custom Seals in Australia...

I've only just started messing around with an old .177 Shanghai sidelever springer and I can tell you the inside housing that the piston ran through was definitely not a mirror finish (probably no surprise being an older cheap China rifle). It wasn't super rough either,  but you could definitely see tooling marks throughout the length. The cutouts for the sidelever catch were all full of burrs too (did get all those removed) and were shredding the leather piston seal pretty bad even though it had only been shot a handful of times in the last 25 years or so. I ended up just machining out a delrin disc with a groove and oring to replace the leather seal which seems to be working well, just waiting on some replacement urethane breech seals now since the original is in pretty bad shape too and isn't something I can easily fabricate.

When I was in piston class Randy Bimbrose would wrap sandpaper around a shaft connected to a drill and "polish" the compression tube.  We also hand sanded the piston itself.  These are not precision instruments, so I'd imagine taking off .001" wouldn't hurt.  However, you can't be too aggressive.  If you take too much off you cannot put it back on.

Posted by: @straitflite

Over the years I have seen posters show pics of 'mirror like' polished pistons. Is this really a good idea? In my mind (tragic story LOL), it seems like it would be beneficial to leave the minor surface imperfections be, to allow lube to be retained on the surface and to fill those in. The compression tubes are honed for the purpose of 'lube loading' I believe. With that said, does anything I'm saying make sense?

BTW, reason for posting more lately is that I had a recent medical event that has put me on short term disability (no, not STD LOL) from work. I simply have too much time on my hands ? Now if I could just receive the piston seal ordered in Sep. for my P1 project from Custom Seals in Australia...

LOL.....

Perhaps the thought is that polishing the piston would minimize receiver wear, however lipstick can be put on a pig to make it "more perty" and polished internals are indeed "pertier"! ?

I tend to agree with you concerning the finish helping the lube, however I have a habit of polishing the "skirt end" of my HW pistons so the hardened skirt doesn't wear much on the receiver tube ID. Probably doesn't matter but for me it's a "feel good" practice! ? 

Brand new factory HW95 piston.............

Skirt polished..........

.

   In my experience with modern springers, the the only piston surfaces which touch the cylinder walls are the synthetic piston head, and any buttons or bearing surface on the tail end. Accordingly, polishing the piston body would be an aesthetic rather than mechanical choice. 

   On the other hand, if the piston seal is leather it is meant to hold lubricant that slightly combusts under compression (diesels by design) with each shot. In such a case, roughening the cylinder walls to hold lube could be a benefit.

Way back when, on the old Yellow, the general consensus was that you were to polish compression cylinders of leather sealed guns and cross-hatch those of synthetic sealed, the latter to hold lube. If I recall, some owners who polished synthetic sealed guns reported a slight loss in fps, supposedly from a lack of migrating lube or fumes, thereby missing that bit of combustion at end of stroke. It was a grand time for experimentation. 

Stratflite, I hope you mend soon before you end up buying something more due to over-browsing. Been there, done that, repeat, repeat. ?

Posted by: @redfeather

Way back when, on the old Yellow, the general consensus was that you were to polish compression cylinders of leather sealed guns and cross-hatch those of synthetic sealed, the latter to hold lube. If I recall, some owners who polished synthetic sealed guns reported a slight loss in fps, supposedly from a lack of migrating lube or fumes, thereby missing that bit of combustion at end of stroke. It was a grand time for experimentation. 

Stratflite, I hope you mend soon before you end up buying something more due to over-browsing. Been there, done that, repeat, repeat. ?

I think you're right.  I've refurbished a ton of leather-sealed guns, and for the most part, their compression cylinders have been "work-polished" to near mirror finish.  When I have tried to "upgrade" to a synthetic seal, invariably I have experienced a drop in MV, which I attributed to seal stiction.  A very light cross-hatch with a brake cylinder hone usually solved the problem.  But in my experience, a leather-sealed gun is best left as a leather-sealed gun.  With proper care, they can last at least a couple of lifetimes.

Posted by: @straitflite

Over the years I have seen posters show pics of 'mirror like' polished pistons. Is this really a good idea? In my mind (tragic story LOL), it seems like it would be beneficial to leave the minor surface imperfections be, to allow lube to be retained on the surface and to fill those in. The compression tubes are honed for the purpose of 'lube loading' I believe. With that said, does anything I'm saying make sense?

BTW, reason for posting more lately is that I had a recent medical event that has put me on short term disability (no, not STD LOL) from work. I simply have too much time on my hands ? Now if I could just receive the piston seal ordered in Sep. for my P1 project from Custom Seals in Australia...

That's a good question--one that I think needs mentioned.

I'm with you.

Unless the finish on the skirt is so rough you're afraid it will damage the receiver, I don't--and I wouldn't--bother. A few small imperfections will hold some lube, and help prevent galling, just like you described. Those things are a plus.

That said, the real area it helps to cross-hatch for such a benefit is the wall of the receiver itself. It may also be easier. Some pistons are hardened, while the receiver tubes aren't.

While some really like buttoning or 'ringing' a piston skirt with Delrin/acetal to prevent, or repair such galling that has already taken place, I've found that a diligent cross-hatch on the walls of the tube usually takes care of it. It's not a theory. I've done it on dozens of springers over the years, and it works.

Of course, the use of buttons or rings do have other advantages, like repairing major receiver tube damage, and providing ultra-smoothness in both the cocking and firing cycles. They also tend to keep cocking effort at an absolute minimum, and basically eliminate any vibration caused by a too-loose/sloppy fit of the piston skirt inside the receiver tube.

Most Euro-guns don't have that problem with the fit, but others do. Just don't over do the sizing of the buttons or rings. Too tight a fit will unnecessarily-reduce velocity.

As to a mirror finish, I once did it on the area of the receiver where the piston seal travels. I was real-proud of myself, too, lol :).

Before I tell you the result, think about what probably happened. It will help if you take a look at a bicycle, and look closely at the rims and the brakes. 

Put that smooth synthetic piston seal up against a mirrored receiver, and you've just made yourself the perfect caliper brake!

Yep, epic fail. The seal started squawking inside the tube like there was no tomorrow. Re-lubing it helped for about 10 shots or so. I had to take it all apart and 'remove the mirror' on the walls to fix it. You can bet that I never did THAT again.

BTW, best wishes with your disability issue.

Also, I think Custom Seals In Australia is the down-under place listed on EBay, where I've ordered seals a couple of times. It went very-well.

Posted by: @sonnysan

When I was in piston class

Sonny, it would be cool if you or any reputable member could host an online class for tuition...I'd love to see you in action on the rams as well. Disclaimer: If I wind up being the class clown, it would only be because someone has to do it LOL.

Posted by: @nced

I have a habit of polishing the "skirt end" of my HW pistons so the hardened skirt doesn't wear much on the receiver tube ID.

I like it!

Posted by: @redfeather

Stratflite, I hope you mend soon before you end up buying something more due to over-browsing. Been there, done that, repeat, repeat.

Thank you for the well wishes! Yup, financial health can be important too. Weekend online sprees are bad enough. I have enough too keep me busy right here as it is and that should help keep me from check out carts. (I think I can, I think I can... ? )

Posted by: @ekmeister

Before I tell you the result, think about what probably happened. It will help if you take a look at a bicycle, and look closely at the rims and the brakes. 

That visual contrast makes it clear to me. Thank you for the well wishes Ed.

I'll upload the notes from the piston class, as this was well before cell phone cameras.  Been thinking about it for some time.  Don't see me doing another springer unless necessary. 

My next endeavor is rebuilding a Dual Magnum very soon.  Now that is esoteric.  I'm imagining the rebuild will be very similar to an eliminator.  The pop-up loading port and dual cocking action (probably another notch in the ram) will be interesting.

@straitflite

If Sonny does a Ram class, I'm turning my phone off! 🙂

Posted by: @straitflite

 Now if I could just receive the piston seal ordered in Sep. for my P1 project from Custom Seals in Australia...

Is that how long their orders always take? I ordered a seal for a Webley Stingray and I didn't receive it until long after I already put the gun back together. It took so long. All that was wrong is the "spring tamer" guide was broken. I made a new guide from delrin. Do they send your nasty airgun parts "surface"? UK sent my airgun stock like that once. Surface took 6 weeks. Normally I get from UK in about a week.