Help define "deburring" and "polishing"

[Democritus]

I've been searching high and low for what "tuning" means. It seems to mean to do what the factory should have done, but didn't; clean it up and make the tolerances consistent and correct. Okay, fine, if that how business is done around here. But this leads to the next problem words; de-burr and polish.

Thread after thread dealing with tuning seems to contain some version of "de-burr and polish everything." That's great for those in the know. I'm not in the know, so I'm hoping some of you would be gracious enough to educate an ignoramus like me regarding these terms.

De-burring; break every sharp edge that you can find? Just enough so it doesn't catch a fingernail, or put a slight bevel on it? And really, every edge? How do you control the loose burrs that this process creates? Start with a needle file, or just a whet stone, or one followed by the other?

Polishing; to me that means a mirror finish. Is that what is meant? On all contact surfaces? Are you using emory and rouge? I usually see polishing referenced to the action. Every piece of the action? Is that after I de-burr those same pieces because if I "de-burr everything" then I've already done that, so am I now polishing these parts?

Perhaps I'm over analyzing this, but I take the the guts of a gun very seriously. I'd rather leave it alone than risk doing anything that might cause injury. That being said, the precision of my NP XL is unacceptable and several folks have stated that tuning my gun is required for optimal performance. I'm game as long as I feel that I know what I'm doing. Right now, I don't.

Any direction along these lines will be eagerly read and appreciated. Thanks.

Jeff

[dkwflight]

Hi

To my mind polishing in referance to these guns does not mean "Mirror" finish.
Useing 200 grit cloth and 6-800 in others is what is required.

Example. I had a piston in one of my Crosman Titans that had a sharp edge on the opposite side from the cocking link. During the cocking cycle there is a lot of pressure on the piston.
The sharp edge was forced into the inside of the cylinder like a cutting tool.
I took 200 grit emery cloth and sanded the sharp edge off on the piston. I then took some of the same 200 grit cloth and rubbed the area that was galled. I took off the high spots and smoothed the rest.
The 200 grit left small ridges and grooves that in my opinion held the grease better than a mirror finish would have.
The cocking action smoothed up as a break in proceeded.

Other areas may need a finer finish. In most cases you will end up with a better finish than the factory left.
You will develop a judgment of what is required as you work on these guns.

[lizzie]

I asked a similar question when I first came here and started acquainting myself:

http://www.gatewaytoairguns.org/GTA/index.php/topic,14605.0.html

[RedFeather]

Don't forget "cross-hatching".  And you want to cross-hatch the compression tube on a synthetic sealed gun, but keep it polished smooth if the gun has a leather piston seal.  Confusing, yes? 

[Addictedtoair]

Lizzie, you didn't mention that you got such an excellent response to your question(s) from ezman604! Democritus, tuning encompasses many sub tasks that are meant to increase the ability of the air rifle to be more consistent. Consistency is the key. Each shot cycle needing to be as close as possible to the last. The definition of tune may not be in our glossary of terms, but it is in the dictionary; "2. to adjust for maximum performance" (American Heritage Dictionary). This definition pretty much covers the scope of an air gun "tune". It is also a task that while the information on how to do it can be written down, it often takes special tools and experience to get the best results for your money. Plus, and most importantly, be sure to take all safety advice to heart as these "toys" can hurt, maim and kill if not given the proper respect that they deserve. Just because something can be DIY doesn't always guarantee the results of a professional doing the job coupled with decades of experience.

Brett

[MustangMike]

Try to find a tuner that's in your area if you can, so that way you can get a pro to tune it and you can watch/ask questions during the process to get a better idea of what to do and what to look for..

Id love to tune my big cat myself as I hate paying for something I can do myself but with out watching it being done at least once, I won't attempt it

[lizzie]

Lizzie, you didn't mention that you got such an excellent response to your question(s) from ezman604! Democritus, tuning encompasses many sub tasks that are meant to increase the ability of the air rifle to be more consistent. Consistency is the key. Each shot cycle needing to be as close as possible to the last. The definition of tune may not be in our glossary of terms, but it is in the dictionary; "2. to adjust for maximum performance" (American Heritage Dictionary). This definition pretty much covers the scope of an air gun "tune". It is also a task that while the information on how to do it can be written down, it often takes special tools and experience to get the best results for your money. Plus, and most importantly, be sure to take all safety advice to heart as these "toys" can hurt, maim and kill if not given the proper respect that they deserve. Just because something can be DIY doesn't always guarantee the results of a professional doing the job coupled with decades of experience.

Brett

Yes, it was an excellent and very helpful answer, so I thought I'd link it. Guess I should have quoted it also.

Plus, and most importantly, be sure to take all safety advice to heart as these "toys" can hurt, maim and kill if not given the proper respect that they deserve.

Most definitely. Even when I buy an old ar, I'm hesitant to even shoot it for the first time. When buying old and used guns, you don't really know for sure what you're getting, unless you can shoot it first, and my experience is that this isn't usually the case.

In fact, I bought a Benjamin pump a couple of weeks ago that I haven't shot yet, after reading the exploding pump threads on here.

[RedFeather]

Let me restate what I said about polishing smooth, especially since Lizzie has some old, leather-sealed guns.  Those with leather pistons like it smooth inside the compression tube.  From what I've read, cross-hatching or roughing up the tube does not work as well as keeping it polished.  The reason for cross-hatching a synthetic sealed gun is to provide a surface that retains lube which is then transported via the seal wiping it forward to provide "combustion fuel".  In the leather sealed gun, the leather soaks up the lube, thereby providing fuel.  At least, that is how it was explained to me.  So don't cross-hatch the 35 or 50, Liz.

[Addictedtoair]

"combustion fuel"??    

Brett

[Deane]

Studies and experiments show that up to 40% of the speed (power) of an air gun depends on the pressure created by the piston compressing the air behind pellet actually causing the tiny amount of oils to combust, just like in an automobile engine. Not to be confused with dieseling (same phenomenon, but more intense like a diesel engine) or detonation (an uncontrolled explosion behind the pellet).

[Tactical Tom]

Wow...I'm new to this to & all this info...OVER LOAD ! Can some one post some pics to help out ?

[uncle paulie]

Go through the library, there's a ton of info there on tuning and just about everything else relating to AG's. You can also google air rifle tuning and find a bunch of stuff that way. The more you know....the more you know!

pv