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stevenorlando
December 20, 2010, 10:43 PM
Hello All,

For polishing gun parts, but not wanting to change any angles of engagement, what grit (s) of sandpaper is recommended?

Steve

DiscoRacing
December 20, 2010, 10:45 PM
depends on if your just polishing and existing polish finish...or if you are trying to polish from beadblast to shine.... i start out with 400 grit on beadblast,,,then 800, 1000, 2000

HiBC
December 20, 2010, 11:10 PM
To each their own.I worked in a shop that made a lot of prototype plastic injection molds.After we had used paper and other methods for years,we sent some work out to a master mold and die polisher.The results were impressive,and reasonably priced enough,he had to have an efficient process.I was sent to his shop to understudy him for a week.
In regard to quality of finish required and preserving form and dimension,mold work is at least as exacting as gun work.
I use polishing stones and brass or hardwood laps with diamond polishing compound.I also use end brushes and mounted hard felt.
Brownells sells a product that is a liquid matrix with grit in it.It can be painted on wheels,but it can also be painted on tools made of rock maple or other hardwood.It comes in various grits.I am quite impressed with this product .It seems to not have oversize "digger" rocks,or the clumps of grit that score a finish.It cuts fast,and holds up well.Make the wooden tools,dip them,and hang to dry.

mete
December 21, 2010, 10:55 AM
If you're talking about a trigger job and dealing with engagement surfaces use stones not paper !! Small ceramic stones medium and fine are what I use. Brownells or Spyderco are good sources .

natman
December 21, 2010, 11:51 AM
For polishing gun parts, but not wanting to change any angles of engagement, what grit (s) of sandpaper is recommended?

The "angles of engagement" part makes me think you are talking about polishing sears and/or trigger parts. If that's the case, mete is 100% right, you need a good hard, fine stone and oil, not sandpaper.

GURU1911
December 23, 2010, 10:36 AM
Steve: I have been polishing 1911 actions for almost 30 years & my customers are always pleased with the results. "sandpaper" is generally used on wood. "metal finishing paper" is for polishing metal.

If you do not wish to invest the $$$$ for the proper ceramic stones, a small piece of red "crocus cloth" wrapped around a wooden popsicle stick & carefully applied to the surfaces you wish to polish, will get the job done. Remember to only polish & not attempting to remove metal. Maintain all machined angles & do not attempt to alter the angle.

If you have a dremel tool, install a felt polishing tip, rub in a dab of flitz or maas metal cream polish, & buff the newly polished surfaces. Remove the polish with a clean piece of soft denim & final polish with a piece of cotton flannel material.

Jolly Rogers
December 24, 2010, 11:40 AM
One cannot polish metal without removing some of the metal. One can only argue about how much metal was removed during the polishing.
Joe

Unclenick
December 24, 2010, 05:47 PM
That'll get an argument started in some circles. Check out some of the sites on optics grinding and finishing any you will find theories of polishing that have as much to do with smearing and burnishing the surface as they do with cutting. I'm not sure what to make of them. I think if you buff a surface with something and it turns black, that's removed metal. I got into a disagreement with somebody about Flitz one time. The company claims it is non-abrasive, but if I rub copper with it, the cloth turns black and if I hold that black surface to the right angle in sunlight, a copper colored sheen shows up. Brass colored if I polish brass, white metal colored with aluminum, and so on. But that's just my simple way of interpreting the evidence.

Sandpaper for engagement surfaces should not be used without rigid backing, IMHO. If you don't use a rigid flat support, you'll get rounding of edges or a tendency to take planes out of flat. I have a piece of hardened flat stock that I worked over with a surface grinder to give me flat surfaces and corners and a wedge-shaped edge. I can adhere sandpaper to any surface on it to use as a replaceable, variable grade stone surface. A little spray-on latex contact adhesive and you're good to go.

Jolly Rogers
December 24, 2010, 10:58 PM
There is a chance that spray bonded sandpaper can "bunch up" when the adhesive warms up from friction as the work piece is stroked on the paper. I know that when using abrasive paper bonded to substrate to hone woodworking tools that bunching can cause "dubbing" or slight rounding of the face being honed. This could change the angle of a hammer or sear if it is used to work the contact angles.
Joe

Bill DeShivs
December 24, 2010, 11:46 PM
Sandpaper is not a solid substance, so there is a slight cushioning effect even when using it backed by glass.

Molly429
January 21, 2011, 09:04 PM
Blessed with an unpublished 'Machinist-Gunsmithing' book by a late uncle, an entire chapter subjects 'blueing' - the preparation of components 'optical (high definition reflection) quality' polishing; it speaks of the the minimization of pores (and accompanying friction, causing wear-erosion) via employment of 'jeweler's rouge' (a catalytic bonding medium, sometimes called 'pipestone' - a sobriquet derived from the active granular ingredient <finer than abrasive constituents of dentrifice> of a red clay found in 'Pipestone, Minnesota) as it is applied to impart a polish - with minimal - alteration of surface structure, prior to immersion in blueing tanks.

PetahW
January 22, 2011, 02:09 PM
Never, EVER, use any kind of abrasive paper or cloth (sand/emery/etc) on/in a gun without a hard backing shaped the same contour as the surface to be polished - concave/convex on curved, flat on flat, etc.

Sometimes the backer has to be custom/hand made for each application.

If a finger/hand is used as a backer, edges/corners/angles will for sure get rounded off as the flesh gives way.

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