I'm going to go over something I don't see a lot here, that is quite applicable to gunsmithing on fine rifles.

That is, detail metalwork and finishing.  I'm going to use a buttplate I'm currently working on as an example.   

I have a little bit of background in metal finishing.  I worked as a bench jeweler for several years, and when you're the apprentice, one of the things you learn first, and do for the entire shop, is finish polish the work.   

A few of the lessons the master in the shop taught me, that have stuck with me through the years were:

1)  You have to learn to use a file effectively.
2)  Using a file correctly will keep all your lines straight, and planar, without gouges, divots, and scratches.
3)  When you're working on a piece, you need to know what you want it to look like, use every step in the process to make it the shape to match your vision, and never let the mechanics of the finishing process dictate what the piece comes out like.
4)  You have to go through all the steps in the shaping/finishing process, never skipping them to get top results.
5)  Mechanical polishing is never a substitute for proper shaping, preparation, and finishing.

In my example I'm using here, I'm starting with a pretty standard 2 prong buttplate casting as received from CPA, Track of the Wolf, etc.

I detest working from castings, but they're a necessary evil.  Whether they're investment cast, sand cast, or mold cast, they always have a rough rind.  I always file the mating surfaces where they meet wood down to clean steel and fit the wood and metal together before starting in on the finishing.  If you don't shape it first, do the wood, and then run into sand pits and porosity, you can end up with the plate undersize for the wood.

Here's a picture of the casting I'm starting with, it's been edge filed and fit to the wood stock.  I'm going to start in finishing it by filing the rind off, and shaping it to the detail I want in the final piece.

Initially I'm not worried about the surface finish, as I know a lot of filing will be needed to remove the rind, so I clamp it in a vise without worry.  I use a pretty coarse metal rasp to remove the surface.

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I'll continue in another post.

This is something the master in the trade shop showed me, that I've never seen anybody else do.  

This is how to make "sandpaper files".  

The need for sandpaper files comes from the desire to make things flat and planar.  If you hold sandpaper with your fingers, it follows the surface contours, and polishes it smoother, but doesn't keep it flat.  In keeping with the objective that you want to pick what your surface is like, and then work towards that every step, you need to be able to smooth out file marks and mechanical sanding marks while making and keeping a flat surface.  The filing operation if done by shearing while pushing the file two directions, makes a flat, planar surface.  If you can do the same with sanding, you'll have a good finish.

To make sandpaper files, rip some hardwood (mahogony or walnut is what I typically use) into 3/4" x 1/4" x 13 to 14" lengths.  Make sure it's smooth without saw swirl marks, plane or sand them out if needed.  keep the corners sharp.  

Place a sheet of wet/dry silicone carbide grit down on the table.  Align the wood strip along the short edge, perfectly aligned with the top and edge.  Using a moderately dull knife blade, lightly score the paper along the wood edge.  What you're trying for is just enough score to make it fold easily and sharp.  Turn the block up, folding the paper as you do.  Push the wood back tight into the corner of the paper, and score again.  Fold, score, repeat, until the paper is wound tightly around the wood, with sharp, square corners.  Trim off the last sliver if needed by scoring all the way through the paper.

Now, secure with an ordinary thumb tack at the handle end.  Twist in most of the way, and then tap tight with a hammer.

The paper will now stay in place on the block, tight and flat.  I write the grit of the paper on the handle with sharpie.

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Back to the original point of this post.

A lot of metal finish looks fine, but "not quite right".  That not quite right is the lack of fine detail precision.  Surfaces not planar.  Transitions not smooth, dips, nicks, gouges, rounded off edges.   

Here's some pictures of various lack of detail:

First, a typically amateurish finish.  Not flat, rounded over, not precise.

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Here's a better one, this on a $3000+ Meacham High wall.  Still lack of detail at the end button scroll, and flat spot and not quite all scratches removed.

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How I approach this starts with the filing.  I use needle files to shape the fine details, get them right as to shape, flatness, continuity and form, and then smooth them more with each successively finer grit.

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I pay attention to corners and edges.  Don't just sand along them and take whatever results; carefully craft each edge to the radius you want, paying attention to getting it consistent, even and attractively proportioned in size.   

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This is where I am to as of tonight.  Will add more as I do more work.  I'm at 180 grit, will go 220, 320, 400, and maybe 600.  Then will send off to be nickel plated.

I'm into this buttplate 5 hours as you see it.

Great informative thread post Dave! I do much the same, except for one thing. I fought keeping paper stuck to my various sticks, and then I remembered my body working pads and sandpaper I use for my car projects. I went to the shop and grabbed some of my self adhesive sandpaper rolls and my 3M Durablock sanding pads. I use these for larger areas to do the sanding, and for tighter areas I set the Durablock aside, and still use the self adhesive sandpaper rolls on my various sticks. I cut the paper to the width and length I need and just apply it to the sticks. Peel it off when it wears out, and stick new paper on. It makes keeping the paper on the sticks easy, and quick to change. I buy the 3" wide 50 ft. rolls and cut it to fit in various grits.
I also have a 1/2" wide belt hand held power sander, and a 1" belt table top sander that I use at certain steps to get the cast finish off quickly before moving to the hand finishing.

Serendipitous timing! I'll be working down a cpa cast plate soon myself

Oh now you tell us all this stuff... Well better late than never I guess. Very good useful information for anyone who does even the least amount of metal work. I have used any manner of flat material to fasten sandpaper to usually whatever is handy but your example of what to use and how to affix said sandpaper will be followed to the letter. Maybe my ride on the struggle bus will be less bumpy. I must admit I often loose patience when finishing a project and it shows in the end result. Your example of tools and methods will help a lot. Thanks and bring us more. Old machinists can still learn new tricks...


JMH

Thanks, Bob, for bringing up a couple of things I'd glossed over.   

As you said, sanding angle is critical to seeing your progress.  I alternate directions when I change grits.  That way, when all the marks going the other direction are gone, you know you've sanded everything at least to the level of the last grit.  Now, only additional blending and shaping remain for that grit.

And, wearing out of paper is a critical issue  Less so with silicone carbide than with aluminum oxide.  Silicone carbide seems to cut pretty well until the paper starts to deteriorate and tear, and the grit breaks down so it gets finer.  Al-Ox doesn't seem to wear, but it starts cutting slow, and worse, as you press harder, the few coarser grains cause scratching.  Use a light touch with Al-Ox, and change it when it slows down.

A key characteristic of the sandpaper files as I use them is that they have 4 cutting surfaces.  The ones nearest the loose edge should be the most worn.  When they get worn out, just tear them off to reveal new paper.  The opposite side has the sharpest, hardest corners, the flattest face, and the newest grit.  The narrow edges are good for getting into tighter areas or applying more pressure.

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I did 220 grit and 320 grit today.  Not a lot of detail that my camera will pick up.  One thing I start doing at the end of 220 grit, is I go over the entire piece with a slack piece of 220 held with fingers only, more or less parallel to the longest lines of the piece.  This gives a good visual for the angled pattern of the next grit, as it gets hard to see the fine scratches.  It also tends to blend the surface slightly from the minute flat areas left by sanding with a backer.

I've tried to show the angle and how the coverage shows up in the angled pattern, but I'm at the limits of what my camera shows well.   

I'll finish with 400 and 600 tomorrow, and send it off to be plated.

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I did the final 400 and 600 polishing steps, and I'm happy with the results.  Now, need to countersink and fit the screws, and then do a final repolish and send off to be plated.

I'm into this 7 to 8 hours.  A lot more time than you would expect for as small as it is.

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