This article deals with restoring metal surfaces. It’s applicable to just about any time you have occasion to pick up a file, whether to fit or repair old bronze boat hardware, antique tools or automotive parts. My training aid is a badly abused but classic hunting rifle from 1936 I recently restored…a good choice as these objects are the subjects of close scrutiny by discriminating clients and require a degree of precision useful for demonstration.
File Pattern and Type. Files come in far too many patterns and cuts to treat in detail here, but are generally either Machinists or Engineers Files for shaping, Saw or Sharpening Files for sharpening, Aluminum Files for that soft material, Rasps and smaller Rifflers with coarse teeth for wood, Needle Files for small work or large Blacksmith Files. There are also innumerable specialty files like metal checkering files, lathe files, curved tooth files, cantsaw files and even triangular dovetail files with two “safe” or smooth faces.
Either American or Swiss pattern Files are common here, the difference only being the pattern standard used to manufacture the file and how the fineness or coarseness of its teeth is measured. The shapes themselves are similar, but Swiss files have longer, thinner tapers, are slightly slimmer, are made to closer tolerances and come in finer grades of cut. They also cost more. Any edition of Machinery’s Handbook by Industrial Press will provide additional detail.
Type of Cut. Single cut files have a series of parallel teeth running diagonally across the width of the file surface and are generally used for sharpening or fine finishing. Double cut files have two series of parallel teeth running diagonally across the width of the file surface with one series crossing the other. These are best suited for rapid removal of material.
Coarseness of Cut. Bastard Cut in American Pattern files is the standard for shaping and dressing steels and castings. The Swiss Pattern equivalent is #00 Very Coarse. Second Cut American is for lighter removal and for hard metals. The Swiss equivalent is #0 Coarse, with a finer grade of #1 Medium Coarse above it. Smooth Cut American is for finishing and hard metals. The Swiss equivalent is #2 Medium with #3 Medium Fine and #4 Fine above it.
Once filing skills are mastered on both metal and wood, these finer grades of file will often pay for themselves in the cost of abrasive paper saved. Flea market machinist files too worn for steel still work just fine on wood, and will save lots of sanding and paper.
Cross Filing. Using the file in its normal direction of cutting perpendicular to the axis of the file. Files cut in one direction only and when they get dull, they are relegated to soft materials like wood or discarded…if you develop the habit of lifting the file on the return stroke, you will literally double the life of your files.
Draw Filing. Draw filing is used to produce very smooth and true surfaces. To draw file, hold the file at right angles to the direction of the strokes, with your hands close together to prevent breaking the file. Pressure should not be great and can remain the same for the back stroke, as the teeth cut in both directions when using the file in this manner.
Break In and Care. Files are of hard and brittle steel and new files have a slight wire edge on their cutting teeth. Using a new file fresh from its wrapper to cut hard materials is a mistake, as this wire edge can break and take part of the cutting edge with it. A better practice is to break the file in…removing that wire edge…by filing lightly on brass or bronze before proceeding to steel. Files should never be used with force, as too much pressure causes the teeth to clog quickly and causes the file to rock and round the corners of the work piece. Also take note of the fresh file brush and blackboard chalk that live with the files. Keeping the work surface wiped clean of shavings and the teeth of the file clean and unclogged will prevent those disastrous deep scratches that are the bane of finishing work. Chalking the file makes it easier to clean and lessens its tendency to clog with shavings.
Files should not be stored loose in drawer or toolbox where they touch each other…I prefer to store them either hanging by their handles or upright with their tangs in a holed block affixed to the back of the bench. Yeah, I know…the files in my picture are dirty and rusty…I should clean them before storage and then again before and as I use them. But what’s important is clean teeth touching the work piece, and out of laziness I skip a step and clean them thoroughly with WD-40 and the file brush and a dental pick if necessary before use and with chalk and the file brush and during use.
Removing the scope mount on this first-year Remington 141 restoration was an unpleasant surprise….small, 6-48 holes are filled and the repair hidden relatively easily, but these larger, off-center and misaligned 8-40 holes will be difficult to repair without the repair showing. What a rat’s nest!
And the aftermarket sling swivel mounted off center will also be removed and the original finish restored, and I’ll do that job first. These are threaded studs and are screwed in and sometimes also soft soldered as there is very little thread bearing surface in the thin band it is mounted to. This one is soldered. I can either unscrew it using 450 degrees of heat and pliers then fill the hole or I can simply grind and file it flush, which has some disadvantages you will see below.
I grind off the stud on the buffer grinder and crossfile with a single cut mill file until I am close to the original surface….
…then I draw file the stud flush with the surface…
…. followed by aluminum oxide wet-or-dry paper lubed with WD-40 and a sanding block in 180 through 600 grits without skipping a grit to polish. I could wrap the paper around my file instead of using a wood block…and I do that for flat surfaces…but for curved surfaces I prefer the softer wood as backing. A sanding block is important, as freehanding will result in an untrue surface…. especially in the joint filled by softer solder that is easily dished.
Continued…
I thought about doing your fix but the writing is still buggered. Oh well, maybe the next one will be better.
My family had a 30-40 back in the 20's-30's somewhere so I want to get one that would be "period" to what they would have had. Had the roll stamp been intact tho I would get or make filler plugs with the screw driver slot in them, fill the holes that way and got Elk hunting.