surface prepuration question - Engraving Forum.com - The Internet's Largest and Fastest Growing Engraving Community

Tang · #1 07-17-2010, 12:11 PM

I have a question that relates to preparing metal prior to engraving. I understand that items should be polished prior to being sent to the engraver but in the event this does not take place I am sure some on this forum have expertise. My question is simple can you use automotive polishing compund to accomplish a final polish by hand? If so what type would you use.

If the answer is no way under any circumstances I need to know that as well.

Thanks for your thoughts.

jlseymour · #2 07-17-2010, 01:10 PM

What are you polishing???
That the question...
Post something you have a question on....
I'm a jeweler and we use different polish compounds for different metals'''
Jerry
And where are you... It's nice to know where we are talking too...

Tang · #3 07-17-2010, 05:22 PM

I am thinking of using it on mild steel hope that helps.

Steve Lindsay · #4 07-17-2010, 08:08 PM

Sandpaper backed with a block. Depending how bad of finish it is to start with but you might start with 220 and work through the grits up to 1200grit. Change your sanding directions each time you change grits and sand with that grit until you clean all the scratches up from the last grit. 220, 340, 400, 600, 1200. You can even take up to 2000 grit for a nice line polish. Find 1200 through 2000 grit at an auto supply store. It is used for wet sanding car paint.

Damien Connolly · #5 07-18-2010, 12:20 AM

Tang...how expensive an engraving job is it? There arent many, in fact, no factory finishes that don't need to be completely re-filed and polished prior to a proper engraving job. If you haven't used a file much, then this may not be something you can do yourself. I expect to spend around 20 hrs polishing a Colt SAA, and that is pretty representitive of most jobs.

However, my method is: File the minor flats and rounds with as coarse a file as necessary to cut the pits, dished screw holes and soft edges away fast. I generally use an 8" or perhaps 10" 2nd cut bastard for this, as close to new as possible. Using too fine a file reduces control due to the excessive pressure required.

Take and 8" smooth mill file and remove the coarse file marks in long slicing strokes, wiping the filings from the file teeth every 3-4 strokes with the fingers, and every so often with a file card. (brush) Then with a piece of ordinary chalk, fill the teeth of the file and begin the final cut. Keep the teeth brushed clean with the fingers as you file in slicing strokes. This will deliver a very good finish, devoid of drag marks caused by filings "pinning" in the teeth. Inside trigger guards, extended bottom tangs, hammers and the like require needle files to finish file, while concave are best done with a riffler. Don't be tempted by the Dremel tool and rotary stones or sanding bands, it always shows....and ruins a job.

Then go to the major flats and do the same, but here you have to watch that the new edges you produce are coming up square, parrallel and straight. Watch for it , and go back and correct it before going on. The engraver won't thank you for having to follow a wonky edge with a wonky line.

The best and crispest finish from here is undoubtedly obtained with stones. I only use 2 grits, 320 and 600, used with lots of a WD40 and kerosine mix. I should say, that it is possible to do and "ok" job with W&D paper. It's best to glue it to the block to eliminate the bagging effect where it wraps around the block. This has a very noticeable effect on the overall crispness of the job. And that's what polishing is about, providing the cleanest, crispest canvas possible for engraving.

After the stones, I use (very carefully I should say) 600 and 800 paper glued to whatever shape block or mandrel fits the surface to be polished.

I do have to admit to being a bit extreme here, but to get the ultimate in crispness around double gun fences, trigger guard spurs and similarly critical areas, I use shaped mild steel laps with silicon carbide paste. The difference shows, and people notice.

Prior to engraving, I take a wad of 000 steel wool with some 700g silicon carbide paste and go all over the job in a tight circular motion. This gives a very fine multi directional surface that is receptive to pencil marks, chinese white, or the flash coat of white acrylic spray primer that I use to draw on.

After the design is laid out and outlined with the chisel, I go over it with the 800 paper on a stick, then both 700g and 1200g on 0000 steel wool. Beware the edges with the steel wool though, it cuts aggressively and indiscriminately.

The surface produced by this sequence, is a high lustre finish of the finest non directional satin, that to me, complements engraving like no other.

Damien connolly.