Metal Prep

[Lazarus]

Folks, a lot is said about tweaking our firearms for best operation, but little is discussed when it comes to the most important part of finishing or refinishing - and that is metal prep. I must admit I know very little about this phase as it is routinely done for better or for worse by the person who blues your gun. Mostly, one hears horror stories about how a beautiful gun is trashed by someone who got carried away with a buffing wheel!

I am not too interested in setting up a chemical lab in my basement to do hot bluing, but I would be interested in some techniques for proper metal preparation. Anyone have experience in this field? Can the metal prep be done by hand, or is the power wheel a necessity? How to preserve straight sharp edges while polishing a flat surface...not as easy as it sounds. Any interest in this subject?

-Lazarus

[Spindly61]

I haven't done any blueing. To keep flat surfaces flat I use a piece of sandpaper on glass. Glass is very flat. For any of the spray on finishes Glass beading is recommended as a prep. There are ways to do it by hand. Other more knowledgable will reply I'm sure.

[gbw]

I mirror finished, then had blued, the first guns I built, a matched pair of Gold Cup copies. Told the bluing guy to just clean and dunk, do not do any polishing. They came out very well - much better than the pics. Flats are near perfectly flat, edges are sharp and clean.

Pics are at thread " To build from scratch or buy and build up?? " on pg. 3.

They were polished using successively finer grades of paper from 320 through 2500 (avail at auto paint stores). You must glue the paper to a FLAT surface, or it will ride up and round off corners - glass, or I used a piece of granite counter top, which is thicker and easier to hold. Get a can of spray adhesive for this. Practice. Then be prepared to get your arm / hand very tired. Glue paper onto shaped sticks for getting into corners and doing things like safeties and slide stops. Some parts you can do using the paper shoeshine fashion, but be careful of the edges. On complex parts do the flat surfaces last, this will tend to clean up any edges you may have accidently rounded over. Do pin ends in a drill press or lathe.

Also, on cast frames, Caspian and Essex at least, the flats are NOT flat. It takes a lot of work to get them that way. Same for the Colt slides, although they look as if they were finished on a surface grinder.

You can get the parts to mirror gloss, if that's what you're after. After bluing the parts are so smooth that they will look wet!

I tried using a buffing wheel at first, it was not possible (for me) to get the results I wanted. The wheel/compound is used only at the end for a VERY light finishing buff.

For dull parts, cheap sand blaster (avail at Wal Mart for $10-$15) works fine - but you do need compressed air to run it. Any of the larger 5hp / 120v home air compressers will do, and the smaller ones may work also.

Do this after polishing is done, otherwise you tend to smooth out areas you want dull. You can use sand or glass beads, and control the finish quite well by varying grits and by how close / long you blast the part. Mask polished areas with electrical tape, trim tape with single edge razor blades - carefully. Hope this helps, good luck.

[Lazarus]

Thanks for the comments, and I'm glad to hear about the success of the bluing jobs. I think gb has the right idea for the use of sanding sticks and sanding blocks. From the little I know, special polishing wheels made with stiff leather were used in the original Colt finishing shop which allowed the flats retain their sharp lines during the work.

Something to consider as already noted by gb, is that the "flat" surfaces of the gun are not really flat. The next question would be if it is really necessary to make them flat in order to achieve a good polished appearance? I suspect not. I use a glass surface all the time for finishing small parts, but I'm thinking that semi-flexible sanding blocks are still the way to go when working with flats. An example might be a block of hard rubber that would allow polishing without alot of unnecessary metal removal. Remember that some of the guns have roll marks and other lettering that would probably get hammered using the glass surface method.

Carding wheels are another prep method I know little about. They are rotary wire wheels that use very fine wire and produce a semi-polished appearance. Many commercial A1 Colts have carded flats. A good reason to limit the level of polish is that you are always wiping off fingerprints and worrying about the finish! One of my guns has flats polished to 400 grit and that seems to be a good compromise between practical and display-only quality.

Gb...now that you have some pistols that go beyond 1200 grit finish...are these in your display case or are these guns used regularly? Thanks for the pointers on sanding blocks.

-Lazarus

[gbw]

Hi - I shoot the guns regularly. One is at ~5000 rds., the other at ~2000. Normally I leave them coated with silicone, and I'm careful to wipe them off when done. The only display gun I have is an 1882 SAA .45 w /factory ivory and nickel my grandfather had.

The mirror finish is fragile. But I wanted shiny guns - no particular reason except I think they're purdy. But you're right, at any stage you can call them done and have a very nice finish.

I found that any flex in a sanding block will attack sharp edges, as will any slack in the paper - hence the glue - but that could be a technique problem on my part. With a mirror finish large flats do have to be flat, otherwise the reflections show (actually magnify) distortions. I don't mind if the steel raised up by roll marks are removed - the mark remains, and look more finished.

I had no luck using any sort of wheel where I wanted to preserve a sharp, clean edge, but again could be 'cause I'm an amateur, still learning.

[Deacon Aegis]

Lazarus,
There are many ways that the metal may be prepared to take the final finish and the equation for best results often depends on exactly which type of finish one desires and what type of alloy is being worked. For instance, parkerizing works best when the surface metal being parked is roughed up with a medium-fine grit abrasive blast, delivering a surface that yields larger phosate crystal growth far exceeding the thin phosphate tint polished steel would induce.

For a matte finished stainless steel, I'd spend an excessive amount of time with a paint stirring stick wrapped in 220 grit sandpaper, followed by 320 grit wet sanded to remove any hint of tooling marks, then I'd do an abrasive blast to even-out the steel's surface (and reveal any flaws or tool marks I missed). I'd follow the abrassive blast with a soft brush cleaning in mineral oil, blow it dry, then do a glass bead blast for the final surface texture.

If my goal was to apply a polymer coat to the metal, I'd prep as before with a series of finer and finer wet sandings to remove tooling marks, then apply an abrasive blast to the steel to give the polymer coating some bite to adhere to. Some folks might do a parkerized finish prior to coating with polymer and I have seen arguments supporting both camps of direct to steel applications and polymer over park groups and the jury is still out for me as which is best.

Blued finishes can go matte, gloss-high polished, matte on round gloss on flats, etc. Following the same process to achieve the matte finishes on stainless (abrasive blast followed by glass bead blast) delivers a nice matte surface for the rounds while high polished flats may require a surface grind, then be wet sanded at 400 grit to 600 grit with a precise flat block to achieve that level of polish that always appears wet. The surface grind may not be neccessary in many cases, but to pull out some tool marks prior to a high-polish job it could save a huge amount of time.

Hard chrome surface prep looks to be very similar to the above, as far as I am lead to understand it, however I have no experience at all on preping the surface for this process. I imagine it is very close to the above method though.

Aluminum anodizing is likewise another that I know virtually nothing about.

Anyway, I've by no means achieved much more than an initial famiarity with many of these processes, though I am learning more and more as each week slides by. Hope this has helped a tad. :D

[Lazarus]

Thanks again. There is considerable skill and knowledge needed in this field. More often than not I hear of guns that were ruined at the finisher instead of coming back professionally blued.

I have never owned a mirror-finish gun and don't think I want one. GB, do you have photos of these guns posted? In that case I can see that flat should really be flat. In 99 per cent of the cases it is a polish that is desired. And, furthermore, I believe that taking a slide down using a glass surface is going to entail a whole lot of metal removal. That is not noted by most people until the have developed arthritis in their arm from the polishing.

Perhaps someone has some reference materials on this subject. The correct use of carding wheels and special hard leather wheels is getting to be a lost art. Seems to be SOP to use the bead blasting to prepare the matte areas, and matte can cover up a lot of things that polishing does not.

-Lazarus

[gbw]

I like the mirror finish, but it took far more time that it's likely worth, and you do have to be careful NOT to remove serial numbers. I'm afraid I'm not near photographer enough to show the finish. Anyhow...

http://forum.m1911.org/showthread.php?t=18996&page=3

[Spindly61]

I always thought that the flats were a ground finish. I'm sure different manufacturers have different machining processes and will vary from maker to maker. I made them years ago and everything has to be dead flat for fixturing. Oh well I guess things change.

[Greg Derr]

Lazaras: On the carding wheels. I believe that Colt used a horse hair wheel to obtain that brushed look. The wirewheels are far to abrasive. Got that from an old Colt employee in the custom finishing dept.

[gbw]

I can tell you for sure they are not flat - certainly not cast Essex or Caspian frames. But you can get them flat if you want to spend the time and have a useful arm ( I USED to). The Colt slides are closer, but not there either. All were checked with a dial indicator on a surface plate.

But I think these days it doesn't matter so much insofar as the manufacturers are concerned, they still manufacture very high quality. They can now locate everything nearly perfectly with the CNC tools they have - they just keep measuring from whatever index they use.

[Lazarus]

Thanks for the tip about the horse hair wheels. I haven't seen one of those advertised at Brownells lately! Nice photos of your blasters, EG! How's your arm doing?

I think everyone can appreciate the difference between a "wire wheel" that is typically used for rust removal or maybe for brazing prep...and a carding wheel made from much finer and shorter wires. Just as there is a difference between a buffing wheel of loose muslin cloth that will round any straight edge...and a stiff, stiched polishing wheel made from canvas or leather.

Nobody disputes that a painstaking ordeal with glass and sandpaper will produce a nice finish. But I wouldn't be suprised if we're talking removal of up to several thousandths in certain places to get there. My point was that a very nice polished finish can be done without going to an optically flat surface, and that in most cases a medium polish is the desired end result.

I'd like to know when bead blasting was introduced as a method of producing a matte metal finish? Were the early Colts polished overall, or did they use the matte finish on rounds also? If so, I wonder if that was done with a coarse wheel?

-Lazarus

[Jerry Keefer]

Spindly61
I always thought that the flats were a ground finish.
Spindly;

I surface grind to true all flats first. It would take a week to do some of these out of square guns on a plate by hand. Then hand finish 800 thru 1200 grit, and then buff. Again not to be disagreeable, but I don't know how you can beat a buffer and white 555 for finish luster.
Take Care
Jerry

[gbw]

Well, maybe not a week. It just seems like it. The surface grinder is the way to go, if you have one and know how to use it.

I used a buffer as well, for the very last finish polish.

More I think about it, I have a pair of SS guns awaiting to build, and since my arm is recovering I may shine them up too. Or maybe not.

[Lazarus]

Jerry, you did what to get your guns flat? I'm not sure I've ever seen a surface grinder; perhaps you can introduce us to the machine? Are these routinely used in the machine shop for final surface prep, and if so, what kind of applications? Once again, I can't dispute that these methods will ultimately result in a nice gun finish, but I'm still going to be a little sceptical about whether one really needs this level of technology to achieve a medium polished finish.

-Lazarus

[auto45]

I did "polish" my 1991A1 that had the matte blued finish on it.

It now looks a lot better than when I bought it. Used 220- 320-400 grit with the paper taped to a piece of glass and worked the frame and slide back and forth. Also used a semi-flexiable sanding "pad" when needed. And some "shoe-shinning" in certain areas of course.

Not hard to do and it "looks" better than any production blued 1911 I've seen...but it won't be mistaken for a master polishing job I've seen for about $300. ;) I rounded some edges here and there, some on purpose and others not. So, IMHO, easy to do if you are not that "picky". Skillfull job if you want your gun on the front page of American Handgunner.

[gbw]

It's a common machine shop tool.

The grinding wheel is stationary, with a table underneath the wheel.

The part is clamped to the table. The table can be adjusted vertically, and moves back and forth horizontally.

After the part is positioned and fixed, the table is raised vertically until the part will be contacted by the grinding wheel to a disired depth. Then table is moved back and forth horizontally. The result on good machines is a nearly mathematically flat surface. Good surface grinders are capable of incredible accuracy.

[gbw]

Missed second part of your last post, Mr. Lazarus. You surely do not need surface grinders and surface plates and such for a very nice medium finish, one which will look very good.

(A surface plate is just a thick piece of granite, usually, finished to a near perfectly flat surface. Mainly used for QC checking stuff, I think.)

I was after a mirror finish, and I don't have access to a surface grinder. They are very expensive. It took a very long time, a lot of work, but it IS doable if anyone else should be so foolish as to try.

Mr. Keefer can get the same result much, much faster by beginning with a ground flat surface, and it's probably better.

[nick50471]

The finish on any metal part cast or machined is normally achieved through vibratory means. There are hundreds of different type of media and compounds used to achieve different finishes. Hand polishing is a very labor intensive and therefore expensive.
All gun makers use some sort of vibratory de-burring/finishing in their processes before the piece is sent to be blued,Parkerized,case hardened etc. There are several "job shop" vibratory shops located around the US that could easily prep your gun to be blued,Parkerized,hard chromed whatever. This would be much faster and very likely turn out much better than hand finishing. It is difficult to get a uniform finish by hand.
The company I work for has been building vibratory machines for 75 years and has finished, de-burred and cleaned almost any part imaginable.

[Jerry Keefer]

[QUOTE=Lazarus]Jerry, you did what to get your guns flat? I'm not sure I've ever seen a surface grinder; perhaps you can introduce us to the machine? Are these routinely used in the machine shop for final surface prep, and if so, what kind of applications? Once again, I can't dispute that these methods will ultimately result in a nice gun finish, but I'm still going to be a little sceptical about whether one really needs this level of technology to achieve a medium polished finish.

gbw's explanation is somewhat accurate.
The part(s) are held in place by magnetism. The table moves in the x and y axis.(horizontal planes) Only the wheel moves in the z axis. (vertical plane) It will produce very precise, accurate dimensions. The part(s) are flooded with a coolant/lubricant. It will produce a very flat, smooth, near mirror finish with the correct wheel grit/hardness. The part(s) will be flat and true. If you mic the frame or slide it will not vary over its entire dimension. The corners/edges will be razor sharp and distinct. Very little after prep work is necessary. As I said yesterday. Most frames/slides are more than several thousandths out of parallel, and that much is difficult to correct on a surface plate and sand paper. I am reluctant to use any grit under 600, so the removal rate is slow, Coarser grits may remove material faster, but the surface finish they create is difficult to repair, and can be detected when buffing. Invisible scratches that suddenly appear when buffing and bluing are the result of course grits....
And your scepticism is founded. You can get a reasonable finish without high end machines, but for those of us in the trade, .....time AND perfection is money..
Take Care

Jerry

[Deacon Aegis]

Surface grinding - One of the reasons I tend to believe the Les Baer frames are a typically superior base for a custom build is due to the fact that they are intentionally left oversize in width out of spec knowingly and purposefully done as such. No full build is without the dings or scratches of bench and vise manipulation, therefore the LB frames are delivered taking that into account so that once the pistol is basically fitted, and near completion, the frame's flats then are surface ground to pull the frame's width dimensions into spec. The extra material was there to absorb the dings and dents asndf nicks and scratches that accompany many a build. Of course, that is also why the LB frame is not for the typical kitchen-table builder. They are cost prohibitive to most home builders, require machining at a level only full-blown shops generally can handle, and the steel itself feels to me as if it is a bit more difficult to cut and work, but ultimately the resulting frame is extraordinary. I've got 4 LB's right now for the damascus project and they are certainly a beast all to themselves. I have no doubt though that these four pistols will be superior in every way. Perfection, in the tens of thousandths of an inch.