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Metal Refinishing for the Gunsmith 05/22/2010 - By Tim Whealton
An overview of how guns are refinished in todays gunshop
Metal Refinishing for the Gunsmith
I have always loved to hot blue. If you hot blue a gun no one can dispute that you are a gunsmith. I did my first one for a paying customer 40 years ago and I still like to see them come out of the tank all black and shiny. It makes me feel like the alchemist of old except this time the chemistry worked. You put polished clean steel in the boiling tank that is usually a light dirty brown and it comes out black and beautiful. It really is magic.
I already told you the secret of beautiful blue jobs, you put polished clean steel in the tank. Anything else and you will be sorry. For sure anything you can see on the metal before you blue you will see after you blue. Bluing does not fill in or cover up. It changes the color of the surface of the steel and nothing else. It does not change the size or shape. This is a good thing when you are trying to put the gun back together. Bake on finishes and plating can be a real pain when allowed to build up on sliding parts and inside screw threads but bluing has no effect on any of these. This also makes bluing popular in industrial applications as well. I frequently blue parts for aircraft and food processing machinery. These are applications where a small patch of plating or paint chip could cause great harm. Industrial applications donít call it bluing however, to them it is black oxide finish.
Although this work is not exactly gunsmithing it might be an additional source of income for the gunsmith that keeps his bluing tanks operational. Try contacting the machine shops in your area and ask if they have need of your services for small parts. Typically they will bring parts that require nothing more than running thru the tanks. No disassembly, no polishing and no assembly make this type of bluing mighty easy.
While preparation is the key, before bluing a gun some other decisions have to made first. First question is this gun a good candidate for rebluing. Is it a gun with collector interest that will be devalued with rebluing? Is it in such poor condition that rebluing will be of no value or is it a cheap gun not worth rebluing? Maybe it is a gun that cannot be hot blued and requires another method. Double barrels, alloy frames, heat treated and case hardened frames cannot be reblued and look correct. Some part might even be damaged by the caustic or heat of bluing. You donít want to tell the customer that after rebluing his Daddyís double barrel he now has two single barrels!
Bluing guns is not difficult if you can follow directions. It can be extremely dangerous and painful if you are careless. You will be working with super heated caustic. It causes permanent damage to human tissue even at room temperature, imagine what it will do at temperatures well above boiling. Caustic in the eye equals blindness. Even before you get to the bluing tank the spinning wheels of the buffer have injured many workers who got a ďlittle carelessĒ. John Wayne said ďlife is tough, its tougher if you are stupid. I use Brownells Oxynate 7 bluing salts and they come with the most complete directions I have ever seen. A large part of these instructions are about safety. Read them through many times before you start, it will pay to observe all the precautions.
Getting a gun ready to be blued starts with disassembly. For rebluing this means total disassembly for anything that will go in the bluing tank. Even a plug screw can cause you a major headache if left in place. It might look fine before going in the tank but traces of oil and dried grease from years ago will loosen at the high temp of the bluing tank and creep out across the surface preventing the bluing from taking around the screw. If it can come off or out then it has to before bluing. A general cleaning in a degreaser or warm soap solution will be a good start. Now you can separate the parts that will not be blued. Maybe the bolt will look better polished, maybe some of the parts are alloy. Whatever the reason set these aside and where they wonít be lost.
Now inspect the parts to be blued. If lightly pitted most of the time they can be polished out to a like new surface. Understand this process is cutting down the surface of the steel till it is level with the bottom of the deepest pit. If the pit is more than a few thousands deep you might have to remove too much metal. Many time this is just not possible and the gun will look much better if some pitting is left and the surface is not taken to the high polish finish. The more the shine the more the pit shows. This is where experience comes in and you get by spending time at the buffer. After you have done a few you will usually be able to look at the gun when it comes in the door and tell what type of finish will look the best.
Gunsmith Kinks has great directions on polishing. Read it before you start so you can have a better idea of the objective. Keeping flats flat and keeping flats from appearing on the curved parts while not funneling screw holes or removing lettering might sound easy but when the wheel is turning 1800 rpms bad things happen fast, some of them to the gun and some to you.
Once when I was volunteering as an EMT we responded to the local plating shop where a person was going to polish a machete. The ten inch fluffy wheel grabbed the blade and it hit his thigh just below the crotch and traveled down the front cutting off muscle and stopping just above the knee. It took a lot of surgery to save the leg and a lot of blood to save his life. Donít learn the hard way with buffers, these are powerful and dangerous tools.
If you travel around you will doubtless see a lot of things called buffers. It seems like a lot of us start out poor and try to save money by rigging some sort of power to a shaft and attaching a cotton wheel. Nothing wrong with this idea if it has enough power and turns true and vibration free, only problem is most homemade rigs leave a lot to be desired. I struggled with these setups for years till I finally got a Baldor buffer from Brownells. It was love at first pass. My quality improved so much I havenít turned on the homemade rig since. If making a polisher is irresistible, then do it, but make sure it has at least ĺ horsepower at 1800 rpm and enough separation between the wheels to allow you polish a barrel without the other end hitting the other wheel. If more than 1800 rpm the glue type polish will be thrown from the wheel and the snatch and grab problems will be more serious. Some type of soft floor mat can save a lot of work by cushioning parts that slip from the fingers. Good lighting will be necessary for inspecting the progress of the job. A heavy shaft helps too. Remember if it vibrates this will be transferred to the finish on the gun being polished.
Brownells gives good advice on polishing wheels. Your will need several but they last a long time. At least 2 for each grit. I use medium felt and loose muslin for 240 and 400 and a hard felt and loose muslin for 500 and 555 polish. These wheels will also put a shaving edge on a knife. They will also throw that knife through your legs and feet if you turn it the wrong way so wait till you have some experience before putting a knife to a loose wheel.
I have tried several types of grit polish and always came back to polish-o-ray. Seems I paid more with no benefit or spent less and had something unsuitable. I keep mine in an ammo can with a damp rag and it doesnít dry out. When you leave it on the bench it becomes a brick but will eventually soften if kept damp. Keep the whole thing in the refrigerator and it will load on the wheel better and last longer. Follow directions for truing the wheels and applying the polish. No matter how strong and smooth the buffer you canít get a good finish with an out of round wheel. Cut off the buffer and apply the grit polish as the wheels slow down. This helps prevent polish being thrown from the wheel before it hardens on the periphery of the wheel. It also helps to apply it when stopping for the day too so the buffer will be ready to go when you come back.
Polishing and buffing is not a skill that you can acquire by simply reading. It is a mixture of art and science that takes time and attention to detail. Start with the coarse grits and donít change until the only marks are the scratches from the grit. In other words if you start with 240 stay with it until there are only 240 grit scratches. The coarse grits remove metal faster and you will save time. It just seems irresistible sometimes to go ahead and change when the pitting is almost gone but it just slows you down. Unless the pitting is excessive I start with 240 on a felt or stitched wheel and when the pits are gone change to the loose wheel just to make the scratch pattern uniform. After repeating with 400 grit I will usually use a blending wheel to soften the scratch pattern and even it up. If going for the high polish you would finish with the 555 on hard felt and loose muslin. We are talking about a mirror finish and a lot of work.
Pay close attention to your technique while you have a gun part in contact with the wheel. The part must stay in motion and the edge of the wheel must not go over any edge of the part. Steady light pressure will allow the cutting edges of the grit to do the work without excessive heat buildup. Wearing a pair of light cotton gloves helps you hold parts that heat up quick and keep you from getting dirty fingerprints on the surface. They can be removed but smudges make it harder to judge the surface being polished. Be careful with the edge of grit covered wheel because it will cut a groove in your part in a second if you are careless. Practice on junk parts until you are satisfied with the result. Having your first rebluing job turn out well will be the mark of a smart and careful workman.
Whatever level of finish when you stop it is time to blue unless you take special care of this exposed steel to prevent it from rusting. Oils are not a good idea before going to the bluing room but Brownells sells a product called Hold that works great on bare steel and doesnít interfere with the bluing process. Just spray it on like oil and the part stays just like it was just polished.
When setting up your bluing room it is a good idea to talk with someone with experience. If finding a mentor isnít possible then study the directions until it becomes clear and you can do a mental walk thru of the whole process. Set up everything with safety in mind. This includes wearing personal protective equipment. It might not be comfortable but it sure feels better than a third degree chemical and thermal burn.
Good ventilation is needed to pull out the caustic vapors. If the bluing setup is in your shop it should be in its own room with an exhaust fan or at least in a corner with an exhaust hood. The extra moisture will raise havoc with tools and gun part exposed to it so plan a way for the steam to be pulled out of the work area. It doesnít have to pull your hat off when you walk by or suck the flame off the burner but it should at least pull out the rising steam.
The bluing process itself is simple. Suspend your parts on wires so they are covered with solution. First the cleaning tank that is 190 degrees. This is a soap type solution and it helps to scrub with a brush while using it. Then a rinse tank and straight into the boiling blue tank. It usually has all the color it will take in 15 minutes but some steels require longer. Winchester nickel steel and those old hard Springfields might take 45 minutes. After the blue tank another rinse is necessary to remove the salts that cling to the surface. After rinsing it is time for water displacing oil to cover all the parts. Immersion in a tank is best but I have sprayed with ok results if you are careful. Just make sure because you donít want to have to polish and reblue again before you reassemble because you forgot to oil.
Maybe one of the most overlooked skills when bluing is how to add water to the tank to maintain temperature. No solution can be heated hotter than its boiling point. You can turn up the heat and boil very vigorously or turn it down till it barely boils and the temperature will not change. It will however change its boiling point and the temperature will rise as the water is boiled away and the solution become more concentrated. By adding water in small amounts the boiling point can be kept constant while keeping the tank at a boil. It is very important that the boiling action not stop while the parts are in the tank because particles will settle on the surface and cause uneven coloring. Keeping the tank agitated by maintaining a rolling boil will prevent this. The technique is to gently spread the water on top of the salts evenly by using a ladle and spreading the water from end to end. If the water is poured in the tank forcefully then the water that boils at 212 degrees is forced into the solution boiling at 298 degrees. This causes the water to instantly turn to steam and expand 1700 times while under the surface of the boiling solution. This causes a spattering eruption throwing the boiling solution on the operator. While it is good to learn from your mistakes it might be better to learn from me on this one a problem blueing.
This is an overview of blueing and not a complete set of directions. Brownells will give you a complete set and if you follow them you will not have any problems.
While hot blue is the king of modern gun finishes it might not be the best choice. Several things have to be taken into consideration before making a decision. Does it have soldered parts? Is it heat treated steel? Is it an alloy that wonít blue ( stainless or 94 Winchester post 64)? Is it aluminum? Luckily the modern gunsmith has many excellent choices. Cold blue, hot water blue, Parkerizing, nitre blue, color case hardening and bake on paint finishes are all possible for the modern gunsmith.
Cold blue use to be the mark of the amateur but that has changed. We now have cold instant blue that is so good it can even be used for a total reblue. No it isnít the best but it is ok for the gun that is not worth the cost of hot blue but needs ďsomethingĒ, but mostly the real value of cold blue is touch up for a worn area or scratch. Without having to disassemble of polish or heat tanks and reassemble it can save the day when all you need is a touch up. Following directions usually gives the best results ( not man style but it can save a lot of headaches!).
Hot water blue or Belgium blue has been around quite some time. It is similar to rust blue but doesnít require the rusting time period between coats. Its main use is for double barrels or shotguns with soft soldered ribs. The pre cleaning and polishing is the same as hot bluing. Clean polished steel with imperfections removed before you start is the first step in a professional job. Like anything else a little technique is required when the blue is swabbed on the steel. You want smooth even coverage but no runs. I use swabs that I make for this and rust blue as well. I use a small swatch of a pair of ladies nylon hose wrapped around a piece of absorbent terry cloth. This gives me a swab that will hold enough solution to wet the steel from one end to the other without dripping. The drip causes damage to the newly formed blue and makes a spot that will not totally go away or blend in even after several coats. Another benefit of this swab is it gives you a really good explanation in case a pair of nylons show up in an unexpected place. Again the manufacturer knows what will give the best results so try to read the directions.
Rust blue is beautiful. Once you do a good rust blue you will never be satisfied with anything else. Durable and attractive are not qualities that usually show up together but for rust blue this is the case. A lot of gunsmiths read the directions for rust blue and never try it but it really isnít hard, it just takes a long time.
The old time gunsmithing books have many formulas for rust blue. I think it best to buy premixed and avoid the headaches of finding chemicals of obsolete name and measure not to mention having to interview with Homeland Security about why you want it. The process is described in detail in all the old books so I wonít waste a lot of time but rather remind you of some pitfalls. Number 1 problem is keeping oily fingerprints off. Degrease well and wear rubber gloves. Keep the work area and the rusting cabinet away from sprayed oil. An unexpected source of oil an contamination is the drain hole in the under rib on doubles. When you pick the barrel up out of the boiling water allow this to drain so that it doesnít run around the barrel. Even after cleaning as best you can it seems a little can still come out and leave a mark. Make sure the rusting cabinet will not allow condensation to form, this will cause spotting. Depending on your local humidity you might have to become inventive to create the perfect tropical air mass. Not usually a problem in Eastern N.C. but maybe other areas are not so lucky as to have 99% humidity. Of course a drop of sweat off your nose is just as bad if it hits where it will show ( and you know it will every time!).
Nitre blue is a specialty finish to highlight a receiver or make parts stand out. Almost iridescent, it can really be striking. It doesnít seem to hold up well to heavy usage but not every gun is built for heavy usage. As the color is controlled with the heat it can be used to make replacement parts look correct or restore correct finish to a worn part like a straw colored extractor.
Color Case hardening is an old process that has seen renewed interest in the last 20years. Maybe partly from Cowboy shooting but I think mostly because beautiful has never gone out of style. Just like every other finish you have to start with clean and polished steel. The part is packed in a crucible ( fireproof container) with high carbon media all the way around. This can be commercial compound or bone meal and leather scraps. The whole thing is heated to a red temperature and held there long enough for the carbon to enter the surface of the steel. Then it is quenched and the colors freeze in beautiful swirls of the rainbow. This piece of steel then has an extremely hard wear resistant finish around a soft core that resist cracking. Perfect for a lot of gun parts. Some people have specialized in this work and done rather well for themselves.
No matter which of the metal finishes the customer chooses it will be the skill of the craftsman that will make it a thing of beauty or just another reblued gun so do good work, it is the only type that makes a difference!