Basic Gunsmithing Skills
April 07, 2016
A home gunsmithing project may call on a variety of mechanical skills, and perfecting them beforehand will make your projects turn out much better. Here are a few skills that home gunsmiths should clean up and perfect before attempting work on a firearm.
Spray Gun Operation
One of the most common gunsmithing procedures is applying a finish to wood or metal firearms parts. Old time traditional gunsmithing work typically featured hand-rubbed oil finishes on wood and hot tank bluing on metal. Today sprayed on wood and metal finishes are probably more common than the traditional finishes.
Extremely durable metal finishes such as Brownells GunKote and LCW DuraCoat are easily applied with spray equipment in hobbyist gunsmithing. Even in these days of plastic stocks wood stocks, when used, are usually sprayed with lacquer or polyurethane finishes.
Small automotive type spray guns or airbrushes are used to apply many of today's firearm finishes. Full-size automotive type spray guns are overly large for gunsmithing purposes. Airbrushes and what is known as an auto touch up gun are sized more appropriately for firearms and small gun parts.
The touch up gun is fully adjustable for pattern shape, fluid flow and atomization. Spray patterns can be adjusted from wide to narrow. Generally, one adjusts the spray pattern width to about 1½ times the width of the workpiece, depending on user preference.
The thickness of the liquid finish (also known as viscosity) can range from barely flowing through the gun to as thin as water. Volume of material can be adjusted from almost nothing to a flood of finish.
By adjusting the pattern shape, fluid flow and thickness and the air pressure, you can apply a finish as rough as a corncob or smooth as glass. Airbrushes are intended for very small projects or parts. They are adjustable for fluid flow, but the patterns are fixed in a round or cone shape.
Liquids sprayed in an airbrush must be very thin to flow through its tiny passages. Their small size and limited fluid flow capabilities mean they are not good choices for large projects that require large volumes of fluid to be applied in a short time.
Other than understanding how a spray gun works, it does little good to try to teach spray gun usage, since almost everyone sprays differently. The best way to learn how to spray is to pick up the spray gun and start experimenting. I spray painted on a production line for more than 15 years with a couple dozen other painters and never found any two that sprayed the same way.
The best general purpose advice I can give to anyone in the gunsmithing hobby is to always keep the spray gun moving while liquid is being sprayed. If you stop while spraying, you will make a heavy spot and probably make a "run." Always remember to take your finger off the trigger when you get to the end of the part you are painting.
Don't try to apply to much finish at one time or per pass. If the finish is too light, you can always put on a second coat before the first one dries, but you can't take off too much finish after it is sprayed on.
Two or three light passes over the portion being sprayed are better than one heavy coat. When learning, be prepared for some failures, spraying finishes such as paints and firearms finishes is something of an art form that isn't learned to perfection on the first day.
Many military arms, and some commercial guns, feature many rivets in their construction. Firearms such as the AK-47, the Browning 1919, and FN-MAG feature heavy use of rivets. Rivets may look old-fashioned, but they are actually perfect for many uses in hobby gunsmithing. Unlike screws, they seldom ever come loose. In an industrial setting, they are fast, inexpensive and easy to install.
Production rivets are installed with riveting tools that are either not available or too expensive for the hobbyist. The home gunsmith can install rivets with nothing more than a hammer, punches and backing blocks. I have installed hundreds of rivets using only hand tools.
Yes, it is slow to hand-set rivets, but it costs almost nothing, as opposed to spending big bucks on rivet tools you may only use a few times. Riveting in its most basic form is just installing a soft metal cylinder in a hole between two tightly clamped pieces and then smashing a head on the unformed end so it can't pull out. Medieval man installed rivets and you can, too.
To install rivets with hand tools, you first install the rivet in a proper sized hole in the parts you are securing together. Hole size should only be a few thousandths larger than the rivet shank. Trim the excess rivet shank length to have just enough material to form a head. The amount will vary depending on the size of head you want to form.
Be sure to have your parts tightly clamped together. Back up the preformed rivet head with a heavy steel block. Start flattening the exposed rivet shank with a hammer. After you have it flattened somewhat, start tapping around the edges to round over the sides into the shape of a rivet head.
Use dozens of small taps to form the heads, not a few heavy blows. Continue forming the head until it is tight against the workpiece. Check often to verify the rivet head under the workpiece is staying tight against the work.
Be sure to hammer on the rivet only and make absolutely sure the rivet is fully supported. You want all hammering force going into the rivet, not the workpiece. Rivet setting can be made easier with a self-made rivet punch. This is nothing more than a flat-faced punch that has had a semi-circle ground in its face to approximate the shape of a rivet head.
As you hammer the punch onto the rivet shank, the soft metal will deform and fill the recess in the head. If you're skilled, hand-set rivets can look nearly as good as machine-set.
Anytime you do metal working in home gunsmithing, you'll have to cut material with a hacksaw. The heart of the saw is its blade. For cutting steel, you should use blades made from high speed steel. This type of steel is marketed under many trade names such as Bi-Metal, HSS, etc.
Blades made from plain steel should be avoided except for use on soft materials. Hacksaw blades are available in many tooth count sizes, but 18, 24, and 32 teeth per inch are the most common. Eighteen-tooth blades are best for thicker materials, since they remove more material per stroke than finer blades.
The 32 tpi blades are better for thin materials, since the finer teeth will not dig into thin materials and bind. When cutting thin materials, cut at an angle. That will give you as many teeth as possible engaging the material. This prevents the blade from bouncing as each individual tooth passes over the thin material.
If you are like most people (myself included) you may have trouble sawing straight. A simple sawing guide can be made by clamping a square block to the material and then lightly resting the blade against the guide as you cut. This guide will also make starting on your mark easier, since the saw won't skip across the workpiece before it starts cutting.
Firearms are full of coil springs. Many times these springs are odd sizes that aren't commonly available. I recently needed a 17/32" diameter by .045" wire spring about 8 feet long. I couldn't find one anywhere, so I had to make one myself out of music wire (also known as spring wire).
Music wire is available from hobby shops, steel suppliers and gunsmithing suppliers. If you have a metal lathe with thread-cutting capability, you have the means to wind any size spring you want.
To wind springs on a lathe, just set up your lathe for the coil count per inch you want, just as if you were setting up for thread cutting. You then place a mandrel in the lathe around which to wind the spring. The mandrel size depends on the size spring you want to make.
Take a lathe bit-sized piece of steel and drill a 3/32" hole in it and place it in the tool holder. A piece of pre-hardened music wire will be fed through the hole. Drill a hole in the mandrel to allow the end of the music wire to be inserted and secured to the mandrel.
Once the wire is attached to the mandrel and the carriage lined up with the starting point, engage the lead screw to lock the carriage in gear. Then start the lathe and allow the wire to wrap around the mandrel as the carriage is moving forward.
This needs to be done at the lowest possible speed, preferably in an inching mode, since even a 36-inch length of music wire will wrap up fast. Be prepared to shut the lathe off quickly.
To wrap tight, the wire will need to be pulled tight as it is winding. I grasp the end with vise grips and pull it tight. The spring, when loose, will not be as small as it is when it is being wound because the stiff steel wire springs back. How tight you tension the wire as it is winding and the mandrel size will determine finished spring size.
Considerable experimentation will be required to get the right size. Once you have a correct size spring wound, remove it from the mandrel and trim the ends. You should now temper the spring in a 500Ëš oven for an hour to help set the shape.
If you don't have a lathe, you can still make coil springs although you will be limited as to size. You can wind music wire onto a threaded rod or bolt while it slowly turns in a drill.
Many gun parts are attached with screws or pins, but some low-stressed parts are soldered in place. This is an especially common sight attachment method. Many old-time double-barrel shotgun barrels were soldered together. Common solders are known as lead/tin solders and are seldom used for gunsmithing.
Most solders for gunsmithing are known as silver solders and are made from tin and silver. One of the most popular low-temperature gunsmith silver solders is Brownells High Force 44 solder. It is available pre-fluxed or as bare solder wire.
Bare wire still requires flux, but you apply it with a brush. Flux cleans the steel and allows the solder to flow out evenly rather than bead up.
When soldering, surface preparation is key to a good joint. The steel must be completely clean and free of any finish such as bluing, Parkerizing, paint, etc. The solder area should also be roughed up a little with sandpaper or a file. The rough surface will give the solder a better grip on the steel.
Since solder melts at a low temperature, soldering can be done with a common propane torch. When heating the parts, heat them only enough to melt the solder completely and don't overheat, as this will burn off the flux and make soldering difficult.
If possible, the parts to be joined should be "tinned" prior to assembly. Tinning is just applying a thin layer of solder to each surface beforehand rather than depending on capillary action to draw the solder into the joint. Place the tinned parts together and evenly heat them back up so the solder re-melts.
Once the solder melts, lightly press down on the parts to squeeze the excess solder out of the joint. If you have any gaps in the solder joint, fill them in. After the work has cooled, remove excess solder with a knife or sandpaper. Usually, joint clean up takes much longer than the actual soldering.
Improvised Groove Cutting
Occasionally in home gunsmithing, you need to make a part with a groove in it. Usually, a milling machine is used for this purpose, but if you don't have a mill, you can still cut a reasonably accurate groove with a Dremel Moto-Tool. Stack enough thin cutoff wheels on a cutoff wheel mandrel to allow cutting the groove just slightly under finish size.
Thin Dremel brand cut off wheels are only .010" to .015" thick, so it will take quite a few to cut a 1/8" groove. Use a piece of steel as a guide to allow accurate groove location. Let the head of the screw in the mandrel ride against the steel so the abrasive wheels don't cut into the guide.
Just work the wheels back and forth till you have a groove about the correct depth. Finish the groove to size with a file.
I hope these ideas, techniques, and procedures help you in the gunsmithing hobby. Hobby gunsmithing by its nature requires improvisation and you should be prepared to come up with your own unique ways of doing things. Experimentation will help hone your gunsmithing skills. Hobby gunsmithing can be a rewarding hobby so why not give it a try?
To get all of the gunsmithing supplies and information you need, contact Brownells at 1-800-741-0015 or visit the company's website.