July 10, 2013

Choosing Milling and Drilling Machines

If you’re looking to move to the next level in your gunsmithing, a milling machine might give you the versatility you need.

While recently going through one of the two gun magazines I read, three advertisements for correspondence gunsmithing courses caught my eye. Among things I learned was the fact that courses in upholstery and satellite dish repair were also available should gun repair not be my cup of tea. That’s always good to know.

The one that really caught my eye, though, said stuff like “Make $50 an hour doing what you enjoy. Become a gunsmith; it’s easy to cash in. Everything is included.” All that is accompanied by a photo showing a middle-aged fellow wiping down a lever-action rifle with a small white cloth. I gotta tell you, for 50 bucks an hour, I’ll wipe down guns for 16 hours a day. I’m sure you would too. The mental image of a UPS driver tying up traffic out front for several days dropping off “everything that was included” really made me chuckle.

Don’t get me wrong, I’m not pooh-poohing every correspondence course for gun repair. It’s just that I really wonder if they know how much can be involved.

Whether you are just starting out in the gun repair game or you’ve been in it a while, you know what equipment costs can amount to. While almost all gunsmiths have a drill press and a lathe in one size or another on hand, some claim they can get by without a milling machine. That’s fine, but I just can’t imagine not having a mill at my disposal because of the versatility it affords me. I would surely enjoy the indulgence of a series II Bridgeport vertical knee-mill with a 2J head and 58 inch table but my budget has never permitted such extravagance.

My initial training on milling machines involved the larger mills like the Bridgeport, Gorton and Kearney and Trucker machines. These large, rigid floor models are not affected by surrounding vibrations and are of tool room quality. They also cost as much or more than a new 4 X 4 pickup truck and are not necessary for most gunsmithing needs. If you envision a milling machine in your future, several options can be considered before a purchase becomes reality. In major cities, the yellow pages of your phone book will probably list new and used machinery brokers or your newspaper may have a classified ad section for machinery and tools. Once in awhile, you’ll also see auctions offering machinery from a bankruptcy liquidation. The point is that there are options to buying brand new equipment. When shopping for used machinery, you can avoid costly mistakes by taking someone you trust, who will know what to look for, along with you.

I use what’s normally known as a bench-type milling and drilling machine. This machine is affordable for those just starting up a shop and is suited to easily do about 99 percent of the work you’ll encounter. Milling barrels that are longer than 26 inches, especially if they need to be milled to octagon-shape or fluted, is more complicated with this machine. The job can be done, but requires extremely careful setups and close attention to detail, usually doing half the length at a time. One option to consider is a power table feed. It costs almost $400 more, but contributes to smoother milling cuts and eliminates the arm-tiring cranking required when making the long cuts sometimes needed on a rifle barrel.

Tools & Techniques, Chapter 16 Milling

Courtesy, American Gunsmith

A good vise will hold work more accurately than the one that usually is provided with a new mill.

Most of the currently available bench mills are made in Taiwan, Korea or China, which may be problematic for those who abhor the idea of purchasing foreign products. Because no American manufacturer I know of offers bench-style mills, the foreign makes are about your only options in new bench-type machines. Enco, Grizzly Imports and Blue Ridge all stock these mills, with prices ranging from $900 to $1,800 plus delivery charges. With most of these mills, you get what they call a tooling package that usually includes a drill chuck, face mill cutter, some metric Allen wrenches and a cheaply-made vise of some sort. Most are powered by a 2-horsepower motor and will run on common 110 volt current.

Before you commit to purchase a new or used milling machine, consider how you’ll get it to your shop and where you’ll put it once it arrives. A new mill will likely be shipped by trailer truck. If it is delivered to your premises, it is your responsibility to get the crated mill off the truck. Most semis do not have dropping gates.

Prepare the area where it will be placed in advance of the machine’s arrival. A separate electrical line and outlet box is the best arrangement. A good solid base will make your new machine as accurate as the builders intended it to be. Wall, ceiling and side clearance are all to be considered, along with the machine’s height, width and depth. Table length and the amount of travel the table affords are very important factors. A 4-foot table would be ideal but is rarely found on bench type mills. The longest table presently available is the Grizzly Imports’ 32-inch model.

Length is a major consideration because fixtures will take up usable space on the table. For example, an indexing head at one end with a 6-inch base and a tailstock center with a 4-inch base at the other end has taken up 10 inches of table and left you with about 22 inches in between. If you need to mill a 24-inch barrel, you’ll have to make other provisions. Two plates with equal dimensions will have to be made and secured under these fixtures so they can be extended out an inch on either end to accommodate the 24-inch barrel.

Wide Range of Speeds

The mill you consider should have a wide range of speeds, with a low of at least 150 revolutions per minute. When working on gun steels, most milling operations are done at lower speeds, ranging from 150 to 800 rpm. Work on aluminum or brass gets you into the higher ranges. Speeds are usually controlled with a three pulley, two drive belt system. Some mills have a variable speed control accessible from the outside of the machine so speed can be quickly changed if necessary. This is a convenient option.

Cheaply-made angling vises are usually included in the tooling packages for these bench mills but they are almost useless for any sort of accurate milling or drilling. The one that came with my mill is used to hold parts while they are being cut or welded.

Tools & Techniques, Chapter 16 Milling

Courtesy, American Gunsmith

The power-table feed option results in smoother cuts on long work pieces.

A good, accurate milling table vise will cost from $100 to $500. An optional swiveling base will cost you about $50 more. The secret to a good milling vise is in the front movable jaw. On a good vise, the front jaw will force the work piece down and back toward the stationary jaw. The jaws are hardened steel and have been ground flat, along with the inside bottom of the vise.

Once you get your vise mounted on the milling table, the stationary rear jaw must be zeroed with a dial indicator. With an indicator in a collet in the quill, place the indicator’s tip on the face of the back jaw and turn the indicator dial to zero. Run the table back and forth to see if the vise is out-of-square; we want it to run parallel with the table. This is where the swiveling base comes in handy. Loosen the base of the vise and move it until the dial on the indicator reads the same as when the table is moved back and forth. Lock the base down and cut a witness mark on it with a cold chisel so you’ll know that this is the new zero point. Now, when you have a work piece in the vise that needs to be milled, your milling cut will be 90 degrees or parallel without being crooked.

These mills all come with the provisions for using R-8 draw bolt collets in the quill to hold endmills. Drawn tight, these collets hold endmills very securely. R-8 collets are sold separately and are available in almost every decimal size. Don’t buy the cheaper collets, as they are not guaranteed to be without run-out. If the collets have 0.005-inch run-out, your endmill will have a like amount and your milling cuts will not be made to an accurate width.

Cutters

Endmill cutters can be purchased in either two or four-flute configurations. The four-flute endmill’s four cutting edges give a much better finish on the surface being cut. The burden of the cut is also better distributed by the four blades, which extends tool life. The titanium nitride (TiN) coatings or platings we are now seeing on endmills even further adds to the life and extended performance of the cutters.

Dovetail sight cutters, ball end endmills, serrating cutters and saw blades with holding arbors for the blades will make your milling machine even more versatile. A good set of parallel bars will elevate a work piece in your vise when dealing with parts lower than the height of the jaws. These sets usually come in one common thickness but with height variations of 1/2 to 1 inch.

Ball end endmills come into play when fluting barrels or lightening scope bases. Serrating tools will make quick work serrating the tops of auto pistol slides or barrel ribs. Saw blades of the proper thickness will cut screw driver slots in the end of a bastard screw you have to make for an old antique shotgun or rifle. A Woodruff keyseat cutter will cut extractor grooves into barrel shanks. You probably get the idea by now that a milling machine can open a whole new spectrum of gun work that can be performed in your shop rather than be sent out.

Tools & Techniques, Chapter 16 Milling

Courtesy, American Gunsmith

Cutting tools used on a milling machine are, from left to right, roughing mill, endmill, ball-end endmill, dovetail base cutter and Woodruff keyseat cutter. A saw blade mounted on a holding arbor is in the foreground.

Indexing Device

Another optional piece of equipment that should be considered is some sort of indexing device. A dividing head and tailstock center, or some sort of indexing spacer, will accurately divide a round surfaced-work piece so that it can be milled to a square, hexagon, octagon or any other shape variation desired. With a three-or-four-jawed chuck attached to the dividing head, any sort of oddly-shaped part can be held for milling. The dividing head can be rotated 90 degrees, and then used as a rotary table. A setup such as this is handy when you need to mill a convex radius.

If you ever get the chance, look over some of the work done by those doing custom metal work out there. These guys use a milling machine much like Cinderella’s fairy godmother used her magic wand. Starting with a 11/8 inch blank, they can mill an octagonal barrel with a quarter rib, front sight base, rear sight base and front swivel barrel band all integral to the barrel. This attention to detail translates to a very expensive end product.

My philosophy is that if one human being did it, so can another if he wants to badly enough. Some may think that’s fine and dandy, as long as you already know how to use a milling machine. But at one point, everybody who knows how to run a milling machine had to learn. Night classes may be available at your local high school or there could be a technical college in your area where you can learn the basics. Most of the big-name gunsmithing schools are actually teaching tool room machinist courses, including hands-on lathe and mill experience. You might even be able to find a home shop machinist who is willing to show you what you need to know about a milling machine. Most all of the distributors that sell milling machines will tell you who in your area has one of their machines. Talk to this person about his recent purchase and find out how they like that particular machine. Is it living up to their expectations? Would they let you visit and see the machine up close and personal? Maybe they would even trade some training time for some expert work on their firearms.

A milling machine will open up a bunch of avenues for you and expand the versatility of your gunsmithing. You’ll need to pay your dues in learning how to use the machine and the initial investment will take some time to recoup, but a milling machine will not be any cheaper next year.


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