Thinking of setting up a home machine shop? If you’ve not pondered such, consider this: the Wright Brothers and their machinist, Charlie Taylor, made the parts for their gliders and original flyer, including the engine, with only a drill press and a small lathe (See “Charlie Taylor: The story of America’s first A&P,” by Bob Fritz, Kitplanes® October, 2008).
If you’re not familiar with machining and metal working, a reasonable second ponder at this point might be: I want to make my own parts, but don’t know what machines to buy—and even if I did, I don’t know how to use them.
Metal working machines are not difficult. It may take some time and a healthy dose of patience, but almost anyone can master the basic principles of machine work and make useful, precision parts. Each step toward proficiency is rewarding, sometimes beyond expectation.
Books, videos, local community college courses or even private instruction are among the many ways you can go about acquiring the basic knowledge. I’ll touch on that in a future installment of HSM. Let’s start by talking about machines (which is way more fun).
Lathe or Mill
A basic home shop will usually consist of a lathe and a vertical milling machine. You might also find a grinder, a vise, a good bench and some storage for tools, cutters, holders and work fixtures. Other machines like a drill press, a band saw, a bender, etc., are great to have, but acquiring them usually depends on a combination of factors such as space, budget and the type of project.
Choosing what to buy first, a lathe or mill, is an interesting question. All things being equal, I would probably recommend a lathe. But it depends on so many factors that it’s impossible to make a universal recommendation. Basically you need both to make airplane parts—a lathe for round parts and a mill for flat parts. (Not to complicate things so soon, but with the right set-up you can make flat parts on a lathe and round parts on a mill.)
Lathes and milling machines come in a ridiculous array of sizes ranging from micro and mini hobby tools to humongous industrial machines bigger than a freight car. Except for the novelty of knowing that there are lathes and milling machines that big, the point of this article is to discuss machines that might fit in the average garage.
Tabletop, Bench Top or Free Standing
Micro-sized machines, also called tabletop machines, are offered by several companies, including Sherline, Taig and Proxxon. These are designed for model making and other small-scale work. They offer excellent precision and some of the things people do with these machines is amazing. Impressive as the work is, these machines are neither large enough nor heavy enough for the needs of an airplane builder. The price for these machines might be attractive and their size not so intimidating, but they are too small.
The mini mill and mini lathe represent the next class of machines. These bench-top machines are hobby tools that fit at the “just barely” end of the capability spectrum, but they are great starter machines. If you are a DIY learner, I recommend starting with a mini-class machine.
Most of the mini machines weigh around 100 pounds, but you can also find incrementally larger lathes and mills still classified as bench machines, including several multi-function machines (lathe and mill two-in-one machines) that weigh over 800 pounds. (Yes, that’s some bench!)
All lathes are sized by the maximum theoretical capacity in diameter (called swing) and length. The most common mini lathe is the 7 x XX series. They are made in China by Sieg Industrial and sold in the United States by various catalog companies. The 7, as in 7×10, is the diameter capacity and 10 is the length capacity. Mini lathes range from 7×10 to 7×14. These machines typically weigh around 90 pounds. For a detailed comparison chart of the various brands and models, visit LittleMachineShop.com and click “Reference” and then select “Mini lathe comparison chart.”
A 7×14 size lathe does not mean the lathe can turn a part 7 inches in diameter and 14 inches long at the same time. It means in one case the lathe can face turn a diameter up to 7 inches, and in another case the lathe can lengthwise turn (also called spindle turning) up to 14 inches (see photos). The carriage and cross slide mechanism (see photo “Parts of the lathe”) has to traverse the bed to turn the lengthwise axis. Accordingly, the true lengthwise diameter of a work piece is limited by the spindle center-to-carriage or cross-slide clearances. In the case of a mini lathe, the clearance over the cross-slide is about 11/16 inches. This means the largest diameter piece that is practical for longitudinal (lengthwise) turning is 21/8 inches. Larger diameters up to 7 inches (the swing dimension) are possible, but you are limited to face turning or boring operations where the carriage does not have to traverse the part. You do not need to worry about it, just be aware of this quirk when comparing lathes.
Vertical Milling Machine
Vertical mills are advertised according to their table dimension, but it’s the X (left to right), Y (front to back), and Z (up and down) travel dimensions that more accurately reflect the workpiece capacity (a.k.a. the work envelope). Like the mini lathe, most mini mills are made by Sieg in China and have table sizes around 15 or 16 inches long and 33/4 inches wide. The X-axis travel is typically 8 inches (about half the table length), the Y about 4 inches, and the Z about 8 inches. These machines typically weigh about 120 pounds. For a detailed comparison chart of the various brands and models see the Mini Mill Comparison chart at www.littlemachineshop.com.
Mill manufacturers also provide a spindle-to-table maximum clearance to give you an idea of how much space you can expect for a vise, as well as how long a tool you might be able to anticipate using. The typical mini mill has a table-to-spindle clearance of 11 inches. If you mount a vise (a common work holding strategy), it might set your part 2 inches off the table. If your part is 4 inches thick, you’ll only have 4 inches of vertical clearance. This is OK for side milling (entering or cutting from the sides), but it leaves very little room to mill from the top and not enough room at all to use a drill chuck or to drill deep holes. You could still drill holes, but you’d be limited to stub (short length) drills in sizes that fit your collets. You can get those 2 inches back by removing the vise and clamping the part directly to the table, or you could transfer the part to a drill press for basic (vertical) drilling. This is a classic example of how the equipment dictates the setup and work flow strategy. There could be several ways to make a given part. They are dictated as much by the equipment available as the experience of the person doing the machining.
An experienced machinist using these machines might be a little frustrated with their rough edges and somewhat-clunky function, but with a little TLC you can make good parts with reasonable precision. Little Machine Shop (www.littlemachineshop.com) offers several DVDs showing various techniques and capabilities of the mini lathe and mill. These are excellent references for anyone considering these machines or just interested in metalworking.
Basically, any machine with an integrated base or built-in cabinet is a freestanding machine. With a few exceptions, anything freestanding can be considered an industrial-grade machine. There are so many brands and models available, both new and used, that it’s impossible to provide even an overview of the category in the space of one article, so I’ll just touch on a couple basics.
Just about any industrial machine that you can fit in your garage would be suitable for a beginner or student machinist, providing you can get hands-on tutoring or have a mentor to help you out. I do not recommend an industrial machine for the DIY approach to learning. Except for the big, powerful motors and several thousand pounds of cast iron, they are essentially the same as a bench top machine. The power and weight mean they are designed to be abused, and unless you know what you are doing, they can abuse you right back.
The bigger and more powerful the machine, the more features (in the form of the levers, switches and controls) it will have that you won’t find on a hobby machine. Hobby machines are stripped down to be simple and easy to use for basic work. Industrial machines are the opposite. They may have built-in speed and feed-rate controls (lathes and mills), gearboxes to control traversing rates (lathes) and various adjustments to orient the work to the cutter (mills). These features, once you become familiar with them, are awesome timesaving necessities for the experienced machinist.
My advice is pretty simple: Depending on what type of training you can get, buy the largest machine you can afford that will fit in your available shop space. By fit, I not only mean in terms of floor space, but also vertical space. I have one friend that had to poke a hole in his garage ceiling to accommodate the unexpected height of his new milling machine!
Matching machine-to-machine capabilities is worth thinking about. In other words, it would be a little weird to have a $10,000 full-size tool-room lathe at one end of your shop and a $500 mini-mill at the other. Generally, it is better to take that $10,500 and spend about $4k each on a mill and lathe and the rest on assorted tooling (cutters, holders, clamps, etc.). Depending on the circumstances and budget, there are infinite exceptions to that rule, but you get the idea.
In addition to the space needed to accommodate larger machines, you need 220v power. Most houses and garages are wired for 220v so that should not be a problem, but it’s worth mentioning. With inverter drives, you can run a modest size three-phase machine (up to 3 horsepower) on household 220. This option increases the variety of machines you can consider.
As I mentioned a few paragraphs ago, you’ll need to invest in assorted tooling.
By that I mean the cutters, holders, clamps, and vises that are needed to cut metal, not the wrenches that came with the assembly instructions. If you are buying the machine from a dealer, you want to ask if there is some kind of basic starter package or tooling package available. For lathes you could expect this to consist of a small assortment of cutters, center drills, one or more drive dogs for faceplate work, and maybe a tailstock-compatible drill chuck. A tooling package for a mill would typically consist of a collet set, assorted cutters, a vise, a T-slot clamping kit, and parallels.
That’s where I’ll leave it for this month. Next month we’ll talk about CNC in the home shop, buying new versus used, and options for learning machine shop basics.
Special thanks to Jerry Foss, Sam Boyd, Mark Beattie, and Chris at Little Machine Shop.
Bob Hadley is the R&D manager for a California-based consumer products company. He holds a Sport Pilot certificate and owns the VW-powered Victory Stanley Fun-Kist.