Metal in the Wood ShopComments (0)
This article is from Issue 88 of Woodcraft Magazine.
Work wood? Then you probably work metal from time to time. Here are some excellent tips for fabricating aluminum, brass, and steel as nicely as you craft wood.
At some point in our woodworking pursuits, most of us work a bit of metal in the shop. Whether we incorporate it in our work for structure or decoration, or use it for workshop jigs and fixtures, metals—mostly soft metals such as brass, copper, and aluminum—are comfortably at home in the wood shop. One fact is guaranteed: Cutting and smoothing metal is a challenge due to its inherently much harder (and sharper!)nature. The good news is that typical woodworking tools like the bandsaw, table saw, drill press, and miter saw will do a fine job of cutting these materials as long as you take a few precautions. Throw in a hacksaw, and you’ve just about got a complete metalworking shop—for us wood guys, anyway.
While woodworking is inherently dangerous, working with a much harder material like metal raises the safety bar a few notches. Proper setup and tooling are key, as is taking appropriate safety precautions (see box, right). In this article I’ll address metalworking basics, from marking and layout to cutting and drilling soft and hard metals. I’ll show you how to finish and smooth edges, and how to polish surfaces to make them glow. I’ll discuss tooling, and help you choose the right bits and blades. (Relax; you probably already have ‘em.) We’ll also take a look at a few metalworking tools and supplies that you may not be familiar with, but which won’t break your budget.
You can buy metal through catalogues and online, but a better alternative is to ask a local metal supplier for scraps, or falls. A more fun approach is to visit your neighborhood metal recycler, where you can root through bins and barrels for interesting and unusual bits. (Bring along a magnet to check for ferrous metal hidden under various coatings.) I think you’ll find that expanding your skills into metal working can really increase your woodworking capabilities.
Playing it Safe
Sharp edges, flying chips, and red-hot, skin-sizzling material are real hazards for you and your shop. To keep things safe, clamp your work securely, and slow your feed rates substantially to avoid ‘grabbing’ or catching. Sweep and clean your work area, and turn off all dust collection. Heated shards can start a fire if they come in contact with a small pile of dust, especially inside a wind-driven dust pipe. To protect yourself, don this safety gear when things heat up:
Unlike wood, metal doesn’t respond very well to pencil marks or pricks from an awl. Instead, markers, paint, and punches allow you to make accurate layout marks and cut lines. Before marking, it’s smart to clean metal surfaces with a solvent to remove any dirt and oxidation. A swipe with a rag dampened with denatured alcohol will remove most of the dirt. For tougher spots, try mineral spirits.
Most clean metals can be marked with a black felt-tipped pen. However, reflective metal surfaces can impede visibility. In these cases, it’s better to incise a line with a hard marker, such as a carbide-tipped pen. For even clearer sighting, you can paint the surface, and then score a line through the paint. When drilling, a spring-loaded punch will create a small divot that registers the tip of a drill bit to prevent wandering.
Seeing red or blue. When dark lines won’t show, try cutting through some paint instead. Dab or spritz some alcohol-based red layout fluid or machinists’ bluing on the area to be marked, and then scribe a line that’s easy to see.
No skitter. Indenting your mark with a metal punch accurately registers the tip of the bit precisely where you want to drill. On hard metals such as steel, repeat the punching process two or three times for a deeper dimple.
Sawing soft metals
A typical woodshop table saw and bandsaw are perfectly capable of cutting thin sheets of brass, aluminum, and other soft metals. Sheet thickness is indicated by a gauge number, with higher numbers representing thinner sheets. In my opinion, a 12-gauge sheet (about 3/32") is about as thick as you can cut safely on these machines. Metal plate, bar stock, and other thicker material should be sawn elsewhere, perhaps on a miter saw or with a jigsaw equipped with a metal cutting blade.
As for blades, the more teeth the better, as they’ll provide clean cuts with minimal wear on the blade. A triple-chip grind (TCG) table saw blade is a good choice, as is a 14-TPI bandsaw blade with regular teeth. For safety and cleaner cuts, use a zero-clearance throat plate. A 60- or 80-tooth crosscut blade often comes standard on miter saws and will do a serviceable job if you saw very slowly.
Pack it flat. Sandwich thin metal between two pieces of hardwood or MDF screwed together, using shims at either end to equalize pressure over the package. Use a push stick to keep hands clear of flying debris, and push slowly and consistently.
Mild Angles for Mild Metals
Because of their hardness, ferrous metals such as cast iron, and mild, carbon, and stainless steels pose a significant challenge to most of our stationary woodshop machines. Forget the bandsaw, table saw, and miter saw. Instead, get out a hacksaw and a jigsaw outfitted with a metal-cutting blade. Whenever necessary, wear heavy gloves to protect your hands from sharp edges and excessive heat caused by the friction of cutting. Steel can retain heat for a long time, so be cautious before handling freshly cut work with bare hands.
Keep in mind that cutting steel generates sparks, a potential prelude to fire. So work in a clean, dust-free area, and check your surroundings after cutting to make sure stray metal particles haven’t mixed with any overlooked dust.
An old standby. A hefty metalworking vise provides a steady clamp for accurate cutting with a hacksaw. Oil or wax the blade for smooth action, and pad the metal jaws with wood to protect the work.
The do-all tool. A jigsaw equipped with a metal-cutting blade can tackle straight cuts and curves. A “zero-clearance” throat insert helps to control chips and minimize burred edges. You can spot a metal-cutting blade by its wavy edge and numerous small teeth (inset).
The drill press and a hand-held power drill are important metalworking tools, especially when equipped with the right bits. Standard twist-style, high-speed steel (HSS) bits do a fine job drilling into most metals. Look for bits with a flatter, 135° tip angle. Bits with 118° tips are meant for wood and cut too aggressively for most metals, especially steel. Cobalt- and titanium-coated bits last longer and are definitely worth the extra money. Drill metal slowly, and lubricate the process with light machine oil to help prevent overheating. Keep a few countersinks on hand—both single-flute and multi-flute—to allow seating screw heads and the like in soft and hard metals.
Keep it straight. A drill with a ½" chuck has the heft and muscle for boring big holes, especially when using a handle extension to help control the extra strong torque. Start a big hole by first drilling a small hole as a guide for the bigger bit.
Counter culture. Single-fluted countersinks do a better job and leave a smoother surface on soft metals like brass and aluminum. For steel and other hard metals, a multi-fluted bit is your best bet.
The virtues of a vise. Firm clamping is essential for safe, accurate drilling. A small machinists’ vise has enough grip and heft that a single handhold is sufficient when drilling small holes or counterboring.
Cut and drilled edges on metal are typically rough and sometimes razor sharp. You’ll need to remove tool marks and ease over sharp corners, or arrises, for a workmanlike job that’s comfortable to the touch. Here, routers and hand planes sit idle; it’s time to grind, sand, scrape, and file. If your edges are really rough, an angle grinder makes quick work of clean-up and beveling. Sharp edges can also be sanded smooth with coarse grits, and a deburring tool is handy for removing burrs, or flashing. A mill file is another important part of your kit, letting you smooth long edges as well as file into inside corners.
Just like a fine finish on wood, metal deserves special care once all the shaping and smoothing are done. There’s a wide spectrum of surface finishes possible, from a sanded, dull surface all the way to a high polish. Begin by sanding with progressively finer sandpaper if necessary to remove any scratches or crud that won’t wash off. Then, for a finer finish, you can follow up with polishing compounds, which also come in coarse- and fine-cutting versions. Automotive rubbing compound, which leaves a matte finish, is your best bet for fast stock removal, especially for harder metals. For a more reflective shine, use buffing compounds, starting with white diamond and finishing up with tripoli. Be sure to separate your polishing wheels and pads to prevent cross contamination.
Power buff. To put a shine on larger surfaces, you’ll save time by using a random-orbit sander faced with a pad that’s charged with buffing compound.
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