This is a good working lathe that makes up in hardware availability what it might lack in historical accuracy. You can build this lathe with common lumber and hardware store materials, but it does require some heating and hammering to bend the crankshaft and forge the drive center. If you are not set up to do this yourself, it's a fine opportunity to support your local blacksmith.
The lathe frame is just three right triangles connected by four horizontal 2-by-4 rails. Two rails form the bottom, and two serve as the bed of the lathe. The tool rest and the tail stock are the same as on the spring-pole lathe, so I'll concentrate on the moving parts, starting at the foot and working upward.
The treadle is all 1-by-3 stock, cut away to half that width wherever possible to keep it light. The rear pivots on two lag screws set into the frame at both ends. On the left front is the protruding bolt that links to the connecting rod and transmits your foot power to the crank. The cantilevered cross-bracing in the treadle keeps it stiff, even when you're working at the right end—far from the connecting rod. The drawing shows how the diagonal cross brace that runs to the left front passes over the other one in a half-lap.
The connecting rod transmits the treadle action to the crankshaft, which transforms the reciprocating motion into continuous rotary motion. The crankshaft is a 1/2-by-12-inch bolt, sawn off to the finished length after heating and making the two right-angle bends.
1/2" Ball Thrust Bearing m2"x W Hex Bushing / (drilled out to 1/2")
Before bending the bolt, you may want to slip a bronze flange bearing on the end to ease the friction of the connecting rod. You need to heat the bolt at least to a dull red before bending it, and the bronze sleeve has to go on quickly before it cools. Of course the iron shaft expands as you heat it, so the bearing may be a tight fit. You can heat the area of the bend with the bearing already in place, but remember that bronze bearings are permeated with oil, so don't be surprised when they flame up.
The first bend is just an inch below the bolt head — just enough to give the connecting rod a place to run. The second bend defines the length of the lever—the crank arm. The length of the crank arm helps determine the rise and fall distance of the treadle, but the connecting rod influences this as well. If you want more treadle travel for more torque, link the connecting rod closer to the rear of the treadle. Linking the connecting rod more toward the front of the treadle reduces travel. Try a crank offset of 2 1/2 to 3 inches and adjust the connecting rod link to give you about six to eight inches of treadle action.
The remainder of the 1/2-inch shaft both supports and transmits power to the flywheel. There's a lot of shearing force at play where the shaft connects to the flywheel, but a single steel tension pin passing through the axle and the iron plumbing flange will serve—if the lathe is driven rhythmically and sympathetically. A proper historical treadle lathe uses much more blacksmithing and a lot less time pondering plumbing parts, but this does the job.
The inertial mass of the flywheel smoothes the action and stores energy as it spins, supported by the ball thrust bearings mounted in the frame. The four spokes are just two 1 1/2 inch thick pieces half-lapped at the center. The perimeter of the wheel is a sandwich, glued and nailed together in overlapping quadrants. The filling of the sandwich is made of four pieces of the same thickness as the spokes, butted together at their ends. The bread of the sandwich, the 3/4 inch thick layers on the outside, overlaps the butt joints and holds everything together.
The flywheel is also the driving pulley for the lathe. The cord transmits its power to the driven pulley in the head stock. For every single turn of the flywheel, the driven pulley has to make about 14 turns, the difference between their diameters accounting for the increase in speed. The difference in diameters also causes a problem—the cord slips on the small pulley. The large driving pulley spreads the cord so much that it contacts only a small area of the driven pulley. There isn't enough grip, and the cord slips.
I originally used flat leather belting on my lathe, so I needed an idler pulley to make the belt run tighter around the driven pulley. This idler is just a wooden shell with bearings stuck in either end. Once, however, when the flat belt came unstitched at a critical moment, I substituted a round cord tied with a square knot — and then I never went back. The cord runs in a groove cut around all the pulleys and is easy to tighten as it stretches — just retie the knot. Using a round cord also offers an alternative solution to the slipping pulley problem—crossing the cord so it runs in an infinity figure. This makes the flywheel turn in the opposite direction from the wood, but that matters not at all. The gripping problem is gone.
In the headstock pulley, power goes from the two-inch diameter wooden shell down to the small shaft. The collars set into the ends of the wooden shell give enough surface contact to prevent slipping. Holes drilled through the wooden shell give access to the set screws in the collars that tighten them to the shaft. The shaft drives the workpiece, pinched between it and the dead center on the tail stock. The pinching grip on the turning workpiece imposes lateral pressure on the shaft, pressure carried by the left-hand collar running against the ball thrust bearing in the head stock.
The headstock shaft poses the final challenge. At one time you could buy lathe drive centers that fit on any 1/2-inch shaft. I have not seen these around for a while, so you will probably need to forge a spade-type drive center. This older style of drive center with two blades was used for centuries and works just as well as the familiar four-bladed version. The hex head of the 1/2-inch bolt used for the headstock shaft will give you enough metal to reforge into a shape resembling a modern spade bit. Leave the central spike oversized so you can true it with a file as it spins in the lathe.
In use, the lathe takes a light touch, with the ankle doing most of the work. Until folks get accustomed to it, most don't lift their foot enough to let the wheel make it all the way around every time. This jerking motion is hard on the crankshaft connections, so let new users take the time to feel the rhythm before they start cutting wood.
Was this article helpful?
There are a lot of things that either needs to be repaired, or put together when youre a homeowner. If youre a new homeowner, and have just gotten out of apartment style living, you might want to take this list with you to the hardware store. From remolding jobs to putting together furniture you can use these 5 power tools to get your stuff together. Dont forget too that youll need a few extra tools for other jobs around the house.