Metal Turning

Metal Cutting

In “Getting the Most Out of Your Lathe” Delta Manufacturing Co. announces in the manual accompanying their early model lathes that “Without any special equipment metal turning can be done free hand on the wood lathe using handled lathe tools of hardened steel in much the same manner as in wood turning.” Lathe tools we use today are typically of M2 high speed steel, hardened to between 62 and 64 Rockwell. This is equivalent in durability to the bits we readily use to drill through steel. Cryogenically hardened and powdered metal tools available for wood turning are even more durable at 67-69 HRC.

The wood lathe, more than any other tool in our shop, is in its self a unit capable of producing a wide variety of finished work. The purpose of this note is to encourage broadening our scope of work we might consider when need or desire arises. I will show three examples of free hand turning of brass, aluminum and steel. For work of higher precision the Delta manual suggests mounting a Compound Slide Rest on the bed of the wood lathe. In my first note of this series I described a compound X-Y vise that I mounted to my lathe to help me turn the bottoms of deep vases flat, and to face sector rings flat to the tolerance I wanted when I glued them together for bowls. Compound X-Y vises are available from Grizzly, Rockler, Sears and Woodcraft.
To start, our wood lathe makes an excellent drilling machine. It has important features superior to a drill press or hand held electric drill. A feature we can apply to our advantage is the center of headstock rotation and the center of the tailstock are in perfect alignment. Pressure applied by advancing the tailstock quill is in direct line with the center of rotation.

There are two drilling modes with the three jaw chuck on a Morse Taper in 1) the headstock, or 2) the tailstock.

Mode 1): Assume the bit is rotating in the headstock and the hole to be drilled is centered with the aid of the tailstock point. The metal object is supported from the lathe bed in a manner (and this is important) that will keep it from rotating should the bit grab as it breaks through. Using a cushioning block of scrap wood pressure may be applied from behind by advancing the quill until the bit advances through the metal piece into the scrap wood.

Mode 2): Work is held in the four jaw chuck with the axis of the hole to be drilled in line with the axis of rotation. The bit is advanced into the work by rotating the tailstock hand wheel. In this mode, since both the work and the bit are securely held, there is no need for specially ground bits to avoid grabbing while drilling holes in brass, copper or aluminum.

With the lathe stopped threads may be put in the freshly drilled hole by holding the tap in the three jaw chuck and rotating the headstock by hand. Alternatively and my preference, the tap may be held in a tap handle using the tailstock point to accurately center and advance the tap as the tap handle is rotated. Those who have broken a tap because it was not perpendicular to the work can appreciate the alignment advantage the lathe offers for this task.

The ½ inch capacity chuck fitted to a Morse Taper works well for holding small objects such as shown in Fig. 1. Here I wanted to make a fitting for a vacuum attachment to my lathe. The nib of this 3/8 inch pipe fitting can be held nicely by my three jaw chuck. In this figure I am turning the 3/8 pipe thread down on my lathe until it just fits the bearing that can be seen resting on the lathe bed at the bottom left hand corner of Fig.1. This bearing will be epoxied into a cone shaped piece that is part of a vacuum adapter for the headstock of my lathe. (I intend to give details for making a vacuum pump and how I outfitted my lathe for vacuum chucking in a future note.)

I have used a Oneway four jaw chuck to hold the objects shown in Figs. 2 and 3. The aluminum vase in Figure 2 is 18 inches high and 4 inches in diameter with a heavily weighted base. I turned a jam chuck to adapt its end so I could steady it using the tailstock. Stability and additional damping from the wooden jam chuck helped to reduce harmonic vibrations excited by the gouge. Vibration is more of a problem in this instance because aluminum, as opposed to wood, is so lossless that the excited resonances attain larger amplitude. Adjusting speed also helped reduce vibration. A little more rounding is needed at the top, after which I intend to sand and polish through 0000 steel wool. I will finish this aluminum vase with Butcher’s wax. Gouges and scrapers I used on this aluminum vase showed wear little different from that experienced turning seasoned oak and cherry.

Sylvia, my painter wife, asked me to make a bracket for a large roll of paper she had purchased. The holder I designed was sized to use ¾ inch black iron pipe. However the pipe would not fit into the mandrel-ends about which the paper was wound. The simplest solution was to turn the ends of the pipe to fit into the mandrels. Fig. 3 shows part of the 40 inch long pipe that is supported by a ball bearing center in the tail stock. The other end is held in my Oneway chuck. My purpose is to turn down the diameter without regard to spit and finish. The wire edge quickly disappeared from the powdered metal gouge I used. However a little honing was all that was needed to prepare this gouge for removing the center of a bowl I worked on following reducing the diameter of steel pipe as shown in Figure 3.

In this note I have discussed cutting metal with the wood lathe. It is a useful, sometimes advantageous alternative for the drill press. I have shown three examples of turning brass, aluminum and steel on my wood lathe. I would be very interested in learning how you have used your wood lathe for cutting metal.

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Posted Oct 2006