Welding-site conditions and welding-wire diameter govern efficiency and size of power supply required for a job. Select a 100-A unit that runs from single-phase 115-V input for low-duty-cycle welding of sheet to l/s in. thick, feeding wire to 0.030-in. diameter. Medium-duty power supplies, 150-200 A, normally take single-phase 220-V input to weld steel to 3/16, in. and 0.035-in. shopfoxdrillpress wire at low-duty cycles. For high-duty cycles, as in mechanized welding, select a 250-A machine, single or three-phase input at various voltages-these weld material to 1/2 in. thick with wire as large as 0.045-in. diameter. Taking three-phase input only and wire up to 1/6-in. diameter, 400-A units serve for mechanized continuous-welding applications. For pulsed GMAW, shops use inverter and transistor power sources, constant-current or constant-voltage, that offer independent setting of pulse parameters. They employ synergic controls preprogrammed for a range of wire-feed speeds-the operator sets only one dial, for average current.

The Chicago Pneumatic Air Scribe is a bit noisy and also produces quite a bit of dust and grit as it disintegrates the rock matrix, making both a dust mask and ear protectors necessary when the unit is in use outside a dust-collecting chamber. A silencer that fits snugly around the hand-held unit is not available from the manufacturers but can easily be made with a few common household tools. By cutting a piece of metal tubing to the length of the air scribe''s handpiece and notching one end so that it can be crimped to conform to the tapered bit end of the tool, a very simple noise insulator is produced. A foam rubber plug inserted in the bit end forms a snug fit. The only disadvantage to this noise protection is that the natural stream of air emitted from the tool end is blocked, and dust is not readily blown off the working surface. Likely some innovative tinkerer will soon solve this problem. Simple ear plugs or muffs are adequate to help provide hearing protection. Another minor problem with the air scribes is the absolute necessity of lubrication. Producing an effective reciprocal motion to any tool involves very complex valves and close-fitting parts. This is especially true when the tool is designed to be very small. Depending on the duration of use, an air scribe must be oiled from once to several times per day. This involves shopfoxdrillpress shutting down the system, dismantling the air supply, and inserting several drops of high-quality air-tool oil. In-line oiling systems are available that can make this process far simpler. Additionally, regularly flushing the unit with oil will eliminate microscopic particles of metal and grit and will greatly extend the life of your air scribe. Sandblastin shopfoxdrillpress.

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