SETTING UP YOUR LATHE AND BASIC CUTS
You just received or picked up your lathe from the tool company or maybe you bought a previously owned unit and now you want to get started as soon as possible. These first few hours need to be spent carefully reading the instruction manual that came with the tool to enable you to familiarize yourself with this great new machine you longed to have for the last may months. One of your first concerns should be to designate a permanent or if you must, a semi permanent space to set up your lathe. You should provide a separate mounting board to screw the lathe onto. Laminated (Formica) particle board is ideal for this application and it should be large enough to allow at least at least six inches of space all around the footprint of the lathe plus room for the motor if it does not come with one. The small lathes we are dealing with are very light weight, bordering around the 12 pound range. There is a range of 4" swing lathes that are much heavier but are also way out side the "hobby" price range we are dealing with here. This board can be further attached to a heavy work bench. The level of the table should be such that it will place the bed of the lathe about belly button height. This is just about perfect for me but it could be changed to suit the individual worker. The lathe itself has very few moving parts when compared to other machine tools. The head stock or the business end of the lather has an outboard pulley that is driven by the motor via a belt. Within the head stock is a solid steel spindle supported at both ends with permanently sealed and lubricated ball bearings. The inboard end of the spindle is threaded to accept chucks and other attachments and it is also bored through its length to allow a long work piece to be inserted so only the portion being machined is exposed. The headstock is factory aligned to maintain a condition of parallel alignment to the bed. The lathe bed houses the longitudinal carriage and it slides of 45 o dove tails. There are some bronze slides that bear on the "V"s of the bed and these are adjustable with some screws and are able to take up any slop created through wear as the machine ages. The carriage moves in the X direction, that is, along the bed from the head toward the tail or the other way around. On top of the carriage rides the cross slide which performs the Y movement across the lathe bed. On top of the cross slide, bolted to it is the tool holder or tool post. The tool post holds the cutter in a slot with some screws and the post can be rotated in a complete circle to position the cutter in any angle desired. More on that later. The tail stock normally holds a center that provides extra support to the end of a long chucked work piece. It is also used in drilling holes on the center of a work piece. A drill chuck can be installed to the center and the drill chuck and bit are advanced into the spinning work by turning a crank or knob (Sherline) or with by lever action as with a drill press (Taig). We just discussed that the tail stock not only supports the ends of a long piece can also drill holes, but it also can tap threads on a freshly drilled hole and also with help of a die holder, can thread the end of a shaft turned to size on the end of a piece. Although it is possible to do many different operations on the lathe, its primary job is to turn metal. There are three very basic types of lathe cuts that when combined will produce 90% of all the objects made on a lathe. The turning cut is done on the outer perimeter of the stock and is primarily used to reduce the diameter of the stock to the size needed. The edge of the cutter faces the surface of the stock at a slight angle and the tool is advanced from one end to the other, reducing the overall diameter of the stock. Is two different diameters meet, a shoulder will be created between the two. Turning cuts are made with the longitudinal carriage while adjusting the tool bit inward with the cross slide after each pass. The ends of a work piece are often sawn from longer stock and will have rough surfaces that need to be machined clean. The facing cut will clean those ends up by bringing the cutting edge across the end surface by advancing the cross slide and deepening the cut by advancing with the long carriage after each pass. Shoulders on the end of piece can also be machined with a facing cut. The turning cut and the facing cuts are both square and at ninety degrees to each other but some times you will want a tapered cut instead. This can be accomplished in two ways with both the TAIG and the SHERLINE, In the TAIG, the tail stock slides laterally as much as one inch away from center to shift a work piece held between centers at an angle. The Sherline head stock swivels in an arc, effectively doing the same thing. Any object held at an angle other than square to the lathe bed will effectively be machined at that very same angle times two. A ten degree angle setting with produce a twenty degree include angle on the final work piece. It is sort of like equating a radius to a diameter. A great way to cut the tapered barrel on a miniature brass cannon! More traditional methods of cutting a taper involve the use of a compound slide or top slide as it is some times known. The compound attaches on top of the cross slide and is set to one half of the final included angle needed and the tool is advanced during the cut with the compound slide while the depth of cut is set with cross slide. Perfect chamfered ends can be easily produced with the compound slide followed with a little sanding or filing. The last basic machine operation is boring. Boring is utilized after drilling to insure concentricity to the hole. Most, if not all drill bits tend to create holes that are neither the size of the drill or perfectly round. To create as perfect a bore as is possible you should drill out most of the material and bore out the hole to the final size required. Very small hole can be drilled undersize and reamed to the final size. More on reaming later. A boring tool is designed to produce a turning cut on the inside surface, to remove material and enlarge the diameter of the bore. It is held in the regular tool post so the only the cutting edge touches the inside walls of the hole. The tool is advanced into the hole and the tool is adjusted toward the operator with the cross slide after each complete pass. Blind bores as well through ones can be cut with the boring tool. The perfect way to machine the cylinder of a model engine! There is one last cut, although is did not include it originally. The parting cut is done to cut off a part either after it is fully machined or to inverted on the chuck for further machining operations. More on this later. Other specialized types of cuts and techniques will be discussed in later sections.