BORING IN WOOD
Twist drills, although intended for metal drilling, may also be used for boring holes in wood. However, machine spur bits are generally preferred for wood working; they cut a flat bottom hole and are designed for removal of wood chips. Do not use hand bits which have a screw tip; at drill press speeds, they turn into the wood so rapidly as to lift the work off the table and whirl it.
For through boring, line up the table so that the bit will enter the center hole of the table to avoid damage. Scribe a vertical line on the front of the column and a matchmark on the table bracket, so that the table can be clamped in the center position at any height.
IMPORTANT: When the workpiece is long enough it should always be positioned on the table with one end against the column, as shown in Fig. 32. This prevents the workpiece from rotating with the drill bit or cutting tool, causing damage to the workpiece or personal injury to the operator. If it is not possible to support the workpiece against the column, the workpiece should always be fastened to the table using clamps or a vise.
Fig. 32
Feed slowly when the bit is about to cut through the wood to prevent splintering the bottom face. Use a scrap piece of wood (A) Fig. 33, for a base block under the work; this helps to reduce splintering and protects the point of the bit.
A
Fig. 33
DRILLING METAL
Use clamps to hold the work when drilling in metal. The work should never be held in the bare hand; the lips of the drill may seize the work at any time, especially when breaking through the stock. If the piece is whirled out of the operator’s hand, he may be injured. The drill will be broken when the work strikes the column.
The work must be clamped firmly while drilling; any tilting, twisting or shifting results not only in a rough hole, but also increases drill breakage. For flat work, lay the piece on a wooden base and clamp it firmly down against the table to prevent it from turning. If the piece is of irregular shape and cannot be laid flat on the table, it should be securely blocked and clamped.
14
