Bosch Power Tools PS21BN Drill Bits, Drilling Wood, Drilling Metal, Running Nuts and Bolts

BM 2610007871 12-09:BM 2610007871 12-09 12/17/09 7:25 AM Page 13

First, clamp the pieces together and drill the first hole 2/3 the diam eter of the screw. If the material is soft, drill only 2/3 the proper length. If it is hard, drill the entire length.

Second, unclamp the pieces and drill the second hole the same diameter as the screw shank in the first or top piece of wood.

Third, if flat head screw is used, countersink

the hole to make the screw flush with the surface. Then, simply apply even pressure when driving the screw. The screw shank clearance hole in the first piece allows the screw head to pull the pieces tightly together.

The adjustable screw drill accessory will do all of these oper ations quickly and easily. Screw drills are available for screw sizes No. 6, 8, 10 and 12.

DRILL BITS

Always inspect drill bits for excessive wear. Use only bits that are sharp and in good condition.

TWIST BITS: Available with straight and reduced shanks for wood and light duty metal drilling. High speed bits cut faster and last longer on hard ma erialst.

CARBIDE TIPPED BITS: Used for drilling stone, con crete, plaster, cement and other unusually hard nonmetals. Use continuous heavy feed pres sure when employing carbide tip bits.

DRILLING WOOD

Be certain workpiece is clamped or anchored firm yl. Always apply pressure in a straight line with the drill bit. Maintain enough pressure to keep the drill “biting”.

When drilling holes in wood, twist bits can be used. Twist bits may overheat unless pulled out frequently to clear chips from flutes.

Use a “back-up” block of wood for work that is likely to splinter, such as thin materials.

You will drill a cleaner hole if you ease up on the pressure just before the bit breaks through

the wood. Then complete the hole from the back side.

DRILLING METAL

There are two rules for drilling hard materials. First, the harder the material, the greater the pres sure you need to apply to the tool. Second, the harder the material, the slower the speed. Here are a couple of tips for drilling in metal. Lubri cate the tip of the bit occasionally with cutting oil except when drilling soft metals such as alu minum, cop per or cast iron. If the hole to be drilled is fairly large, drill a smaller hole first, then enlarge to the required size, it’s often faster in the long run. Main tain enough pressure to assure that the bit does not just spin in the hole. This will dull the bit and greatly shorten its life.

RUNNING NUTS AND BOLTS

Variable speed control must be used with caution for driving nuts and bolts with socket set attach ments. The technique is to start slowly, increasing speed as the nut or bolt runs down. Set the nut or bolt snugly by slowing the drill to a stop. If this procedure is not followed, the tool will have a tendency to torque or twist in your hands when the nut or bolt seats.

-13-