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HOW TO DRILL HOLES

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In metal In wood In masonry In glass In mixed layers

In metal
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Use HSS (High Speed Steel) drill bits that are properly sharpened.

HSS drill bits are always black.

Use a centre punch to mark the place where the hole should be and to give the drill bit initial grip.

Most electric drills run too fast at top speed for successful drilling. Slow the drill down to just above its slowest speed. Do not use excessive pressure. Let the drill and drill bit do the work.

Constant pressure at low speeds is more effective and better for the drilling machine than switching the drill on an off while drilling.

When drilling large holes first drill a small pilot hole.

If the hole is so large that you have to use reduced shank drill bits be especially careful and take it easy. If an unreduced drill bit does not fit the chuck of your drilling machine the machine was obviously not made to drill holes of that size. However, one can drill large holes with small machines as long as one lets the machine and the drill bit do the work and one does not force the issue.

When drilling through metal make sure that the underside of the metal is clear of obstructions or place the job on a piece of scrap wood.

When drilling into or through square tubing prevent the drill bit from slamming into the opposite side of the tubing. Go slowly when you feel you have reached the point of breakthrough. To drill all the way through make sure that you hold the drill straight.

Always clamp small pieces of metal in a vice.

When drilling through a pipe it is a good idea to place a dowel into the pipe to prevent distortion. If you do not have a pipe vice, place a block of wood with a V-shape cut into it on each side of the pipe before clamping it in a vice.

In wood
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For small holes up to 6 mm diameter use a hand or electric drill with HSS drill bits.

To drill larger holes, use spade bits with an electric drill, or auger bits with a carpenter’s brace. For very large holes with a diameter of up to 76 mm use an expansive drill bit in a brace.

To prevent splintering when drilling through wood with a brace either place a piece of scrap wood on the exit side of the hole or watch for the point of the bit to come through the wood and then reverse drill.

This is not possible with spade bits and a piece of scrap wood must always be used on the opposite side of where the hole is started.

Holes can be drilled in very thick pieces of wood like tree trunks using a Scots auger.

In masonry
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Use masonry bits.

Masonry bits are always silver

Mark the place where you want to drill the hole with a centre punch or nail.

Apply steady pressure at slow speed.

If you have to drill through a 20 cm wall use a extra long masonry bit of 6 or 8 mm diameter to drill a pilot hole. Finish by drilling from both sides with your larger drill bit.

Do not start drilling with the machine set on “hammer action”. Let the drill bit first bite a hole in the wall. One should only use the “hammer action” if the concrete or brick is too hard for the drill to cut away.

In glass
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Use a special drill bit for glass or a multipurpose drill bit.

Make a little wall of putty around the place where you want to drill the hole. Fill this little dam with turpentine and drill slowly and patiently.

The centre of a small “X” made with a glass cutter will give you your starting point.

In mixed layers of materials
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Use multipurpose drill bits.

Multipurpose drill bits are always gold

Never use these bits with “hammer action”. They may look like masonry bits but their tips are specially made for cutting and will disintegrate under a “hammer action”.



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