Bits have different ends and are primarily round with spiral grooves to clear the cut material or flat used only with soft material - wood or plastic.
The bit may be turned with a motor or by hand. It is held by a chuck or collets. These permit various bits to be used in the more expensive hardware. Collets are more precise but each one has a very limited range of adjustment.
The motor drive may be a battery powered screwdriver, a hand-held, geared-down motor in a pistol shaped housing powered by a battery or AC power, or a larger AC motor belt driving a moveable head - a drill press. The best results (straight hole in the right position) with the material clamped to the platform of a drill press, but this is not always necessary or possible.
Hand drive of drill bits is possible, usually in a tool that speeds up the turning of the bit from the hand motion, but hand held drilling is likely to be uneven from wobbling.
When drilling metal it is best to use a center punch to mark the starting point and make an indentation to catch the end of the bit.
A simple use for a tap is to clean up threads that have become damaged, by carefully turning it into the hole. Of greater interest is putting threads in holes so that nuts do not have be used, thus reducing projections and/or making narrower or cleaner tools or fittings.
| In the image below are examples of two tapping handles and a tap (top center and left). The top left hand tap handle has an adjustable T-handle that can be pushed to one side for clearance and has a ratchet mechanism to permit use in tight quarters. The tap is held by a chuck with v-jaws. The center handle with the V-slot will handle bigger taps but only where there is clearance. The tap (top center) has a square end for gripping in the handles and then a smooth portion which has printing to identify the tap and often the drill needed. The threaded portion has clearance grooves for the chips taken out. This is a plug tap, which tapers at the end to fit in the drilled hole before cutting the threads. A bottoming tap is square on the end and has full threads to the end to cut to the bottom of a hole. (A tapered tap is one for tapered holes, as in plumbing connections, full threads down a taper.) |
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| The handle in the center bottom takes dies like the one above it to the right, a 1" hexagon die. The die fits in the handle and is held by the set bolt on the side. Clearance is assumed. Other die holders exist which fit in a brace and drive the die from behind. When larger material is to threaded, much more massive handles are required and the system for threading larger pipe involves three section dies, a head several inches across, and a 2-3 foot long handle. Parts for this cost several dozen dollars each vs. a couple of dollars for hex dies. |
| The cutting fluid to the right in the picture is vital for taps and dies and very useful for drilling and cutting metal. Often called cutting oil, more correctly called cutting fluid, it serves several functions, cooling the fine teeth doing the actual cutting and keeping the bits of metal from welding to the teeth. It provides some lubrication and carries off trash bits if used liberally. (There is another cutting fluid mixed with cooling water for large cutting operations, as on a lathe.) It is hard to explain to some people why an "oil" is used in cutting, "Doesn't that just make the blade slip?", but cutting is not grinding - an abrasive action - it is cutting, the edge of the teeth is getting into the material being cut and digging out bits, more or less together. |
Torch welding is considered more difficult by some, but it is quieter and less exciting in stuff thrown about. A torch combines gas from a regulated acetylene tank and oxygen from another regulated tank and produces a small very hot flame which is used to create a puddle of molten metal which is moved along the joint. A thin welding rod may be used to add material. A special torch head can be used to cut steel and another to provide broader heating. Besides steel, lead and aluminum may be welded (with care) usually with other gases.
Arc (electric) welding is done with a power supply that converts wall electricity (higher voltage) to high current, lower voltage. A thicker rod or wire conducts the current to work piece which completes the circuit. When the conductor is touched to the piece and pulled back, an arc forms which is brilliant and hot. The heat melts the end of the rod/wire and the work piece and the melted material flows together. Very good eye protection is required for arc welding and onlookers must be protected also. Normally a lot of sparks are thrown, so the area must be flame resistant for many feet around. When wire is used, it is automatically fed and commonly is surrounded by inert gas to make welds in materials that don't take welding with a larger rod or torch all that easily - like stainless steel or aluminum. MIG welding is metal in gas and the wire is related to the material being welded. TIG is tungsten in gas and the wire is tungsten and is used up much less rapidly. Lower cost MIG welders are available to run off household current and may be rented.
Noun: the tool used for countersinking that produces a V shaped top to the hole so that the matching V bottom on the fastener fits in. Cylindrical countersinking is done with a larger drill bit. 2006-03-13