The Number One power tool for any homeowner or apartment dweller who tackles almost any home maintenance or improvement job is a portable electric power drill. You almost can't run a household without it. The time and money the drill will save you will far outweigh its initial cost. There are several different types or models of portable electric drills available. Some are designed for specific projects - such as drilling and hammering into concrete. The purpose of this How-To Booklet is to acquaint you with this drill assortment and provide you with the data you will need to operate the equipment efficiently.
Size Considerations
There are three basic drill sizes available: 1/4-, 3/8-, and 1/2-in. The fraction size refers to the capacity of the chuck - the business end of the drill where the bits are locked in. The size you buy really depends on the type of project for which the drill will be used. For all around work - a "general drill" - we recommend a 3/8-in. drill with a variable speed and a reversing feature. It is powerful enough to handle almost all repair jobs, yet light and compact enough to follow your commands.
For your comparison:
The 1/4-in. drill. This is the lightest of the three drills and is the least expensive. The drill will handle drill shanks up to 1/4 in. for 1/4-in. holes in metals and 1/2-in. holes on wood and other "soft materials" without a special hole saw or oversized wood bits. If possible, buy a drill with a variable speed feature. This feature lets you start the drill into the material you are drilling slowly, then increase the speed once you have the drill started squarely into the work.
Some 1/4-in. drills offer a reversing feature, but you may pay extra for it. Most of the drills do not have a low-torque feature, and the drills will not stand up to a lot of constant hard work, such as drilling multiple holes in concrete, brick and stone. However, a 1/4-in. drill is adequate if your household drilling chores are infrequent and light.
The 3.8-in. drill. This drill will give plenty of power and it will drill up to 3/8-in. holes in metal and 3/4-in. holes in wood - without a hole saw or special bits that increase the hole size. You can lean on this drill and the 1/3rd to 3/8ths (or more) horsepower windup keeps on turning without noticeable slow-down. The larger chuck size lets you use up to 3/8-in. twist drills and special large-shanked accessories.
Many models have the variable-speed feature, some with a hammer mode that lets you drill easily into concrete and masonry materials. Buy the reversing feature if you can; it will let you draw and drive screws. This can be important and very time-saving when you have a lot of fastening work to be done - installing hinges, for example.
The 3/8-in. drill offers a mid-range in speed, which permits clean hole drilling wood. Its motor has lots of power and will take on a great deal of constant hard work and abuse.
The 1/2-in. drill. This is the model the professional buys, and it is the most expensive of the drills. It can punch holes in almost any material.
The 1/2-in. drill will drill up to 1/2-in. holes in metal and 1-in. holes in wood - or larger holes with accessories such as hole saws. Some drills have a hammer mode and different drill chucks for different materials. The quality drills have variable speed with low rpms and high torque. Most have trigger locks.
The hammer feature. A drill with an impact or hammer mode actually adds another tool to your assortment. With a flip lever on the handle of the drill, the drill becomes more or less a wood chisel that is capable of making mortise and other type joints. The accessories available will give you an idea of what the hammer mode will do: drill bits, masonry bits, mortar chisels, scrapers, and a full set of wood chisels.
Cordless drills. You can buy drills that run on battery packs and they are recommended if you are involved in projects where you can't plug the drill into power. The batteries hold up fairly well. But don't expect to run the drill full out all day long on one battery set or battery charge. The pros use them for assembling metal grid work for suspended ceilings and joining metal duct work - among other jobs - where prolonged use is not necessary.
Drill Accessories
All three size drills offer many accessories: screwdriver attachments, paint paddles, wire brush attachments - even attachments to convert the drill into saws, lathers, and other woodworking tools.
The list of helpful drill accessories includes: paint mixers, hole saws, an assortment of spade bits, drum sanders, right angle drives (to drill at right or acute angles), wire brushes, wood countersinks, metal working drills, grinding wheels, rotary rasps and files, drill stands (to make a drill press out of the portable drill), and drill stops for depth drilling. These accessories cost extra, so buy them as your work dictates and ask for a demonstration in the store, if possible, before you make a purchase.
compatible size: plywood, screws, and drills
|
| Plywood Thickness |
Screw Length |
Screw Size |
Drill Size for Shank |
Drill Size for Root of Thread* |
|
| 3/4" |
1-1/2" |
#8 |
11/64" |
1/8" |
| 5/8" |
1-1/4" |
#8 |
11/64" |
1/8" |
| 1/2" |
1-1/4" |
#6 |
9/64" |
3/32" |
| 3/8" |
1" |
#6 |
9/64" |
3/32" |
| 1/4" |
1" |
#4 |
7/64" |
1/16" |
|
| *If splitting is a problem (as in edges) make hole for threaded portion 1/64" larger (9/64", 7/64" respectively). |
|
Drill Bits and Hole Saws
Making holes, of course, is the primary purpose for which the electric portable drill is designed. There are a variety of drill bits for them. Unlike the square-tanged shank of a brace bit, the shank of a power drill bit that is held by the drill chuck is round and smooth.
Most common is the twist bit, which has a sharp point and two spiral-shaped cutting edges that lift chips out of the hole as the bit turns. High-speed steel twist bits are suitable for drilling wood and soft metals. Diameters range from 1/16 to 1/2 in. While they can be purchased individually, twist bits are less costly if purchased in sets.
The spade bit cuts larger holes than a twist bit. It has a flat driving end with a pointed tip. Cutting diameters range from 3/8 to 1 in. Boring bits have round cutting heads to drill holes in the same size range as spade bits.
For still larger holes, a hole saw may be locked into the chuck of the drill. The hole saw consists of a rim saw blade and a centered pilot bit. Common diameters range from 1 to 4 ins.
A wood screw pilot bit (sometimes called a "Screwmate") has three widths of cutting edge. The narrowest drills a pilot hole for screw threads. The next widest makes a shaft for the unthreaded screw shank. The widest makes a recess, or countersink, for flat head screws. A counter bore bit is similar, except that it drills the countersink below the surface of the wood so that the screw head can be concealed by a wood plug.
Masonry bits are available in a variety of sizes for drilling holes in concrete, concrete block, cinder block, brick, stone, ceramics, and glass. The bits are tipped on the cutting edges with carbide so the edges remain sharper longer. If there is any "trick " to using masonry bits it's not to force them in tot he material by pushing down hard on the drill. Use a little pressure and then let the drill do the work. Let the bit cool from time to time. For large holes, start with a small bit and change to a a larger bit. The work will go faster.
Safety Considerations
Most - if not all - portable electric drills are "double insulated." This means that electrical wiring and metal parts are isolated within the housing of the drill so that electrical shock is not possible. If you buy a drill that is not double insulated, it should be grounded with a three-prong plug grounding device. The device is worthless, however, unless the power source also is grounded in a three-wire system. Most of them are.
Even with this built-in safety equipment, we would advise you never to stand in water or on wet or damp ground when using a portable electric drill.
When using a drill, always keep the work locked in a vise or clamped to a table when drilling into the work, unless, of course, the work is fastened to something. Do not hand-hold the work. If you try to hand-hold it, the drill can catch on a knot or other imperfection in the material and cause the work to spin out of your hand.
When drilling in any material, please wear safety glasses or goggles. Drills can stir up a lot of sawdust and can flip metal shavings and chips across a room.
Gloves are a good idea, too, especially when working with metal, masonry and glass.
