Portable Power Tools

One of the many changes which have taken place in recent years is the development of small portable power tools for home workers. Woodworking is well catered for, although the tools are not as robust or powerful as their industrial counterparts. The power source is always domestic mains electricity and the tools are as portable as the availability of a power outlet and the length of lead on the tool or added as an extension. A safety point to stress right away is that extension leads on reels should be fully opened out when used for more than a few minutes, otherwise the wound up cable overheats to an extent which may burn out the insulation.

The power drill and its attachments

Most of the popular power drills have many attachments or accessories available for them, which either fit in the chuck or can be attached to the drive after the chuck has been removed. In general terms an attachment means that the chuck has to be removed — a simple operation — while an accessory fits the chuck. With these, the power drill owner can convert a single tool into a multi-purpose piece of equipment.

Drill sizes and types

The smallest and cheapest drill on the market has a chuck capacity of 6 mm. This means that the shank of drill or other accessory being fitted cannot exceed that size. Also explicit in the specification is the warning that attempting to drill in metal over 6 mm diameter will seriously overload the machine and probably destroy it.

This type of drill has a speed of around 2 500 revolutions per minute when running free, or unloaded. When the drill is actually under load, or working, the speed will drop. Long before this stage is reached the user should have reduced the load.

Chuck capacity and no-load speed are standard specifications for power drills. The speed quoted is quite satisfactory for boring small diameter holes in wood but it is too fast for drilling in steel or masonry. Power output of the motors fitted in these small drills varies from maker to maker but typical working capacities are 6 mm diameter holes in steel and 13 mm in hardwoods.

A very popular drill for home use is one with a chuck capacity of 10 mm. The power is uprated above the smaller capacity drill and the 10 mm drill should be able to drill in steel up to 10 mm diameter and 19 mm in wood. With this capacity of drill variations are available in no-load speeds. The first is a two-speed model providing a fast speed suitable for wood and a slower speed intended for drilling in steel or masonry. Typical speeds are around 3 000 r.p.m. and 700/850 r.p.m.

The problem of drill speed and the need to have fast and slow revolutions has been overcome by some manufacturers with various electronic circuits which reduce the current flowing to the motor, thus reducing its speed. Some infinitely variable speed drills can run from only a few revolutions a minute up to maximum by trigger control only, the trigger acting rather like an accelerator.

Speed-changing accessories

Other devices to change the speed of a drill are available as accessories. One is in the form of a secondary chuck which fits into the drill chuck. It is, in principle, a small gear box which reduces the speed by about half. Some patterns can be reversed, thus increasing the speed, while others are arranged so that the drilling is done at right angles to the machine’s axis. This arrangement can on occasions be quite useful in awkward or constrained situations.

Another piece of equipment which can be used to vary the speed of a drill is in the form of an electronic variable control which is plugged in line with the drill lead. By operating a knob the speed can be reduced from maximum to minimum, within the control design. The principles on which these gadgets work are, broadly, rapid interruption of the current flow which in effect switches the drill off and on again; makers claim that this system, whether plugged in line or built into the drill itself, does not reduce the torque, or turning power, of the tool.

Drill stands

For most of the time a drill is used it is hand-held and used free-hand. Indeed, for many drilling operations this is the only way it can be used. There are, however, many occasions when a drill becomes far more efficient and easier to use when it is clamped in a drill stand. Repetition work and when drilling metals are two examples of when a drill is more efficient when in a stand. Most leading manufacturers make stands for their own drills and some make stands which will accept other makes of drill. In the domestic range one, at least, makes a stand for drilling which also forms part of a small wood-turning lathe, powered by the drill. There is a certain amount of interchangeability between drills and stands of various makers but this should be checked before purchase.

A drill stand should be robust and smooth in action, with no backlash in the linkages. For safety it should be bolted or screwed to a suitable bench. If this is not practicable it should, at least, be clamped or otherwise secured to the work bench or table.

Mortising bits and attachments

Not only do stands make drilling operations easier to perform, they also open up the way for further attachments to be used. The bigger and stronger stands can be equipped to make mortises, using the very efficient hollow, square mortising chisels and bits, sold by good tools shops.

This type of tool has a special bit which revolves in the hollow centre of the chisel. When the chisel is pressed down on the wood the bit bores a hole, ejecting the waste through a hole in the top of the chisel, which continues the cut, converting the round hole to a square one. By taking a series of cuts side by side a mortise of any length can be made. For the most satisfactory cutting of mortises, the chisel should equal the width of the mortise.

Because of the limitations inherent in this system, the largest bit which can be used is ½ in- These chisels are not made by the firms who supply the drills but by specialist firms. A leading firm supplies them in five sizes, from V4 to l/1 in, but not as yet in metric sizes.

Shaper cutters

A recent development in power tool attachments is the shaper cutter, which fits directly in the chuck. They can be used in conjunction with a drill stand or in a hand shaper attachment. One supplier of these cutters produces a universal shaper table, designed for fitting to popular drill stands and providing a fixed work table with an adjustable fence. With a slotting type cutter a groove the width of the cutter can be made, or by repeating the cut after some adjustment to the fence a wider groove can be made. This can be repeated to form quite wide grooves. By grooving from two adjacent faces, rebates can also be made. With large panels it is better to use the hand shaper, rather than move the wood across the shaper table

It would be far more difficult to move such a piece across the small table in a drill stand than to move the attachment along the timber.

Circular saws

Circular saw attachments for power drills can be used for many jobs, especially ripping and cutting man-made boards. They have blades up to approximately 127 mm diameter and can be used at the place of work, with an extension lead plugged in at a convenient socket outlet. The saws are easily attached to the drill and have adjustable depth and angle of cut. The blade is enclosed by a guard when not actually cutting and the guard snaps closed by a light spring when the saw finishes its cut.

Most saws have a ripping fence which can be adjusted to about 300 mm from the face and the fence can be removed as required. The sole plate of the saw has a cut-out section at the leading edge of the blade so the operator can see the line of cut and many have a guide line on the sole plate to assist the lead-in to the cutting line.

Saw bench

A small saw bench to which the circular saw attachment can be mounted further increases the scope of a power drill. Maximum depth of cut is about 38 mm but thicker material can be ripped by first grooving then turning the timber over and completing the cut. The work should not be forced through the saw, just lightly thrust against the revolving blade and pressed firmly against fence and table.

The ripping fence is adjustable and frequently a mitre and cutting-off fence is provided. Circular saw blades

Most circular saw attachments are supplied with a ‘general purpose’ blade. This has coarse teeth of the rip saw profile, for cutting along the grain. Tips of the teeth, however, are sharpened with side bevels as shown, so that the outer tips of the teeth cut first. This is a requirement for cross-cutting as it helps to prevent the grain from splitting on the underside of the wood.

The blade can therefore be used for most wood-cutting functions, but has slight drawbacks. The teeth are quite large and tend to tear the grain, especially on thin sections.

Smaller teeth give a cleaner finish and absorb less power from the drill; the power of the motor tends to govern the speed of the cut, rather than tooth size. For the person who expects to do a lot of sawing, a tungsten carbide tipped blade is a worthwhile investment.

These blades are relatively expensive but have a life between sharpenings of fifty times or more greater than an ordinary steel blade. They also leave a much smoother cut surface. Home users cannot, however, re-sharpen them, and they must be sent to a specialist for servicing.

Jig saw

Another saw attachment available for many makes of drill is the jig saw. This has a short, narrow blade with which curves and awkward shapes can be cut. The blade reciprocates in an up and down movement, with the teeth so shaped that it cuts on the upward stroke. These saws cut quite well on thinner material but the rate of cutting can become rather slow on wood near the saw’s maximum capacity, usually 19 mm.

A jig saw is particularly useful when it is required to cut a hole of some sort from the centre of a panel or board. A hole may be needed to introduce the saw, but with some types of jig saw they will ‘work themselves in’. How this can be done is explained in the instruction leaflet.

Woodturning lathe

Mention has already been made of a drill-powered lathe. A woodturning lathe is usually a fairly heavy and robust type of machine, so it may be realised that those which are basically power drill attachments are very much in the lightweight class. In spite of this they are capable of producing satisfactory work so long as it is accepted that they have limitations and that only fairly small work can be turned on them.

Lathes of this type will turn work up to about 457-508 mm in length and 100 mm in diameter. The length of work possible is referred to as ‘between centres’ capacity. They will cope with face-plate jobs up to about 102 mm diameter.

For the beginner who wants to start off on woodturning, there are sets of woodturning tools below the size normally used on standard lathes. A recommended set, made by one of the best known tool manufacturers, comprises three principal tools in the small-size range: a 13 mm gouge, same size skew chisel, and a parting tool.

Grindstones

The cradle which holds the power drill, forming the head-stock of the lathe, can be used for other purposes. One is to enable the drill to be used to turn a small grindstone. The maximum size of stone which can be mounted on the drill is about 127 mm diameter, by 13 mm thick. It is used in conjunction with a special mandrel, or arbor, on which the stone is mounted at one end, the other going directly into the drill chuck.

Disc sanders

One of the most simple attachments is the disc sander. This is a circular, flexible rubber pad of 127 to 152 mm diameter, mounted on a small arbor. The shank fits chucks of V4 in capacity upwards. A disc of abrasive paper is held by a screw in the centre of the pad, which is dished to keep the screw below the working surface. When in use the outer edge of the disc is lightly kept in contact with the work and constantly on the move – the abrasive action is quite effective, especially if a coarse one is being used.

Because of the circular action much of the sanding is across the grain. Asa result, there is a tendency to scratch the surface, leaving circular marks. Because of this the disc sander is only really suitable for work which is to be painted, when slight surface scratches will be obliterated, or when trimming across end grain, edges of plywood and hardboard, or ‘fairing off when boatbuilding.

Abrasive discs

As well as the traditional abrasive paper, other abrasive discs can be obtained which, it is claimed, have certain advantages over the paper. One of these is a thin metal disc, shaped and dished to fit the rubber backing pads. At a stage in the manufacture small particles of tungsten carbide are bonded to the surface. Because of the extreme hardness of the abrasive granules, a very long life is claimed.

Another type of disc is in the form of resin-bonded matting, woven from abrasive-impregnated materials. Although the disc itself is rather stiff the weave is ‘open’, thus allowing dust to pass through. This means that the disc does not clog up, which is one of the problems of ordinary abrasive papers.

Orbital sanders

A much more gentle abrasive action is achieved with an orbital or finishing sander, also available as a drill attachment. Used correctly and with a fine abrasive sheet, the finishing sander produces a smooth matt surface which is used extensively on modern furniture. With coarse grits, orbital sanders can be used to rub down paintwork but they are not intended to clean off rough or sawn surfaces.

Drill bits

Many other attachments and accessories, not necessarily for woodworking, are available for power drills and, with such a wide range available, it is easy to overlook what the power drill is primarily designed for: to bore holes.

In order to bore holes properly and precisely, the correct type of bit must be used. Bits intended for holding in a carpenter’s brace cannot be used as they have square, thick, shanks which cannot be gripped in the power drill chuck.

There are different qualities of this type – the cheapest are referred to as ‘jobbers’ quality’, suitable for occasional use in soft materials. These drills do not like a high speed and if used in a single power drill to bore in metals, they will quickly lose the cutting edge and stop drilling. Jobbers’ drills are not made to a high degree of accuracy but they are close enough in tolerances for wood.

A rather better type of drill is made from carbon steel. They also do not like high speeds when drilling metal -especially steel – but are unaffected when drilling wood. High speed when drilling a hard material causes friction, and this in turn creates heat. Only a slight excess of heat is enough to draw the cutting edge temper and once this is lost friction and heat build up until the drill tip turns blue and is useless. Sharpness of drill, slow speed and moderate pressure are essential when using carbon drills.

The best type is the high-speed drill. These can be run at high speed without damage, and with sensible care will give many years of service. Engineers’ drills are available in metric and imperial sizes, and also in a ‘letter’ range. For woodworking purposes these drills are ideal for boring the sort of holes needed for screws, when it is important that the holes should be just the right size to match the gauge of screws. The drills are also useful for drilling pilot holes when using large nails and it is desirable to pre-drill to prevent splitting the wood.

When fixing a drill bit in the chuck first be sure that the drill is disconnected from the power supply. Then check that the bit is properly centred in the chuck before tightening up with the chuck key, usually a lever device which plugs into holes bored in the chuck body. A small toothed wheel engages with similar teeth cut around the chuck. When the chuck is sufficiently tight fit the lever in the next hole and tighten again. Do this in all the holes. This ensures that the bit is truly central and secure.

Many domestic woodworking jobs involve fixing pieces of wood to the walls. This means drilling and plugging the wall for screws; a power drill with the correct type of boring bit will make quick work of a job which, by hand, would take many times as long and would be extremely tiring.

A masonry drill is essential. Such drills are numbered to match plug and screw sizes, and it is important that they do match for many reasons. These drills must not be driven at a high speed, which leads to overheating but they should have a moderate amount of pressure. Too little pressure means that the tip rubs, rather than cuts.

Although a tipped masonry drill will retain its cutting edge for a good while when properly used, it needs to be sharpened from time to time. For this purpose a special grinding wheel is needed. Tungsten carbide is too hard to be sharpened on an ordinary grindstone or oilstone. For tipped drills the stone to use is known as a ‘green grit’, and it operates without creating sparks. These drills, however, are best left to specialist firms, unless one wishes to experiment with the smaller, cheaper sizes.

All engineers’ drills can be re-sharpened on an ordinary grindstone, smooth or medium grit. It is essential to retain the original angles and shapes and this can be achieved with a little practice. There are special grinding jigs and machines for ‘touching up’ engineers’ drills and they do not cost a lot.

When holes are made for screws it may be necessary to countersink for the screw head. It is always better to slightly over-countersink to ensure that the screw head does not lie above the surface. Sometimes the countersinking is made deliberately excessive so that the head of the screw can be concealed by filling with ‘stopping’.

These bits have a small central point, slightly longer than the cutter spurs, which are characteristic of many patterns of wood-boring bits. They are made in many sizes up to 25 mm but with 6 mm shanks on the smaller sizes and 13 mm on the larger. These bits are excellent for boring holes of the size and type used when making dowel joints.

For the home woodworker, flatbits are the cheapest for use in power drills. They are very simply made and were developed especially for portable power drills. They have a large point on which the flat cutting part rotates – the two cutting edges, in fact, scrape rather than cut. Despite this they bore quickly in wood and sharpening is easy, using a fine file. The bits are available up to 38 mm m diameter and all have 6 mm shanks. Although they absorb little power the largest of these bits may be too much for the cheaper drills with 6 mm chucks.

More specialised bits, which can only be satisfactorily used when the drill is in a stand, include the screw Jennings pattern, the Forstner pattern, and the saw-tooth centre bit. The first two are similar to those used in a carpenter’s brace, excepting the shank. Special bits, sometimes called end mills, are now made for machine-boring the holes for ‘concealed’ hinges used extensively on modern furniture.

Single purpose or integral machines

Excellent though most attachments are, they do not perform quite as well, or have the same capacity, as a power tool designed for a single function. With an independent machine power and speed are matched for optimum performance, and this can never be achieved in quite the right balance with a single power source.

Separate, or integral, machines are easier to use, often requiring only one hand compared with two for the equivalent attachment. The range of independent machines is very wide and covers a great many woodworking operations.

Orbital, dual motion and belt sanders

Sanders are possibly among the more popular in this range of integral machines. Most are of the type called ‘orbital’ because of the circular motion which the rectangular sanding pad makes. The amount of wood they are capable of removing is only slight, therefore a surface should be in a reasonable state before this type of sander is used.

There are some sanders on the market which are classed as ‘dual-motion’. They can operate as a normal orbital sander or, by moving a small lever, the movement changes to a straight up-and-down, or in-line action. This means that the sanding can always be arranged to be with the grain — an orbital movement is bound to have part of the stroke across the grain. However, because of the nature of this machine, the extent of swirl-scratching is only slight. The in-line sander does not produce a matt surface, as the orbital one does, so the dual motion sander at least gives a choice of finish.

By far the best type of portable sander is the belt sander. The abrasive is an endless belt about 102 mm or more in width. The machines are usually designed so that on one side the belt extends beyond the body, thus allowing the sanding to take place right up to the edges. Belt sanders are capable of moving quite a lot of wood fairly quickly, and because of this the bigger and more powerful machines are fitted with dust bags or dust extraction systems. Cutting action is in one direction only and wherever possible this should be arranged to be with the grain. Belt sanders are very effective but their cost is many times that of an orbital sander.

Abrasives

Machine type abrasive paper or cloth must be used in all power sanders. This is normally bought to suit the size and type of machine for which it is needed. The grit is nearly always aluminium oxide and, although a wide range of grades is manufactured, popular packs are often available in assorted sizes: coarse, medium and fine.

When used on wood which is resinous, there is often a tendency for the paper to stop cutting because clogged with resin and dust, rather than normal wear. A rub with a wire brush will usually clear the surface, and extend the life of the abrasive paper considerably.

Jigsaws

The jigsaw machine is available as a single- or two-speed tool. As with boring holes, a fast speed is needed for wood and a slow speed for metal. Blades have a limited life but are quite cheap and quickly changed, being held in place by a set screw or on some makes, two screws. Various types of blade can be fitted, large or small teeth for cutting wood and very small teeth for metals. Because of the upward cutting action, sawdust is deposited on top of the work, right on the cutting line. Many of the better jigsaws have built-in blowers to clear the dust from the line.

When a hole has to be cut in the centre of a panel, it is necessary to bore a hole in the centre of the panel to ‘start’ the saw. It is advisable to bore holes at all sharp angles, the diameter equalling the width of the saw blade. Although jigsaws are particularly suited to cutting holes inside panels, and for cutting shaped pieces, they can also be used for straight cutting. Some makers provide a guide fence which can be fitted to the sole plate, for sawing parallel to an edge. It is not likely that the fence can be used for cross-cutting or for cuts well away from the edge but a batten can be temporarily fixed to the board and this used to guide the saw. It is also possible to make a simple jig which can be G-cramped to the board and thus give an accurate, square cut every time. They can also be used for circular saws.

Portable power saws

Portable power saws are capable of quite heavy cutting. Blade sizes range from around 152 mm to 229 mm. A popular size is about 190 mm and this machine will cut timber up to 63 mm in one pass. Most of the saws are fitted with a safety clutch which automatically stops the blade from revolving if the motor is being overloaded. In the interests of safety the trigger is spring loaded and returned to ‘off if released. A retractable blade guard is fitted which uncovers the blade as it works into the wood and returns as the saw clears from the cut or the wood.

A fence can be fitted to the sole plate, enabling cuts to be made parallel with an edge. Grindstones and their use

Machine driven grindstones are useful in a busy workshop. Small ones are in two main sizes: 127 mm diameter by 13 mm thick, and 152 x 25 mm. Most of the machines are double-ended, enabling different grades of wheels to be mounted. Those usually fitted as standard are medium and fine; adjustable tool rests and guards are now a standard requirement on grindstones, with eye shields. If the grindstone does not have eye shields then safety glasses or goggles should be worn when using the machine.

These grinders will cope very adequately with all the general requirements of home and workshop. When grinding cutting tools on these ‘dry’ grindstones there is the risk of overheating the cutting edge and ‘drawing the temper’. This means that the metal in the cutting edge has changed its characteristics and will not retain its cutting edge when used. If the heating becomes excessive the end of the blade turns blue or purple. This burnt area would then have to be ground away to reach unspoilt cutting steel.

Two main points need watching in order to prevent this overheating from taking place. One is to use only gentle pressure. Too much pressure, in a bid to speed up the grinding, creates excessive friction and heat. Secondly, keep a container of water handy so that every few seconds the tool can be dipped in the water to cool it. Many grinders have a container or trough attached to them for this purpose. Although the motors are usually well protected, do not splash water over them – water and electricity are a dangerous combination.

Other precautions are: keep the tool on the move as far as this is possible, and ensure that the grindstone itself is cutting properly. Wheel dressers can be purchased for truing up and resurfacing grindstones.

Bandsaws

Mention should be made of bandsaws. There are some on the market which are portable in the sense that they can be carried to the working area. A bandsaw is a fine, versatile machine which does require careful and considerate handling. After some practice the operation of a bandsaw should present no difficulties and such a tool is worth considering when skills and requirements develop.

Do’s and don’t ‘s for power tools

All machine tools have an element of danger in their handling and use. Correct wiring up is the first safety check to make. Proper earthing of most tools is essential but an exception is tools classed as ‘double insulated’.

We have already warned about having a drill connected to the power source while fitting attachments or accessories. Other ‘do’s and don’t’s now follow.

DO learn to understand the tool, what it can tackle, and also its limitations. Read and apply the information given in the instruction booklet.

DO NOT experiment with it or try to perform functions for which it is not designed.

DO keep the guards and safety devices fully operational.

DO NOT tie them back out of the way or jamb them with a match stick or nail.

DO maintain tidy habits, and keep the work area well lit, clear and clean.

DO NOT work in your own light.

DO store tools properly when not in use. Keep them out of the reach of children.

DO NOT allow children to get too close. They are naturally curious but do not appreciate potential danger.

DO use the correct tool for the job.

DO NOT force tools. Experience soon shows at which speed the tool performs best, this being the speed for which it was designed.

DO hold the workpiece firmly with cramps or in a vice.

Keep hands away from moving parts.

DO NOT adjust or service a machine with the power supply on – always disconnect.

DO keep tools in good working order. Blunt tools can be dangerous – cutting edges must be kept sharp.

DO NOT put them away while dirty or wet. Clean them up properly.

DO switch off the power source, or disconnect tools when not in use.

DO NOT leave power tools switched on when unplugged from the power supply. This could lead to accidental starting when plugging in again.

DO make sure that chuck keys and other tightening devices are removed before switching on.

DO NOT leave them lying around on the bench or in the workshop but tie or clip them to the machine power lead.

DO be most careful when a machine has been switched off and is being put down. It is very easy to catch the cable or something while the drive is still revolving.

DO NOT place it where it can be knocked off or tripped over.

DO ensure that when extension leads are used they are positioned where they will not be damaged or tripped over.

DO NOT leave a lot of spare cable wound on a reel – open it out but place it tidily.

DO be tidy in your dress. Loose ties and cuffs can easily be caught in moving parts.

DO NOT scorn overalls or protective clothing.

Sorry, comments are closed for this post.

Share On Facebook
Share On Twitter
Share On Google Plus