İnşaat Mühendisliği

Instructions Of a Portable Power Saw And Power Sander

PORTABLE POWER SAW

With a portable power saw, wood can be cut at least ten times faster than by hand, and the cuts will be far more accurate and look much better. Saws range from little ones, weighing 27/4″ pounds and cutting to a depth of 5/4″, to large 12″ units, weighing 34 pounds. It’s best to buy the smallest that will do the job. An inexpensive saw will cut 15/8″ deep; that is sufficient for more than 97 per cent of the cutting you will do. If you do have to cut deeper, it’s simple to reverse the wood and saw across it to meet the first cut.

For the man who does his work in an apartment or the homeowner who plans only small jobs, the small 4″ diameter saw is completely adequate. It can cut up to 5/4″. A variety of blades are available, and adjustable guides can be added.

Calculate the distance of the saw plug-in from the power source. If you will be working at a considerable distance, use an extension cord of sufficient wire size to prevent a drop in power voltage. For distances up to 35′, use a No. 14 wire or heavier; up to 100′ use a No. 12 wire or heavier. Extension cords in specific sizes can be purchased with that purpose in mind.

Don’t overwork your light-duty saw. Cut the pieces one by one, as you measure and mark them, rather than do all the marking at one time and the cutting at another. Never force the blade into the work; an easy, steady pressure is best. Start the saw and listen to it come up to full speed before you enter the wood, and then let it cut its way through – you just guide and engineer the job. Any time the cut seems to bind the blade, force a screwdriver or wedge into the cut behind the blade to keep the cut open. Make especially sure your work is well supported. Any movement of the board being cut binds the blade or deflects it from the guide line.

And don’t let the motor overheat. If you find the motor housing too hot to touch, stop sawing and do something else while the motor cools because further use will cause motor damage. As with all cutting tools, always use a clean, sharp blade and keep an extra on hand. Clean the blade with kerosene to soften the pitch and gum it will pick up in cutting unseasoned wood. Wiping the blade with kerosene prior to cutting such wood prevents gumming during use.

Portable saw blade teeth cut upward, leaving the best edge on the bottom side of the cut. In cutting plywood, do the marking on the back surface and work with the better face down to protect it. On thinner grades and veneers, this practice is an absolute must. Plan your cutting so that the broader base remains on the supported section as the cut is made – this is usually to the left side of the blade. If possible, use guides; they provide far more accuracy than only a marked line.

For general crosscutting and ripping, a combination blade will work well. If you have a large amount of one kind of work, change to the appropriate blade. A crosscut blade works best on plywood and in cutting across wood grain. For large quantities of ripping, switch to a ripsaw blade. A miter blade gives a much better, smoother finish to the cut. Use this where the appearance of the cut is important – for example, on such work as exposed edges and grain ends.

In addition to the cuts shown in the photographs, you can make rabbets along board edges with two cuts to the measured depth at right angles to each other. Also, you can make dado cuts by setting the blade to the desired depth, making two parallel cuts and removing the scrap with a chisel. You may also utilize special washers to complete these cuts, attaching them to the spindle next to the blade.

POWER SANDER

When the family handyman goes shopping for a power sander, he may very well ask for “a sander to do everything about the house”, and it no more exists than does the perfect house or the cure-all pill. In general, there are three kinds of power sanders: disc, belt and finishing. Each kind has its own advantages and disadvantages since each was designed for a specific purpose.

Disc Sanders

All disc sanders have a circular rubber pad mounted at right angles to the drive spindle of the motor. The abrasive discs are attached by a flange and screw that threads into a steel rod which is held by the drill chuck. Discs are easy to change and, in the 5″- and 6″-diameter sizes, the choice of grits (degree of roughness) is great.

Disc sanders usually have an rpm in excess of 3,000, and their main function (by design) is to re- move stock rapidly and roughly. If you have a lot of paint to remove or a large amount of wood to sand off, the disc sanders will do it best. They are not designed, and hence not recommended, for finish work. All too many new owners of disc sanders attack (and “attack” is the only word) a sanding job as if they planned to push the sanding disc through the work. The results are swirls, gouges, clogged or torn discs and a motor that gets overheated. Sanding with 1 flexible disc is best done with speed, not pressure. If the tool is slowing down so that you notice it, ease off. For best results, keep the disc nearly flat and moving over the surface lightly. Keep three grits on hand – coarse, medium and fine – and use the right grit for the right job. On really stubborn jobs like outside window ledges and much-painted porch floors, where discs keep loading in seconds, try a No. 7/2 open-coat disc. It’s long-lasting and loads very little. All disc sanders can be used as polishers. Just remove the abrasive and cover the pad with a lamb’s-wool bonnet.

Belt Sanders

A belt sander should not be considered by the handyman who plans to have only one kind of sander. By and large, belt sanders are for heavy-duty work over large, flat surfaces. The portable types are excellent for smoothing large, flat areas preparatory to finishing. In the shop, a stationary belt sander may be pressed into use for joining work as well as finishing. Instead of being guided over the work, the work is pushed against the whirling belt. For most of its jobs, the belt sander will use medium- and fine-grit abrasive belts, and they can remove a lot of material quickly. Belt widths are available from 2″ to 4″, with lengths from 21″ for the 2″ width to about 28″ for the 4″ width.

Finishing Sanders

Finishing sanders have many names – orbital, reciprocal, straight line, vibro and flat – but they all have one purpose in common, that of providing a surface with a fine finish. They won’t remove paint rapidly or do a good job of taking down wood, but they will provide a smooth, fine surface.

With finishing sanders, the abrasive is laid flat on the surface to be finished and moved with very short, rapid strokes in all directions. The tool has a wide variety of uses owing to this versatility. The choice of abrasives is equally broad, but since finer work is the chief purpose, medium, fine and very fine grits are likely to be used with it. Use a medium grit for smoothing plaster patchwork and dry-wall taped joints. Use fine and very fine grits for furniture finishing. A “sand screen” abrasive cloth may also be used for such purposes after it has been cut and fitted over the sander pad.

When refinishing furniture, remove the old varnish or shellac first with a good chemical remover, for an abrasive rough enough to remove finish may also scar the wood, and the use of finer abrasives will be of no help since the grit will load in the first few seconds. Change grits often. Don’t try to do a job from start to finish with one grade of abrasive. Use a finer and finer grit as the job progresses. This doesn’t mean you have to waste paper. Save the sheets you change and use them on another job. And on really fine work, don’t use a fresh sheet. Run a fresh sheet on some scrap for a moment and then use it. Fine finishing paper may sometimes have an abrasive clump on it which will leave swirl marks with orbital sanders. Always be sure the paper is on tight; otherwise its efficiency will be lost.

Etiketler
Daha Fazla Göster

İlgili Makaleler

Bir cevap yazın

E-posta hesabınız yayımlanmayacak. Gerekli alanlar * ile işaretlenmişlerdir

Başa dön tuşu
Kapalı
Kapalı