The band saw is one of the most versatile machines in the workshop; it is also one of the most misused. Ideal for making timber smaller, you can use it to rip and crosscut. Unlike the table saw, it will cut curves as well as perform deep ripping or re-sawing tasks. It is one of the safest stationary saws, and one of the quietest. Compact band saws are suitable for the bench, with bigger saws floorstanding.
As substantial tension is applied to the blade, a handsaw frame should be completely rigid and is usually made from heavy-gauge steel. The narrow, continuous blade is tensioned by a device that compensates for slight variations in blade length, and must be fitted and tensioned correctly for best performance. If you allow the blade to become blunt, you will need more effort to push the timber through the saw. It then becomes more difficult to cut to a line and there is a greater chance of the blade breaking. Fitted with a suitable blade, a band saw can also be used to cut nonferrous metals and plastics.
The table on a band saw may be cast iron or alloy. You can move a rip fence across this and lock in position for straight cutting. Most tables also have a slot in which you can slide a mitre fence. Used for crosscutting, you can lock it at various angles for mitre sawing via a protractor scale. For bevel cuts, you can tilt the table by releasing a lever underneath.
Some small hobby band saws may have three band wheels, although most machines have two larger diameter ones. Three wheels increase throat capacity and therefore the cutting width, but there is a greater tendency for the blade to snap. Rubber or cork tyres on the band wheels are usually cambered, and provide grip for the blade.
You raise or lower the upper guide mechanism according to the depth of timber being cut. It incorporates a blade guard and should be lowered to just above the work piece. You then position guide blocks either side of the blade to keep it running in line. A thrust wheel behind the blade rotates to take up the pressure when sawing.
Motor and Controls
Fitted at the back of the machine, the motor powers the lower band wheel, usually via a drive belt. Band saws may be single, two-speed or variable. There is a simple push button to activate the saw and a separate stop button.
Important dimensions on a band saw include the height under the guides when fully raised. In theory, this is the maximum thickness, or width, of timber that you can saw. Most small band saws should really be restricted to cutting timber of no more than about 102-152 mm (4-6 in). Bigger, more powerful machines may have a depth capacity of up to 406 mm (16 in), although 254 mm (10 in) is more common. The other critical dimension is the throat capacity. This is the distance from the blade to the pillar of the band saw. A throat of about 380 mm (15 in) is usually adequate for most cutting operations in a small workshop.
How To Fold A Band Saw Blade
1 Wearing suitable gloves, grip the blade with both hands palms outwards. Hold it down with one foot, blade teeth facing outwards.
2 Form a loop in the blade by turning your hands in towards each other.
3 Form three coils in the blade by crossing it over and allowing it to fall to the floor.
Some band saws will accept blades as narrow as 3 mm (1/8 in), for cutting radii as tight as 10 mm (3/8 in). Big machines may take blades as wide as 38 mm (1½ in), ideal for re-sawing deep, heavy timber. For general sawing, a width of 12 mm (½ in) is a good choice, capable of cutting radii of 64 mm (2½ in).
Blades are available in two types: normal and skip tooth. Regular or triangular tooth pattern is common above 10 tpi, where less wood is removed. A skip tooth has a wide, shallow gullet with plenty of space for waste to accumulate, more suitable for cutting dry hardwood. Bimetal steel blades have teeth hardened by heat, producing harder tips and longer life. The rear of the blade is untreated and so more flexible. Standard steel teeth can be re-sharpened many more times than bimetal versions, although the time involved makes this uneconomical on small blades. Owing to their hardness, bimetal teeth cannot be reset.
Adjusting The Band Saw
Place the blade over the band wheels and tension using a knob at the back of the machine. The blade should run approximately central on the band wheel. Known as tracking, adjust this by turning the knob at the rear of the top band wheel. Check by rotating the band wheel by hand with the door open. Once the blade is tracking correctly, adjust the guides above and below the table. They should support the blade but not rub against it. Paper thickness is sufficient clearance. Check these adjustments each time a blade is replaced.
Word Discription :
Gullet The valley between two teeth points. tpi teeth per inch (25 mm)
Trunnion A casting on which the band-saw table is mounted, enabling it to tilt; usually has a protractor scale to set the angle accurately.