The hacksaw

The hacksaw is used to cut metal. Where large amounts of waste metal have to he removed, this is more easily done by hacksawing away the surplus rather than by filing. If the workpiece is left slightly too large, a file can then be used to obtain the final size and surface. 

The hacksaw blade fits into a hacksaw frame on two holding pins, one of which is adjustable in order to tension the blade. The hacksaw frame should be rigid, hold the blade in correct aligmnent, tension the blade easily and have a comfortable grip. 

The blade is fitted to the frame with the teeth pointing away from the handle. Fig. 2.5, and is correctly tensioned by turning the wing nut to take up the slack and then applying a further three turns only. A loose blade will twist or buckle and not cut straight, while an overtightened blade could pull out the ends of the blade. 

The standard hacksaw blade is 300 mm long x 13 mm widex0.65mm thick and is available with 14,18, 24 and 32 teeth per 25 mm i.e. for every 25 mm length of blade there are 14 teeth, 

A hacksaw blade should be chosen to suit the type of material being cut, whether hard or soft, and the nature of the cut, whether thick section or thin. Two important factors in the choice of a blade are the pitch, or distance between each tooth and the material from which the blade is made. 

---

Use the hacksaw and file to round off corners of the side plates and cut off excess material. 

Tubing cutter - not necessary but handier than the hacksaw for cutting drain pipe. The hacksaw Is still needed for other cutting. 

The barrel Is composed of a steel liner 3/8 00 and an aluminum outer sleeve that Is 3/4 OD at the mark. You want to cut through the outer barrel only, so draw a line on the hacksaw blade 3/16 above the teeth. Cut the barrel at the file mark, rotating It as you go, until the entire cut is 3/16" deep. If you saw slowly, you can feel when you reach the steel liner,... 

The liner Is epoxied Into the outer barrel, so you remove it by heating the outer barrel with the torch, expanding it and breaking the epoxy bond. (Epoxy breaks down at about 300 ) Clamp the rear of the barrel in the vise, and use the vise grips or large pliers to slowly twist and pull the outer barrel section off the liner. If it won t turn when heated, go back to the cut, remark the hacksaw blade and find the spot that is not completely cut through. Go easy when removing the outer barrel, it s easy to bend the inner liner. 

The shaft collar is now installed on the barrel. The outer barrel Is tapered it measures about 3/4 00 at the hacksaw cut and is about 1/16 larger. V back (2 from the rear of barrel). Carefully file this V wide area until the shaft collar will snugly slip over the outer barrel and rest flush with it. The collar Itself... 

A. Using the hacksaw and padded vise cut the scope mount as shown in Fig. II. Sand all rough edges smooth. 

Separating Tools Once layout is complete, the material must be separated. Common hand separating tools either remove chips (for example, a saw) or shear the material (for example, a pair of scissors) (see Figure 8-14). Common handsaws include the handsaw, the hacksaw, the coping saw, and the hacksaw. We can cut thick metal with a hacksaw, and we can shear thin metal with aviation... 

Like a file, the hacksaw cuts on the forward stroke, which is when pressure should be applied. Pressure should be released on the return stroke. Do not rush but use long steady strokes (around 70 strokes per minute when using high-speed-steel blades). The same balanced stance should be used as for filing. 

Tube cutter. The tube (or pipe) cutter is a specialized cousin of the hacksaw. It s not as versatile, but it does the job of cutting copper pipe so much more efficiently that it s worth adding to your kit. A tube cutter can look like a wrench with a pizza-cutter-like tooth, or it can be a clamp with the same round blade. Either way, the tube cutter fits around a pipe and you spin it, making a clean slice. Expect to pay about 20. 

Figure 12 shows, for each trial configuration, the variations in the tool wear coefficient, according to the thickness being cut. Wear in the hacksaw blade and the plasma torch nozzle are too small to be shown. 

The plasma torch is the most rapid tool from 500 to 600 mm of cut per minute in 10 mm thick steel, while the hacksaw is the slowest about 10 mm of cut per minute in 10 mm steel. The power requirement of the hacksaw is less than one tenth that of the plasma torch. 

Since the wear on the hacksaw blade and on the nozzle of the plasma torch are very low, they may be taken as negligible. The trials have thus not provided an indication of the lifespans of these two tools. 

Grain size distributions are bimodal for the hacksaw, the grinder and the arc air. 

The hacksaw is the slowest tool and shows little tool wear but is not suitable for thicknesses of more than 30 mm, particularly in stainless steel... 

The hacksaw produces the largest aerosols, minimum diameters being around one tenth of a micrometre (compared to a few hundredths of a micrometre for the four other tools) and the first peak being around 1 micrometre (compared to a few hundredths of a micrometre for the other four tools). 

---