Holding tools (other)
Nuts & bolts
Layout & testing
Layout, using paterns
Lumber & lumbering
Measuring with rule
Nails for woodwork
Structure of wood
Try square usage
The metalworker uses
a hacksaw for cutting metal just as the carpenter uses the crosscut
and ripsaws for cutting lumber. The hacksaw consists of a rigid
frame with replaceable saw blades.
The frame may be solid or adjustable.
An adjustable frame, since its length can be changed, will take
blades of various lengths. A solid frame takes a blade of just one
Selection of grades of hacksaw blades
Hacksaw blades are made of tool steel,
properly tempered. The all-hard type is hardened throughout; only
the teeth are hardened in the flexible type.
Blades range in length from 6"
Length is the distance between the two holes,
one near each end of the blade. The blade is mounted on the frame by inserting
the frame pins (on each end) in the blade holes. Blades are from 7/16”
to 9/16" wide and are 0.025" thick. They contain from 14 to
32 teeth per inch. (The number of teeth per inch is called "pitch
Hacksaw frames are so constructed that the
blade can be attached parallel to the frame or at right angles with the
Direction of teeth with relation of cutting
If the teeth of any saw are just as thick
as the rest of the saw, there is no clearance for moving the saw through
the material; there is no space for the chips to come out. The result
is that the saw binds. Therefore there must be a set to the teeth of the
hacksaw blade. This set consists of a slight bend to the teeth so that
they are at a small angle to the rest of the blade. With the teeth thus
set, the saw makes a cut a trifle wider than the rest of the blade.
Hacksaws have three kinds of set: alternate,
raker, and undulated. With alternate set, every other tooth is slightly
bent to one side and all the other teeth are slightly bent to the opposite
side. In a raker set, every third tooth remains straight, or unbent. The
other teeth are bent as they are in alternate set. When the set is undulated,
short sections of teeth are bent in opposite directions, the teeth in
each section gradually increasing and decreasing in degree of bend.
In choosing the correct blade for the particular
job, there are two main considerations: (1) Should it be all-hard or flexible,
and (2) what should the number of teeth per inch (pitch) be? The answers
- For brass, tool steel, cast iron, rails,
and other stock of heavy cross section, use the all-hard blade.
- Use a flexible blade for hollow shapes
and metals of light cross section, such as channel iron, tin, tubing,
copper, babbitt, and aluminum.
- Use a coarse pitch, such as 14 teeth
per inch, on machine, cold-rolled, or structural steel.
- Use an 18-tooth blade on solid stock,
aluminum, tool steel, babbitt, high-speed steel, cast iron, and the
like. In fact, this pitch is for general use.
- For tubing, tin, copper, brass, channel
iron, and sheet metal of over 18 gage, use blades with 24 teeth per
- For thin-wall tubing, conduits, and sheet
metal thinner than 18 gage, use blades with 32 teeth per inch.
Using the hacksaw
- Select the proper blade, as explained
in the previous section.
- Mount it tightly in the frame.
- Mark the stock where it is to be cut,
with a scriber, pencil, or soapstone. If high accuracy is required,
mark the place with a file cut. This can be used to start the saw.
- Grip the work tightly in the vise so
that the place of cutting will be very near the jaws of the vise.
- To prevent marring the work by the clamping
of the vise jaws, wood or a softer metal should be placed between the
work and the jaws. To hold oval or circular work in a square-j aw vise,
filler pieces of wood, leather, or copper should be used to grip the
work and prevent scarring. Be sure that metal fillers are bent down
over the. jaws of the vise out of the way of your fingers.
- Expose as much surface as possible of
any odd-shaped work, so that a corner can be cut gradually, not sharply.
In this way, a maximum number of teeth can engage the work at one time.
- Start hacksaw cuts by having the blade
almost parallel to the surf ace along which the cutting is to be done
— never at a broad angle to it.
- The teeth of the blade should always
point toward the work and away from the worker. Mounting the blade in
the frame in this manner makes the cutting take place on the pushing
motion, away from the body.
- At the end of the pushing motion, relieve
the pressure on the saw, lift it slightly, and then draw the blade straight
back. Never saw f aster than 60 strokes per minute.
- After starting the cut with a number
of short strokes, make all other strokes as long as possible without
banging the saw frame against the work.
- Always keep the blade at the same angle.
Changing the angle will bind the blade in the cut and prevent its being
- In cutting very thin metal, place the
work between two pieces of wood or soft metal or against one piece of
thick wood alone. Cutting through this assembly prevents chattering,
produces a smoother cut, and avoids damage to the material.
- To make a cut deeper than the frame,
turn the blade sideways.
- When the work is nearly cut through,
raise the saw slightly to prevent the teeth from catching.
- Do not bear too hard on the cutting stroke.
The strain may break the blade, and when the pressure is suddenly removed
the blade or material may jab into your hand.
- Keep the blade cutting in the same direction
all the time. Twisting the blade may break it and result in an accident.
- Do not use a blade with broken teeth,
for they prevent smooth sawing strokes. When the jagged part of the
broken teeth hits the work, the saw may jump out of the cutting groove
and throw you off your balance.
- If the work is not held tightly in place,
it may slip and break the saw blade.
- Slow up the last few cuts. Towards the
end, the saw may cut through suddenly and let your hands hit on the
sharp edges of the metal.
- When using filler pieces of metal in
a vise to prevent scarring the work, be sure that they are bent down
over the vise jaws. Jagged edges sticking up in the air may cut your
Just as the woodworking shop has its circular
saw, so the metal shop has its power hacksaw. The power hacksaw does all
the work just described for hand hacksaws, but does it more efficiently
and more quickly. The power hacksaw is found in every machine shop except
the very smallest. It is used for cutting up bar stock, tubing, pipe,
and similar metal forms.