What is a hacksaw?
A hacksaw is a fine-toothed saw, originally and mainly made for cutting metal. The equivalent saw for cutting wood is usually called a bow saw. Most hacksaws are hand saws with a C-shaped walking frame that holds a blade under tension.
Such hacksaws have a handle, usually a pistol grip, with pins for attaching a narrow disposable blade. The frames may also be adjustable to accommodate blades of different sizes. A screw or other mechanism is used to put the thin blade under tension.
On hacksaws, as with most frame saws, the blade can be mounted with the teeth facing toward or away from the handle, resulting in cutting action on either the push or pull stroke. In normal use, cutting vertically downwards with work held in a bench vise, hacksaw blades are set to be facing forwards.
A hacksaw is a hand-powered, small-toothed saw used for cutting metal pipes, rods, brackets, etc. Hacksaws can also cut through the plastic. The hacksaw has a U-shaped frame and a handle at one end. Hacksaws have small pins at each end of the frame that receives a blade.
A tensioner nut or knob is then used to extend the length of the frame, which puts tension on the blade and locks it in place. The blade can be installed to cut on either the push or pull stroke; cutting on the push stroke is more common.
Here are the basic parts:
- Tensioner knob
- Blade tensioner
- Blade Pins
Many hacksaws have a two-part adjustable frame and a pistol grip handle.
Hacksaws are used by plumbers to cut pipes and occasionally by electricians to cut conduits. The hacksaw got its name because historically these saws did not cut smoothly. However, developments in tooling have improved the cutting precision of the hacksaw.
These days, most pros cut metal parts with a reciprocating saw, but they keep hacksaws on hand for jobs that need a more delicate touch.
A hacksaw is a fine-tooth saw with a blade under tension in a frame, used for cutting materials such as metal. Hand-held hacksaws consist of a metal frame with a handle, and pins for attaching a narrow disposable blade. A screw or other mechanism is used to put the thin blade under tension.
Standard hacksaw blade lengths are 10 to 12 in (250 to 300 mm). Blades can be as small as 6 in (150 mm). Powered hacksaws may use large blades in a range of sizes, or small machines may use the same hand blades.
The pitch of the teeth can be from fourteen to thirty-two teeth per inch (TPI) for a hand blade, with as few as three TPI for a large power hacksaw blade. The blade chosen is based on the thickness of the material being cut, with a minimum of three teeth in the material.
As hacksaw teeth are so small, they are set in a “wave” set. As for other saws they are set from side to side to provide a kerf or clearance when sawing, but the set of a hacksaw changes gradually from tooth to tooth in a smooth curve, rather than alternate teeth set left and right.
Hacksaw blades are normally quite brittle, so care needs to be taken to prevent brittle fracture of the blade. Early blades were of carbon steel, now termed ‘low alloy’ blades, and were relatively soft and flexible.
They avoided breakage, but also wore out rapidly. Except where cost is a particular concern, this type is now obsolete. ‘Low alloy’ blades are still the only type available for the Junior hacksaw, which limits the usefulness of this otherwise popular saw.
For several decades now, hacksaw blades have used high-speed steel for their teeth, giving greatly improved cutting and tooth life. These blades were first available in the ‘All-hard’ form which cut accurately but was extremely brittle.
This limited their practical use to benchwork on a workpiece that was firmly clamped in a vice. A softer form of high-speed steel blade was also available, which wore well and resisted breakage, but was less stiff and so less accurate for precise sawing.
Since the 1980s, bi-metal blades have been used to give the advantages of both forms, without risk of breakage. A strip of high-speed steel along the tooth edge is an electron beam welded to a softer spine. As the price of these has dropped to be comparable with the older blades, their use is now almost universal.
The most common blade is the 12 inches or 300 mm length. Hacksaw blades have a hole at each end for mounting them in the saw frame and the 12 inches/300 mm dimension refers to the center-to-center distance between these mounting holes.
The kerf produced by the blades is somewhat wider than the blade thickness due to the set of teeth. It commonly varies between 0.030 and 0.063 inches / 0.75 and 1.6 mm depending on the pitch and set of the teeth.
Types of Hacksaw Blades
Following are the main types of hacksaw blades:
- Course Grade Hacksaw Blade
- Medium Grade Hacksaw Blade
- Fine Grade Hacksaw Blade
- Superfine Grade Hacksaw Blade
- Ail Hard Blade
1. Course Grade Hacksaw Blade
Hacksaw blade of this grade is used for cutting thickness of mild steel, copper, aluminum, and brass, etc. It contains 14 to 18 teeth per inch.
2. Medium Grade Hacksaw Blade
Hacksaw blade of this type is used for cutting all kinds of metals such as cast iron, tool steel, aluminum, brass, high carbon steel, etc. From 20 to 24 teeth per inch are cut in this hacksaw blade.
3. Fine Grade Hacksaw Blade
This type of hacksaw blade is mainly used to cut thin pipes, sheets, tubes, etc. It has 24 to 30 dents per inch.
4. Superfine Grade Hacksaw Blade
For cutting extraordinary solid metals and thin metal sheets, a thin type of hacksaw blade is used. There are 30 to 32 dents per inch in this type of hacksaw blade.
In all the hacksaw blades of various grades mentioned above, teeth are cut on one or both edges. These blades are hardened in two different processes and these depend on their nature.
5. Ail Hard Blade
Blades of this nature are hardened and tempered only except for the ends having holes. These are used for cutting articles cast iron or mold iron etc.
6. Flexible Blade
In blades of this nature only the cutting teeth and nearby part it hardened and tempered. But this process becomes elastic and there is less risk of their being broken in the event of a shock. These blades are used for cutting thin sheets, pipes, curves, etc.
How is a hacksaw used?
Hacksaws were originally and principally made for cutting metal, but can also cut various other materials, such as plastic and wood; for example, plumbers and electricians often cut plastic pipe and plastic conduit with them.
The basics of operating a hacksaw:
- Be sure that the blade is tightened and tensioned
- Mark the pipe or conduit at the appropriate length
- Line up the blade with the mark
- Draw the saw back and forth on the mark
Tips for using hacksaws
- Wear appropriate work gloves and safety glasses
- Be aware of burs and sharp edges during and after sawing
- Selection of hacksaw blade should be done according to the metal for which it is to be used.
- While fixing the blade on the frame it should be ensured that its teeth should cut the metal when they are driven forward.
- The job should be held in the vice in such a way that its cutting lines are clearly visible.
- Before starting a cut with a hacksaw blade, the blade should be kept on the marking line, the left-hand thumb should be placed with its support as shown in fig. It would ensure that the blade would move only on the line there would be no risk of its slip.
- After marking with the support of thumb we should hold the handle with right-hand palm and fingers and with the left-hand palm and fingers, we should hold the other end of the hacksaw frame as shown in fig.
- You should stand on the left hand of the vice and keep your right foot backwards and the left foot a little ahead of the right.
- Contact between the blade and the job should be in such a way that at least two teeth should remain in contact with the surface of the job.
- The speed of operating hacksaw should be 40 to 50 strokes per minute.
- Pressure should be exerted on the forward stroke and it should be withdrawn on backward stroke.
- Before finishing cutting with a hacksaw the cutting speed should be slowed down.
What are the Differences Types of Hacksaws?
- Some hacksaws can hold both 10-in. and 12-in. blades
- There are 6-in. hacksaws available
- Handle styles vary
- Compact/mini hacksaws consist of just a handle and a blade, similar to a knife
- Tensioner mechanisms vary
- Some hacksaws can pivot the blades to a 45° angle to allow for flush cuts
Precautions of Using Hacksaw
Following are the precautions of using hacksaw:
- Hacksaw blade should be fitted on the frame very carefully. It should not be very tight nor very loose.
- The job which is to be cut should not be held in a vice much high otherwise there would be vibrations in it.
- While cutting thin metal sheet, packing of wood, plastic or any other appropriate material should be used in its front and back.
- Hacksaw blade should not be allowed to become slanting while using a hacksaw. If it becomes slating, there are chances that it may break.
- If the blade starts cutting in a slanting manner, we should start a fresh cut. Operating a hacksaw in an old cut may break it.
- If a blade gets broken while working, then we should replace it with a blade which has been used almost for the same period rather than using a brand-new blade. The new blade can break if it is operated in that old slot.
- If necessary, water should be used as a coolant.
- After using a hacksaw either its blade should be taken out or it must be made loose.