Hacksaw

How it works

The blade is narrow and thin and is held straight by tension in the frame. Disston’s 1916 history states that in use the hack saw blade is strained in a frame, and describes frames with a solid steel back, frames with extension backs for blades of different lengths, and frames in which the blade can be turned at a right angle.

The teeth are fine so that several are always in the cut. CCOHS tells the user to select a blade for the material, to secure it with the teeth pointing forward and tighten the nut until the blade is under tension, to cut with steady strokes directed away from the body using the entire length of the blade, and to use light machine oil to keep the blade from overheating and breaking. Blade pitch is given in teeth per inch; Disston’s 1926 catalog gave 18 points for steel and light angle iron, 24 for brass, copper, drill rod, iron pipe and sheet metal, and 32 for tubing and metal thinner than 22 gauge.

Anatomy

Frame: Solid or adjustable steel bow. Disston’s 1926 No. 36½ extension frame is adjustable by half inches for blades 8 to 12 inches long, and its No. 110 adjustable frame takes blades of 8 to 12 inches.
Handle: Hardwood on Disston’s 1926 frames; pistol-grip and straight forms are not sourced here.
Sockets and pins: The blade ends hook over pins in sockets; Disston’s 1926 sockets are riveted and reversible, so the blade can be turned to cut sideways.
Tensioning nut: A wing nut or knob on the frame draws the blade tight (CCOHS).
Blade: Narrow, with teeth on one edge. Disston’s 1916 history says blades are 6 to 16 inches long, some hardened throughout and others on the tooth edge only, leaving the back soft.

Variants

Hand hack saw (unframed): Disston’s 1926 catalog describes a longer blade held in a handle, for structural ironworkers and others where the framed saw cannot be used because of the limit on depth of cut. It is 12 points to the inch, 10 to 30 inches long, hollow ground, and requires no set.
Rail hack saw: Disston’s 1916 history describes a frame 9 to 18 inches deep from tooth edge to back, used in construction work for cutting steel rails and beams.
Hollow-ground blade: A blade ground concave so that it runs without set; Disston’s 1916 history says Disston made it before about 1866 and that it was still used where accuracy was wanted.

Specifications

Blade length · in: 12Disston’s 1926 frames take blades of 8 to 12 inches.
Teeth per inch · tpi: CCOHS gives 18 to 32 tpi for thinner metals or plastic up to 1/4 inch.

Made to

ISO 2336-1
BS 1919

Safety and care

Safety

Wear safety glasses or goggles (CCOHS, hand saw guidance).
Do not apply too much pressure on the blade, because it may break (CCOHS).
Do not twist the saw while applying pressure (CCOHS).
Do not use the saw when the blade becomes loose in the frame (CCOHS).
Clamp thin, flat pieces that require edge cutting (CCOHS).

Care

Keep blades clean and lightly oiled (CCOHS).

Tips

Pitch is counted in points, and points are one more than teeth
Disston’s 1926 catalog states hack saw pitch both ways: 18 points or 17 teeth to the inch for steel, light angle iron and hard metals, 24 points or 23 teeth for brass, copper, drill rod, iron pipe and sheet metal, and 32 points or 31 teeth for tubing and metal thinner than 22 gauge. The two numbers describe the same blade.1
Finer blades for thinner metal
Disston’s 1926 table assigns the finest pitch to tubing and metal thinner than 22 gauge. CCOHS gives a coarse blade of 2 or 3 tpi for thicker stock and 18 to 32 tpi for thinner metals or plastic up to a quarter inch.1 2
Turn the blade to cut sideways
Disston’s 1926 frames have riveted sockets that are reversible, so the blade can be set at a right angle to the frame for sawing sideways. The stretchers are reversible and do not fall out while the blade is readjusted.1
Do not set the teeth of a hand hack saw blade
Disston’s 1926 catalog says its hand hack saw is hollow ground for clearance, requires no set, and that an attempt to set the teeth may break them. The clearance comes from the grind instead of from bending the teeth.1
Set in groups of teeth to keep the blade from binding
Clemson’s 1898 patent bends the cutting edge alternately in opposite directions in rectangular bends, each bend extending over several teeth. He states that this reduces friction, stiffens the blade at its cutting edge so it is less likely to break, and prevents the binding that wear would otherwise cause.1

History

Earliest documented

1770 (English catalogs, as reported in 1916)

England

Disston’s 1916 history says the actual beginning of the hack saw does not seem to have been recorded, that there is a tradition that the first was made in Ireland, which the company treats as a rumor, and that old catalogs show complete hack saws were made in England in 1770, by which time the industry was well established. The catalogs are not identified.1

The origin of the hack saw is not documented in the sources read. Disston’s 1916 history says so directly: the beginning does not seem to have been recorded, an Irish origin is a tradition that the company dismisses, and English catalogs show complete hack saws in 1770. The same history calls the fret saw the forerunner of the hack saw, which links the metal-cutting frame saw to the lighter frame saws used for fine ornamental work.

The early blades were imported and made for resharpening. The 1916 history says they were polished like butcher saw blades, and reports that the old English blade was thick, coarsely toothed, with little set, slow-cutting and heavy to work. Disston records its own hollow-ground blade of crucible steel from before about 1866, which ran without set, and the arrival in the early 1880s of cheap, very hard blades that were discarded rather than sharpened.

Blade hardness and breakage have been the central problems since. Clemson’s 1898 patent names breakage and binding as the problems and addresses both with a corrugated set of rectangular bends covering several teeth. Disston’s 1916 text notes that some blades were hardened throughout and others on the tooth edge only with the back left soft.

Demand grew with the use of metal in building. Disston’s 1916 history describes older practice of shaping metal by forging, shearing and filing, and says hand hack saws and circular saws made it possible to employ metals in the trades at a nominal cost; it credits the frame hack saw and machine saw with almost entirely replacing nicking and breaking and cutting off in a lathe.

Standardization came in the twentieth century. BSI issued BS 1919 for hacksaw blades in 1953, and later versions covered hand and machine blades. These records show the standards and their dates but the standards’ texts were not read.

Timeline

1770
Old English catalogs, according to Disston’s 1916 history, show complete hack saws being made.1
before 1866
Henry Disston is making a hollow- or concave-ground hack saw blade of crucible steel with milled teeth; the 1916 history places this “over fifty years” earlier.1
early 1880s
The first hack saw blades somewhat like those of 1916 are made, cheap and hard, and are thrown away when dull because they cannot be refiled (Disston’s 1916 account).1
1898
George N. Clemson of Middletown, New York, is granted US Patent 601,947 for a hack-saw blade with a cutting edge bent alternately in opposite directions in rectangular bends spanning several teeth, to reduce friction, stiffen the blade and prevent binding.1
by about 1891
Disston’s 1916 history says the first hack saw blades for power machines were made in its plant at least a quarter of a century earlier, for the building of the Philadelphia City Hall tower and the Congressional Library.1
1916
The Saw in History describes the frame hack saw, rail hack saw and hand hack saw, and says the frame hack saw and machine saw have almost entirely supplanted the old methods of nicking and breaking or cutting off in a lathe.1
1926
Disston’s catalog lists the No. 36½ extension frame, the No. 110 adjustable frame, Chromol blades and a hand hack saw of 12 points to the inch, with the pitch table by material.1
1953
The British Standards Institution publishes BS 1919, Hacksaw blades, on 5 January 1953; it was withdrawn on 28 September 1967.1
1993
BSI publishes BS 1919-1:1993, Hacksaw blades: Specification for hand and machine hacksaw blades, on 15 November 1993; the record lists it as withdrawn.1

Where the sources disagree

Where and when was the hack saw first made?

There is a tradition that the first was made in Ireland; the company regards it as a probable rumor.1
Tradition as reported and dismissed by Henry Disston & Sons, The Saw in History (1916)
Old catalogs show complete hack saws made in England in 1770, by which time the industry was well established, so the exact origin cannot be located.1
Henry Disston & Sons, The Saw in History (1916)

Gaps in the record (9)

The English catalogs of 1770 that Disston cites are not identified and were not located; Disston’s 1916 history is a company publication and the only source for the early history.
The introduction of high-speed steel and bi-metal blades, the dates and inventors of the hard-edge spine blade, and the origin of the modern pistol-grip frame were not located from fetched sources.
No museum object record of an early hacksaw was found; the Science Museum Group search returned only surgical saws.
The text of BS 1919 was not read; the standard slugs are guesses at how they will be indexed. BS 1919-2:1995, reported in a search snippet as the current cutting-performance part, was not fetched.
Disston’s 1926 pitch table is read from an OCR scan with the first row missing; the 18, 24 and 32 point rows are legible.
Etymology of the word hacksaw was not sourced: Online Etymology Dictionary returned 403, and dictionary.com gives a 1645–55 first record that was not checked.
Removed for sourcing: the tips on checking blade wear by fingertip and on tightening the wing nut and orienting the blade, the junior hacksaw variant, the blade-change safety and replacement-interval items, and the 18/24 tpi general-workshop note, all of which cited Tameson, an industrial supplier; no manufacturer or other acceptable source for them was reached (the Stanley support page on blade changes returned 403).
Removed for sourcing: the 1996 timeline event and the specification note for ISO 2336-1:1996 (300 mm hand blades, pitch up to 1.4 mm), which cited a Genorma standards-reseller listing; the iso.org page is blocked from this machine and no other ISO-run page was reached. The standard slug remains listed.
No independent test data has been located, so buying is null.