Drywall saw

How it works

Gypsum board is firm and resists penetration, yet it crumbles where it is sawn. Bachta’s 2002 patent states that the drywall saw therefore has offset cutting teeth that do not bind and that are adapted to remove crumbled material during sawing. His own saw has teeth set in two parallel rows in alternate sequence at 8 teeth per inch, with spillways between the teeth that pass the crumbled material.

Because a first cut from an edge of the sheet cannot make an opening in the middle of a panel, a keyhole must first be made. Bachta describes a hand saw with a sharpened point at the tip of the blade that is plunged through the board; the user then saws in the normal way from the keyhole. Klein Tools describes its jab saw in similar terms, with a beveled blade point for scoring and plunge cuts.

Anatomy

Blade: Short and rigid. Klein’s model 725 has a 6-inch blade of hardened carbon steel on a 12-inch overall tool (the company’s specification).
Teeth: Coarse, 8 teeth per inch on the Klein 725 and on the saw in Bachta’s patent. Coon’s 1995 patent describes in-line teeth with large clean-out areas between tooth pairs; Bachta describes offset teeth in two rows.
Point: A sharpened tip used to plunge through the board and to score. In Bachta’s patent the free end has a tapered cutting edge forming a pointed tip, about a 90 degree tip edge in claim 7.
Handle: Klein’s handle ends in a flat grip for palming or punching through drywall; Bachta adds a hand stop on the top of the handle that braces the hand during a plunge; Coon’s handle is two parts through which the whole blade passes.

Variants

Jab saw: The name Klein Tools uses for its model 725, described as a saw for drywall, wallboard, plywood and plastic.
Keyhole saw: The older form: Disston’s 1916 history describes a keyhole or pad saw with an adjustable blade held in a socketed handle by a thumbscrew, and Disston’s 1926 catalog lists a 10-inch keyhole saw.
Compass saw: Disston’s 1916 history describes it as having a fine tapering blade, used principally for cutting circles after a hole is made with a center-bit.
Plunge drywall saw: The saw in Bachta’s 2002 patent, assigned to Vaughan & Bushnell Manufacturing Company, with a sharpened point and a hand stop.
Folding jab saw: Klein lists a folding model beside the fixed jab saw.

Specifications

Blade length · in: 6The Klein Tools 725 is specified at 6 inches; Coon’s 1995 patent says sheet rock saws then in use were generally about 7 to 8 inches long.
Teeth per inch · tpi: 8Klein 725 and Bachta’s patent both give 8 teeth per inch.

Safety and care

Safety

Klein warns: always wear approved eye protection, never use on or near live electrical circuits, and never use the blade as a prying device.
The Gypsum Association commissioned a 2015 laboratory study of respirable crystalline silica emissions when sizing 5/8-inch Type X board, and says the study does not relieve contractors of their monitoring obligations under the OSHA respirable crystalline silica rule for construction.

Tips

Start in the middle of a panel with the point
Bachta’s patent identifies the need: when a first cut from an edge cannot do the job, an initial cut must be made through the sheet, normally with a special tool. A pointed, sharpened tip plunged against the board makes a keyhole through which the saw is then used in the normal way. Klein’s jab saw has a beveled blade point for plunge cuts.1 2
Grip with the thumb on the hand stop for the plunge, then reverse the hand to saw
In Bachta’s patent the hand grips the handle as for a striking blow with the little finger braced against the hand stop during the plunge, and in the sawing position the fingers are under the handle with the thumb pressed on the stop. Klein’s flat end is meant for palming or punching through drywall.1 2
Let the teeth clear the dust
Gypsum board crumbles when sawn, so a drywall blade has open spaces between teeth. Coon’s patent shows the fines falling to either side of the board as the saw is pushed and pulled; Bachta’s spillways pass crumbled material.1 2
Check whether the saw cuts both ways
Klein describes its jab saw blade as cutting in both directions, push and pull, and Coon’s patent aims for a saw that cuts on both the push and the pull. A saw with offset, set teeth is described by Coon as of lesser steel because the teeth must be bent and cannot be effectively sharpened.1 2
Use the tip to scribe the line
Coon’s patent sharpens the free end of the blade so that it can be used to scribe cutting lines on the boards without a second tool, and Klein describes a beveled blade point for scoring.1 2
The same saw cuts other thin sheet material
Klein lists drywall, wallboard, plywood and plastic as materials for its jab saw.1

History

Earliest documented

by 1995 (documentary); the earliest drywall saw itself has not been located

United States

Coon’s 1995 patent states that the sheet rock saws then in use were about 7 to 8 inches long, had a cylindrical handle and had offset teeth of the type shown in the 1961 Carroll patent, which is a knife for frozen food. The board itself dates to Sackett’s patent of 1894. No earlier source describing a saw made for gypsum board was found.1 2 3

The drywall saw follows the board. Before Sackett, walls were commonly finished in wet plaster over lath; IPWatchdog describes Sackett’s board as a faster alternative, and Sackett’s own 1894 patent describes board of paper and plaster in layers, three-sixteenths of an inch thick for ordinary purposes, that could be nailed to the studding. Walls & Ceilings reports that it became a replacement for wooden slat lath in many areas and that by 1916 it had evolved into a ready-to-finish panel. A saw specific to the material appears in the patent record only in the later twentieth century.

The older keyhole and compass saws were available to cut the board. Disston’s 1916 history describes the compass saw for cutting circles from a bored hole and the keyhole or pad saw with an adjustable blade, and Moxon’s 1703 text already describes a compass saw whose broad edge and thin back allow it to turn in the kerf. The compass saw needed a hole bored first. Bachta’s patent states the corresponding need for drywall, a keyhole through which the saw can enter, and meets it with a sharpened point on the saw itself.

The material set the tooth design. Bachta in 2002 and Coon in 1995 agree that gypsum board is firm but crumbles when sawn, so a saw must not bind and must clear the fines. They disagree about teeth. Bachta keeps offset teeth, in two rows at 8 teeth per inch with spillways between them. Coon, who says offset teeth cannot be made of high-grade steel because the teeth must be bent and cannot then be effectively sharpened, proposes in-line teeth in a blade thicker at the cutting edge than at the top. Each inventor’s statement of the other’s shortcomings is a patentee’s argument and has not been tested in the sources read.

The tooth pattern in use traces to a different tool. Coon attributes the offset teeth of sheet rock saws to the 1961 patent of Carroll and Whitcomb, a knife assigned to Quikut for slicing frozen foods, in which trapezoidal notches between pairs of teeth also clear the cut of fines. Coon’s own invention is described as usable as a general-purpose knife.

Today’s manufacturer’s description combines these features. Klein Tools says its jab saw has triple-ground teeth for a fast cut, cuts in both directions, has a hardened carbon steel blade, a beveled point for scoring and plunge cuts, and a flat end for palming or punching through drywall. These are the company’s claims and were not independently tested.

Timeline

1888
Augustine Sackett and Fred Kane produce Sackett Board, plaster of Paris between layers of felt paper, after unsuccessful earlier tries from 1880 (Walls & Ceilings).1
1890
Sackett files the application that issues in 1894 as US Patent 520,123 for a board of alternating paper and plaster layers to be nailed to studding as a substitute for lath and plaster.1
1894
US Patent 520,123, Inside-Wall Covering, is issued to Augustine Sackett on 22 May 1894.1 2
1909
Sackett sells his plasterboard company to United States Gypsum (Walls & Ceilings and IPWatchdog both give 1909).1 2
1916
Sackett Board has evolved into a ready-to-finish panel of paper-covered gypsum in standard 4-foot widths, after edge wrapping was introduced in 1910 (Walls & Ceilings).1
1926
Disston’s Saw, Tool and File Book lists a 10-inch keyhole saw with a handle slotted for adjusting the blade, nests of saws, and a 14-inch plumber’s compass saw blade for wood with nails; no drywall saw by that name was read in the catalog.1
1961
US Patent 2,973,578 is issued to Carroll and Whitcomb, assignors to Quikut, Inc., for a knife with two kinds of teeth for slicing frozen foods; Coon later cites this tooth type as the pattern of sheet rock saws.1 2
1995
Michael Coon is granted US Patent 5,448,833 for a hand saw with in-line teeth, a blade thicker at the bottom than the top, cutting on the push and the pull, a sharpened tip and a two-part handle through which the blade passes.1
2002
Robert P. Bachta’s US Patent 6,357,122, assigned to Vaughan & Bushnell Manufacturing Company, is issued for a plunge drywall saw with a sharpened pointed end and a hand stop.1

Gaps in the record (8)

The earliest saw made for gypsum board has not been identified; Coon (1995) is the earliest document read that describes drywall saws in use. The trade catalogs of USG, National Gypsum and the hardware makers were not located.
No drywall saw patent between 1961 and 1995 was read.
The name jab saw has no sourced origin, and the difference between a jab saw, a drywall saw and a keyhole saw is not established; Klein’s page calls the model a jab saw while its description text calls it a key hole saw.
Search results not fetched gave 1909 and 1910 for Sackett’s sale to USG; the two pages read both say 1909.
Gypsum Association guidance GA-216 on application and finishing of gypsum panel products was not read, so no cutting practice from it is stated; the Gypsum Association pages reached describe only the silica study.
Standards for the board (for example ASTM C840 on application and finishing) exist but none governs the saw; standards is empty.
Care has no sourced entries.
No independent test data has been located, so buying is null.