Worm-drive saw

How it works

The motor shaft lies in the plane of the blade and carries a worm, a screw-shaped gear. The worm meshes with a worm wheel on the arbor, which is set at a right angle to the motor shaft. Wodack and Haas described exactly this in their 1926 application for a portable circular saw: a saw arbor at right angles to the motor shaft, a worm gear on the arbor, and a worm on the shaft meshing with it.

The gear set turns the drive through a right angle between the motor shaft and the arbor. The gears run in an oil bath that, according to Fine Homebuilding, provides cooling and lubrication; the oil becomes contaminated with use and must be changed. SKIL describes its current 8-1/4 inch saw as having a high-torque motor and precision-machined worm-drive gears, which are the company’s claims.

Because the motor lies behind the blade, the saw is long and narrow and is held with the rear handle. A 2002 trade-magazine history reports that inline saws weighed from 13 pounds to almost 17 pounds, against 9 or 10 pounds for a typical sidewinder.

Anatomy

Motor: Mounted behind the blade, its shaft parallel to the plane of the blade.
Worm and worm wheel: Gear pair that connects the motor shaft to the arbor at a right angle (Wodack and Haas, 1926).
Gear housing and oil fill: Holds the oil bath. On the saws Fine Homebuilding describes, the spindle lock and oil filler share a plug that a one-half inch wrench removes, and the Skilsaw gearbox is filled to the bottom of the threads of the fill hole.
Arbor and blade: The blade sits at the left of the housing, which AskToolTalk says lets a right-handed user see the blade and the line of cut.
Rear handle and trigger switch: The saw is carried and guided from the rear handle.
Shoe, depth and bevel adjustments, lower guard: As on any circular saw; see the entry for the circular saw.

Variants

Skilsaw Model E and Model 77: AskToolTalk says the worm-drive Model E was manufactured until 1939 and that Edward Sterba built the first Model 77, with a 7-1/4 inch blade, in 1937. The Journal of Light Construction says the 77 accounts for nearly 90 percent of the worm-drive market.
Magnesium-housing worm drive: The Journal of Light Construction reported in 2002 that Skil had explored magnesium housings to reduce the weight of the 77. Fine Homebuilding refers to the Skilsaw 77 and Mag 77.
8-1/4 inch worm drive: SKIL lists an 8-1/4 inch aluminum worm-drive saw with a 60 degree bevel.
Hypoid inline saw: Motor behind the blade with a sealed hypoid gear train. The Journal of Light Construction credits Makita with pioneering hypoid gearing in an inline saw in the 1970s; DEWALT’s inline saws use it. Fine Homebuilding says hypoid and sidewinder saws have sealed bearings and need no oil service.

Specifications

Blade diameter · in: 7-1/4The Model 77 pattern; SKIL also lists an 8-1/4 inch worm-drive saw.
Weight · lb: 13 to 17Inline saws surveyed by the Journal of Light Construction in 2002; the survey does not separate worm-drive from hypoid models.
First oil change · hours of use: 10Ridgid and Skilsaw both said so to Fine Homebuilding in 2018. After that Ridgid said every 50 hours and Skilsaw said yearly.

Made to

UL 62841-2-5
IEC 62841-2-5
OSHA 1910-243

Safety and care

Safety

OSHA 29 CFR 1910.243 requires guards above and below the shoe on every portable circular saw with a blade larger than 2 inches, which includes worm-drive saws.
The kickback and guard precautions in DEWALT’s circular-saw manual apply to a worm-drive saw as to any other; see the entry for the circular saw.

Care

Change the gear oil after the first 10 hours of use. Ridgid then says every 50 hours, and Skilsaw, maker of the 77 and Mag 77, says every year (Fine Homebuilding, 2018).
To change the oil, run the saw free for about three minutes to warm the oil, remove the spindle lock and oil filler plug, tip the saw on its side and pour the oil into a container for recycling, then refill to the level the maker specifies (Fine Homebuilding).
Use the oil the maker names. Skilsaw offers its own; Ridgid says to use Mobil SHC 636 synthetic oil (Fine Homebuilding).

Tips

Find out which gearing the saw has before servicing it
A true worm-drive saw has an oil-bath gearbox that needs periodic oil changes. Hypoid saws and sidewinder saws have sealed bearings and need no such maintenance, according to Fine Homebuilding.1
Fill to the bottom of the threads of the fill hole
Fine Homebuilding reports that a Skilsaw gearbox is filled to the bottom of the threads of the fill hole. Ridgid’s saw has a sight glass for checking the level.1
Do the first oil change early
Both Ridgid and Skilsaw told Fine Homebuilding to change the oil after the first 10 hours of use. Because most cuts take seconds, the magazine notes that this is a longer service interval than it first appears.1
Use the worm drive for thick non-ferrous metal, at slow speed
Skil’s 1959 catalog lists blades for slitting copper, brass and thin aluminum, and says that for cutting thick metals the blades should be used with its Super-Duty (worm-drive) saws, preferably at slow speeds. It gives its ferrous-metal friction blades only for the Model 77 or larger.1
The blade is on the left to keep the line of cut in view
According to AskToolTalk, the worm-drive saw keeps the blade on the left so that the user can see the blade and the line of cut; the sidewinder’s motor first stood to the right of the blade and was moved to the left because of its weight.1

History

Earliest documented

1 June 1920

Hahnville, Louisiana

Ernest Hubert Madere’s US patent 1,342,294, filed 24 July 1919 and issued 1 June 1920, describes a hand-controlled rotary cutter for sugar cane with a motor on the handle, a flexible shaft, and a worm meshing with a worm wheel on the cutter shaft. The patent also names butchering uses, including slicing meat and sawing bones.1

A worm gear was part of the portable saw before the saw existed. Madere’s 1920 patent, written for cutting sugar cane in Louisiana, puts a motor on the handle and drives the cutter through a worm and worm wheel in a casing. The gear lets the motor lie along the handle while the blade turns in a plane that contains the motor’s axis. Michel’s 1922 application cites Madere’s patent as the device he proposed to improve.

Whether Michel’s own patent covers worm gearing is disputed in the sources. Skil staff and the Journal of Light Construction tie the machete to a worm gear and credit the patent with the first worm-drive circular saw. The text of Michel’s patent, as far as the scanned page can be read, describes gearing with a gear on the cutter shaft and a gear on the extremity of a second shaft and does not use the word worm. The first patent found in which a worm on the motor shaft drives a worm gear on the arbor of a portable circular saw is the one filed by Wodack and Haas in 1926, assigned to a Chicago company of a different name.

The Model 77 gave the type its lasting form. AskToolTalk and the Journal of Light Construction credit Edward Sterba with the first 77, in 1937, with a 7-1/4 inch blade. The company’s 1959 catalog still sold it under the heading of Super-Duty worm-drive saws, and the Journal of Light Construction reported in 2002 that the 77 held nearly 90 percent of the worm-drive market, so the pattern had persisted for at least 65 years.

Gearing also split the market geographically. The same journal says Skilsaw owned the worm-drive patent and that Porter-Cable therefore built a direct-drive saw with the motor beside the blade; the author reports that worm drives were the only saws he saw on framing sites in Colorado and New Mexico and that carpenters there called sidewinders “bowling balls,” while on the East Coast he rarely saw another worm drive except on timber-frame or commercial sites. AskToolTalk offers a different cause for the split, the location of manufacturers and the lines that distributors carried, not the preference of carpenters. The two accounts are by one author each and neither is supported by sales data in the sources read.

The Journal of Light Construction sets the worm drive against the hypoid inline saw as well as the sidewinder. Hypoid advocates, the journal reports, say that its sealed gear case needs less maintenance and runs quieter; its critics say it has less shock resistance. The journal’s author concluded that the weight and balance of a saw influence users more than the gear type does. No independent durability tests of either gear type have been located.

Timeline

1920
Madere is granted US Patent 1,342,294 for an electric hand-controlled rotary cutter with a worm and worm wheel.1
1921
Edmond Michel builds a power machete in Louisiana: a small circular blade, a motor on the handle and a worm gear, according to Skil staff and the Journal of Light Construction.1 2
1924
Michel is granted US Patent 1,512,296 (filed 23 October 1922) for a portable rotary cutting implement with gearing between the motor and the cutter shaft.1
1929
Oscar Wodack and Joseph Haas are granted US Patent 1,708,345 (filed 11 June 1926) for a portable circular saw in which a worm on the motor shaft drives a worm gear on the saw arbor.1
1929
Porter-Cable enters the circular saw market with a direct-drive saw, because Skilsaw owned the patent on the worm drive, according to the Journal of Light Construction.1
1937
Edward Sterba builds the first Model 77 with a 7-1/4 inch blade; the Model E worm-drive saw is manufactured until 1939.1 2
1941
A Model 77 sold for $105, according to AskToolTalk.1
1959
Skil’s catalog lists “Super-Duty (worm-drive)” saws and the Model 77.1
1970s
Makita pioneers a hypoid gear train in an inline saw, according to the Journal of Light Construction.1
2002
The Journal of Light Construction reports that the Skil 77 captures nearly 90 percent of the worm-drive market and describes a divide between worm-drive use in the West and sidewinder use in the East.1
2018
Fine Homebuilding reports Ridgid and Skilsaw as the makers of the two most popular worm-drive saws then on the market.1

Where the sources disagree

Did Michel’s 1924 patent cover a worm-drive circular saw?

Michel and Sullivan received a patent for the first worm-drive circular saw in 1924.1
Journal of Light Construction, 2002
Michel’s power machete had a motor connected with a worm gear on the handle, and the saw developed from it.1
Skil staff, quoted in Woodworker’s Journal
The specification of US 1,512,296 describes gearing from the motor to the cutter shaft but, in the scanned text read here, does not use the word worm. Madere’s patent of 1920 already shows a worm and worm wheel in a hand-held rotary cutter, and Wodack and Haas’s patent filed in 1926 shows a worm drive on a portable circular saw arbor.1 2 3
The patents themselves

When did the direct-drive (sidewinder) saw appear, and why?

Porter-Cable entered the circular saw market in 1929 with a direct-drive saw by Arthur Emmons, designed around Skilsaw’s worm-drive patent.1
Journal of Light Construction, 2002
Arthur N. Emmons invented the sidewinder in 1928, according to the author’s understanding; the eastern and western preferences arose from where saws were made and which lines distributors carried.1
AskToolTalk

Gaps in the record (6)

Skil’s own history pages were not readable; the Model E’s year of introduction is not sourced here.
No patent was located for the Model E, the Model 77 or Emmons’s direct-drive saw. The connection, if any, between Wodack Electric Tool Corporation and the Skilsaw company has not been established from the sources read.
The scanned text of the Michel patent is imperfect; a clean reading may change the statement about the word worm.
No independent durability tests of worm-drive, hypoid or direct-drive saws have been located, so buying is null.
Skil’s own current owner’s manual for the Model 77 could not be retrieved from a manufacturer site; the oil service figures rest on Fine Homebuilding’s calls to the makers.
The standard slugs are guesses and the standards were not read.