Concrete saw

How it works

The cutting is done by abrasive grains, not by teeth. In an abrasive wheel the grains are bonded in a composite; in a diamond wheel, according to the STIHL TS 400 manual, the wheel is steel-centered and diamond particles are embedded in its cutting edges. The wheel turns at high speed and grinds a narrow slot.

Water is fed to the wheel. STIHL says wet cutting gives a diamond wheel longer life, and OSHA’s construction silica rule requires hand-held, walk-behind and drivable saws used on silica-containing material to have an integrated water delivery system that continuously feeds water to the blade, unless the employer instead measures and limits exposure.

A hand-held saw such as the TS 400 has a two-stroke gasoline engine that drives the wheel spindle by a V-belt, a wheel guard that is adjusted to deflect sparks, dust and cut material away from the operator, and a water attachment that is included with the machine.

Anatomy

Cutting wheel: Composite abrasive wheel or steel-centered diamond wheel. The wheel must be marked for the material: STIHL lists stone, steel, asphalt and ductile iron types. An arrow on the wheel shows the direction of rotation.
Wheel guard: Adjusted so that sparks, dust and cut material are deflected from the operator and away from flammable surroundings.
Spindle and thrust washer: STIHL TS 400: 20 mm arbor; minimum thrust-washer diameter 103 mm, which sets the maximum depth of cut.
V-belt and cast arm: Drive from engine to spindle on the TS 400; STIHL stresses correct V-belt tension and tight collar nuts on the cast arm.
Water attachment: Supplies water to the wheel; included with the TS 400. OSHA 3902 describes nozzles, a hose, a pump and a water basin as typical parts of the water delivery system.
Throttle trigger, stop switch and handles: Controls that STIHL says must be checked before operation.

Variants

Hand-held cut-off saw: Engine-powered, with a 12-inch or 14-inch wheel on the STIHL TS 400 (300 or 350 mm).
Walk-behind saw: OSHA Table 1 category (iv); the compliance guide says walk-behind saws used to cut roads and pavement are most commonly used outdoors, though they can be used indoors to cut concrete floors.
Drivable saw: OSHA Table 1 category (v); Table 1 limits this entry to tasks performed outdoors.
Stationary masonry saw: OSHA Table 1 category (i); must have an integrated water delivery system that continuously feeds water to the blade.
Rig-mounted core saw or drill: OSHA Table 1 category (vi), listed separately; a tool with an integrated water delivery system that supplies water to the cutting surface.

Specifications

Wheel diameter · mm: STIHL TS 400: 300 mm (12 in) or 350 mm (14 in), 2.6 to 6 mm thick. Single model read.
Maximum spindle speed · rpm: STIHL TS 400: 5,350. The wheel’s rated speed must be at least the spindle speed.
Depth of cut · mm: STIHL TS 400 with a 103 mm thrust washer: 98.5 mm with a 300 mm wheel, 123.5 mm with a 350 mm wheel.
Engine displacement and power · cm³, kW: STIHL TS 400: 64.1 cm³, 3.2 kW (4.4 hp).
Weight · kg: STIHL TS 400: 9.1 kg with 300 mm wheel capacity and 9.3 kg with 350 mm, with water attachment and stop limiter, without wheel.

Made to

OSHA 29-CFR-1926-1153
ISO 19432
EN 13236
ANSI B7.1

Safety and care

Safety

When wet cutting is not used, wear a respirator approved by NIOSH/MSHA for the material being cut (STIHL). OSHA Table 1 requires at least an assigned protection factor of 10 for hand-held saws used more than four hours a shift outdoors, and for hand-held and walk-behind saws used indoors or in an enclosed area.
Wear eye protection with top and side protection meeting ANSI Z87.1, a hard hat and hearing protection (STIHL).
Never use circular saw blades, carbide-tipped blades, rescue blades, wood-cutting blades or toothed blades on a cut-off machine; STIHL names blade contact, thrown objects and reactive forces including kickback as the risks.
Check that the wheel’s maximum rated speed is at least the spindle speed. A wheel that is not so rated may shatter or break (STIHL).
Replace a cracked or warped wheel immediately (STIHL).
Stop the engine before putting the machine down or carrying it; the wheel keeps turning for a short while after the throttle is released (STIHL).
Respirable crystalline silica in concrete, stone, brick and mortar dust causes silicosis, an incurable lung disease, and lung cancer, according to OSHA. The silica rule sets a permissible exposure limit of 50 micrograms per cubic meter as an 8-hour average and an action level of 25.
Indoors or in an enclosed area, OSHA’s compliance guide requires employers to provide additional exhaust, as needed, to minimize the accumulation of visible airborne dust when hand-held or walk-behind saws are used.

Care

Store abrasive wheels away from direct sunlight and other heat, in a dry place with no risk of frost, because they are heat sensitive (STIHL).
Before remounting a used diamond wheel, inspect it for undercutting, flatness, core fatigue, segment damage or loss, overheating discoloration and arbor-hole damage (STIHL).
Clean dust from the powerhead regularly; dust around the carburetor can absorb gasoline and create a fire hazard (STIHL).
Check V-belt tension after one hour of operation and correct it if necessary; keep the collar nuts for the cast arm tight (STIHL).
Keep the water system working: OSHA’s compliance guide lists an adequate water supply, working spray nozzles that are not clogged or damaged, and intact hoses and connections.

Tips

Match the wheel marking to the material
STIHL notes that wheels are specially marked by material: stone (also usable for concrete, masonry, reinforced concrete and brick), steel, asphalt (also for aggregate concrete) and ductile iron. Using the wrong wheel or cutting a material it was not designed for may make the wheel shatter.1
Mount a diamond wheel with its arrow in the direction of rotation
STIHL says to fit the wheel so that the arrow on the wheel points in the direction of rotation of the spindle.1
Wet cutting makes a diamond wheel last
STIHL says diamond wheels can cut wet or dry, and that wet cutting gives the wheel a longer life. OSHA’s Table 1 makes the integrated water delivery system the specified control for hand-held and walk-behind saws.1 2
Set the guard to throw debris away from you
STIHL says to adjust the wheel guard so that sparks, dust and cut material are deflected away from the operator and cannot reach flammable surroundings.1
Check flow rate and nozzles, not just that water is present
OSHA says Table 1 specifies no minimum flow rate; water must be applied at the flow rate specified by the manufacturer, and the nozzles must work, be unclogged and undamaged, with hoses and connections intact.1
Diamond wheels are for masonry, not metal
STIHL says diamond wheels can be used for concrete, asphalt, natural stone, clay pipe and brick, and are not normally suitable for cutting metal or other materials.1
Following Table 1 replaces air monitoring
OSHA’s fact sheet says employers who follow Table 1 correctly are not required to measure workers’ exposure to silica from those tasks and are not subject to the permissible exposure limit for them.1

History

Earliest documented

reign of Khufu (Old Kingdom Egypt), per Petrie

Egypt

Petrie describes plain faces of saw cuts in syenite waste, a basalt block from Khufu’s temple, and the granite sarcophagus of Khufu, where a cut ran too deep and was brought further out. From the length of the cuts he infers a copper blade of about 9 feet, with the cutting itself done by some hard stone. At Tiryns he found in a saw cut a lump of corroded copper containing lumps of emery, which he took to prove saws with set stones for cutting hard limestone. These are saws that cut stone with an abrasive; concrete, a different material, is not discussed.1

The principle is old and the blade is a carrier. Petrie, writing in 1917 from the Egyptian collection at University College London, found saw cuts in granite, basalt and quartz rock and reasoned that a copper blade of about nine feet could cut them only if hard stone did the cutting. At Tiryns he identified lumps of emery embedded in the remains of a copper saw, which he took as evidence for set-stone saws, while for soft alabaster plain sand was enough. A modern diamond wheel applies the same principle with the cutting particles bonded into the edge of a steel disk.

The modern hand-held form is an engine, a drive and a wheel. The STIHL TS 400 manual of 2007 describes a 64.1 cm³ two-stroke engine driving a spindle by V-belt at up to 5,350 revolutions per minute, with a guard, a water attachment, and wheels of 300 or 350 mm. Husqvarna dates its first power cutter to 1968 and says it was a redesigned saw, and the company says its 2002 purchase of Diamant Boart International made its construction business a world leader. The company history does not say which saw was redesigned, and the first concrete saw has not been dated.

The hazard changed the tool. OSHA’s fact sheet says crystalline silica is a common mineral in sand, stone, concrete, brick and mortar, and that cutting, grinding, drilling or crushing these materials creates very small respirable particles that can cause silicosis, lung cancer and other disease. STIHL’s manual of 2007 already warned that a respirator is needed when wet cutting is not used. In 2016 OSHA’s standard turned that into a rule with a permissible exposure limit of 50 micrograms per cubic meter, an action level of 25, and a table that names the saw types and the controls required for each.

Under that table, water is part of the saw. For hand-held saws of any blade diameter, walk-behind saws and drivable saws, OSHA’s Table 1 specifies a saw equipped with an integrated water delivery system that continuously feeds water to the blade. The compliance guide says the system is supplied by the equipment manufacturer and developed specifically for the tool in use, and that it usually includes a nozzle near the blade connected by hose and pump to a water basin. Employers who follow Table 1 correctly do not have to measure exposure for those tasks, according to OSHA’s fact sheet.

Timeline

Khufu
Saw cuts in granite, basalt and quartz rock show that Egyptian workers sawed hard stone with copper blades and an abrasive, according to Petrie.1
1968
Husqvarna’s first power cutter, which the company calls a redesigned saw.1
2002
Husqvarna acquires Diamant Boart International; the company says its construction business doubled in size and became a world leader in its segment.1
2007
STIHL’s instruction manual for the TS 400 Cutquik, a 64.1 cm³ two-stroke cut-off machine for 300 or 350 mm composite or diamond wheels, carries a 2007 copyright. It says diamond wheels have much better cutting performance than composite abrasive wheels.1
2016
OSHA publishes the respirable crystalline silica standard for construction, 29 CFR 1926.1153, in the Federal Register of 25 March (81 FR 16875–16882 in the section’s source note). It sets a permissible exposure limit of 50 micrograms per cubic meter and an action level of 25 for an 8-hour average, and its Table 1 specifies controls for saws. The section takes effect on 23 June 2016.1
2017
On 23 June all obligations of the construction silica section commence, except the requirements for methods of sample analysis.1
2018
On 23 June the requirements for methods of sample analysis commence.1
2019
The section’s source note records an amendment published on 14 May 2019 (84 FR 21597). The content of the amendment was not read.1

Gaps in the record (7)

No source has been found for the invention of the concrete saw, the walk-behind flat saw, the wall saw, the wire saw or the first diamond blade for concrete. The Concrete Sawing and Drilling Association’s history pages returned a 403 error and could not be read, and no patent or trade history was located.
The Egyptian saws cut stone, not concrete. Concrete is first treated here only through 20th-century company histories, and no source on the history of cutting concrete before 1968 has been located.
Husqvarna’s 1968 power cutter is the company’s own claim, and Stihl’s date for its first cut-off machine was not found.
The amendment to 29 CFR 1926.1153 of 14 May 2019 was not read, and OSHA’s enforcement date for construction (the CFR text gives 23 June 2017 for obligations) was not checked against another source.
The STIHL manual is read from machine-recognized text and covers one model; no typical specifications have been sourced.
No independent test of saws, blades or dust controls has been located, so buying is null.
The standard slugs other than OSHA 1926.1153 are guesses (ISO 19432 for hand-held cut-off machines, EN 13236 for superabrasive wheels, ANSI B7.1 for abrasive wheels) and have not been read.