OSHA's general industry standards separate constant pressure controls, lock-on controls and positive on-off controls for hand-held power tools in 29 CFR 1910.243, "Guarding of portable powered tools," paragraph (a)(2), "Switches and controls." This explainer answers one practical question from that paragraph: which hand-held power tools need a constant pressure switch, and when is a lock-on control or a positive on-off control allowed? Nothing here describes a rule change.
Group 1: a constant pressure control, with no lock-on mentioned
Paragraph (a)(2)(i) states: "All hand-held powered circular saws having a blade diameter greater than 2 inches, electric, hydraulic or pneumatic chain saws, and percussion tools without positive accessory holding means shall be equipped with a constant pressure switch or control that will shut off the power when the pressure is released."
For gasoline chain saws the same paragraph adds: "All hand-held gasoline powered chain saws shall be equipped with a constant pressure throttle control that will shut off the power to the saw chain when the pressure is released."
Unlike the next group, paragraph (a)(2)(i) says nothing about a lock-on control for these tools; it requires a control that will shut off the power when the pressure is released.
Group 2: a constant pressure control, and a lock-on is allowed
Paragraph (a)(2)(ii) states: "All hand-held powered drills, tappers, fastener drivers, horizontal, vertical, and angle grinders with wheels greater than 2 inches in diameter, disc sanders with discs greater than 2 inches in diameter, belt sanders, reciprocating saws, saber, scroll, and jig saws with blade shanks greater than a nominal one-fourth inch, and other similarly operating powered tools shall be equipped with a constant pressure switch or control, and may have a lock-on control provided that turnoff can be accomplished by a single motion of the same finger or fingers that turn it on."
So a lock-on control is permitted on these tools only with that condition: one motion of the same finger or fingers that turn the tool on must also turn it off.
Group 3: a positive on-off control is allowed
Paragraph (a)(2)(iii)(a) covers all other hand-held powered tools: "All other hand-held powered tools, such as, but not limited to, platen sanders, grinders with wheels 2 inches in diameter or less, disc sanders with discs 2 inches in diameter or less, routers, planers, laminate trimmers, nibblers, shears, saber, scroll, and jig saws with blade shanks a nominal one-fourth of an inch wide or less, may be equipped with either a positive 'on-off' control, or other controls as described by paragraph (a)(2)(i) and (ii) of this section."
How saw blade shanks are measured
The dividing line for saber, scroll and jig saws is the blade shank width. The rule adds three details:
- "Blade shank width shall be measured at the narrowest portion of the blade shank when saber, scroll, and jig saws have nonstandard blade holders" (paragraph (a)(2)(iii)(c)).
- "Nominal in this subparagraph means ±0.05 inch" (paragraph (a)(2)(iii)(d)).
- Saws with nonstandard blade holders "may use blades with shanks which are nonuniform in width, provided the narrowest portion of the blade shank is an integral part in mounting the blade" (paragraph (a)(2)(iii)(b)).
Where the switch must be placed
Paragraph (a)(2)(iv) states: "The operating control on hand-held power tools shall be so located as to minimize the possibility of its accidental operation, if such accidental operation would constitute a hazard to employees."
Tools the switch rules do not cover
Paragraph (a)(2)(v) states: "This subparagraph does not apply to concrete vibrators, concrete breakers, powered tampers, jack hammers, rock drills, garden appliances, household and kitchen appliances, personal care appliances, medical or dental equipment, or to fixed machinery."
Quick summary
| Paragraph | Tools (as listed in the rule, shortened) | Control required or allowed |
|---|---|---|
| 1910.243(a)(2)(i) | Circular saws over 2 in. blade; electric, hydraulic or pneumatic chain saws; percussion tools without positive accessory holding means; gasoline chain saws | Constant pressure switch or control (constant pressure throttle for gasoline chain saws) |
| 1910.243(a)(2)(ii) | Drills, tappers, fastener drivers, grinders and disc sanders over 2 in., belt sanders, reciprocating saws, saber/scroll/jig saws with shanks over a nominal 1/4 in., similar tools | Constant pressure switch or control; lock-on allowed if one motion of the same finger(s) turns it off |
| 1910.243(a)(2)(iii) | Other tools, such as platen sanders, grinders and disc sanders 2 in. or less, routers, planers, laminate trimmers, nibblers, shears, saber/scroll/jig saws with shanks a nominal 1/4 in. or less | Positive on-off control, or the controls above |
Two related rules in the same subpart
The section just before it, 29 CFR 1910.242, adds two general rules for tools:
- Tools workers supply themselves. 1910.242(a) states: "Each employer shall be responsible for the safe condition of tools and equipment used by employees, including tools and equipment which may be furnished by employees."
- Compressed air for cleaning. 1910.242(b) states: "Compressed air shall not be used for cleaning purposes except where reduced to less than 30 p.s.i. and then only with effective chip guarding and personal protective equipment."
Study with goraedu
Our OSHA general industry safety hub collects our general industry study guides and practice tests. The machine guarding study guide covers the general machine guarding rules, and the electrical safety study guide covers Subpart S, the electrical rules that 1910.243(a)(5) says portable electric powered tools must meet.