OSHA Power Press Guarding: When Is a Point-of-Operation Guard Required? The Quarter-Inch Rule and Table O-10

In the US federal standard for mechanical power presses, 29 CFR 1910.217(c)(1)(i) makes the employer responsible for providing, and ensuring the use of, point-of-operation guards or properly applied and adjusted point-of-operation devices on every operation. The single exception, in (c)(1)(ii), is a point-of-operation opening of one-fourth inch or less (about 6.4 mm). Any larger opening must be protected, and any guard used must respect the maximum openings in Table O-10.

The baseline duty under 1910.217(c)(1)(i)

The wording is deliberately broad. The employer must provide and insure the usage of guards or devices, on every operation performed on the press. OSHA applies it to setting work as well as production: its 1979 directive STD 01-12-024 states that die setters running test and production parts, setting dies or troubleshooting must be protected by point-of-operation guards or devices, and that failing to do so is a violation of 1910.217(c)(1)(i).

The vocabulary comes from 1910.211(d). The point of operation is the area of the press where material is actually positioned and work is performed, whether shearing, punching, forming or assembling. A guard is a barrier preventing entry of the operator's hands or fingers into it. A device is a press control or attachment that restrains or withdraws the operator's hands, prevents normal press operation when hands are inside, or stops the stroke when a sensing field is broken.

Check the scope before applying any of this. Paragraph (a)(5) excludes press brakes, hydraulic and pneumatic power presses, bulldozers, hot bending and hot metal presses, forging presses and hammers, riveting machines and similar fastener applicators. For those, the general requirement of 1910.212(a)(3)(ii) still requires the point of operation to be guarded where it exposes an employee to injury.

The quarter-inch exception, in inches and millimetres

1910.217(c)(1)(ii) reads: the requirement of (c)(1)(i) shall not apply when the point of operation opening is one-fourth inch or less. The rationale is that a gap that small will not admit fingers. Converted, 1/4 inch is 0.25 × 25.4 = 6.35 mm. Because the legal threshold is in inches, a gap of 6.4 mm, which rounds the conversion up, is technically just over the line; work in inches when you are close to the limit.

• 5 mm gap (about 0.20 in): within the exception for that opening.
• 6 mm gap (about 0.24 in): within the exception.
• 8 mm gap (about 0.31 in): outside the exception, so a Table O-10 guard or a properly applied device is needed.

The same quarter inch appears elsewhere in the section. Under 1910.217(d)(4), a guide post in the immediate vicinity of the operator that separates from its bushing by more than one-fourth inch counts as a point-of-operation hazard and must be protected under paragraph (c).

Table O-10 with millimetre equivalents

Once an opening exceeds 1/4 inch, every point-of-operation guard must conform to the maximum permissible openings of Table O-10 (1910.217(c)(2)(i)(b)). The further the opening is from the hazard, the wider it may be. The millimetre columns below are our conversions of the official inch values (inches × 25.4, rounded to one decimal place).

The explanatory note attached to the table describes how it is measured: the openings lie between the bottom edge of the guard and the feed table, at various distances from the danger line. The minimum guarding line is half an inch from the danger line, hence the table's starting point. A clearance line marks the distance needed to stop the guard touching moving parts, and the widths are set so that, for average-sized hands, the operator's fingers will not reach the point of operation.

Worked example for a European-built guard

Say a guard drawn in metric has a 20 mm feed slot (20 ÷ 25.4 ≈ 0.79 in). In Table O-10, 3/4 inch (0.75) is too small and 7/8 inch (0.875) is enough, so the slot fits the 6 1/2 to 7 1/2 inch band: the guard must sit at least 6 1/2 inches, roughly 165 mm, from the hazard. At 150 mm it would only be in the 5 1/2 to 6 1/2 inch band, where the limit is 3/4 inch, and the slot would be too wide. The regulation also says that after installing a guard and before releasing the job, a check should be made that the guard actually stops the operator's hands reaching the point of operation.

Worked conversions like this are easy to get wrong across two unit systems. The OSHA machine guarding knowledge base returns the relevant Table O-10 row and paragraph reference, so your design review can cite the text rather than a spreadsheet.

Design, fixing and adjustment requirements for the guard

1. It must stop hands or fingers reaching through, over, under or around it.
2. It must conform to Table O-10.
3. It must not create a pinch point between itself and moving parts.
4. Its fasteners must not be readily removable by the operator.
5. It must facilitate its own inspection.
6. It must offer maximum visibility of the point of operation consistent with the above.

Mounting depends on the type: a die enclosure guard fixed to the die shoe or stripper; a fixed barrier guard fixed to the press frame or bolster plate; an interlocked press barrier guard interlocked with the clutch control, whose hinged sections may not be used for manual feeding; and an adjustable barrier guard, which may only be adjusted by authorised personnel who know Table O-10. An enclosure that does not meet Table O-10 may only be used together with point-of-operation devices, under (c)(2)(vii).

Devices, and the 63 inches per second formula

Where hand feeding into the die is unavoidable, the alternative is a properly applied device under (c)(3). Two prohibitions matter for anyone specifying equipment: a presence-sensing device may not be used on a press with a full revolution clutch, and the sweep device may not be used for point-of-operation safeguarding. Light curtains and two-hand controls must also be positioned beyond the safety distance Ds = 63 inches/second × Ts, Ts being the stopping time measured at approximately 90° of crankshaft rotation.

Illustration only: with a measured stopping time of 0.15 s, Ds = 63 × 0.15 = 9.45 inches, about 240 mm (9.45 × 25.4). The device must be further away than that. Note that the hand speed constant is fixed in inches per second in the US text, so do the calculation in inches and convert at the end.

Pitfalls when exporting or auditing presses

• Assuming a metric guard is compliant without converting its openings and distances to Table O-10.
• Rounding 6.35 mm to 6.4 mm and treating a 6.4 mm gap as inside the quarter-inch exception.
• Fitting a light curtain to a full revolution clutch press.
• Protecting only the front of the die area when the sides and back remain open; (c)(3)(iii)(f) requires guards on every entry not covered by the sensing device.
• Letting operators adjust an adjustable barrier guard.
• Using an older edition of the rule; the base's copy of 1910.217 is the eCFR text up to date as of 1 October 2026, which showed no changes to the section after 3 January 2017.

Always confirm against the official eCFR text of 1910.217 before signing off a design. For a second opinion on a specific layout, ask the machine guarding base a question such as "Under 1910.217(c)(1)(ii), is a point-of-operation guard required when the opening is only 0.2 inch?".