Part 313 min

3.3 The maintenance shop's own machines

The maintenance shop is the one place in a plant where a mechanic is both the operator and the maintenance department. The bench grinder, the drill press, the cutoff saw, the hydraulic press, the parts washer and the air hose are your machines, and nobody audits them the way production equipment gets audited. Two of them have their own OSHA standards with numbers in them, and one of them — the bench grinder — is the single most cited machine in a general industry shop.

1 The bench grinder: four numbers

1910.215 governs abrasive wheel machinery, and four of its requirements come with dimensions. Learn these four and you can inspect any grinder in the building in ninety seconds.

The four dimensional requirements of 29 CFR 1910.215 for a bench or floor stand grinder
What	Requirement	Paragraph
Work rest gap	"Work rests shall be kept adjusted closely to the wheel with a maximum opening of one-eighth inch to prevent the work from being jammed between the wheel and the rest, which may cause wheel breakage." The rest must be of rigid construction, adjustable to compensate for wheel wear, "securely clamped after each adjustment," and the adjustment "shall not be made with the wheel in motion."	1910.215(a)(4)
Tongue guard gap	The peripheral protecting member must be adjustable to the constantly decreasing wheel diameter, and "the distance between the wheel periphery and the adjustable tongue or the end of the peripheral member at the top shall never exceed one-fourth inch."	1910.215(b)(9)
Exposure angle	For bench and floor stands the angular exposure of the wheel periphery and sides should not exceed 90° or one-fourth of the periphery, and "this exposure shall begin at a point not more than 65° above the horizontal plane of the wheel spindle." Where the work requires contact below the spindle's horizontal plane, the exposure shall not exceed 125°.	1910.215(b)(3)
Guard coverage	"The safety guard shall cover the spindle end, nut, and flange projections," mounted to maintain proper alignment with the wheel, and the strength of the fastenings shall exceed the strength of the guard.	1910.215(a)(2)

The eighth-inch and the quarter-inch are the two that decay on their own, because both of them grow as the wheel wears. A grinder that was compliant when the wheel was new is out of compliance a month later unless somebody adjusts it, which is why (a)(4) requires the rest to be "adjustable to compensate for wheel wear" and (b)(9) requires the same of the tongue.

Common mistake: adjusting the work rest with the wheel coasting. 1910.215(a)(4) forbids it in seven words — "The adjustment shall not be made with the wheel in motion" — and the reason is that the tool you are adjusting with becomes the thing that jams between the rest and the wheel.

2 The ring test, spelled out by OSHA itself

1910.215(d)(1) is unusual for a regulation: it describes a manual technique in detail. "Immediately before mounting, all wheels shall be closely inspected and sounded by the user (ring test) to make sure they have not been damaged in transit, storage, or otherwise. The spindle speed of the machine shall be checked before mounting of the wheel to be certain that it does not exceed the maximum operating speed marked on the wheel. Wheels should be tapped gently with a light nonmetallic implement, such as the handle of a screwdriver for light wheels, or a wooden mallet for heavier wheels. If they sound cracked (dead), they shall not be used."

Two conditions on the test itself, both in (d)(1)(i)-(ii). "Wheels must be dry and free from sawdust when applying the ring test, otherwise the sound will be deadened," and organic bonded wheels "do not emit the same clear metallic ring as do vitrified and silicate wheels." The method: tap about 45° each side of the vertical centerline and about one or two inches from the periphery, then rotate the wheel 45° and repeat. "A sound and undamaged wheel will give a clear metallic tone. If cracked, there will be a dead sound and not a clear 'ring.'"

Check the spindle speed against the wheel's marked maximum before mounting — (d)(1). This is the step that turns a wheel into a fragmentation hazard when it is skipped.
(d)(2) Arbor size. Wheels shall fit freely on the spindle and remain free under all grinding conditions; the machine spindle is made to nominal size plus zero minus .002 inch, and the wheel hole suitably oversize, to avoid excessive pressure from mounting and spindle expansion.
(d)(3) Surface condition. All contact surfaces of wheels, blotters and flanges shall be flat and free of foreign matter.
(d)(4) Bushings. A bushing used in the wheel hole shall not exceed the width of the wheel and shall not contact the flanges.

3 The air hose: 30 psi, and two conditions people drop

1910.242(b) is one sentence and it has three parts: "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."

Reduced to less than 30 psi — which is a nozzle or a regulator, not a habit of feathering the trigger. And then only with two more things: effective chip guarding and PPE. Meeting the pressure limit alone does not satisfy the paragraph. Unlike the construction counterpart at 1926.302(b)(4), the general industry rule has no exception written into it at all.

The paragraph above it is broader than its title suggests. 1910.242(a): "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." Your own tools, brought from home, are inside the employer's duty — which cuts both ways, and is the paragraph behind a shop rule that inspects personal tools.

On the job: the standard says nothing about blowing yourself off, and the reason people do it anyway is that there is no alternative in reach. Put a vacuum and a brush at the bench, and the 30-psi argument stops happening.

4 Cords, tools and the shift inspection

Every corded tool in the shop is inside 1910.334(a)(2)(i), and the interval is per shift: portable cord- and plug-connected equipment and flexible cord sets "shall be visually inspected before use on any shift for external defects (such as loose parts, deformed and missing pins, or damage to outer jacket or insulation) and for evidence of possible internal damage (such as pinched or crushed outer jacket)." Equipment that remains connected once in place and is not exposed to damage need not be inspected until it is relocated.

And (a)(2)(ii) removes the discretion once you find something: "If there is a defect or evidence of damage that might expose an employee to injury, the defective or damaged item shall be removed from service, and no employee may use it until repairs and tests necessary to render the equipment safe have been made." Repairs and tests.

Three more from the same paragraph that describe a real shop drawer: cords may not be used to raise or lower equipment and may not be stapled or hung so as to damage the jacket, under (a)(1); adapters that interrupt the continuity of the grounding connection may not be used, under (a)(3)(iii); and locking-type connectors "shall be properly secured after connection," under (a)(5)(iii).

5 The fan, the fixed machine and the fire

Three short requirements from elsewhere in Subpart O that a shop breaks constantly. 1910.212(a)(5): when the periphery of a fan's blades is less than seven feet above the floor or working level, the blades shall be guarded and "the guard shall have openings no larger than one-half inch." That is a specification, and most shop pedestal fans fail it.

1910.212(b): "Machines designed for a fixed location shall be securely anchored to prevent walking or moving." A drill press or a grinder pedestal that walks under load is not a nuisance; it is the paragraph.

And 1910.334(d), which belongs to the shop that stores solvent near a grinder: "Where flammable materials are present only occasionally, electric equipment capable of igniting them shall not be used, unless measures are taken to prevent hazardous conditions from developing. Such materials include, but are not limited to: flammable gases, vapors, or liquids; combustible dust; and ignitible fibers or flyings." A Note points to 1910.307 for locations where flammable materials are present on a regular basis — the subject of the Hazardous Locations course on this site.

6 A shop inspection that fits on a clipboard

Nothing here needs an audit program. It needs somebody to walk the shop once a month with the four numbers in their head.

1
Grinders: work rest gap one-eighth inch and clamped, tongue guard gap one-fourth inch, guard covering spindle end, nut and flange, wheel within its marked speed, and the wheel dressed rather than grooved.
2
Wheel stock: stored dry and undamaged, ring tested immediately before mounting, spindle speed checked against the wheel marking, blotters and flanges flat and clean.
3
Air: a regulated nozzle under 30 psi for cleaning, with chip guarding and eye protection at the point of use — and a vacuum available so nobody needs the hose.
4
Cords and portable tools: visually inspected before use on any shift, defective items removed from service, no adapters that break grounding continuity, no cords used to hoist anything.
5
Fixed machines: anchored, guards fastened, fan guards with openings no larger than one-half inch below seven feet.
6
Solvents and flammables: stored away from ignition sources, and no electric equipment capable of igniting them used where they are occasionally present — 1910.334(d).

Key takeaways

A bench grinder has four numbers: work rest gap one-eighth inch (1910.215(a)(4)), tongue guard gap one-fourth inch ((b)(9)), 90° exposure beginning no more than 65° above the spindle plane ((b)(3)), and a guard covering the spindle end, nut and flange ((a)(2)).
Both gaps grow as the wheel wears, which is why the standard requires both the rest and the tongue to be adjustable — and forbids adjusting the rest with the wheel in motion.
1910.215(d)(1) spells out the ring test and requires the spindle speed to be checked against the wheel's marked maximum before mounting; wet or dusty wheels give a false result.
1910.242(b) allows compressed air for cleaning only below 30 psi AND with effective chip guarding AND with PPE — with no exception in general industry.
1910.242(a) makes the employer responsible for the safe condition of tools and equipment used by employees, including tools employees furnish themselves.
1910.334(a)(2) requires a visual inspection of cord sets and portable equipment before use on any shift, and removal from service until repairs and tests make a damaged item safe.

Free educational content — not OSHA-authorized training, no certificate or card issued. Follow your employer's program and the standards cited.