The work rest must sit within one-eighth inch of the wheel surface according to Legal Information Institute.
Key takeaways
- Rest gap: Keep the work rest at a distance not to exceed one-eighth inch from the surface of the wheel, according to Legal Information Institute.
- Ring test: All abrasive wheels shall be closely inspected and ring-tested before mounting to ensure that they are free from cracks or defects, according to Legal Information Institute.
- Guard limit: The maximum angular exposure of the grinding wheel periphery and sides shall be not more than 90°, except that when work requires contact with the wheel below the horizontal plane of the spindle, the angular exposure shall not exceed 125°, according to Legal Information Institute.
How close the rest must sit, in one paragraph
The work rest on a bench or floor grinder must be kept at a distance not to exceed one-eighth inch from the surface of the wheel, as stated by the Legal Information Institute. This specific gap requirement applies to the work rest itself, which supports the material being ground. It is distinct from other clearance measurements found on different regulatory pages. For example, the California Department of Industrial Relations specifies that a different clearance, defined in their text, shall not exceed one-sixteenth inch. Do not mix these two numbers. The one-eighth inch figure refers to the distance between the work rest and the grinding wheel. The one-sixteenth inch figure refers to a separate clearance requirement described in the California Code of Regulations. When setting up the grinder, measure the gap between the rest and the wheel to ensure it does not exceed one-eighth inch. This measurement is the primary check for the work rest position before use. The side clearance mentioned by the California Department of Industrial Relations is a different metric and should not be used to adjust the work rest. Keep the work rest gap and the side clearance separate in your mind and on your checklist. The one-sixteenth inch clearance is a separate protection device requirement. By keeping these distinct, you avoid applying the wrong measurement to the wrong part of the grinder. Your task is to verify the work rest is within one-eighth inch of the wheel. This is the standard you must meet before anyone uses the tool.
The federal one-eighth-inch rest and the ring test
Before the wheel spins, the work rest must be positioned so the gap between it and the wheel surface does not exceed one-eighth inch. This specific distance is the limit printed in the federal rule for abrasive wheels and tools. According to Legal Information Institute, such work rests shall be kept at a distance not to exceed one-eighth inch from the surface of the wheel. It is not a side clearance or a guard opening measurement. Keep this one-eighth inch figure distinct from any other dimensional requirement on the same page or in other state regulations.
In addition to setting the rest, the wheel itself requires a specific pre-mounting check. The same federal source requires that all abrasive wheels be closely inspected and ring-tested before mounting. According to Legal Information Institute, this inspection is to ensure that the wheels are free from cracks or defects. The ring test is a separate step from adjusting the rest. You do not adjust the rest to perform the ring test, nor does a successful ring test replace the need to measure the rest gap. The ring test verifies the structural integrity of the wheel material before it is secured to the spindle. Both steps are required before the grinder is used.
Washington's 1/8-inch rest rule
Washington State Legislature’s WAC 296-155-365 page specifies the exact gap for the work rest. According to Washington State Legislature, you must adjust such work rests to a distance not to exceed 1/8 inch from the surface of the wheel. This requirement applies to the work rest on the grinder. The page identifies this as a mandatory adjustment for the equipment. Contractors should verify the rest position against this specific measurement before the wheel spins. The one-eighth inch figure is the limit for the distance between the rest and the wheel surface.
The same page also sets the limit for the guard opening. According to Washington State Legislature, the maximum angular exposure of the grinding wheel periphery and sides must be not more than 90°. There is an exception for work that requires contact with the wheel below the horizontal plane of the spindle. In that specific case, the angular exposure must not exceed 125°. The 90-degree limit is the standard for the periphery and sides. The 125-degree limit applies only when the work position is below the horizontal plane.
California's one-eighth-inch rest and the separate one-sixteenth-inch line
The California Code of Regulations, Title 8, Section 3577. Protection Devices, specifies two distinct measurements for grinding equipment that must not be confused. The first measurement applies to the work rest, which is the adjustable support positioned near the grinding wheel. According to the California Department of Industrial Relations, work rests shall be kept adjusted closely to the wheel with a maximum opening of one-eighth inch. This one-eighth-inch gap is the specific limit for the work rest itself. When setting the rest on a bench or floor grinder, measure the space between the face of the work rest and the face of the wheel. If that space exceeds one-eighth inch, the rest is not adjusted closely enough and must be moved inward before the machine is used. According to the California Department of Industrial Relations, the work rest shall be secured after each adjustment. The adjustment shall not be made with the wheel in motion.
The second measurement on the same page refers to a different part of the protection device. The regulation also states that a specific clearance shall not exceed one-sixteenth inch, according to the California Department of Industrial Relations. This one-sixteenth-inch limit is a side clearance, not the work-rest gap. It is critical to keep these two numbers separate in your site record. The one-sixteenth-inch figure governs a different clearance requirement on the same page. Do not write the one-sixteenth-inch number as the work-rest gap. If you record the wrong number, you may set the rest too far from the wheel or misinterpret the guard requirements.
Section 3577 applies to the protection devices used with grinding wheels in the contexts covered by Title 8. The page title is "California Code of Regulations, Title 8, Section 3577. Protection Devices." You should refer to this page by that title when documenting your checks. The rules here are state regulations from the California Department of Industrial Relations. They are not federal rules, nor are they identical to the federal rule, although the work-rest gap happens to be the same one-eighth inch in both cases.
A filled reference table of the grinder rules by publisher
The table below lists the work rest gap, ring test requirement, and guard opening limit for each publisher.
| Publisher | Rest gap | Ring test | Guard opening |
|---|---|---|---|
| Legal Information Institute | not to exceed one-eighth inch | closely inspected and ring-tested before mounting | not more than 90° (or 125° below horizontal plane) |
| Washington State Legislature | not to exceed 1/8 inch | closely inspect all abrasive wheels and ring-test them before mounting | not more than 90° (or 125° below horizontal plane) |
The Legal Information Institute page, titled "29 CFR § 1926.303 - Abrasive wheels and tools. | Electronic Code of Federal Regulations (e-CFR) | US Law | LII / Legal Information Institute," states that work rests shall be kept at a distance not to exceed one-eighth inch from the surface of the wheel, according to Legal Information Institute. The same page requires that all abrasive wheels be closely inspected and ring-tested before mounting to ensure they are free from cracks or defects, according to Legal Information Institute. For the guard, the maximum angular exposure of the grinding wheel periphery and sides shall be not more than 90°, except when work requires contact with the wheel below the horizontal plane of the spindle, where the angular exposure shall not exceed 125°, according to Legal Information Institute.
Check the rest gap against the specific page you are using for your site record.
Illustrative example of a rest check
A crew checks 1 bench grinder before work. 2 people split the job. 1 person ring-tests the wheel. The other sets the rest while the wheel is still, then secures the rest. They write 3 lines on the site record: the rest gap, the ring test, and the guard opening. The guard line for this task uses 90°, not 125°, because the work does not sit below the spindle. This example names no product.
Check the rest before anyone starts
Write the measured gap and the page name on your site record before the grinder is used. The federal rule states that work rests shall be kept at a distance not to exceed one-eighth inch from the surface of the wheel, according to Legal Information Institute. Measure the opening, secure the rest after the adjustment, and do not adjust the rest with the wheel in motion. For a related grinding record, see Concrete grinding controls: 5 checks to record. Before any repair on the machine, see Lock out the circuit: 5 checks before repair starts.
FAQ about the grinder rest before use
What gap does the federal page print?
The federal page prints a rest gap of one-eighth inch. The rule states that such work rests shall be kept at a distance not to exceed one-eighth inch from the surface of the wheel, according to Legal Information Institute. This applies to the abrasive wheels and tools section of the Electronic Code of Federal Regulations.
What does Washington print?
Washington prints a rest gap of one-eighth inch. The regulation requires you to adjust such work rests to a distance not to exceed 1/8 inch from the surface of the wheel, according to Washington State Legislature. This appears in the Washington Administrative Code.
What does California print for the rest?
California prints a rest gap of one-eighth inch. The rule specifies that work rests shall be kept adjusted closely to the wheel with a maximum opening of one-eighth inch, according to California Department of Industrial Relations. This is found in the California Code of Regulations, Title 8, Section 3577.
What is the one-sixteenth-inch line?
The one-sixteenth-inch line is the side clearance, not the rest gap. Do not mix this side clearance measurement with the one-eighth-inch work rest gap on the same page.
What to write down before use?
Write the gap and the page name on the site record. Before the grinder is used, set the rest and record the specific gap the page names. This entry belongs on today’s site record to verify the adjustment was made.