ISO 7010:2019 / ISO 3864-1
ISO P033 Do not use for wet grinding Sign
ISO P033 Do not use for wet grinding Sign means the grinding wheel it labels must be run dry: its bond and porous structure are not rated for water or coolant, which soak in unevenly, unbalance the wheel, and can degrade the bond until the wheel cracks or bursts at operating speed. It should be used where the cited standard, facility risk assessment, SDS, emergency plan, or written safety procedure requires this hazard or safety message to be communicated.
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Reference artwork: Wikimedia Commons · License: Public domain
Technical Data
| Legal Standard | ISO 7010:2019 / ISO 3864-1 |
|---|---|
| Color Codes | #FF0000 / Closest practical match: RAL 3020 Traffic Red |
| Viewing Distance | 50 mm: close equipment or package label; 100 mm: approximately 5 m; 200 mm: approximately 10 m; 300 mm: approximately 15 m; 400 mm: approximately 20 m. |
| Review Status | approved / last reviewed 2026-07-07 |
| Jurisdiction Scope | Global, United States, European Union |
| Keywords | p033, iso 7010, prohibition, not, use, wet, grinding, prohibit, disc |
Standard Dimensions Table
| Sign Size | Recommended Visibility |
|---|---|
50 mm | close equipment or package label |
100 mm | approximately 5 m |
200 mm | approximately 10 m |
300 mm | approximately 15 m |
400 mm | approximately 20 m. |
Where This Sign Is Used
It appears chiefly on the product itself, printed on disc faces, blotters, and packaging alongside speed markings and the other abrasive restriction pictograms, and repeated in the safety leaflet packed with the wheels. Workshops running mixed processes also post it at bench grinders that must never be plumbed to coolant and in wheel stores, keeping dry-only stock out of coolant-fed machines.
In-Depth Guidance
Why Water Ruins Certain Grinding Wheels
ISO 7010 P033 marks grinding discs that must be used dry. Bonded abrasive wheels are porous composites, and on wheels not formulated for wet service, water and coolant attack them in two ways. First, moisture soaks unevenly into the porous structure: a wheel that has stood with its lower edge in liquid becomes heavier on one side, and that imbalance produces vibration at operating speed that can crack and ultimately burst the wheel. Second, some bond systems are themselves degraded by prolonged water exposure, softening the matrix that holds the abrasive grains.
Wet grinding is a legitimate and common process — coolant controls heat and dust — but it requires wheels whose bond and structure are rated for it. P033 exists to keep water away from the wheels that are not, and its presence on a label is the manufacturer stating that this specific product's bond has no wet rating.
How the Label Is Used
Like the rest of the abrasive misuse trio, P033 lives primarily on the product: printed on the disc face, blotter, or packaging together with the speed marking and the FEPA-style restriction pictograms, and repeated in the safety leaflet packed with the wheels. Sites with mixed dry-only and coolant-fed machines sometimes also post it at bench grinders that must never be plumbed to coolant, or in wheel stores as a reminder that dry-rated stock stays out of wet processes.
Storage discipline matters as much as use. The bonded-abrasive codes — ANSI B7.1 in North America, EN 12413 in Europe — underpin two standing rules for wet-capable machines: never leave any wheel standing partly immersed in coolant, and run a wheel that has been used wet until the coolant is spun out before stopping it. For dry-only wheels the rule is simpler — they should never meet liquid at all, in storage or in service.
Distinguishing P033 From Its Neighbors
ISO 7010 groups three prohibitions on bonded abrasives, and they answer different questions. P032 restricts the grinding orientation (edge only, no side grinding). P034 restricts the machine class (not for hand-held grinders). P033 restricts the process environment: this wheel runs dry. A single cut-off disc can legitimately carry all three symbols, and reading them as a set is part of pre-mounting inspection.
Confusion occasionally arises with P016, the do-not-spray-with-water sign, which concerns spraying equipment or areas — typically electrical — during cleaning. P033 says nothing about hoses or washdown; it is a materials-engineering statement about what the wheel's bond tolerates while grinding. If a labeled wheel does get wet, the safe course is to withdraw it rather than dry it and hope, since internal moisture and any bond damage cannot be verified from outside.
Frequently Asked Questions
What happens if you use a dry-only grinding wheel with coolant?
Water soaks unevenly into the porous wheel, unbalancing it, and can degrade bonds not formulated for wet service. The imbalance causes vibration at full speed, which can crack the wheel and lead to a burst. Because the damage is internal and invisible, a dry-rated wheel that has absorbed liquid should be taken out of service.
Why can't a grinding wheel just be dried out after getting wet?
You cannot verify from the outside whether moisture has fully left the porous structure or whether the bond was weakened while wet. A wheel that looks dry can still be unbalanced or internally damaged, and the consequence of guessing wrong is a wheel burst at operating speed. Manufacturers and abrasive-safety codes treat withdrawal as the safe default.
Is wet grinding dangerous in general?
No — with wheels rated for it, wet grinding is standard practice and helps control heat and airborne dust. The P033 prohibition applies only to wheels whose bond has no wet rating. Even with wet-rated wheels, good practice is to never leave a wheel standing in coolant and to spin coolant out before stopping the machine.
How do I know if a specific disc is wet-rated?
Check the printed label or blotter and the manufacturer's datasheet. Dry-only products carry the crossed-out wet-grinding pictogram (ISO 7010 P033) among their restriction symbols; wet-capable wheels state the approved coolant use instead. If the marking is missing or illegible, treat the wheel as unrated and do not use it wet.