24S and 36P describe two selection variables, not two national standards. In conventional bonded-abrasive specification notation, 24 and 36 are grit designations; S and P are grade letters. The number relates to abrasive grain size, while the grade describes how firmly the bond retains the abrasive. Neither designation alone tells you that a wheel is flexible or suitable for a particular grinder.
| Marking element | Meaning | What it does not establish |
|---|---|---|
| 24 versus 36 | 24 is coarser than 36 within the same grit system | Not a measurement of motor power, speed or wheel flexibility. |
| S versus P | S is a harder grade than P in the conventional alphabetical grade sequence | Not the intrinsic hardness of the abrasive mineral. |
| Complete wheel specification | Also identifies abrasive, bond, dimensions and other product-specific details | Two wheels sharing a grit and grade need not behave identically. |
In practical terms, a coarser grit generally leaves a coarser scratch, while a grade change affects abrasive retention. However, removal rate and finish also depend on abrasive type, wheel construction, tool power, contact area, pressure and the workpiece. A label cannot be reduced to “24S is faster” or “36P is cooler.”
Grit size is the abrasive particle-size designation. Grade concerns the bond's retention of those particles. Abrasive type concerns the cutting material itself. Flexibility comes from the product's construction and permitted use; it is not encoded by the grade letter alone.
A harder grade does not mean a disc is safer or more suitable for heavy loading. It also does not necessarily mean longer useful service: if the combination cuts poorly, extra grinding time and heat can offset apparent low wear. Compare the complete product and the accepted result.
Do not treat either marking as proof of JIS, EN or ANSI compliance, country of origin, certification or a maximum speed. Standards and conformity claims require their own supporting documentation. Wheel operating limits must come from the actual label and instructions.
Grade letters are also not a universal performance scale across manufacturers. When changing supplier, request an application recommendation rather than assuming the same letter will reproduce the same behaviour. For FUJI, confirm the available product code before ordering; this comparison does not mean every semi-flex family is available in both designations.
| Job condition | Question to answer before testing |
|---|---|
| Substantial excess material | Is a separate rough-grinding stage more appropriate than a semi-flex blending operation? |
| Scratch-sensitive finish | How much finishing remains after the wheel reaches the required profile? |
| Thin stainless component | Can the process achieve the profile without unacceptable heat or distortion? |
| Wheel rubbing or glazing | Does the complete abrasive and bond specification suit the material and operating conditions? |
| Rapid wheel consumption | Is wear acceptable for the removal achieved, and is the approved method being followed? |
Use equivalent parts, an approved grinder and consistent acceptance criteria. Record total time, wheel use and follow-up finishing. Change one relevant selection variable at a time where possible. A comparison between 24S and 36P changes both grit and grade, so it does not isolate the effect of either one.
Start with the alloy, weld or burr geometry and finish requirement. Then check the exact FUJI specification and grinder compatibility. The FUJI Ace product page provides a product starting point; our Ace stainless-steel weld blending guide explains its application role.
For a complete trial method, see how to select a semi-flex grinding wheel. If the current wheel loads or heats the part, use the loading and glazing troubleshooting guide before guessing that a different grade will solve the problem.
The wheel diameter, bore, thickness, approved tool arrangement and maximum RPM must match the grinder instructions. A peripheral-speed value in m/s is not RPM. Do not run a wheel above its marked limit or infer a speed rating from 24S or 36P. Follow required backing-support and contact-angle instructions for the particular semi-flex product.
P is a softer bond grade than S in the conventional sequence, but compare like-for-like products and manufacturer guidance. The 36 and 24 digits describe grit, not softness.
No. The abrasive system, grinding conditions and required finish also matter. Evaluate the scratch pattern and subsequent finishing work on representative parts.
No. It is specification notation. Use the wheel and tool instructions for angle, mounting and speed.
Norton: Grinding Wheel Basics explains grit and grade and cautions against assuming direct grade equivalence between manufacturers. Product-specific FUJI information remains necessary for selecting an actual wheel.
Send the workpiece material, operation, grinder model and speed, wheel dimensions and current difficulty. Include a photo of the wheel label and your required finish so we can discuss a suitable specification and a controlled trial.
