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When purchasing an attachment such as a grinding disc, cut-off wheel, or polishing pad, always ensure that the maximum rated RPM of the attachment is equal to or greater than the maximum speed of your tool, whether the tool is pneumatic or electric. Using an attachment with an insufficient speed rating may result in serious injury due to attachment failure.

 

Identifying the Maximum Tool RPM

Pneumatic tools:

The maximum speed is typically indicated directly on the tool label as free speed (n/min or RPM).

AC Electric tools:

Many electric tools display the maximum RPM on the specification label. If the RPM is not listed, it can be estimated using the following formula:

N(RPM)=120×Frequency (Hz)/P(Number of motor poles)

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Next, calculating Attachment Peripheral Speed

To determine the maximum circumferential (peripheral) speed of the attachment when used with your tool, use the following formula:

V (m/s)=π×D (disc diameter in mm)×n (tool free RPM)/60,000

 

Safety Comparison

Compare the calculated speed V (m/s) with the maximum allowable speed marked on the attachment (referred to as Vd).

If Vd < V → DO NOT USE this attachment. It is not designed for the tool speed and may fail.

If Vd ≥ V → The attachment is suitable for use with the tool.

 

Important Safety Reminder

Safe operation involves more than speed compatibility. Users must also understand:

Proper use of the grinder guard

Correct grinding angle and permitted contact surfaces

Mounting procedures and inspection before use

Tool handling and personal protective equipment (PPE)

Always read and understand the tool manufacturer’s instructions before operation to ensure maximum safety and efficiency.