Determine power rating of induction motor
The motor of a hand-held tool is often underrated because it's intended to be used intermittently. Sometimes the tool will even say 10 sec / 1 min or something, to make this clear.

It might also not have adequate cooling for continuous use, even if you kept the fan and ducts from the original power tool intact.

You could try running it and measuring the temperature over time, until it stabilises. Using a series of loads (fans) you could find a power level which results in a reasonable temperature rise.

Unfortunately, you might find that there is no load small enough to prevent it from overheating. In designing the cheapest motor for intermittent use, the copper and iron may be too light, or have too few turns. The only way to run it continuously might be to run it at a lower frequency, or a lower voltage.