<td>Cutting generates a lot of heat, making oil based coolant preferable. Many machining spindles require 2000 rpm or more, to provide adequate cutting torque, which means that you have to use relatively small diameter end mills in order to end up with surface speeds this low. If not using coolant, then max surface speed is 50 ft/min.</td>
</tr></table>
</tr>
<tr>
<td>Insulation foam</td>
<td>1000 ft/min</td>
<td>Good for large moulds and as core for wings.</td>
