Metalworking Calculators

Machining speeds, bend allowances, thread sizes, welding consumables and metal weights. 12 calculators for the shop floor.

Cutting speed converts surface speed to spindle RPM, and getting it wrong is expensive in both directions. Too fast burns the edge off a tool in seconds. Too slow rubs instead of cutting, work-hardens the surface, and then the next pass is into hardened material. Surface speed is a property of the material and the tool, not of the machine, so the RPM changes every time the diameter does. A 6 mm end mill and a 25 mm one in the same steel want completely different spindle speeds.

Tap drill size is where the useful detail lives. The standard chart figures give about 75% thread engagement, which is not an accident or a compromise to fix. Going to 100% engagement adds only a few percent of thread strength while roughly doubling tapping torque, and that is how taps snap in blind holes. 75% is the right answer, not a rounded-down one.

Bend allowance takes a K-factor rather than assuming one, since the neutral axis shifts with material and bend radius, and flat patterns cut to a generic allowance come out short.