I have a question about torque

as i understand the usual way to measure torque is Nm (one newton weight at one metre). Now, this uses WEIGHT not mass (mass would be say a kilo) Why then does the unit foot-pound (or pound-foot I'm not sure) use a unit of MASS not weight.

Actually pound can be used as a unit of mass or a unit of force (confusing I know!). 1 pound-mass is equivalent to about 0.454 kilograms. 1 pound-force is equal to 1 pound-mass x acceleration due to gravity or 32.17 ft.lbm/s^2

You are correct that torque units are force x distance so you need to use pound-force. Much easier to use SI units...

Hope that helps...

Incidentally a slug is equivalent to about 32.17lb (mass)

"pound-foot " unit is lbf-ft. lbf is pound force. lbm is pound mass, and it is not used for torque.
The imperial system of units is so confusing.

I second Rouse. A pound is a unit of weight. Think about it, your weight in pounds changes on different planets due to different planetary accelerations.

Torque is force times distance, Newton is force. The pound in torque is pound force, not pound mass.

Pound is not mass it is a force unit as is the Newton. In the imperial system the unit "slug" is mass.