Canvas for machine tool covers

I now seem to have a number of machine tools, and some do not get a lot of use and need protecting from dust and such.



Canvas covers seem the most appropriate material, but what sort of canvas is best to make the covers out of?



I would be looking at buying a reasonable sized roll to make up the covers... In fact I wonder if a pulley system above the machine to raise the cover so it is out of the way when the machine is in use... The shed has a fairly high roof...