- HD6700C - Heavy Duty Sewing Machine - Gray - 2500513961 - Heavy Duty Extension Table for Computerized HD Machines The Heavy Duty 6700C computerized sewing machine is designed with your heavy duty projects in mind, from denim to canvas. Thanks to the machines powerful motor, you have extra high sewing speed to save you time. The throat space (working space between the needle and tower) is 6.4 or 163 mm.