questions on XL Timing Belts

knurled or do they mean that the "interface" where the

The outer of the insert will be knurled for good adhesion to the plastic. The bore will be smooth.

screw is drilled ?

?? Dunno...is not the hole for the set screw. Maybe a spot mark for second hole if you want to drill one to put another screw in?

knurled or do they mean that the "interface" where the

The pulley itself is polycarbonate - a rather soft plastic material. The aluminum insert, to which the shaft is affixed, is knurled so that it "grips" the polycarbonate material. You don't want the metal insert to slip within the plastic pulley.

screw is drilled ?

That's exactly what that is. A spot drill is also distinct from the familiar twist drill, in that it is like a rotary shaper, without the twists to extract cut-away material. A shallow cut (as opposed to a hole, all the way through) should be made in the shaft at the indicated location for the set screw to engage.

You could ask these questions directly to the source (sdp-si) for truly authoritative answers.

JM

Thanks to both John & Fullyautomatix for the info !