In case anyone actually is interested, I speced out some drive pulleys for my Mendel. I am all for printing as many parts as possible, but at the same time their are benefits of using stock materials when I can. Here are some of my reasons.

1.) When price is not significant, accuracy is more important then making the part myself. I think these parts are going to be more accurate then anything I can print right now.

2.) The printed parts are the hardest to get right now. If you are trying to Repstrap these would help a lot.

Anyway here is a link to the pulleys
Drive Timing Belt Pulley
They cost $7.40 each

They have 10 teeth, where as the printed pulleys are only 8. This means you lose a little torque and gain a little speed, but I think the difference is pretty minimal.

Cheers,
Josh

As said in another thread, I will provide any serious repstrapper with a set of mendel gears for free + shipping.

Well that is very kind of you. I must not have come across that while browsing the forum. I still feel a little better with using these because the drive pulleys are so critical to avoid slipping of the belt and because I will not have to file my motor shafts.

cheers,
josh

I changed the design a little with a 4.8 mm hole, so you can just press the pulleys on the motor shaft. It gives a really thight fight, there won't be any slipping. In fact I think you would have a hard time to remove them without destroying.
But sure the precision of of the shelf gears will be better, if it affects the positioning precision is anther question.
To be honest I also bought the big gears, but I wasn't able to find a shop which offers small gears (<20 tooth) in my area.