SS Conversion Chainline
 

This might be a very dumb question, but I'd rather be sure before I start my build so that I know I have the proper tools. I did some searching and couldn't find a definitive answer.

I'm build up a single speed using a road frame with a rear spacing of 120mm. I will be using Shimano Dura Ace Track hubs and a Dura Ace Track BB and Crankset. Since the spacing is the same as a track frame or will the chainline be straight? Logic tells me it will.

Measure... once the hub is built up and the wheel in the frame,
you make the front chainring parallel to the center line of the bike itself.
through a combination of BB spindle length and crank design.

If you have the sprocket and hub already it's easy to predict where the chainline will needs to be set.

Spin the sprocket onto the hub up to the shoulder, but don't bother tightening it. Now measure from the right lock nut face, to the center of a tooth (parallel to the axle), subtract that from the axle locknut width, which should be either 110 or 120mm, and that's the center to sprocket distance, or chainline. Your crank chainline should be set as close to that as possible, or within 1-3mm to either side.

I don't have the parts yet, trying to plan it out. I guess I will have to just take a chance on parts. But in theory it should all line up, right?

If you're starting with a road double and using the inner chainring position it'll be very close.

Typical road double chainline is a few millimeters wider than typical track or road SS. Then the inner ring is about 3mm inboard form the chainline (middle between the 2 rings), so that will come very close to making up the difference. But then again that supposes that your road cranks have the correct road chainline to start.

In theory, yes. But we all know what theory gets us.

Communism. ;)