true a sprocket

With the wheel off the bike I wrap a peice of coathanger around the axel and tighten it down. Then bend the coathanger point to where you want it. I usually do it for center first touching the outside of teeth, then for true place the tip of wire on the side of sprocket and tighten appropriate nuts.

I use my "truing stand" which I also use for wheels.

It's a piece of plywood with an oval hole in it, then two drywall screws on each side where the axle sit (they are screwed in at an angle to form a "V")

I then screwed a piece of pine to one side and I can "adjust" it to the rim or the sprocket. I push the pine in until it touches, then turn the wheel to find the high and low spots.

Good ideas, but before you do that, make sure the sprocket is flat. Use a straight edge across the sprocket and make sure that it is flat, and if there is any gap, the gap is consistent all the way around.

If it is not (my 48 tooth sprocket was not), mark where it is not flat with a Sharpie and remember which way it has to be tweaked. I clamped it in a vice with the part that needed to be bent up, inserted a pry bar and tweaked it slowly until it was flat according to the straight edge- then install and true as above.

Good tip...let's not fail to mention that the center hole is not always drilled straight and no matter what you do in the tightening sequence, the sprocket will never run true until the hole is fixed.

I hold a black marker near it and spin the wheel.