I got a lotta tools, but a straightedge isn't among them! That piece of cold roll was the best I could do .....
The sprocket is from JT Sprockets. It's one of their JTR239 series. C49 high carbon steel. Available sizes from 35 to 50T. HUGE catalog to pick from.
http://www.jtsprockets.com/catalogue/
My potential for chain rash went up today when my feeble brain realized I've been looking at this with the axle adjusted all the way back. That's the best case scenario.
With the axle all the way forward, which is worst case, clearance to the seat stay is less than 3/16". I gotta think that's too tight.
I think I'm gonna shave an 1/8" off the carrier. Where the sprocket bolts on is a 1/4" thick and it ain't like I'm puttin' a Harley motor on this thing! Leaving that section an 1/8" thick should be just fine.
That of course leads to the next problem which is one I'm sure Tom knows about. It's the process ...
When I made the carrier I did almost all of the work with it mounted on an arbor. The last thing I did was grab it by the outside to open up the center to fit the bike hub, which means it ain't gonna fit on that little arbor no more!
But all that means is finding a piece of metal big enough to make a 1.25" arbor. And
then I can shave an 1/8" off.