These start off as .058" walled 1.125" 4130. I hogged off a little more then .028" of wall thickness to do three things:
1. Make them blend a bit more visually
2. Thin them out to better match the wall thickness of the joining tubes for easier pre-heat and better brazing.
3. Drop some weight
I find number three the most amusing. I weighed both a non-machined mock up and the mid-stage version with the thin walls. For a 3.25" sleeve the weight dropped from 66g to 30g. In bike world, Shimagnolo charges $100 for that. That means I just saved enough weight to "settle" on a carbon Chorus rear derailleur! Of course, since this is for a bike with a Nexus 8 speed rear hub (which weighs about 1600g), I default to reasons 1 and 2 for this particular application.
In other news, if I built bikes in Springfield
I would look like this:
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