I machined this adapter/spacer for the sprocket. The webs in the hub best facilitated a three bolt pattern but I already had a four bolt pattern on the sprocket. This spacer is first mounted to the hub with three bolts, then the sprocket is mounted to the spacer with four bolts. This is a tricky deal because you can't just go drilling holes and plopping in any old bolt that fits. There are actually all sorts of rules for using fasteners. Look them up and use them. Learn about different fastener's strengths and weaknesses. More importantly, learn how they are designed to work. You can't just throw any bolt in a hole just because it is the right diameter. In this case, it was a no-no to have threads inside the holes of two adjoining plates. As shown in a prior post, the bolt pattern on the hub was set for me as a three bolt pattern. Through, measuring, aligning, and the use of transfer punches, I first made the four holes for the sprocket. I then radiused the center hole to fit the radius on the hub. I used some machinist radius gauges to check. I think it was 5/32" but I can't remember. I first used the lathe putting various radii on the hole, then sanded the remainder. According to the gauge, I hit it pretty close. Once mounted to the sprocket, I centered it on the hub (using the radiused center hole) and used a transfer punch to locate the holes, already in the hub, onto the spacer. I actually did two and located the third after the others were bolted down. I would rather have it slightly out of round than to have to wallow out one or two holes to align everything. This is why you can't just guess on these types of things. It introduces inaccuracies that build on themselves until you have a piece that is not precise at all. Haven't ranted in a while. I spent nearly $20 just for the seven stainless fasteners for this part. Even then, I couldn't find what I needed and had to modify what I could find just to get it to "work". If I had $1 for every time I have had to shorten a bolt or modify a bolt head on this bike, I would have a few coffees to spare. Well, I guess they don't carry shouldered machine-head bolts at Westlake/Ace. Because of this, I set the heads low and the 60 degree heads actually do most of the shear work rather than the threads. The proper use is to have no threads at all inside the hole. Note that I needed the machine heads as the plate had to be flush with the sprocket face. Here is one of the bolts turned down next to two originals for the comparison. I was more fortunate with the four bolts for the sprocket. I found them with shoulders but not in a machine head. I had a little more room on the back of the spacer and oriented then like the studs on a car spindle - sticking out from back to front. I had to taper one flat on each bolt head so it would clear a step on the hub OD. Here is (a blurry shot of) the spacer first mounted to the hub. You can also see the four studs loosely fitted. If you look closely, you can see they are shouldered just enough to fit the sprocket - beautiful! That's the way bolts are supposed to work, using washers to give us the proper spacing, but how often do we do this? I am a little leary of the hub to spacer three-bolt interface but I am confident with this connection this. Then the sprocket mounted to the spacer. I used Locktight and torqued everything to about 25 ft/lbs. I want to distribute the stresses as evenly as possible. Well, that's about it. Not perfect, no cush drive, but back on two wheels.