Yeah had to help someone out and make sprockets for an old chain drive snow trac machine. It was a real odd-ball casting that wasn't what we would call a "stock" item here. I still have to bore out the 2" hole and attach the freshly made drive hub with a little 309L filler. The sprocket is almost 13" in diameter and is set up for a metric chain spaced similarly to an ANSI #80, but narrower. The original part was missing almost half of it's teeth so I ended up using the scan CAD and then hitting the books to figure out what standard it was produced to nearly 60 years ago before it was completely wore out.
Metrology results and research lead me to a British chain standard that looks to have evolved to an ISO 16B1 classification over the years. Overall it was a fun reverse engineering exercise and I'll post some scan stuff and steel cutting on YouTube at some point next week. It will probably be interesting to some folks that don't normally work in steel because I used some HSM for a lot of it and pushed a 3/8" carbide EM to the operational limit for a few lengthy slot cuts. The load meter was yellow for quite a while with no missed steps thankfully. The base material was 3/4" normalized PVQ ASTM a 516 Grade 70. This material should provide a nice balance of toughness and other physical properties for its use out in the frozen tundra of Alaska (304SS would have been ideal, but over the budget). Fun times and was definitely a change of pace from the Titanium and Stainless Steel work that I normally do here. Due to its size I ended up machining it in halves via a fixture and dowels vs. playing around with my rotary table face plate. I figured that this way would provide more rigidity and it worked quite well. Attachment 298994