Hi, I've watched 2 of your gear related videos and now this one as well. I love your content and how you present things in a digestible way. That said, I noticed a few areas you could improve on with your jigs in particular and just wanted to give you some tips that are standard in industry among machinists and tool makers. While there are a lot of specific details I could give, I want to touch on two concepts: chip clearance and bushing sizing. What I've notice in both of your videos is that you don't leave any room for chips to clear out. This is critical as it will extent the life of your cutting tools as well as your jigs, particularly when you use them with metal as you mentioned you only get a single use out of them. The concept is as follows - You want to maintain between 0.25*TD to 1.5*TD of room between the work piece and the bushing (or hole) on your jig. The exact value depends on the depth of the hole, and the material being cut. For example, you could get away with 0.5*TD when drilling cast iron due to the fine chips, however you generally won't go less than 0.5*TD with cold-rolled-steel and aluminum as they produce long, stringy chips. In the case of reaming you would want near 0 clearance and with secondary operations (such as slightly enlarging an existing hole) you can err on the side of less clearance. Of course you always want to minimize the amount of clearance to maximize accuracy. Bushing sizing is much easier to explain, but the concept is that you want the length of the bushing (or simply the hole that is guiding your tool) to be between 1*TD to 2*TD to adequately guide the drill. TD being tool diameter in this case. Additionally, in order to accurately locate cylindrical features and account for deviations in size, you should use "V" features in your jig (see V blocks) rather than matching the contour of the round feature as you did for the jig shown in the first part of your gear video series. Feel free to send me a message and I can forward you some PDFs pertaining to jig & fixture design which would also include some additional details apart from what I mentioned here. I'm enjoying your channel and look forward to watching the other videos in your gear series. Best

This is awesome 😍 Love how It came out !

Keep it coming!

You could in this case have made just one end of your jig and flipped it back and forth, saving material and print time.