Trepan Circle Cutter

Hi folks :)

I have a few modifications and improvements planned for my Dore Westbury mill, one of them is to the hight adjustment system.

The standard approach uses a combination of a keyed coller around the main colomn which has a spiral cut into it. The incorporated key fits the spiral in the coloumn and by inserting a small bar into one of the many holes drilled around the circumference of the coller, it can then be turned one way or the other which moves the head up or down:
https://i.loli.net/2019/04/02/5ca2556d1c2ec.jpg

While quite a neat and compact solution, it can get a bit tedious and found I often put the bar down absentmindedly when concentrating on the job at hand. So before I fully reassemble the mill again (having completed 90% of the restoration), I thought it would be a good time to see what I could do to make the system a little more user friendly.

My thoughts on the matter eventually turned to incorporating a worm and wheel combo and eventually found a set on ebay with a wheel big enough for what I had in mind. The idea is to bore the ID of the wheel to a slip fit for the main colomn and then pin it to the coller (though I may make a new one as there are so many holes in the original). I then plan to make a mount for the worm that will utilise the two colomn clamping points as the bolts for that are quite chunky.

I know iron is often used as a bearing material itself but I would prefer to guard against further wear to the main casting as it shows evidance of such from past use, so I'm going to make a brass washer that will separate the steel coller from the iron casting as I have a pile of coated brass plate I can make one from.

Enter perfect excuse to make another tool for the workshop :p
https://i.loli.net/2019/04/02/5ca24c82d63d3.jpg
https://i.loli.net/2019/04/02/5ca24c5ce0e5f.jpg

The build wasn't as straightforward as I'd anticipated and actually became quite the rollercoaster of fails and successes but I'm pleased with how well it turned out in the end.

I decided to film the build process for my youtube channel and didn't think to take WIP pics at the time (sorry) but for those that are interested in watching, the link below will take you to the playlist:
https://www.youtube.com/playlist?lis...oA0_UFE4rEmwXG