Neat project, I'll be following this.
I have a set of plans to build the Magnatrac 1800, the one that uses a 4spd transaxle. Hopefully someday I'll have the time to build it. Just looks like something fun to build and play with. I wanted to get plans for one of the newer ones like the MT 3000, but they seem real stingy about releasing any plans that use their current track system.
MT 1800:
One bit of advice, and you may already employ this technique, is the use of hole saws. I have found that any hole 1" and over is much easier to make with a good quality hole saw. All the Lenox ones I've used have been surprisingly accurate. I've made holes as big as 2.5" through 1/2" plate with them with great success. I like to drill a 3/16 pilot hole to line them up, then just go slow (200-500rpms depending on dia.) and clean the chips out often. I also keep a bowl of water nearby to occasionally dip the hole saw in to cool it. I stopped using cutting oil years ago in favor of water for any drilling processes. Saves a lot of time cleaning parts before welding and I haven't noticed and reduced life of the bits either.
Also, I really think if everything works well after an initial test run, you should send out all the undercarriage related parts to get professionally heat treated. It's not terribly expensive but will increase track and sprocket life by a lot.
Look great so far. :thumbsup: