I am pretty sure what you have is a machine made by W. W. Grinder in Kansas? Excellent machine, unfortunately the company doesn't exist anymore. They were bought by GardenWay Assoc. (makers of Troy-Bilt tillers at the time) who continued making and selling these chippers, but GardenWay eventually got bought/taken over by MTD. Since MTD had their own design, they didn't take the W. W. Grinder line over. I had heard, but not confirmed that Murray did take it over, but Murray stopped making them some time ago, and Murray no longer exists either. What this is, is a long story to explain that some parts may be hard to find, but the machine is good enough to try to keep it running. As to parts, engine parts are available at any small engine repair/parts shop, bearings are generic and available thru many sources, the drive on these is really simple and those parts are alos easily found. The tougher ones to find are the shredder "T" shaped cutters and the
chipper knife. The
chipper knife can be made by any decent machine shop, and I've seen prices at around $75 to $100 for one. The "T" shaped cutters in the shredder section can be turned 180 degrees for a fresh cutting edge if they haven't been done before, and they too are available if you search Ebay looking for Troy-Bilt Tomahawk and Super Tomahawk parts.