I work on pretty much anything with an engine but I mainly work on small engines.
I rebuilt my 1st old Rochester 2 barrel carb when I was in 2nd grade and completely rebuilt my 1st old 3hp Briggs mini bike engine (with help from my late uncle) shortly after that lol. I opened my own small engine "shop" about 35 years ago. My shop might be small but I have pretty much every tool that I need.
My late uncle went to school for small engines and got certified and ran his own shop down at the family farm for many years. He taught me pretty much everything he knew. 1 thing that he taught me was to Never cheap out on a repair and to be 100% honest with your customers. Every spring I get a hand full mowers that other shops had blundered repairs on. You would be amazed by some of the blotched repairs that I have seen over the years. Truthfully I have lost a few customers because I may be a bit to blunt? in pointing out other peoples mistakes lol.
I could use a good 2 1/2" R8 taper boring head for the old Bridgeport that I have down at the farm. Had one of those $100 chinese Ebay ones and, ya do not buy one. A decent quality US made one is around $300 and a good used reputable name brand one is between $300-$700. Just haven't made it that far yet but I would love to be able to bore and rebuild small engines.
I have no idea why I got so much harmonic vibration with that Chinese boring head but it was really really bad. No matter how tight you clamp your insert down, the vibration would loosen up your insert. I'm thinking that the taper fit not being perfect and questionable metal quality and poorly machined threads might have been the problem. I wrecked 1/2 a dozen good inserts and gouged a K301 block up real good before that thing went in the scrap bin. My uncle is really good with that old Mill and he could not get it to cut worth a darn either. We could get it to cut decent? but you had to crank up the speed which would quickly burn up your insert.