The thing with boring heads is they are designed to do one job, bore accurate holes.
Having used almost all the flavours they come in, from very expensive to a home made job, they still only bore a hole. It is just that some are easier to use than others. They range from the cheapo Chinese ones, to thousand buck 'super accurate' ones, but still it boils down to making accurate holes.
It is like everything else, if used CORRECTLY, most will work superbly, even the cheapo chinese jobs, which I use, and that must now be about 15 years old and bored hundreds of really BIG holes, very accurately.
More expensive doesn't always mean better.
All you need to do is to find one that suits you in cost, looks and range. A 2" or 3" is a good size for normal boring. I would suggest one that you can change the mandrel on, as that will allow you to use it on different fitting machines, and won't become redundant as your shop grows and you get larger machinery.
People seem to think that the size of the boring head is the size of hole that it can bore, that is incorrect. If you wanted to, but I wouldn't recommend it, you could use a 2" boring head to cut a 10" diameter hole, it all depends on what sort of tool you fit into it. What the size means is the range it will work over, so if using normal sorts of boring bars, held in the normal two or three positions, a 2" one could bore from say a 1/4" to a 4" hole, depending on the cutter size, and a 3" one could manage a 6" diameter hole (just double the head size).
I'm sorry if you know all this, but for someone just coming into machining, it could be a bit of a minefield.
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