I apologize for asking such a question, but for a complete novice,
what makes a good saw frame?
No need for apologies, the question is very pertinent. There are 3
things to consider, - stiffness, balance, and alignment.
To my mind alignment should be primary consideration. Under no
circumstances should a blade be allowed side contact. (There are
situations when sides are used exclusively, but it is no longer
sawing, but filling. Blade is often in reverse position.) If this
happens, the life of the blade is shortened significantly and sawing
becomes erratic. The way to tell alignment is look at how blade is
secured. The best way is between 2 flat surfaces. Also, blade can be
aligned when frame is not in use, but get out of alignment once in
use. That is such a common problem.
Stiffness comes next. The reasons are the same. If frame flexes
under the load, blade will expose it's sides with disastrous results.
Besides, when frame straightens out a whiplike shock is sent into the
blade, which it is unlikely to survive.
Balance is not very obvious but highly desirable feature. What it
means is while sawing you should be able to relax your wrist
momentarily. I am not saying letting it go, just relax and not to
loose control. If you can do it, than sawing for long periods of time
is not a problem.