For a saw blade to cut well without badly chewing up the worn and becoming very difficult to control, there should be at least 2 1/2 teeth engaged in the thickness of the cut. Properly tensioned, such a blade will cut pretty quickly.
As you add more teeth than that, the area under the teeth for chips to collect decreases. Add too many more teeth, and the blade has trouble cutting as it is clogging itself - generating more heat than cutting. That's not good for the blade or the quality of the cut.
So how thick is the material you want to cut? Chances are you have a variety of different thicknesses you require cutting. So you need a variety of blades.
For stuff I do, I use #3/0 and #2 a fair bit.
Here's the handy chart:
https://blog.esslinger.com/jewelers-saw-blade-sizes-chart-2/ALWAYS use a quality blade. Rio Laser Gold has been mentioned. They are not bad. Other good ones are Pike, Antelope, Hercules. Perhaps not an exhaustive list. Pike is available on Amazon which makes picking up a few easy. Nowdays I find you can occasionally get a batch of lemons regardless of the manufacturer. But sticking with known quality reduces the odds of a bad batch.
When they start getting dull, replace. But, since you're asking the question, you'll break them before wearing them out. It takes practice to get to where you wear one out! Use lube. Wax works. Oil works - but NOT for wood. Use what you've got or get something to use. Insufficient tension and during the stroke they detension and break. Too much tension and they break. There is a learning curve. Let the blade do the work. Don't force it. Particularly don't force it on the return stroke. Orient the blade to cut on the down stroke - towards the saw frame handle. Use a good saw frame. Cheap ones often don't work nearly as well, any more. It used to be you could purchase the cheap German saw frame and except for the handle being on the thin side, it was good. But, not since production has moved to asia. I like the Green Lion saw frame, The Knew Concepts saw frame with the cam tensioning lever - but not the most recent revision, and an older German with replaced handle. There have been other good ones over the years. I keep different size blades in each which makes it handy. But I have a jeweler's bench setup so YMMV. A saw frame with narrower throat depth is easier to control. But, it can't cut as far without running into the frame. My frames range from 2 1/4" depth to about 5" depth.
Hope this helps some!
Gerald
