Thanks for the advice! I knew I had heard of something along these lines, but "Skip tooth" had completely eluded my recall. I've found a 4TPI skip tooth in 3/8" for my saw (123").
How do y'all check for good blade tension manually? The tension gauge on my saw always seemed questionable...and then the needle on the gauge got bent, rendering it completely worthless. I've generally just plucked the blade and listened for any flapping sounds (too loose).
TIA!
The tension guides in most bandsaws are highly dependent upon the actual length of your blades, and some manufacturers (such as Olsen) sell their blades oversized by up to an extra inch or more, which can really throw off the accuracy of the built in gauge.
The simple, but unsatisfying, answer to your question is that you will get a feel for blade tensioning with experience. Unfortunately, that is not entirely helpful when you are just starting out.
But in general, the greater the span between blade supports (your upper and lower guide bearings) and the thicker the cut the more tension you are likely to require, especially when using narrower and thinner blades stock, in order to prevent barrel cutting (where the center unsupported section of the cut tries to follow the wood grain and a curved, or barrel shaped, cross section results rather than the true vertical cut line you were expecting. The thicker and wider the band material (and these often go hand in hand with blade width, though not always) the less overtensioning you are likely to need to avoid barrel cuts because the wider and thicker blades are so much stiffer and resistant to deflection versus their narrower and thinner counterparts. That is why we often use our largest and thickest blade for thick resawing operations (where there are no curves to be concerned with).
A good starting point is to tension your blade to what you think may be adequate and pluck the backs side of the blade (the portion in the rear column) -- if the tone is muddy and not a pure tone it is definitely undertensioned. Once you have a clean and unmuddied (though often quite low pitch) tone you are at least in the right ballpark and you can adjust up from there based upon your depth of cut and blade width and thickness. Others prefer to judge by blade deflection, setting up the blade and guide bearings and then applying a modest amount of lateral force upon the blade to see how much it deflects, but, again, experience becomes your guide here as well.
Your best bet if you do not yet have that experience level is to save a scrap block of like wood of equal thickness and make some test cuts and curves in it after you have setup tensioning as your best guess suggests ought to work. Then use a straightedge at various points along your test cut and curves a to see if there was in barreling of the cut (convex or concave), if so then increase the tension again and make another test cut in the test block. On the other hand, if the test cut surfaces are true and flat in the cut plane then you likely have adequate tension and should be able to proceed with reasonable confidence and try the real thing.
Either way, you will get the hang of things in fairly short order and you will become much more confident in intuitively adjusting tension.
When you go to setup the guide bearings or blocks, when first learning fold a dollar bill in half, then fold that half in half again over the blade (two thicknesses of the bill, each side), then adjust the side guide bearings/blocks snug to the folded dollar bill (and remove the bill!). Adjust the rear guide bearings/blocks so that the blade is just missing making contact with the blade -- initially you can snug up to the dollar bill there as well. Then run your blade through a full revolution, or at least until the welded joint, and verify the weld joint does not bind with the guide bearings/blocks -- if it should bind then increase the gap between the side guide bearings (perhaps three bill thickness per per side for that blade or possibly smooth out the weld) until the weld clears cleanly with no binding at all. Of course, all of this should be done after you have the blade centered on your wheels and running true as there is no point in setting up the guide bearings until the blade is running stable and centered on your wheels. You will also want to first lower the upper blade guard to about a half-inch, or so, above the highest point of your workpiece before setting up the guide bearings as changing the guard height can affect the alignment of the guide bearings/blocks relative to the blade.
Good luc!. You will master tensioning and blade setup pretty quickly once you start using your bandsaw more, so just use some test cuts in the beginning to give you some initial confidence that things are setup correctly for your intended cuts without the excessive tensioning that can break a blade.