One of the first things to do is identify the material you will be cutting with your band saw. Most home shops are probably wood shops, so this article will address buying wood cutting band saw blades.
There are several factors to look for in all wood cutting bandsaw blades:
First, the blades' teeth should look and feel sharp. Think pointy sharp rather than comb-like!
Second, the teeth -- their angle, size, and placement -- should look uniform. This will provide a smoother and more even cut, as well as a more efficient cut.
Third, look carefully at the weld that creates the necessary band -- or loop -- blade.
8 1 4 Saw Blade
Remember, the blade starts as a long straight piece and is then welded into a circle.
The necessary welds should be smooth.
The two ends should line up cleanly.
The blade's weld should be ground down to match the thickness (or be a bit thinner) of the rest of the blade. If the weld is straight and good, but a bit thick, and everything else looks good,you may choose to grind it down a bit more yourself.
If there are any other problems with the blade, it probably isn't worth trying to fix.
Blade Width
For most wood application, a 1/2" blade will probably work unless you need to small a very small radius. While narrower blades are available, it becomes a matter of balancing blade width with stability.
A more narrow blade is less stable, can be more easily twisted (NOT a good thing!) and can have a tendency to bow when it needs to make deep cuts.
By its very nature-- the ability to saw curves -- a band saw needs to be able to cut as accurately as possible.
In most wood cutting applications, a 1/2"blade will probably the best bet. If you DO need a narrower blade, try a 3/8" blade. Both the 1/2" blade and 3/8" blade come in several different teeth profile options.
Number of Teeth
In addition to blade width, band saw blades are also identified by the number of teeth per inch, known as TPI. Teeth per inch (TPI) can vary from 3 to 24. Generally, the more teeth, the smoother the cut.
There are three general rules to follow when deciding the teeth per inch (TPI) you need on a band saw blade.
A coarse tooth blade (2, 3 TPI) should be used for resawing wood and cutting thicker stock up to 8".
For general wood applications, a 4 TPI blade will cut 3/4" wood while a 14 TPI blade will result in a slower cut but with a smoother finish.
Deciding on the appropriate TPI for a specific task will probably mean a compromise.
Rule 1 - Appropriate Number of Teeth Needed for Optimum Performance:
Having 8 teeth cutting into the wood at any moment is usually the most efficient in terms of performance. Vibration, as well as control, can be a problem if there are fewer than 6 teeth in the wood.
On a band saw blade, the gullet is the space within the curved area between two saw blade teeth.
Problems can arise with more than 10 teeth cutting into the wood, because the area of the gullet is too small and the sawdust isn't removed, causing sawdust to clog.
In an ideal situation, the gullet area of the tooth should fill with sawdust to only about 75%.
Rule 2 - Finding the Proper Feed Rate:
It seems to be instinctive for many of us to feed a band saw too slowly. I know that I have been guilty of this!
As a general rule, try to find a feed speed and pressure that will slightly overload the tooth gullet and then maintain that speed and pressure. The idea here is to use the natural overload to dampen the blade and its tooth vibration and thus provide a smoother run.
As you get more experienced, you will be able to tell the proper overload rate by the sound of the saw as it cuts. As in life, whining is bad! LOL In the case of a band saw, it means that there is too much vibration and the cut is likely to be rough. Aim for pushing the cut to the point that the whine stops. If there is still a problem, you may have too much tension in the blade.
Rule 3 - Exceptions to the Rules
Again, like life, there will always be exceptions. These rules will work on softwoods and the more common hardwoods. Extremely dense woods or resinous woods will likely break these rules.;-)
"Reaching a Compromise"
Many times, when working with detailed or precision cuts, running the cut to the point where the whine stops may result in a speed that is too fast to follow the layout line accurately.
On the other hand, reducing the feed speed keeps the gullet from being loaded enough to smooth the cut and a rough cut edge may result.
In this case, if you can manage to reduce the feed speed without burning the wood, try using a blade with a higher Teeth Per Inch (TPI) rating than is recommended. In this case, reducing the tooth gullet may allow for a slower speed feed and resulting in a smoother cut, simply because the gullets are filling with sawdust.
Another and perhaps better option is to slow down the blade speed enough to accurately follow the cut line while still using the blade with the proper TPI. The reality is that this is rarely an options due to the lack of variable speed bandsaws.
Wood Thickness and TPI
The rule of thumb with band saw blades is that for wood between 1 1/2 inches and 2 inches thick, use a 1/4 inch band saw blade with a TPI (Teeth Per Inch) of 6
For wood about 4 inches thick, move up to a 1/2 inch blade and a TPI of 3. In both of these cases, you will have approximately 10-12 teeth in the wood cut.