When purchasing a band saw there are many options to consider. In this article I will cover the wheels of the band saw. As we all know, the band saw blade runs on two wheels, an upper and lower wheel, that are powered by the motor. Although the lower wheel is fixed, the upper wheel adjusts to allow the blade to be positioned and aligned properly.
Alright, now for the good stuff. The larger the wheel diameter, the longer the blade will last. The reason for this is as the blade gets turned around the wheels, it flexes around the circumference of the wheel.
The smaller the wheel, the more the blade has to bend around the smaller circumference to keep in contact with the perimeter. When the band saw is running, the blade is actually turning a few hundred times per minute around the wheels. This creates a lot of stress on the metal blade.
Eventually, the metal gets brittle, and the blade will break. Bottom line, when purchasing a band saw, look for wheels that are at least 12 inches in diameter. This will lengthen the lifetime of any blade that is being used.
Another important factor about the band saw wheels is the material from which it is made from. Standard wheels are made of either aluminum or cast iron. (However, I've seen cheap ones made out of hardened plastic if you can imagine!) Cast iron is obviously better for its durability and also because of its weight. The lighter aluminum will not have as much momentum as the heavier cast iron wheel.
You'll also notice that the band saw wheel will have a crown, that is , it will have a slight curve on its outside perimeter where the band saw tire rests. This slight curve called the crown keeps the tire centered on the wheel while it is in motion. Some large saw mills will use saws that have flat wheels, but most smaller saws will have a crowned wheel.
The crown will keep the tracking alignment more automatic requiring less tension adjustment from the user. Too much of a crown however is not good for the saw blade as it creates more stress and will reduce the life of the blade.
Lastly, concerning the wheels, in order to work properly, they must be aligned and in proper balance. Otherwise, misaligned wheels will create vibration in the blade as it turns. Ask the salesperson if the alignment was done using static or dynamic balancing.
Without going into the mechanical physics, static balancing is good, but dynamic balancing is better because it means that it has been static balanced plus it has also gone one step further. (If you want to read about the physics involved see this page : http://www.balance.net.cn/phe.htm)
So, to summarize, if you want the best quality band saw, as far as the wheels are concerned, you are looking for:
1) A wheel diameter of at least 12 inches
2) Cast iron over aluminum
3) Dynamically balanced over statically balanced