different materials require diffent speeds!
Most woodcutting bandsaws run between 3000 and 4500 ft per minute.
That's fine for cutting wood because a woodcutting blade will have larger teeth and fewer of them than a metal cutting blade. It allows the woodchips/sawdust to be cleaned out of the kerf easily and quickly. If that doesn't happen, the blade will overheat, or stall and go off the cut path. :sad2:
Metal cutting speeds depend on the metal!
You can cut aluminum up to 1" thick using a wood cutting blade at woodcutting speeds.
Cutting steel has a range of 50 FPM to 200 FPM depending on the type of steel. As you can readily see, 300 FPM is 10X slower than 3000 FPM. So, you need a 10 to 1 speed reduction using the pulley sizes and typically a jack shaft to reduce the 3450 rpm of the motor to a speed that will be appropriate for metal cutting.
Here's a photo that kind of setup:
In order to size your pulleys correctly, you need to determine the proper speed for cutting the material:
As suggested above there will be some calculating required to change RPMs to FPM based on the diameter of your bandsaw wheels. Here's an online calculator where you enter your pulley diameters to get the speed in RPMs:
http://gadi.agric.za/software/renting/pulley_calc.php
The formula for circumference of a circle is: C= 2 ll R or 3.141 X D.
For example using this online circumference calculator we find that a 14" diameter bandsaw wheel has a circumference of 44". Dividing that by 12 to get ft rather than inches, you get 3.6666 ft. Now you know that for each revolution of the driven wheel the blade will move 3.666 ft. So, at 100 RPM it will move 36 ft, at 1000 RPM it moves 366 ft. etc.
You can drive the bandsaw wheel at the same speed as the motor, it will need to be reduced. Motor come in two different speeds, 1725 RPM and 3450 RPM, so depending on what speed your motor is, you can start to calculate the blade speed in FPM. It's a bit of a pain, but there ain't no other way. :sad2:
Grizzly has a good assortment of pulleys:
http://www.grizzly.com/search?q=(machine+AND+pulleys)+OR+(machine+OR+pulleys)
