start of my homemade sawmill

[markct]

how do you measure the tension andy? is that the actual pull on the bandwheel at the end, or is that the actual blade tension measured with one of them fancy gauges they sell? i was just trying to figure out today how much tension i would need.

 

[AndyMA]

The band wheel on the drive end is in a fixed location. The idler band wheel is in a slide and moves toward and away from the drive wheel. It is "jacked" away with a large diameter threaded rod with a T bar handle to turn it. It is loaded with a heavy spring on the rod. Between the springs collar and the at the frame it jacks against is about a 2" diameter round thing that has a liquid filled pressure guage that directly reads out in pounds. You could probably build one, but I bet they are not too expensive from sawmill manufactures. Prior to using these guages, Timberking used a ruler and calculated the force by knowing the spring constant and setting the force by the compression of the spring. Either way is accurate. If you know the springs K factor accurately the measurement method woudl probably be more accurate. The guage is just quicker. When I get near the mill again I try and post a picture as ut is easier to understand that way.

Andy

 

[AndyMA]

Mark

You may already realize this, but the band blade where the cutting is taking place is not riding on the band wheel but rather is being deflected down about an 1/8" or so by a paid of idler wheels. One is usually fixed in location near the drive wheel and the other is adjustable so that it just clears the log being cut. These wheels are usually about 3" in diameter and have grooves. Also remember that a correctly tracking blade rides about 1/4 inch off the face of the band wheels and the idler so as not to damage the set of the teeth. just a few more thoughts that might help.

Andy

 

[Brad_Blazer]

If you have a blade tensioner with a spring, calibrating the K factor should be pretty straightforward. Just string a band (eg pallet band) around the wheels and attach a fish scale in the loop. If a spring type scale requires too much travel, try a digital model. The bigger sports shops have 50lb models pretty reasonable. Harbor Freight sells the spring type really cheap. You might want to approach each measurement from both directions or just jiggle the mechanism to avoid any error due to friction. Counting screw turns from zero tension might be an alternative to using a scale.

Have you seen this site? I'm not a sawyer but I like their blades in my 14" band saw. http://www.suffolkmachinery.com/six_rules.asp
Cool Project!
Brad