Bill Space
11-22-2018, 4:33 PM
I have an old, but well respected, 20” Davis & Wells bandsaw I am setting up as my main bandsaw. But I understand with the factory spring it maxes out at about 15~18,000 PSI on A 3/4” blade. Forgive the generality, I did check what the maximum pull the spring can put on the blade, but forget what that number is at the moment, and also forget what the gage of the blade was when I did the calculations. None of these specifics relate to this question anyway, which is generic in nature.
I put a dial indicator between the upper and lower horizontal sections of the “C” frame of this bandsaw, between the axles, and measured the deflection as I cranked the spring nearly fully compressed. I got 0.012 deflection between the axles.
Now it seems if I wanted to increase the maximum blade tension I could purchase a stronger spring. This would result in more stress on the bandsaw frame. Not sure how much frame deflection would be safe. This got me thinking...
The vertical wood shop bandsaw is not a sawmill. There is likely a practical limit to the width of material that is resawed most of the time. Does one normally resaw a 10” wide x 12” high, or larger, pieces in the home shop. I keep telling myself probably not.
So now to the question. It is likely that for a given bandsaw one could increase the size on the tension spring until the frame of the saw was damaged, while trying to reach a desired level of blade tension. At the same time, resawing is generally ( my assumption) dealing with relatively high and narrow pieces. For example, maybe 12” high (or more) and 4” wide, or thereabouts, or thinner.
So why could one not add a temporary vertical support in the C frame between the axles. Granted, this would require a hole to exist(or be made) in the saw table, to allow positioning of the support. And require the swapping of the tension spring. But the extra support would seem to negate the fear of damage to the saw from the use of a heavier spring. So higher blade tensions could be attained without fear of damaging the saw.
How hairbrained is this thought?
Bill
I put a dial indicator between the upper and lower horizontal sections of the “C” frame of this bandsaw, between the axles, and measured the deflection as I cranked the spring nearly fully compressed. I got 0.012 deflection between the axles.
Now it seems if I wanted to increase the maximum blade tension I could purchase a stronger spring. This would result in more stress on the bandsaw frame. Not sure how much frame deflection would be safe. This got me thinking...
The vertical wood shop bandsaw is not a sawmill. There is likely a practical limit to the width of material that is resawed most of the time. Does one normally resaw a 10” wide x 12” high, or larger, pieces in the home shop. I keep telling myself probably not.
So now to the question. It is likely that for a given bandsaw one could increase the size on the tension spring until the frame of the saw was damaged, while trying to reach a desired level of blade tension. At the same time, resawing is generally ( my assumption) dealing with relatively high and narrow pieces. For example, maybe 12” high (or more) and 4” wide, or thereabouts, or thinner.
So why could one not add a temporary vertical support in the C frame between the axles. Granted, this would require a hole to exist(or be made) in the saw table, to allow positioning of the support. And require the swapping of the tension spring. But the extra support would seem to negate the fear of damage to the saw from the use of a heavier spring. So higher blade tensions could be attained without fear of damaging the saw.
How hairbrained is this thought?
Bill