Originally Posted by
Denis Kenzior
This was confirmed with 2 Lenox tension meters and via stick + .0005 dial indicator. In my testing the 'clamp a digital caliper' over 5" was not accurate or repeatable compared to a dedicated tension meter.
This is one of the reasons that a lot of "our" discussion about tension stays in the theoretical realm. If we all had load cell based strain gauges we could get into the minutia. I have one for 14" cast saws but it isn't useful for these high psi discussions.
I have found over the years that both the commercial strain gauges and DIY methods for measuring strain vary a lot in their precision as well as accuracy. Because I have the load cell based strain gauge for small saws I can get an idea about the accuracy of different methods (at least at up to about 15kpsi). I use a particular Lenox gauge (out of the 3 Lenox, 2 Starrett, an Iturra and the caliper method using both calipers and dial indicators) because it was the most precise (repeatable) and close to being the most accurate, again checked using the load cell. In the end, MY 30k psi is likely to be different than everyone else's 30K psi.
In reality, this is just a fun (for some) internet discussion since our numbers are just too unreliable to compare. It does produce good anecdotal information regarding what blades will work well on what saws and it reinforces the fact that large (for us) carbide and bi-metal blades need a lot of tension which requires a stout frame and a hefty spring and tensioning mechanism to control the spring.
Of all the laws Brandolini's may be the most universally true.
Deep thought for the day:
Your bandsaw weighs more when you leave the spring compressed instead of relieving the tension.