Background: for several decades I have had cheap(ish) bandsaws that I just tightened by pushing and feeling the blade, knowing that such saws cannot really overtighten the blade.
I finally splurged to buy a nice bandsaw from Harvey Woodworking. That got me thinking of finally measuring the blade tension to the design spec. Commercially available bandsaw tension meters are expensive and don't really look that convincing, so I designed and built my own.
For typical carbon steel blades, the usual tension spec target is around 15,000 psi (carbide tipped blades maybe more). Given the elastic modulus of most steel grades that is equivalent to a strain of about 0.05% .
The problem of measuring that over an accessible distance of the blade, (e.g. 6") is that strain is really only 3/1000 of an inch, i.e. barely measurable with a standard dial gage with any accuracy.
So I designed and built a measuring gadget that amplifies the strain movement by a leverage of 1:25, resulting in a well measurable distance with a cheap dial gage from Harbor Freight, i.e. 75/1000 of an inch. Here some pics:
Parts cut from 3/4" bamboo plywood. Other quality BB plywood would surely work as well. But I love bamboo, since it is hard, elastic and cuts without any fuzz.
