This is a simple “Loos” type tension gauge which I made to set the rigging on my yacht.
The main body is made in one piece on a standard 200mm bed.
The springs can be pretty much any common type of spring of roughly the right size and tension as the gauge will need calibrating in any case.
I carried out calibration by using the “wire stretch” method (1mm stretch over 2meter length of 1X19 wire is 5% of breaking load) and then marking the gauge at 5% and 10%.
After testing I found that to be accurate enough to extrapolate and mark the higher tensions.
There can be a very high load on the wire bending lugs and so I added holes so that screws can be fitted to increase the strength.
I suggest using a high number of perimeters and top and bottom layers.
However, I found PLA would stand pretty high loads (at least 15% breaking load) with 3 perimeters and layers and no reinforcing screws fitted.