Maybe testing shaft hardness is a misnomer, I'm less concerned with how hard a spear actually is than how bend resistant it is. More fish have been lost because of broken shafts than bent shafts, and who wants a bent shaft anyways. Also this is comparative testing, measuring shafts against each other, not a standard test. But after enough shafts tested you can develop a standard. I came up with this test because I didn't believe the hype about certain shafts and wanted to know for myself, and feel it's a real world test, the results tell me exactly what I need to know. So here's what you need:
1. Vice attached to something solid.
2. Tape measure.
3. Fish scale
4. Shafts or straight pieces of shafts at least 50cm long.
The shaft gets clamped hard in the vice. The distance from the top of the vice jaws to the flopper pin hole is 40cm. I chose 40 cm because it seems like a reasonable length of shaft that could get torqued on in a spearfishing situation, and will not be extremely difficult to bend in the test situation. You can choose whatever length you want if there's a good reason for it, it just has to be consistent for all the shafts.
The flopper should be facing directly away from the pull direction, this way it will trap the hook of the scale and the scale will not slip off the shaft. It will also allow you to quickly check for the bend because you'll know in which direction it will be. It's nice if the scale is good quality and accurate, and has a sliding marker to clearly show when you've reached the target pull weight.
I pull slowly and evenly to 10lb, that's the weight I decided to start with, remove the spear from the vice and see if it bent. Then do it again increasing the pull weight by small increments until the shaft bends. It's a single clean bend so I can straighten the shaft after. That's it.
