measuring bandsaw blade tension

[mreza Salav]

I always wanted to measure the tension I put on my resaw blade (1.25" resaw king carbide blade). It's a relatively thin blade (0.024"). So tonight spent about 15 minutes to fabricate a very simple jig using a dial indicator to measure. At 12" of blade, depending how much I crank the tension wheel, I could measure around 0.010-0.013" of stretch. That translates to around 24100-31,400PSI which is around the range this blade should be.
When I ordered the blade I ordered a length in the middle of the range specified by the manufacturer. Next time I think will choose a little smaller blade (within the range).

tension.jpg

[Bill Space]

Nice simple setup!

Was there a reason your measurement variability was about 30%? I would have expected you could measure the blade stretch to within a thousandth fairly easily...perhaps a dial indicator issue?

I will have to try a similar setup when I get a new bandsaw, which I hope will be within the next month or two.

Bill

[Van Huskey]

Was there a reason your measurement variability was about 30%?

I don't think he was saying there was that much lack of precision in the setup, he pointed out he was changing the absolute pressure.

We should all thank Mr. Young for his study of linear elastic solids, or given the particular saw maybe Mreza should thank Giordano Riccati, the Italian scientist which did the same experiments years earlier than Young.

I am a big proponent of measuring bandsaw blade tension and setting it correctly for a particular blade, the key is almost everyone has the needed equipment in their shop. It can be as simple as 2 C-clamps and a set of calipers.

[Bill Space]

Perhaps I got confused, because in my mind when changing the tension from zero, which I think you need to do to get a meaningful measurement of blade stretch (and therefore total blade tension), the measured change would be 0~.013", as blade tension was increased.

Measuring stretch on an already tensioned blade would tell one the amount of tension added, but not the total tension on the blade. In my mind anyway...

Not sure now, but on first read I thought the OP was stating a range within which he thought he was tensioning the blade.

I look forward to the OP's response.

[mreza Salav]

I started with no tension on the blade and increased the tension, 0.013 was about the maximum I could crank the tension wheel, 0.01" was about a full turn or so before that.

[Chris Fournier]

Neat use of scraps and universally useful tools to answer some questions for yourself! I did the same thing years ago myself and then went back to how I've always tensioned my BS blades - by feel and experience. The exercise was worth it though as it really is useful in practice to understand that metal moves under tension and compression.

Another cool thing to do is measure how much the BS frame moves when you tension a blade.