Bandsaw Tension Reading

[Ken Massingale]

A thread on another forum has me second guessing myself.
Do you read the tension on the bottom or top of the square nut that's under the tension spring? Not that the markings really mean anything anyway.

[cgallery]

I take a spiritual approach: I set the tension to the top of the nut. I then close my eyes. If I see visions of teepees and wigwams, I realize I've made it two tents, and I back it off a little.

Hope that helps.

[Thom2]

Lmfao!!!!!

[Tom Miller]

FWIW, my BS has a little red washer between the nut and the spring to make it easier to read the tension setting. So, I vote for the top of the nut.

Regards,
Tom

[Ed62]

Not that the markings really mean anything anyway.

'Nuff said!

Ed

[ChrisD]

FWIW, my BS has a little red washer between the nut and the spring to make it easier to read the tension setting. So, I vote for the top of the nut.

Regards,
Tom

Same thing on my Delta. But like you said, Ken, the graduations probably don't mean a thing. So I really don't trust that nut any more than the one who sets it!

[Ken Massingale]

Thanks guys.
Sooo, I need to consult a Shaman, get out the fingernail polish again and mark a line on the top of the nut (the one under the BS spring, not me) and finally, go back to where I am and try to forget that I ever posted this nonsense! :-)

[ExYankee]

I’ve been trying to figure out the principle of this type of guage,

I have a bunch of dial indicators I could dedicate one to if I can figure out how the deflection is measured. I did a search on google and found a ‘shop made tension guage on the FineWoodworking site and because the LOML bought me subscription for Christmas and the first issue came Friday I can get the access to all the electronic plans and articles for $15 I am going to sign up and see how they did it.

[Ken Massingale]

John,
I've been meaning to find time to try that.
It basically relates the stretch of the blade to tension. I saw a chart on FWW (I think) that cross referenced the dial indicator reading to blade tension. So when you tension the blade to a 'distance' reading on the indicator it indicates a corresponding tension.
At least that's my understanding.

[Tom Miller]

I’ve been trying to figure out the principle of this type of guage,

I have a bunch of dial indicators I could dedicate one to if I can figure out how the deflection is measured.

I made one -- it works, but it's a little fiddly getting it clamped (fiddliness could easily be designed out; I haven't taken the time).

The idea is to clamp a support to the blade to hold the dial indicator body, with the blade at zero tension. Then, at some fixed distance lower on the blade, clamp a block that the dial indicator foot can rest on, and zero the indicator.

As you apply tension, the blade will begin to stretch, and the dial indicator will tell you how much.

Two things you need to know: the conversion of linear stretch to blade tension in psi, and how much tension (in psi) is recommended by the blade mfr. The conversion will be a function of how far apart your clamps are spaced. If memory serves, I think if your clamps are 5" apart, then each 0.001" deflection is 6000 psi. Recommended blade tensions may be in the range of 10,000 to 15,000 psi, IIRC.

Since tension is measured in psi, it's normalized to the blade cross-sectional area, so the conversion from linear stretch to psi is the same for any blade size.

Keep in mind that you won't measure any blade stretch until that last one or two turns of the crank.

Regards,
Tom

[bthere]

There was an interesting, but brief, article by Mark Duginske in the last Woodworkers Journal where he said that the markings on the bandsaws tend to be accurate. They tested several aftermarket tension gauges and found that their gauges did not agree with each other and that they were not very accurate either. There wasn't a lot of supporting information on the test methodology, but it was interesting anyway.