Replies

1. 
   forestgirl | Oct 10, 2002 07:30pm | #1

   Iturra Design, 1-888-722-7078 or you can make your own.  More on that later -- have to get some checks in the mail pronto!  BTW, if you own a bandsaw you must have an Iturra catalog! 

   forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl   ;-)

1. 
   user-274461 | Oct 10, 2002 07:53pm | #2

   Thank you for the info.  Iturra doesn't seem to have a web site?? and the number you gave doesn't work from Canada.  Do you have another number?

1. 
   forestgirl | Oct 10, 2002 08:24pm | #4

   Yep, 1-904-642-2802.  They have 3 gauges, ranging from $135 to $350, the latter being the Starrett.forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl   ;-)

1. 
   AlanTurner | Oct 10, 2002 09:56pm | #5

   Just a note to let you know that Iturra was great fro me.  Good stuff, great advice, and I love dealing with the owner and his family when I spend tooling money.  He carries the red link belts, great blade guides, and a wonderful tensioning spring (which is why I went to him initially).  His catalogue is quite informative, and he has written a piece comparing the Delta 14" to the Jet 14" which is quite detailed.

2. 
   alias | Oct 11, 2002 02:08am | #11

   just bought that tension gauge from iturra today and....bought the jet 18" yesterday........i hope i made the right decsion..... how is that gauge 135.00 one the starett was way to much after the bandsaw.............thanks keep that sawdust comin'....... bear

1. 
   forestgirl | Oct 11, 2002 04:22am | #12

   If you have time and remember, could you let us know how you like that gauge??  I too balk at paying $350 for a gauge when I paid barely that for the saw!forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl   ;-)

2. 
   UncleDunc | Oct 10, 2002 08:09pm | #3

   Starrett makes a bandsaw tension gage, and has a web page at http://www.starrett.com but the "On Line Catalog" button on their home page doesn't work for me. They probably have contact information somewhere on the page.

1. 
   DennisS | Oct 10, 2002 10:55pm | #6

   Unc' -

   What I don't understand about these clamp-on type tension gauges -

   Let's say you start with the blade loosely installed on the wheels; no tension at all to speak of. You clamp on the tension gauge and crank it up. The way I understand these to work is that they measure the elongation of the blade. Now say we put the blade on and tension it up to where the on-saw gauge says some reading, maybe even up to where it's supposed to be according to the spring gauge. Then you clamp on the tension gauge. And crank it up to get the elongation that's recommended.

   Wouldn't there be a significant difference between the amount of tension in case one vs case 2 since tightening the blade elongates it some, then tensioning to the gauge elongates it even more.

   Inquiring minds want to know....

   Thanks...

   Dennis in Bellevue WA

   [email protected]

1. 
   rreeger | Oct 10, 2002 11:48pm | #7

   There is an online video on the FW site that shows you how to make and use your own tensioning guide.

   http://www.taunton.com/store/pages/070551_excerpt.asp

   Pretty easy and informative.

   RR

2. 
   DonaldCBrown | Oct 11, 2002 01:12am | #8

   Wouldn't there be a significant difference between the amount of tension in case one vs case 2 since tightening the blade elongates it some, then tensioning to the gauge elongates it even more.

   Yes, of course.  That's why no tension gauge that I know contains instructions resembling your case 2. They are designed to measure total elongation after tensioning, so you have to start from zero. That is, you don't start from lots of tension  (and some unmeasured elongation) as measured on the spring gauge.

   You should first run the blade for a minute or so under whatever moderate tension is required for it to track properly. That takes care of any elongation from heating. Then back off and retension the blade just enough to take out any sags and the like. Then fix the gauge to the blade and measure total elongation as you apply tension.

   Works every time, unless you apply far too much tension and deform (introduce a permanent set to) the blade.

1. 
   DennisS | Oct 11, 2002 09:41am | #13

   Thanks, Don, for the explanation. That's pretty much what I assumed. One just has to take care to have the blade somewhat taught (like you say, no sags is all) and start from there.

   Dennis in Bellevue WA

   [email protected]

3. 
   JeffKurtz | Oct 11, 2002 01:21am | #9

   Are these tension gauges all that great, or is someone just trying to convince us we need another gadget?  I use the "flutter method" described on the Olson blade boxes - its the same way we do it with the big blades at the mill.

   Jeff

1. 
   DonaldCBrown | Oct 11, 2002 01:47am | #10

   I think the average woodworker could find lots more effective ways of spending his money  than buying a commercial tension gauge. The flutter method, hearing the right "thwang", and even using the markings on the saw (provided there's a good aftermarket spring installed) are all effective.

   But the article in FW recently about making your own tension gauge for essentially zero cost certainly makes it attractive to have an actual measurement of tension, even if only to serve as a pitch pipe for identifying the right thwang.

   Edited 10/10/2002 6:50:12 PM ET by Donald C. Brown

1. 
   user-274461 | Oct 11, 2002 07:12pm | #14

   Don,

   I agree  that this gauge is not the first thing a woodworker should buy but my bandsaw is a large 20" model that does not have a built in tension gauge.  It is capable of putting a lot of tension on the blade with a large diameter crank wheel so I don't want to over tension the blade and risk damaging some other parts.  The "twang" method only works if you have some way of knowing what the right tension is and then get used to the sound and feel of the blade for that tension.  I am sure once I buy a gauge and acquire that feel, I won't need to use the gauge any more.

   Anyone want to buy a used gauge about 6 months from now?  :)

1. 
   DonaldCBrown | Oct 11, 2002 07:24pm | #15

   The make-it-yourself gauge I mentioned is covered in FW No. 147 (Jan/Feb 2001). If you don't have that issue, I'll be glad to Email you a copy of the article.

   If you have some feeler gauges, a couple of 6d nails, a block of wood, and a couple of clamps, there really is zero additional cost. The author checked it against  one of the better commercial gauges, and  got readings within 10-15% at all tension levels.                           

1. 
   user-274461 | Oct 11, 2002 07:41pm | #16

   Thanks Don.   I do have that article and I may make a gauge instead of forking out $200 - $300 for a commercial model.  I already have a dial gauge that I purchased for measuring blade run out on my table saw so I may use that to build a more sophisticated gauge.  I am a mechanical engineer so I am pretty comfortable with the calculations to convert an elongation of the blade, as measured on the dial indicator, into blade stress (psi).  If I build it, I will post a picture here. 

2. 
   observer | Oct 12, 2002 07:27am | #18

   I would be obliged if you would run through an example of those calculations.

3. 
   DonaldCBrown | Oct 12, 2002 11:14am | #19

   Dick-

   Steels used for bandsaw blades stretch about 0.001 inch for each 6000 pounds/square inch of tension.

   Blade manufacturers recommend a tension of about 15,000 pounds/square inch for small-shop saws.

   A typical blade is about 0.025 inches thick. So, for a 1/8" blade, the cross section is about 0.003 square inches (1/8 x 0.025), and for a 1/2" blade it is about 0.012 square inches (1/2 x 0.025).

   To achieve 15,000 pounds/square inch tension on a 1/8" blade, then, requires a force of 45 pounds on the blade (15,000 x 0.003) The same tension on a 1/2" blade requires a force of 180 pounds.

   That's the force you must apply and is the reason typical bandsaw tension gauges are marked so that the larger the blade, the more cranking down on the tension you must do.

   But the elongation for tension applied in pounds per square inch of blade cross section is a constant (see first paragraph above). You just have to apply more force to a larger blade to obtain that elongation. Note that the calculation does not depend on the length of the blade.

   To return to the beginning of this explanation, a tension of 15,000 pounds/square inch will cause a blade of any cross section to stretch by about 0.0025 inches (15,000/6000). That's what you measure with a tension gauge.

   Note that the forces calculated in paragraph 4 are for a single section of blade. Because bandsaw blades are loops, there are two sections to which that force must be applied. So double the values in paragraph 4. That is, 90 pounds for the 1/8" blade, and 360 pounds for the 1/2" blade. Other blade sizes scale linearly from those values.

   But the bandsaw tension gauge operator is not measuring force, but rather elongation. Measure elongation to get the proper tension. Then mark on the saw the amount of spring compression or expansion (a measure of the force applied) for that elongation. So long as the spring remains within its elastic limits (no sure thing for the cheap springs supplied as original equipment with many saws) return to your marks for each blade size to achieve the proper tension. The tension gauge is needed for original calibration and occasional checking only.

   Edited 10/12/2002 4:53:41 AM ET by Donald C. Brown

4. 
   observer | Oct 12, 2002 05:33pm | #20

   Thanks Donald

5. 
   UncleDunc | Oct 12, 2002 08:44pm | #21

   Yes, thank you very, very much. Not only will this be helpful in setting blade tension, but I'm also toying with the idea of building a bandsaw, and this gives valuable design information.

2. 
   forestgirl | Oct 11, 2002 07:44pm | #17

   Me!  :-)forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl   ;-)