bandsaw blade tension question

[Carlos Alden]

Got a new bandsaw last month (Jet DX 14" - you may recall some of my questions about buying it...) and assembled it. No problems getting it together.

I installed the riser block kit and put on a blade intended for some initial resawing, a 5/8". This 105" blade balked at being put on the wheels. It took some finessing to get it on. Felt quite snug even when untensioned, and in trying to get it tightened up to the 5/8" mark on the tension indicator. I never got it there because it felt just too tight, and my wrist was cracking from torquing the tension knob.

So far I haven't had any obvious problems cutting things, so my concerns aren't about poor performance.

Questions:

1) I know that the 105" length is nominal, but is there enough variation among bandsaws and blade manufacturers that it's possible that a 105" blade (spec'd in the manual) could be just too short for my saw?

2) If it is on the short side but usable, wouldn't that throw off the tensioning? I know that a blade of this width is calling for higher tensions than I'm use to seeing, but it's really tight.

3) When the quick release arm is loosened, how loose should the blade be? Mine is still snug on the wheel - should it be loose enough to slip off easily?

Thanks in advance,

Carlos

[Chris Padilla]

(1) Certainly, your 105" blade may be too short; you could try measuring it with some string.

(2) Forget the tension gauge on your saw and just learn to tension it by feel. I simply tighten until the blade deflects about a 1/4" or so.

(3) I don't have such a option on my 20" bandsaw; I just crank the wheel until the blade is extremely loose.

[Mike Lipke]

1. No. As long as it fits, the tension is determined by the compression on the spring.

2. No. Your spring could be garbage, but that red washer is a guide to spring compression, and does not move until you start compressing the spring, wherever that may be.

3. It doesn't have to slip off easily. Some expensive saws have two detents on the quick release: One for releasing tension, one for blade change. All you are trying to do is take off most of the tension, to keep the blade from stretching, and keep the wheel tires from deforming. I suppose it also takes the strain from the bearings and frame as well.

[Myk Rian]

I've heard that when you pluck the blade, it should make a musical note. Not any note in particular, just a nice sounding one without a twang.

[lowell holmes]

I changed the tension spring on my 14" Jet (with riser block). It is an Ittura. I set the tenson in accordance with Ittura's instructions.

I set the tension to one size smaller (on the scale) than the blade I'm running. That with the 3/8" Starret blade (from BC Saw), the tension is set at 1/4" (on the scale).

If I am resawing, I will tension it to the blade size. I don't know why, it just seems right to do so.

I tried Timberwolf blades and tensioned with the flutter system. I don't use that set up anymore.
If you can find Michael Fortune's article on tuning a bandsaw, read it. He will answer a lot of questions for you.

[Lee Schierer]

On my bandsaw, I found that my 1/2" blade is on the short side. It takes a little more skill to get it on. I have to "roll it on" rather than just placing it over the wheels. the upper wheel guide doesn't lower the wheel far enough for this blade to simply slip on. Therefore, there is already some tension in the blade from the urethane wheels. Timberwolf has some good instructions for blade tensioning at their web site. Just #

Stand at the head of the machine, with your hand on the turn screw tensioner and your eyes on the band saw blade. Very slowly start detensioning by half turns at a time, keeping your eyes on the band saw blade. The object is to bring the tension of the blade down to a point that the blade starts to flutter. TAKE YOUR TIME.
#

When you see the band start to flutter, you have hit ground "ZERO". Now start ADDING quarter turns of tension, SLOWLY, until the band stops fluttering and is running stable again. At this point ADD one-eight to one-quarter turn of tension.
#

You have now tensioned our blade correctly. Shut off the machine and put your guides back in place. You are now ready to start sawing.

[William Falberg]

When the blade distributors cut a blade to spec, say 105", they make their cut in the center of the closest gullet to that nominal length. The actual blade length will vary as much as 1/2" if it's a 2TPI. If you don't SPECIFY "no greater than 105" " or "no less than 105" you might get 104.5" or 105.5" in the finished blade length. In some saws, like mine, that difference can be critical. To get it right, I had to come up with a more accurate way of measuring blade length without cutting the blade to lay it out flat. String doesn't work very well because it stretches. Wrapping ANYTHING around the outside circumference of the blade doesn't work very well also because you're then measuring a distance one "anything" larger than the blade's circumference. What ended up working best was to roll the blade over my concrete floor like it was a tank tread, starting at the weld (find a crack or make a stop) and ending at the weld (mark it with a magic marker). Tape measure that distance (by dropping the tab into the crack in the concrete) and use it repeatedly for a reference. I use all lengths of blades so I have a whole index from 89" to 116" marked on my floor. It's been there for five years of walking over it. It's always accurate. Rolling the blade is easier than it sounds and more accurate than you'd think. Try it. You can do it multiple times if you doubt your first (or second) reading. Wih tensioning assemblies you want to be sure your final tension setting isn't co-incident to the end of the tensioner's slide. You CAN end up compressing the spring against the end of the slide and wondering why you aren't getting any more blade tension.

[Michael Faurot]

1) I know that the 105" length is nominal, but is there enough variation among bandsaws and blade manufacturers that it's possible that a 105" blade (spec'd in the manual) could be just too short for my saw?

When I got my 14" bandsaw, I had a similar problem, but in the opposite direction. I couldn't get any tension on several brand new blades. I checked the length of the blades and they didn't appear to be too big.

It turns out that on my saw, a Grizzly G0555, I needed to adjust the quick-release tension mechanism. Apparently there's an adjustment that establishes a fixed point where to apply the tension, after which the adjustment knob increases or decreases that. Hopefully that made sense as I'm not sure what the right nouns are to describe this. So check the manual for your saw and see if there's something in there about adjusting the tension system. It may be, all that's required is to reduce things a bit which would then allow your blade to fit more easily.

[Phil Thien]

To accurately determine blade length, I count the teeth and divide by the TPI. Tedious, but very precise.

[Matt Black]

I'm trying to get an older 18" machine running well and I think my spring is beat street. Is it normal to have the spring fully compressed before the blade is fully tensioned?

Thanks,
Matt

[Paul Demetropoulos]

If you can find Michael Fortune's article on tuning a bandsaw, read it. He will answer a lot of questions for you.

FWW Nov/Dec 2004 "Five Tips for Better Bandsawing"

[Chris Padilla]

I'm trying to get an older 18" machine running well and I think my spring is beat street. Is it normal to have the spring fully compressed before the blade is fully tensioned?

Thanks,
Matt

I think your intuition is serving you well but one thing to check is to make sure the blade is not too long.