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SIP Bandsaw Tension

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Dieseldog

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ive just taken delivery of a new SIP bandsaw blade after breaking the one that come with it
i brought it second hand and have no manual for it

What i need to know what tension do i set the bandsaw blade at ?

its a SIP 14inch Heavy duty and the new blade is a 9' 0 1/4'' x 1/2'' x .025'' 6 Skip

Thanks Dave
 

gus3049

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Dieseldog":1fq9wh53 said:
ive just taken delivery of a new SIP bandsaw blade after breaking the one that come with it
i brought it second hand and have no manual for it

What i need to know what tension do i set the bandsaw blade at ?

its a SIP 14inch Heavy duty and the new blade is a 9' 0 1/4'' x 1/2'' x .025'' 6 Skip

Thanks Dave
First off, get your blades from Tuffsaws. Amazing price for what you get - which is the best blades I have ever used, stay sharp for ages and I haven't actually broken one yet. Over here in our equivalent of B&Q (almost the only thing available) I pay over €30 for an inferior blade. I pay around £10 per blade from Tuffsaws

On my Fox machine I just tighten the blade up as hard as I can, so there is almost no flex before I adjust the bearings onto the blade. Maybe your bigger machine needs more careful adjustment though.
 

CHJ

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There should be a rough tension guide on the rear of the upper section, attached to the tensioning mechanism.
Based on width of the blade, but it's a bit hit and miss dependant upon accuracy of blade length and blade thickness etc.
 

John. B

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This may help you. On the other hand it may not.

Either way It's quite interesting to read. :shock: :? :?

From the pages of Fine WoodworkingMagazine

Setting Bandsaw Blade Tension

Learn to set your bandsaw’s tension to ensure cuts that are straight and even

by Lonnie Bird


Finding the correct blade tension always seems to be something of a mystery among woodworkers. There are all kinds of methods out there, such as plucking the blade like a guitar string until it produces a clear tone of a specific musical pitch. Although I have no doubt that this method works for a few musically inclined woodworkers, I question its practicality and accuracy for the rest of us. Other theories are even more abstract, such as the notion that you should find the tension that makes your bandsaw "comfortable." To me, this statement seems too vague.

In an effort to avoid adding to the confusion, I'm going to give you some practical ideas on tensioning blades so that you can adjust your saw for accurate cuts. But first I'd like to make some points about bandsaw blades and tension.

Finding the right tension
Bandsaw blades require tension and lots of it to consistently produce straight, uniform cuts, especially in thick or dense stock. Most blade manufacturers recommend 15,000 psi to 20,000 psi for a common carbon-steel blade.

However, bimetal, spring-steel, and carbide-tipped blades are much stronger than carbon-steel blades, so manufacturers recommend a much higher tension: 25,000 psi to 30,000 psi. Why do bandsaw blades need so much tension? For beam strength. The tighter the blade is stretched, the more rigid it becomes and the less tendency it will have to deflect in the cut.

You only need maximum tension for the most demanding cuts, such as sawing dense hardwoods or stock of the maximum thickness that will fit under a saw's guides. In simpler circumstances, you can back off the tension a little.

All blades, regardless of width, require the same amount of tension for maximum beam strength. The variable factor is the amount of pulling force needed. For example, it takes approximately 200 lb. of force pulling on a 1/4-in.-wide by 0.025-in.-thick blade to create 25,000 psi of tension. Conversely, a 3/4-in.-wide by 0.032-in.-thick blade will require approximately 800 lb. of force to create the same 25,000 psi of tension.

Measuring tension


Bandsaw-blade tension scales are notoriously inaccurate. Tests conducted by consumer woodworking magazines have shown this, and my own tests using six different bandsaws confirmed their results. For my tests, I used a blade tension meter that clamps to the blade and gives an accurate reading on a dial indicator. The readings of all the saw tension scales that I tested, including those on the expensive floor-model saws, were lower than that indicated on the meter. Although the scales on the large machines were close to being accurate, the scales on the 14-in. saws were way off. To make matters worse, the springs used in the tension scales on bandsaws weaken with age, further reducing their accuracy.

So how do you know when blade tension is correct? The most accurate way is to check it with a tension meter such as the one I used in my tests. But tension meters are expensive -- typically around $300. I know what you're thinking -- is there another way? Yes, but none is as accurate as a tension meter. Other tensioning methods will work, but they're a lot like gauging air pressure in a bicycle tire simply by squeezing it.


A good place to begin is to tension the blade until the meter reads proper tension for the next wider blade. For example, if you're tensioning a 3/8-in. blade, I would set the scale to 1/2 in. This works most of the time, since most sawing operations don't require maximum tension.

Another method is to test the tension by the amount that the blade will deflect sideways. First, I set the upper guides about 6 in. off the table. Then using a moderate amount of pressure from my index finger (obviously with the saw turned off!), I push the blade sideways. I don't want the blade to bow more than 1/4 in. Of course, you'll have to develop a feel for how much pressure is moderate.

Although both of these methods work, they are imprecise. But as I stated earlier, in most situations maximum blade tension isn't necessary. I always test the blade tension with a trial piece before making cuts in an actual workpiece. If the blade wanders in the cut (assuming other factors such as blade sharpness and guide setting are correct), I'll gradually increase the blade tension.

Blade tensioning for resawing

Resawing thick, hard stock places the most demands on the blade. If the blade tension is inadequate, the blade will bow and the stock may be spoiled.

I remember a situation some years ago when I attempted to resaw a wide board. It was a plank of deep red cherry -- highly figured with truly awesome curly grain. I wanted to make book-matched panels for a door in a cupboard. Since I was in a hurry, I neglected the necessary precautions such as selecting a blade with the right pitch and tensioning it properly. The blade bowed badly during cutting, making one of the planks terribly thin at the end. The stock was thicker than necessary, so I was lucky enough just to squeeze out the thickness I needed from the resawn plank. But I learned my lesson: A blade needs beam strength for resawing.

Beam strength, the blade's ability to resist deflection, is achieved by combining several factors, including correct blade pitch, blade width, and precise guide settings. But a key factor in achieving beam strength is applying the maximum blade tension that the blade manufacturer recommends.


Some woodworkers may question whether maximum blade tension will in any way damage the saw. Based on years of experience with my 14-in. Delta bandsaw, the answer is no. But I should make it clear that I recommend using maximum blade tension only for occasional, brief periods of resawing. Otherwise, I keep the tension low for everyday sawing. I release the tension when I know I won't be using the saw for a while.

If you've purchased a bandsaw with a wheel diameter of 18 in. or more, then you're most likely planning to do serious resawing from time to time. In that case, I suggest that you also spend the money on a tension meter. Large bandsaws have frames that are capable of overtensioning a blade, which causes it to break. A tension meter is the most accurate way of setting the blade tension.

If you own one of the many consumer bandsaws with a wheel diameter of 14 in. or less, then I would use a blade no wider than 1/2 in. for resawing and tension it until the tension spring is nearly compressed.

Lonnie Bird is a professional woodworker who uses the bandsaw to make custom furniture. He is the author of The Bandsaw Book andThe Shaper Book.

John. B

BTW I concur on the advice about 'Tuffsaws' Excellent blades at an excellent price.
 

Dieseldog

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John. B":3ep5b8kr said:
Finding the correct blade tension always seems to be something of a mystery among woodworkers. There are all kinds of methods out there, such as plucking the blade like a guitar string until it produces a clear tone of a specific musical pitch.

i like the sound of this method








.

Another method is to test the tension by the amount that the blade will deflect sideways. First, I set the upper guides about 6 in. off the table. Then using a moderate amount of pressure from my index finger (obviously with the saw turned off!), I push the blade sideways. I don't want the blade to bow more than 1/4 in. Of course, you'll have to develop a feel for how much pressure is moderate.

think i'll try this method
.

.


. I release the tension when I know I won't be using the saw for a while.

i was going to ask about this as well

BTW I concur on the advice about 'Tuffsaws' Excellent blades at an excellent price.
think i'll get a Tuffsaw blade next time
 

devonwoody

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I had an interesting experience this week with a bandsaw and tension etc.

Cutting some 1/2" thick purple heart to make those contrast strips I do the timber would not stay to the fence and kept deviating, and no pressure using a push stick would keep it to the fence. Consequently the timber finished with a wavy edge.

I thought blade blunt or tension.

wrong.

I tried another piece of timber sapelle 4"deep x 1/2"wide, cut no problem.

It was the timber, purple heart, the grain was wild and steered the blade.

Fortunately I had not changed the tension or blade, so sometimes it the timber not the machinery.
 

tomthumbtom8

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Woody If the wood is choosing the direction for you then I think you are feeding it to fast and not holding the material tight to the fence

OMHO

Tom
 

Robbo3

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I have a friend with the same SIP bandsaw & he bought several SIP brand blades that either broke or blunted very quickly.

I advised him to buy blades from either Axminster, Hamilton or Tuff & he hasn't had a problem since.

I would also add that Screwfix bandsaw blades blunt quickly as well. How do I know? I hit a nail with my last good blade & needed a replacement quickly. The Screwfix blade lost its edge after cutting approx 10 feet of 2" thick timber & was totally useless by 20 feet. In its favour, it was cheap & it got me out of a hole.

Robbo
 

Tony Spear

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Cor blimey!

9 posts about Bandsaws and nobody has yet mentioned Steve Maskery! :shock:

Is this a record? :mrgreen:
 
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