How to tension a bandsaw blade for wood?
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Full article
Why do bandsaw blades for wood break? We know the answers
A bandsaw blade for wood most often cracks when it is over-tensioned, when it is too thick for the saw's wheels, or when it rests against the back bearing even when running idle. You can usually tell what caused a crack from where it starts. Our welds come with a warranty.
Where did the blade crack? Quick diagnosis
Look at where the crack starts. Its location usually reveals the cause.
Where a bandsaw blade cracks (from the back edge, at the weld, from a tooth) and the over-tension test on a cracked blade
Most common causes of cracking and how to fix them
On a standard two-wheel saw, the blade bends around the wheels twice and straightens out twice on every revolution. Anything that puts extra stress on it shortens its service life. Here are the five main causes.
÷ 500
wheel diameter divided by 500 = maximum blade thickness
3 mm
it is enough if the tensioned blade deflects no more than 3 mm when pushed with a finger
0.5 mm
a thinner blade to try on a small saw if blades keep cracking
100–140
N/mm² – tension for woodworking blades (sawmill blades 170–210)
Tension
The blade is over-tensioned
An over-tensioned blade will most likely crack sooner or later – at the weld or elsewhere.
Check without a gauge
✓Machine switched off, cover open – measure on the side without guides.
✓The blade does not deflect sideways by more than 3 mm when pushed with a finger – that is enough, do not tighten it any further.
✓It sounds metallic when tapped.
✓The tensioning disc springs are not fully compressed.
After work
!Slacken the blade. Keeping it tensioned for long periods puts unnecessary strain on the blade, the wheels and the saw frame.
!You can measure the exact value with a tension gauge, but it may not fit into small saws.
| Blade type | Recommended tension |
|---|---|
| woodworking blades | 100–140 N/mm² |
| sawmill blades | 170–210 N/mm² |
Example for a 32 × 0.9 mm sawmill blade: subtract the tooth height (about 7 mm) from the width, which leaves 25 mm. Tensioning force = 25 × 0.9 × 200 = 4,500 N (roughly 460 kg). You will find the full procedure in the article How to tension a bandsaw blade for wood.
Blade thickness
The blade is too thick for the saw's wheels
The smaller the wheels, the more sharply the blade bends on every revolution. The rule is simple:
wheel diameter ÷ 500 = maximum blade thickness
Wheel diameter 420 mm → 0.84 → choose a 0.8 mm blade. The other way round: multiply the blade thickness by 500 to get the smallest suitable wheel diameter.
0.36 mm
wheel from 180 mm
0.5 mm
wheel from 250 mm
0.65 mm
wheel from 325 mm
0.8 mm
wheel from 400 mm
0.9 mm
wheel from 450 mm
1.1 mm
wheel from 550 mm
This is a recommendation, not a prohibition – you can fit a thicker blade on the wheel, it will just be under more stress. If your blades keep cracking on a small saw, try a thinner one: 0.5 mm (we make it in widths of 6, 10 and 13 mm), or 6 × 0.36 mm. A thinner blade copes better with bending over a small wheel, but it is less rigid and wanders more easily in the cut. That is why, with a thin blade, you should choose the greatest width your work and your saw allow.
Bearing and guides
The back edge rests against the bearing or guide
If the blade rests against the back support bearing even when running idle, its back edge gets peened, hardens and eventually cracks. The cracks then start from the back edge.
What to adjust
1Set the back bearing so that the blade does not touch it when running idle.
2Set the side guides as close to the blade as possible, but without pressure. The guides must not touch the teeth.
3Tilt the upper wheel so that the base of the teeth runs on the centre of the wheel (on sawmills, by contrast, the teeth should overhang the edge of the wheel).
4The wheels must be in line with the guides.
Watch out for
!Pre-loading the blade with a grooved bearing (used when cutting tight radii) puts more stress on the back edge – the blade may crack from this side sooner.
→More details in the article Technical set-up of a bandsaw for wood.
Weld
Faulty weld
Does it keep cracking at the weld?
!Repeatedly and soon after fitting → most likely a bad weld.
?If there is no obvious defect on the blades, the cause may also lie in the saw, its set-up or the way you cut – check the tension, blade thickness and back bearing.
We describe how to recognise a quality weld, when the warranty covers it and how to make a claim for a cracked weld in the article Bandsaw blade welding: quality welds and warranty.
Service life
The blade is at the end of its service life
A worn blade with dull teeth will often crack due to material fatigue, sometimes even at the weld. This is not a defect but the natural end of its service life. You can extend it like this:
Do not force the cut
Feed pressure should be light and steady. If the blade will not cut that way, increase the blade speed, slow down the feed, choose a larger tooth or replace the blade with a sharp one.
Choose the speed to suit the job
Reduce the speed for fine work – this can extend the service life up to threefold. Rough cuts in soft and green wood need a higher speed so that the blade can clear the sawdust fast enough.
New blade, new cut
Do not use a new blade in an old cut.
How to prevent cracking
✓Choose the blade thickness according to the wheel diameter (diameter ÷ 500).
✓Tension with care: it is enough if the blade deflects no more than 3 mm when pushed with a finger – do not tighten it any further.
✓The back bearing does not touch the blade when running idle, and the guides support it without pressure.
✓Do not force the cut; replace a dull blade in good time.
✓After work, slacken the blade and clean it with a cloth or a soft brush, never with metal tools.
✓Store the blade in a dry place, coiled smoothly without sharp kinks and with the teeth covered.
You will find more tips in the article Principles of proper bandsaw blade maintenance.
Need a thinner or different blade?
We will weld it to measure for your saw. All you need is the size, or just the saw model.
Other problems with bandsaw blades for wood
The blade is not cracking, but it cuts badly? Rough or crooked cuts, burnt wood and a blade that dulls quickly usually have a simple cause.
fibers are tearing out
band saw blade dulls quickly
wood is burning
band saw blade cuts crooked (wanders)
band saw blade teeth are reversed
FAQs about cracking blades
? Can a blade crack if I do not use dust extraction?
That is very unlikely. It could only happen if the saw were extremely clogged and the sawdust deformed the blade.
? What is the smallest wheel diameter a given blade thickness can handle?
Multiply the blade thickness by 500: a 0.65 mm blade needs a wheel diameter of at least 325 mm, a 0.5 mm blade at least 250 mm. You can use a thicker blade, it will just be under more stress as it passes over the wheel.
? How much should a sawmill blade be tensioned?
To 170–210 N/mm², in practice roughly 200 N/mm². Tension woodworking blades to 100–140 N/mm². You will find an example calculation above.
? My sawmill blade cracks from the teeth. What is causing it?
It is most likely not the back guide – the cracks would then start from the back edge. Check whether the wheels are in line with the guides. Unsuitable sharpening can also be the cause. We will be happy to advise you on sharpening and servicing sawmill blades – just write to us.
? My blades crack at the weld, even though they come from different suppliers.
If there is no obvious weld defect on the blades, the cause may also lie in the saw, its set-up or the way you cut. Go through the tension, blade thickness and back bearing. If you are not sure what to do, write to us.
Didn't find your problem?Ask in the discussion below the article or write to info@dudrsaw.eu – we will be glad to help.
Your questions
Hello, I am attaching a link to Parkside wood saw blades
https://www.dudrsaw.eu/technical-articles-and-advice/blades-for-the-parkside-wood-band-saw-from-lidl
Good day,
most saws require the flywheels to be re-rubbered.
For example, the company AGT in Zlín deals with the renovation of these wheels.
https://www.agtzlin.cz/pogumovani-obezneho-kola-na-pasovou-pilu-p320/
Sincerely,
Vojtěch Volf
Good afternoon, we would be happy if you try our saw blades. If the blades generally break on such a small bandsaw, we recommend a blade thickness of 0.5 mm due to the small wheels. These are blades of width: Flexback 1490x6x0.5 mm or Flexback 1490x10x0.5 mm. Choose the pitch according to the height of the wood being cut or whether you are cutting softwood or hardwood. If the blades break at the weld and too soon, it is more likely due to poor welds, so I would normally recommend a thickness of 0.65 mm, the blade is tougher and holds better in the cut. We have a larger selection there. These are widths: Flexback 1490x6x0.65 mm, Flexback 1490x8x0.65 mm, Flexback 1490x10x0.65 mm. Again, choose the pitch according to the cutting height you are cutting. If a blade from us breaks, you can complain about it to us by sending us a photo of the broken weld. We will assess the broken weld and usually send you a new one immediately. If there is still a problem with breaking at the weld, we would have to look for the cause in the machine itself, but we do not encounter problems with saw blades breaking at the weld on these bandsaws.
Thank you, good luck, regards Pavel Dudr
Good day, there could be several reasons. We would need more information and to see the saw band, at least. It could have happened, for example, due to undercutting during production.
Please contact your colleague Martin Dvořák from the company Dudr Tools tel.: +420 776 566 103.
Thank you, Regards Pavel Dudr
Good afternoon, thank you for your comment. We apologize, there should definitely be more.
If you are going to use the RipperS PREMIUM saw blade intended for logs, expect a tension of 170-210 N/mm2.
Woodworking saw blades FlexBack are tensioned to 100-140 N/mm2.
Good luck, best regards, the Dudr Saw team.
Hello, that is very unlikely.
Theoretically, it could happen if you had a very dirty saw - but it would have to be an extreme build-up of dirt that deforms the blade.
Good day, there is no need for a table for that. It is "wheel diameter / 500".
But that is a recommendation, of course you can use thicker ones too, it's just that the band will be a bit more stressed when passing over the wheel.
S.Kolarik
Hello, we recommend 200 N per mm2 of the saw blade's cross-section. For example, if you have Ripper 32x0.9, after subtracting the tooth height (about 7 mm), we get 25 x 0.9 x 200 = 4500 N/mm2.