Thread: Bandsaw blade twists while cutting

Hi Dengy, was it like that before you had the blade sharpened? Do other blades do the same thing?

In the video he moves the side guides apart to free the blade, I hope he left the rear guide set. Have you checked that the rear ceramic guide has not got a grove in it? possibly holding the back of the blade if it has.

I run the ceramic side guides just touching the blade, can't see how the blade could then twist unless there was a small twist in the blade over a short distance - shorter that the distance between the upper and lower guides.

Are the side ceramic blocks parallel?

Mike

Hi D,
Two things ... firstly ... did the blade cut correctly before it was resharpened ... could be a sharpening error.

Secondly ... that model BS has a 3 functions for "roller"setup. Round backing ceramic plate, side plates for the blade and a swivel angle setting too for the one under the table. It is easy to get that one wrong when changing blades ... worth a check.

The other thing you can do is to swap around the ceramic guides to expose the unused part pf the ceramic bar. The right and left blade guides are interchangeable , the round backing one can be reversed. If you see dark marks then the ceramic has worn off exposing the metal underneath.

Interesting to find out how you go

Regards

Rob

Thanks for your valuable input, MandJ and Tahlee. I forgot to mention that when testing with the MDF pushed along the fence, I had removed the ceramic guides well out of the way at the sides and the rear, so there was nothing to impact on the blade angle. It was cutting quite well before the sharpening was needed.

I was unaware of the swivel angle setting under the blade, will check that out when fitting the guides when I have solved this problem of the blade twisting. The blade was twisted at rest too, by about 2 degrees off the mitre slot / fence line.

Next step is to replace the blade with a new one. Fortunately I have a new 3/4" bimetal 3tpi variable tooth pattern one from Henry Bros. Will see how I go tomorrow, if the rain holds off ( small shed, lots of moving stuff in and out)

If the new blade is at the same angle, would it be feasible to rotate the table on the trunnions so that the slot is parallel to the angle of the blade? Fiddly job.

Too much tension.

I have the same problem with my Laguna SUV14 using the RSK and Lenox WoodMaster CT blades (LWM from Henry Bros, its excellent).

When I use the full power of the tensioner, I get exactly as you describe. Dial it back a bit and the problem disappears. It doesn't NEED masses of tension... not at all.

Also, with the rear ceramic, I don't let it touch while its running, only when wood is being forced onto the blade do I let it touch.

For the top wheel, I rest the front of the carbide teeth just over the front of the tyre. I know what it says about centreing the gullet, but all I've ever achieved from this is blades that snap prematurely.

Originally Posted by Dengue

I was unaware of the swivel angle setting under the blade, will check that out when fitting the guides when I have solved this problem of the blade twisting. The blade was twisted at rest too, by about 2 degrees off the mitre slot / fence line.

I dont think that i have explained the situation very well regarding the lower guides. One of the screw knobs allows the angle of the guide to move horizontally around an axis. If this lower guide setting not correctly aligned with the blade then the horizontal movement will move the blade out of parallel with the fence and mitre slot.

If this lower setting not set properly (swivelled by a few degrees) it create exactly what you have described as the problem


Regards

Rob

The unasked question is why did you get it resharpened and who did the sharpening.

Tahlee, the blade is at an angle with the guides totally removed, and nothing touching the blade anywhere, other than the wheels. And that angle stays much the same irrespective of where the blade sits on the upper wheel, as determined by the tracking knob.

Chris, I was having trouble cutting veneers of uniform thickness after a while, so got the LRK blade sharpened. Have just put it back on. The sharpener is CSK in Deception Bay, QLD. Recommended by Gregory Machinery who sold me the bandsaw.

I put the resharpened Laguna Resaw King (LRK) blade back on because the 3/4" bimetal blade I was using was burning the timber on the right of the cut line too. That was the first time I had burning, and it was quite bad by comparison with the LRK blade I used to replace it. I recall mucking about with the angle of the fence to get the bimetal blade to sit in the middle of the kerf, but was unsuccessful. At best I could get it to sit centrally for about an inch or two of cut, after which it twisted to the right.

Oh, and I just remembered, the bimetal blade had snapped with a very loud bang. That was the primary reason for replacing it, not the nuisance burning Memory is so fickle. It was only when this replacement LRK blade was also burning that I realised I had a bandsaw and not a blade problem, hence this thread to get help.

Right, back in the shed. Set the bandsaw up with no guides, and fence 25mm in from the blade, and parallel to the mitre slot. The blade is centred on the tyres of the upper wheel.

1st off, reduce the tension as per woodPixel's recommendation. It was in the mid centre of the tension range for 3/4" blades, have reduced it to the top of the range for 1/2" blades, as shown on the tension guide on the saw

Using the fence, I then cut along a pencil line drawn 25mm from the edge of a piece of 6mm MDF.

Outcome: the line of cut followed the pencil line accurately, but it appeared that the blade sat along the right hand side of the kerf, with a significant gap between the blade and the LH side of the kerf. Accurately measured the angle of the blade as 1.3 degrees off parallel with the mitre slot.

Not happy Jan Noticed a thin layer of dirt caked on the crown of the wheels ,top and bottom. Next step is to clean the wheel with Pitch Rx and re do the above test, again without guides

Have changed the above post, adding additional information

I also use CSK in Deception Bay, QLD, I had a bimetal blade made and had to take it back because the back of the blade was not true (they said it must have been faulty metal) I was able to give them the exact dial indicator errors and the comparison to a cheap carbon blade so there was no arguments on their part.

I clean the wheels regularly as part of the BS maintenance.

I suppose you know that the blade indicator is a just magnetic label and can be moved (it is on the BX) and Laguna have a video suggesting moving it to show the (roughly correct blade tension) once you have got a bade tensioned and running correctly.

I found out very early that the tension indicator was totally incorrect and it would have over tensioned the blades had I of followed it. It's now in the ball park for the blades I use.

Right, back in the shed after morning tea, getting rather warm.

Removed the blade, examination shows teeth sharp and no gunk attached.

Cleaned the gunk off the wheels, and replaced the blade, no guides or anything near the blade. Also adjusted the brush on the lower wheel to make it clean better. the blade is set to the centre of the upper wheel tyre

Set the blade tension to top of the 1/2" tension ( using a 3/4" blade)

Ran the bandsaw a few times, and the blade was still 1.5 degrees off parallel This angle persisted with the blade tracking to the front, centre or rear of the top wheel tyre, which is not right !!

Don't know what to do next to get the blade running parallel to the mitre slot



P1700443 (Large).jpg P1700450 (Large).jpg P1700457 (Large).jpg P1700464 (Large).jpg

A few things I do differently....

-- the teeth of the blade are not on the tyre, they sit just over the front of it. Only the little carbide teeth, the rest of the blade sits upon the tyre
-- I completely ignore the tension guide. Mine is utterly useless. I tension it a few times just by eye. When the blade bends, its too much and I reduce it by a 1/4 turn
-- Old tooth brushes are mounted on the top and bottom wheels to keep them nice and clean

Keep in mind mine is the SUV14 which may be different, but the tensioner adjustment is a winder on the top (to raise and lower the wheel) and a handle on the back one pulls down to apply the tension. I think that lever can apply far too much tension! The internal cam seems to like the handle swiveled right down. Although it does keep in place if 4/5th's down (just a guess), it seems to like it all the way. I adjust the upper tension knob until it lets me do that.

One last thought, I don't really look at the angle of the blade. Can't remember ever having thought of doing it...

I saw somewhere (snodgrass?) that all one needs to do to "align" the fence is make a cut into some MDF (for example) and simply align the back of the blade so the kerf sits in the centre (the gaps on both sides at the back are the same). Then move the fence to ensure that it is parallel to the en-kerfed woods edge.

Moved the blade way forward to what I would normally do, based on woodPixel's comment, so that the bottom of the teeth gullet was just touching the front of the tyre of the cleaned upper wheel, and I noticed a definite improvement in the parallelism of the blade and the mitre slot, down to 1.0 degrees off line. Cut a piece of 6mm MDF with a line 25mm in from the edge, set the fence parallel to the mitre slot, made sure the guides were well away from the blade, and ran the test piece through the saw against the fence.

I also checked the tension by pushing firmly with a finger in the midpoint between the two wheels, and found it would deflect by up to 4mm. Some books say 1/4" is a good deflection. ( Just found the Laguna manual, which says to aim for 4.7 to 6.35mm defection at a point 6" below the 3 or 9 o'clock position on the upper wheel)

Outcome: The blade ran hard against the right side of the kerf, leaving quite a gap on the left side of the blade. But the blade followed the pencil line quite accurately. Same result as found previously. Which is weird, based on the attached drawing, which says if the blade twists to the right like mine is doing, the blade is too far forward

Bandsaw blade alignment.JPG