Bandsaw blade ‘fore / aft’ pulse

[SVB]

Folks,

I’ve got an issue with my bandsaw where the blade ‘surges’ fore / aft.

I’ve got decent blades from Ian at Tuffsaw and have watched the Alex snodgrass (sp?) advice on setting guides etc.

Short 20 sec clip of issue here

Any tips / suggestions to resolve this as it is fine while hacking bowl blanks but does not help precision cutting to say the least!

THanks in advance,

Simon

 

[Yojevol]

Does it surge at the blade weld? If so, I should send it back because it means the blade was out of line when it was welded or it could have cracked at the weld.
Brian

 

[woodbloke66]

Does it surge at the blade weld? If so, I should send it back because it means the blade was out of line when it was welded or it could have cracked at the weld.
Brian

I'd tend to agree; the blade may not have been welded square n'true so even a slight variation out of kilter will cause the surge - Rob

 

[sunnybob]

plus 1. find the weld, check it for square. If its not possible to file straight, cal Ian, I'm sure he will have a replacement in the post tout suit.

 

[SVB]

No, it’s not obviously at weld and seems to be more than once per revolution although difficult to tell (and does it with all blades I have that are from mixture of APTC and Tuffsaw so unlikely all wrong). :?

S

 

[sunnybob]

Check the top wheel bearings.
With the power OFF, grasp top and bottom of the wheel and try to rock it up and down. Then grasp the sides and try to rock it side to side.
Sometimes there is play in the connecting pieces, repeat the test enough that you can say wheel or mechanism.

Then, have you tried tightening the blade a bit more?

 

[Chris152]

Is the whole unit holding the bearings wobbling? It looks like it in the video but maybe that's just the camera moving? If it is wobbling, could that be the cause?

 

[Eric The Viking]

My guess: bottom wheel bearings (they get much harder use than the top ones do, so I'd expect them to go first). But could be either/both wheels actually. It looks too fast to be a weld problem.

How old is the machine and/or what have you been using it for?

 

[Ttrees]

I would check the bottom wheel for bearing issues
Plum up the machine afterwards, if not level as there seems to be a lot of movement of the guide post...
That might solve that if its tight.

Is there any marks/damage on the tires?
If not, the sawdust tracks could hint something is not right

Is the bottom grub screws/jacking bolts tight?
Tom

 

[yetloh]

I have only had this a couple of times in many years and both times the blade was soon to break, which makes a pretty dramatic noise but, fortunately, with no real damage. You can easily check whether there is a problem with the machine by changing the blade - an old blunt one will do. If the surge disappears, it's not the machine.

Jim

 

[CHJ]

Simon, further to the recommendation previously to check the spindle bearings for side play, with the power off and doors open spin the wheels by hand and watch for one or both 'wobbling' on their axis or the blade hunting across the surface of a wheel.

 

[Phil Pascoe]

... You can easily check whether there is a problem with the machine by changing the blade - an old blunt one will do. If the surge disappears, it's not the machine.
Jim

"(and does it with all blades I have that are from mixture of APTC and Tuffsaw so unlikely all wrong)"

 

[Noel]

I've had similar wobble in the past, it was down to the blade. At some stage it has hit a very hard knot, a nail or carelessness has caused the timber being cut to clamp on the blade. Whatever the cause was it had deformed the blade. You could remove the blade and let it rest on a flat surface or floor and see if it is still in the one plane.

 

[Phil Pascoe]

I've had similar wobble in the past, it was down to the blade. At some stage it has hit a very hard knot, a nail or carelessness has caused the timber being cut to clamp on the blade. Whatever the cause was it had deformed the blade. You could remove the blade and let it rest on a flat surface or floor and see if it is still in the one plane.

"(and does it with all blades I have that are from mixture of APTC and Tuffsaw so unlikely all wrong)"

 

[Alexam]

If it happens with various blades, then it must be the wheels. I would suggest that the tyres may have been damaged and uneven. Take the blade off, turn the wheels by hand slowly and feel the tyres to find out where they are uneven.

Did the blades run true before and if so, when? Also, what position is the blade on the wheel, front, back or central?

 

[beech1948]

I would make out a check list and go down it one by one as in:-
1) Check wheels by spinning them with blade removed and look for wobble. Lower wheel first
2) Check tyres by feeling with hands and also position a piece of wood across the wheel and spin it to look for bumps
3) Check lower wheel for bearing slackness/wobble/etc...up/down and side to side
4) Check upper wheel bearings for movement
5) Observe motor pulleys and shafts look for wobbles
6) Apply very high tension to blade and see if it still wobbles/pulses

After this lot you get to the point where you might need to consider disassembling bits such as

7) Remove lower wheel. These tend to be set at the factory so consider marking the wheel and shaft to help reassembly. Look for bearing wear. Look at wheel hub for wear
8) Repeat with upper wheel
9) If motor and or pulleys seem suspect remove and check for wear on shafts or in bearings

10) Replace all bearings as you go. They are quite cheap from people such as a local bearing factor or Bearing Boys.co.uk

Lucky for you bandsaws are fairly simple machines and careful step by step approach will work.

 

[Bale]

From the video clip you linked to it appears that the blade is running completely free of any guides. If it's not being guided it'll be all over the place. Try adjusting the tracking of the blade so it moves back and runs consistently against the rear guides. It wouldn't hurt to set up the side guides properly as well. Then see if it's any better.

Pete

 

[toolsntat]

Or, could you be tensioning the blade too much....
The top section of the machine looks to be too unstable.
Is it a braked machine as it slows up sharpish?
Cheers Andy

 

[beech1948]

Re above two messages. I agree that the guides are a bit too far back from the blade edges. Side guides should be just shy of the bottom of the blade gullet. If the rear guide is not close ( say 0.5mm or a bit less) from the rear edge of the blade then no real guidance is being achieved. Probably your first adjustment.

I doubt that the blade is being tensioned too much as these small bandsaws can not tension blades above 10mm well and usually fall short by a wide margin. Fully tensioned you will be more likely to crush the spring than to get to a useful beam strength by tension.

 

[Honest John]

My bandsaw will cut perfectly straight fence guided rips with no bearing support at all. I know this as I read it somewhere, Dugzinski ? Perhaps, and decided to try it. Bearing support is required to prevent the blade twisting when the wood is moved into the blade to follow a curve. It should not be “guiding” the blade at all, only supporting it when we try to move the blade. I feel for what my thoughts are worth, that your problem cannot be caused by ill adjusted bearings, but is most likely caused by wheel and or wheel bearing issues. Every problem I have ever had with a bandsaw has turned out to be the blade. Just saying.