Blade movement backwards and forwards

[shep1]

Any ideas on how to correct a problem with a blade that moves backwards and forwards by about 1mm to 2 mm? The problem started after I pulled both top and bottom pulley wheels off to clean the rubbers (this was because I stupidly decided to see what a very green mango tree branch which I has just pruned, would look like after a bit of resawing and ended up with a fine sappy mess over pretty much everything)
The top and bottom guide bearings are all correctly set up and I have centrally aligned the blade in the top pulley. The blade in the bottom pulley seemed to have moved off centre, so I adjusted the bottom pulley using the adjusting screws on the bottom pulley shaft (top and bottom screws only) thinking its a coplanar problem. No luck even now with the blade centred on the bottom pulley (and I checked that the top pulley is also still centred) - I still get the blade movement.
Ther is also a repetitive bumping sound it has also made straight resawing cuts start to wander. Anyone else had this type of problem?

Shep

[Sculptured Box]

Shep

Have you considered the possibility that the bumping sound may be the blade striking either the side or thrust bearings / supports?

[shep1]

Tony
Yes I thought that could have been a possibility, so I backed off all the bearings to see whether that fixed the problem which unfortunately it didn't.
Shep

[woodbe]

Could be the blade. Have you got another one to test?

I had a small 'event' with my resaw blade a while back, caused by not checking buildup of sap on the blade itself. Basically, it came off the rails Anyway, after that, it would wander all over the place and was painful to use. Other blades were fine. Replacement therapy worked wonders...

woodbe.

[derekcohen]

Shep

I assume that you are using the same blade and that this did not occur before, therefore one can discount the blade being at fault?

If it were just the wheels out of coplanar, then the blade would either move to far forward (tension too high) or too far back (tension too low). I reset the coplanarity (if there is such a term!) after the tension is set, especially if I am cranking it up.

If the wheels line up at rest, then I would expect that one (or both) is not seated squarely and moving in an ellipse. Try moving the wheels to determine this.

Regards from Perth

Derek

[eddie the eagle]

SOunds as though you've kinked the blade, Shep. Maybe even a hairline crack where the kink is.

Just a thought and an easy one to check

Cheers,

eddie

[shep1]

Woodbe, Derek and Eddie

Thanks for your responses. I have spent at least 3 hrs searching my workshop trying to find the only other blade that I know I have somewhere !!! (It came with the bandsaw and was relegated to a safe place because it was not a blade I would normally use for resawing, which is the bandsaw's primary function)
I am going to get another new blade anyway so I have at least one spare. This will allow me to check whether the problem is related to the blade. I checked the bottom pulley again and it seems to be running reasonably smoothly and I can't detect significant movement of the wheel rim which would suggest a reason for the blade movement - this remains an option but based on your suggestions I will order a new blade tomorrow and hopefully have it later in the week to try out.

Regards, Shep

[AlexS]

A blade moving backwards & forwards like that can be a sign that it's about to break.

[rsser]

A blade moving backwards & forwards like that can be a sign that it's about to break.

Ouch!

Stand well back. Clear, repeat, CLEAR!

[martrix]

Sounds to me like maybe a bad weld at the join. Turn the wheels by hand and find out if it moves backwards/forwards on the same spot on the blade, like at the join. The bumping sound could possibly be the uneven join passing over the thrust bearings.

[TTIT]

Sounds to me like maybe a bad weld at the join. Turn the wheels by hand and find out if it moves backwards/forwards on the same spot on the blade, like at the join. The bumping sound could possibly be the uneven join passing over the thrust bearings.

I concur ! I had one (out of 3) like this that I bought a while back and I imagine some sort of damage could cause the same symptoms. The blade had not been aligned properly when welded and had a pronounced 'bump' in it that bought the blade about 3mm towards me each lap. Need less to say, I don't buy blades from that mob anymore!