Question for Bandsawists...

[Calpol]

Hullo all,

I'm trying to rip down some 120mm high oak at about 5mm thick on the bandsaw. It's got a brand new blade (25mm x 3tpi) and I'm using the Kreg resaw jig.

Anyhoo the blade keeps jumping off the rear guide under the table, so the blade ends up on the round of the wheel rather than the flat edge, and the cut becomes very un-parallel.

The rubber tyre on the big lower wheel isn't glued to the wheel which I imagine it's meant to be, and I think it's not helping. I have read online (must be right) the rubber is more for narrower blades so whether I can take it off completely for the time being or not might just solve it...?

Anyway I could use some help ASAP if anyone has any thoughts...

Thanks

Calum

 

[9fingers]

In trying to visualise your problem, a couple of thoughts come to mind.

1) I've never heard of operating a bandsaw without tyres

2) if the blade can climb up onto a larger diameter section of the wheel, then either the tension is far too light or something is flexing.

Is the machine in generally good condition and normally copes with this type of work or are you 'pushing your luck' with this job?

Sorry not much help but.......

Bob

 

[Chrispy]

Hello

When I deep cut like your trying to I find a 12mm wide blade with 4tpi hooked skip tooth works for me. the hook gives a very agressive cut sometimes it almost self feeds in to the wood, the skip tooth helps keep the kerf clear, 12mm wide puts much less strain on the machine as modern blades can to tentioned much higher than they used be. as for the rubber tyres glue them on and make sure they run true.

Good luck Chris (Cabinetmaker)

 

[DaveyP]

Hi Calpol

For the blade to jump off of the rear support then it must be flexing around like a flag in a breeze

The first thing I would look at is the position / alignment of the blade on the wheels, centre with no wobble is good

Once you have checked that, then you can set your guides and back stops

However... as its a new blade that's giving you grief (and I take it that previous blades have been ok) it could be that its a crap blade that will never run straight !!

 

[iajon69]

First off - don't take the rubber off as running a blade just on the wheels is not going to improve anything and will probably cause the blade to break or damage the teeth!

It sounds as if either the blade is faulty - misaligned weld etc or your machine is not tensioning the blade sufficiently.

There's no need for a 1" blade for this type of cutting and even a 1/2" blade properly tensioned will be better than a 1" blade that's not tensioned correctly.

What bandsaw are you using?

If you have any narrower blades, then I would try using one of those to find out if it's a blade problem or machine problem.

Ian

 

[Eric The Viking]

The rubber tyre on the big lower wheel isn't glued to the wheel which I imagine it's meant to be, and I think it's not helping. I have read online (must be right) the rubber is more for narrower blades so whether I can take it off completely for the time being or not might just solve it...?

You don't say what machine you're using, but...

The tyre should be there, it should be fixed well to the wheel, and it should be "crowned" i.e. curved gently, like the outer edge of a car steering wheel (only less so). Loose is bad. You need a crown on both wheels to be able to adjust the blade tracking, keep the blade actually on the wheels and prevent the teeth grinding on the wheels.

I assume you mean the back guide roller when you say it's jumping off - from the flat to the rim of the roller. This sounds like the guide roller set isn't positioned/adjusted properly. You need to re-set them each time you change the blade and after any major tension adjustments, but you can't do that unless/until the main wheels are fixed and aligned correctly.

It sounds like the whole machine needs servicing/setting up properly. The tyres can probably be replaced, and there are people here who can advise (at least one person in this thread has done it themselves), but it's not a rush job.

As you describe it, it sounds a bit dangerous! Personally, I'd 'phone a friend' at this point, to see if you can get the material cut locally on a properly set up machine. Then you have breathing space to get yours fixed.

I get the rubber chicken (again) for the first mention in the thread of Steve Maskery's "Workshop Essentials" DVDs...