Help - Bandsaw bladfes keep breaking

**Shedhand** · 3rd January 2009, 03:39 PM

Happy New Year all.
I've got Metabo 317mm Bandsaw and I'm having no luck at all with blades. When the original blade broke after about a dozen cuts I turfed it out and bought a good quality blade. I used it twice and it broke. Took it back to the supplier and he welded it together again. Fitted it and it broke again. So I went to a saw blade expert and he made me a 19mm blade for about 25 bucks. I asked the guy about blade tension recommendations and he gave me a rough idea. I had been tensioning the blades according to the user manual. However, for someone like me who is fussy about such things the tensioning device on the saw itself seems very imprecise. - a compression spring and a ball bearing - with no real indication of what the tension is. The 19mm blade broke yesterday ( and frightened the crap out me) on first use. It also took out the safety stop device which engages when the top door is opened. I have been very careful to fit the blade as per manufacturers guidelines making sure the blade is in the upper and lower guides.
Can some one give me a clue about the correct tension, how to achieve it and how to determine the tension. I have a lot of resawing of small wood I want to do and the breakages are giving me the tom tits to put it mildly - not to mention costly.I'm thinking I should get a bigger saw...
Cheers
Mike

**echnidna** · 3rd January 2009, 03:44 PM

have feeling 19mm is too wide for small dia wheels,
drop down to a 10mm blade and see what happens.

btw not all saw doctors do good bs welds so it may be worth trying another saw service

**Groggy** · 3rd January 2009, 04:57 PM

I agree with Bob. 317mm is tight for a big blade. 3tpi 10-12mm blade should work well.

**Wongdai** · 3rd January 2009, 07:06 PM

Are they breaking on the weld, or just any old place?

**Pat** · 3rd January 2009, 07:36 PM

Mike, is this the animal?

**Shedhand** · 3rd January 2009, 11:19 PM

Originally Posted by Groggy

I agree with Bob. 317mm is tight for a big blade. 3tpi 10-12mm blade should work well.

G'day mate. I thought so myself but the guy (who is an experienced saw doctor) said the 19mm would be ok at 317mm. But the 10 mm blades break too. ANd the specs say the machine will accomodate 6mm - 20mm blades
See other responses below.
Cheers
Mike

**Shedhand** · 3rd January 2009, 11:20 PM

Originally Posted by Wongdai

Are they breaking on the weld, or just any old place?

On the weld every time (different shops have reweled them so its not a particular operator.

**Shedhand** · 3rd January 2009, 11:21 PM

Originally Posted by Pat

Mike, is this the animal?

Yep! That's her! And you'll notice theres no recommended blade tension in the tech specs. Some one must know...

... and I'm almost certain its the tension thats the problem. The manual says the blade shouldn't deflect more than 2 or 3mm with moderate sideways finger pressure and that to me seems to be an awfully imprecise way to measure especially from a reasonably high end manufacturer.

**speedy** · 3rd January 2009, 11:45 PM

Hi,
I suspect you might be over tensioning the blade, thats the only way I can see you breaking so many blades unless you are jaming them. I have a scale on my bandsaw but I still tend to set the tension on the low side. You only need enough tension to stop the blade wondering in the cut. If you do a search of this site or the web you will find loads of info on blade tension.

**Shedhand** · 3rd January 2009, 11:53 PM

Originally Posted by speedy

Hi,
I suspect you might be over tensioning the blade, thats the only way I can see you breaking so many blades unless you are jaming them. I have a scale on my bandsaw but I still tend to set the tension on the low side. You only need enough tension to stop the blade wondering in the cut. If you do a search of this site or the web you will find loads of info on blade tension.

Thanx for that Speedy. I'll try with low tension and work my way up to a non-wandering tension. But it still seems a poor way of setting the tension.
Cheers
Mike
PS. I never let it run without a load. And when I'm not using it I flip the tension lever over to release the blade.

**speedy** · 4th January 2009, 12:12 AM

Can you clarify what you mean by "I never let it run without a load". There's no problem letting the saw run without a load, I let mine run for up to 5 minutes between cuts if I have a number of cuts to make in different pieces or I'm fitting some thing and I need to go and check the fit and then trim a bit more off. If the saw is set up correctly and running well there isn't a problem.
Note- on a saw like yours I think the tensioning should be with the saw running under no load.

**Shedhand** · 4th January 2009, 12:16 AM

Originally Posted by speedy

Can you clarify what you mean by "I never let it run without a load". There's no problem letting the saw run without a load, I let mine run for up to 5 minutes between cuts if I have a number of cuts to make in different pieces or I'm fitting some thing and I need to go and check the fit and then trim a bit more off. If the saw is set up correctly and running well there isn't a problem.
Note- on a saw like yours I think the tensioning should be with the saw running under no load.

I have a little mate ( 7 year old grandson who follows me around like a bad smell and I'd hate to have him stick his hand in the ssaw while is was running and my back was turned. He tends to do things I do (as keen learners will). So its just a saftey precaution really.
Sorry about all the typos, I have this whiz bang new wireless keyboard and it has a bloody minf of its own...might take the damn thing back for a refumd.

**speedy** · 4th January 2009, 12:20 AM

Yes you need eyes in the back of your head with kids about.
Good luck, theres a bit of an art to tensioning bandsaws, read up a bit before you try again.

**jerryc** · 4th January 2009, 09:31 AM

I know I might be stating the bleeding obvious but an out of round wheel or a buggered bearing will cause a blade to flex and fatigue.

Jerry

**Groggy** · 4th January 2009, 11:07 AM

Sheddie, are you cross-cutting smallish round logs by any chance? (I have found this to be a good way to break blades.)

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