Bandsaw throwing blade.

[S.Jamieson]

Hi,
We have a new to us bandsaw that keeps throwing the blade off the driven side wheel.
I have had it set up so it tracks perfectly up against the wheel flanges when in the air, but when I put it in to work, a few seconds - up to 20 or 30 seconds later it throws it off.
Tried with a new blade with no difference.

Any suggestions?

 

[Deutzdx3]

Is it auto feed or pull down? If they are pulled down to fast they tend to pop the blade. Both mine do this if the feed rate is to high. Bloody annoying.

 

[S.Jamieson]

Is it auto feed or pull down? If they are pulled down to fast they tend to pop the blade. Both mine do this if the feed rate is to high. Bloody annoying.

Auto feed. I'm not an expert but I'm fairly sure I've got it pretty slow!

 

[Deutzdx3]

Auto feed. I'm not an expert but I'm fairly sure I've got it pretty slow!

Check bearings,

Over adjust it slightly so it’s running against the rim of the wheel. See if it does it then. Also, make sure there is enough tension on the blade. To loose they pop off as soon as they come under load.

 

[S.Jamieson]

Check bearings,

Over adjust it slightly so it’s running against the rim of the wheel. See if it does it then. Also, make sure there is enough tension on the blade. To loose they pop off as soon as they come under load.

There may be about 1mm or so of play on the driven side, would that be enough to throw it off?

 

[Case290]

Yep I’d say it would
on my band saw there's no play at all

 

[Deutzdx3]

There may be about 1mm or so of play on the driven side, would that be enough to throw it off?

It may well be an issue, my top pulley has movement on both machines so I assume that’s normal for the brands I have. I would make it track towards the shoulder and Make sure it’s really tight on the pulley. See what it does once you’ve over tracked it. If if doesn’t pop as often then great.

Things that make mine pop are not enough tension on the blade. To fast down feed.

 

[S.Jamieson]

It may well be an issue, my top pulley has movement on both machines so I assume that’s normal for the brands I have. I would make it track towards the shoulder and Make sure it’s really tight on the pulley. See what it does once you’ve over tracked it. If if doesn’t pop as often then great.

Things that make mine pop are not enough tension on the blade. To fast down feed.

How do you determine blade tension? I've been tightening as tight as I can with one hand then a couple wee screws more.

 

[farmgineer]

How do you determine blade tension? I've been tightening as tight as I can with one hand then a couple wee screws more.

My apprentice master told us to tension it to make the sound of "B" as a musical note... Not sure it's actually right but I do use the sound of plucking the blade to make sure I've tensioned it right. They have to be tight.

 

[clodshopper]

A new band may be all that is needed

 

[Kidds]

Had a similar problem with mine to start with. Cured it mostly by buying decent quality blades rather than the ones it came with and increasing tension.

 

[Skintagain]

Get a straight edge and make sure the pulleys are aligned.

I have seen one bent once by someone dropping a big bar off a crane into saw twisting the body

 

[JohnBoy]

Any play in the idler wheel bearings?

Basically any misalignment in the wheels can cause bother. I had problems on my 7x12 and it was the shaft the idler bearings run on was loose. Shimmed it with some tin foil and replaced the bearings and its been fine since

 

[tomlad]

Following
Ive one i haven't touched for years because it spits the band off.
On my list to fix now ive a lathe
Are Starret bands 'quality ' id hope so

 

[335d]

when buying blades check you are buying the right blade for the material you are cutting.There are different blades for cutting solid bar than hollow section. If you are running a blade designed for hollow section to cut a large chunk of solid steel, it won’t be able to clear the swarf and can slip, or throw off. Starret would be good. It was one of their reps who visited our workplace and specified a few different blades for different jobs. The guys were trying to cut steel hollow section and extruded aluminium with the same blade. Got 2 different blades and no more issues.