51 x1/2 Bandsaw Tension

What make and type of bandsaw, what size and type of material? Are you cutting straights or curves? Are you using coolant? What sort of pressure are you putting onto the blade? Perhaps a photo of your setup will help.
BobH

Another, non My Time Media, UK, M E magazine had an article on making a tension meter, a few months back.

It used a DTI to measure the blade extension as it was tensioned. Other than the DTI and the Silver Steel pivot and a few small capscrews, it all came from a bit of square bar (15mm from memory)

I made one and used it to set blade tension on my elderly 4.5" bandsaw. Since then no broken blades, and seemingly improved accuracy. The first trial cut off a bit of 38mm round bar, suggested a variation on thickness of about 0,025mm on a 1.5mm thickness. But I don't expect that degree of accuracy!, purely a one off!

So, in my book it is a very useful, but rarely used, device.

Have you checked that all the guide rollers are correctly set and aligned?

The shorter the blade, the more sharply the blade twists as it enters or leaves the wheels. Before the 4.5" I had a little one, and was lucky to cut one piece of 38mm angle iron before the blade broke, despite being carefully set up. Needless to say that went back!

Howard

I was advised by a seller to put on as much tension as I could with the hand knob.

If you put as much tension on it as a guitar's e-string the force would be about 3/4 of a ton ... in other words, you ain't going to snap it.

More important is getting the wheel tacking right and the guides properly adjusted.

Neil

Which way round are you fitting the blade? is the drive pulley pushing or pulling the blade?

This is the 'bible' for setting up hobby bandsaws: John Pitkin Bandsaw Guide

Neil

I was told tighten till it will twang like a banjo - works for me

Agreed, that pdf I linked says 'if it rattles it's loose, it should make a musical note'.

N.

I had one break on the weld recently, I enquired with the seller as what I might do to avoid this, he replied that if it breaks on the weld then it is faulty and gave me a new one for free - nice chap.

The only way to be certain is to set a suitable tension but as you can't directly measure the tension and the hand wheel stiffness will vary with lubrication, contamination etc, plucking the blade as Fizzy suggests is a good way to measure it indirectly. I set mine to give a tone that is probably not far off Middle C although I haven't checked precisely. Certainly, it's close to the limit of what can be achieved with bare hands on my Chinese 4x6 bandsaw using the small handwheel.

Murray

If it breaks on the weld, anneal the weld before use (Like it should have been at the factory). On larger bandsaws where there is an incorporated butt welder, the weld is made and then slowly cooled to allow the joint to anneal. As others have said - It sounds like your blades are a poor quality. You could 'repair" your blades by making a silver soldered spliced joint.
BobH

Ps - look up "Bandsaw blades" on this site.
BobH

The instructions for my bandsaw say to tighten until the blade makes a musical note when plucked, they don't say which note, there is a B on the saw frame casting, so that will do.

Ian S C

Edited By Ian S C on 05/03/2017 09:53:56