band sharpness problem

[jas]

i think i should reset my guides as they arn't that close-maybe back to the drawing board for an overhaul. ive been cutting softwood which has been sat around a while,the softwood definately needs a wider kerf. many thanks for the inputs ,its nice to have some informed opinions

[codlasher]

There were some problems with our Guilliet saw and when we had the wheels re ground the fellow suggested that we ignored the tension meter as he thought it was still too slack......From then on there were fewer wobbly boards as the blade ran better.

Perhaps you could look at this and just check the alignment between the head-rig and the bottom wheel. There is potential for considerable and deliberate adjustment with the bolts that hold the bottom wheel on.

codlasher

[jas]

we did wonder wether this might be an issue,but havn't checked it yet.are you happy that your bands are being pre-tensioned correctly during sharpening?

[wills-mill]

Sawing softwoods is much harder for the saw IMO. Clogging dust, naughty sap, rings of rock hard resinous knots, cheeky band squeezing Larch- it all goes on and makes much more work for the band.

 

I think there's a bit of difference in the use of the word 'tension':

 

Winding the blade up tight between the wheels was usually known as 'straining' the blade for big old bandmills.

 

Stretching and setting the body of the blade (on the saw doctors bench) so that it tracks well and holds the teeth tight and straight when put on a crowned wheel is/was called tensioning.

 

Again, I've only fairly limited wide band experience, but we did notice (when strapping the bands up to go for sharpening) that some of the bands that seemed to have decent teeth but still messed around would not sit nice and flat on the floor when taken off the saw. When they were sat with the width of the band flat on the floor, there are definitely some bands that undulated up and down off the floor and had floppy sections.

 

We've just moved house and everything's boxed up, but I'll try and scan some bits out of this book:

The Art of Saw Doctoring Wide Bandsaws by Simmonds a - AbeBooks

It's good some good explanations of some of the things that go into manually looking after bands, even though the author admits that there are plenty of different opinions and ways to do things. It at least taught me that I never want to try and do my own wide bands.

[wills-mill]

Do Guilliets use a set of weights to strain the band? That's how Stenners do it....

[agg221]

Hope you don't mind me jumping on this thread, but there appears to be some good expertise going on with bandsaw issues here.

 

Very narrow band (3/4") running on a horizontal mill, with a 14" width, and the band has started jumping the wheels, forwards!

 

At first I thought it was a particular, very 'grabby' tree but it has done it since on some nice, clean stuff which had previously been milling well. Bands are good quality and it has done it on both a known good band and one straight out of the box.

 

Any ideas what to look for?

 

Cheers

 

Alec

[wills-mill]

What's the surface of the wheels on your mill? Is it V-belts in a groove like a Woodmizer, or rubber bonded on to steel. There may be grot built up under the V-belt or the surface may be deformed?

 

Can you give us an idea of when the bands jump off? before, during, after cut?

[agg221]

What's the surface of the wheels on your mill? Is it V-belts in a groove like a Woodmizer, or rubber bonded on to steel. There may be grot built up under the V-belt or the surface may be deformed?

 

Can you give us an idea of when the bands jump off? before, during, after cut?

 

The wheels are plain aluminium - never had anything bonded to them (the bands are thin enough to tension such that they don't slip).

 

It jumps off during milling. The forward force is normally fairly moderate hand pushing, but definitely positive force.

 

There are no tracking issues - start the cut and it's tracking fine. The bands tend to be ruined once they have jumped as it stretches them on one side, but put a new band on and tracking is still fine.

 

There could be a problem with the scraper - likely cause?

 

Alec

[youcallthatbig]

Tracking of the wheels,with such a narrow band I suspect it it hyper sensitive to the tracking,check bearings of wheels also so that cutting side(assuming you have front & back bearings on wheel spindle) doesn't deform when tensioning blade therefore affecting tracking......just a thought.

[jas]

Do Guilliets use a set of weights to strain the band? That's how Stenners do it....

 

the guilliet seems to use a counter weight to strain the band from what i can see,although all the gubins inside is only really accesible when the machine is split in two by the looks-the pressure backs itself off a little while the saw is running,but not by much.

the bands not sitting flat on the floor is not something i'd noticed but i will keep an eye on that one when i unpack my 2 from sharpening-good point as welding could deform them. the book you have sounds good ,any info available would be gratefully received -i'd ask the chap in the library van for a copy,but there might be some head scratching there

as an update,the band i have on currently is cutting with pretty good accuracy-cut a knoty piece of douglas into hedging stakes and tidied up a 12" x 12" x 10' piece of oak with good results. the band has been running for over a hour,its got well defined swages at about 3mm

are you running a wide band stenner at the moment?