Thread: So, where should the blade REALLY run on the top wheel?

What Scheppac has to say about Bassato 4

As mentioned above by Elanjacobs about being shown by an old bloke how to adjust the bandsaw during his apprenticeship, I was also shown during mine by an old bloke with years of hands on experience during my apprenticeship. Being shown is far better than trying to glean the info from books and videos. Anyway. The tyres when mounted on the bandsaw wheel have a camber on them. The centre of the the saw blade whether it is 1/4 inch or 1 1/4 inches should run in the centre of the tyre at the top of the camber. The top wheel is pivotted so the blade can track TDC. The correct tension is applied until the right pitch or note is obtained. That I cannot show or describe here. Then by rotating the blade by hand and plucking the blade the sound should be the same throughout the rotation. If the tone lowers and increases it indicates that the wheels are not true which causes the tension to increase and decrease each rotation. This can result in blade breakage. Once the correct tension is reached then the guides are positioned and the thrust bearing adjusted. The guides and the thrust bearing should not run continuously on the blade but some clearance should be given. An old oilstone can be held on the rear of the blade while rotating to remove burrs and sharp corners to assist in blade longevity and thrust bearing surface wear. If the bandsaw is used on a daily basis then the blade can be left in tension. If the saw is used periodically then the blade tension should be slackened off after use. This is to prevent flat spots forming on the tyres resulting in the problem stated above. The tyres need frequent inspection for cracks and dust buildup. Scrape them clean and adjust the tyre brushes if fitted. If there are no tyre brushes you can make some up with toothbrushes. I replaced the original rubber tyres on my bandsaws with urethane. The urethane tyres are not glued in place but are stretched over the wheels. Much better than rubber. If you have any questions just ask.

Col.

Originally Posted by Groggy

This is safest, has least wear and would work for all blade sizes.

Snodgrass' argument is that centring the blade does not work for all sizes, because the guides have to be moved forwards/backwards all the time to suit blade changes.
By centring the rear of the gullets on the crown, he says, you 'will never need to move your guides again'. A little hard to believe. Never?

Interesting discussion.
I've been reading closely.

Looking pretty clear so far, but it's a shame more people haven't tried it for a good comparison.

Hi Hermit & anyone else following this thread,
Well the Snodgrass method has improved BS drift for me.
My understanding is that on a covex wheel if the blade is supported by the crown of the wheel just behind the gullet there is less opportunity for the blade to flex at the front (tooth side) of the blade while still allowing any dust to clear away (for the want of a better term) from the gullet as it approaches the lower wheel. Any flex that may occur at the rear of the blade should not matter as it should technically travel in area that has already been cut away by the front (tooth side) of the blade.

As an aside I asked my BS if it had read its own operation manual but it completely ignored me.

Cheers
Rumnut

Originally Posted by Hermit

Snodgrass' argument is that centring the blade does not work for all sizes, because the guides have to be moved forwards/backwards all the time to suit blade changes.
By centring the rear of the gullets on the crown, he says, you 'will never need to move your guides again'. A little hard to believe. Never?

Interesting discussion.
I've been reading closely.

Looking pretty clear so far, but it's a shame more people haven't tried it for a good comparison.

Teeth sizes change, gullet sizes therefore change and blade width changes. You should always readjust the guides to suit the blade regardless. If it aint broke why do people always feel they have to change things.

Col.

Originally Posted by Col

If it aint broke why do people always feel they have to change things.
Col.

I'm not trying to change things, I just raised the topic for discussion having seen the video.
It's obvious, though, that some people have benefited from changing to Snodgrass' methods.

And you're right, of course, if it ain't broke, why fix it, but for some people it is broke and they're experiencing drift problems when all else seems OK. This is one more thing that could possibly help cure their problems.

There must be something to this method, even if only for some. I'm sure he's not just saying it for no reason.

Originally Posted by tdrumnut

Hi Hermit & anyone else following this thread,
Well the Snodgrass method has improved BS drift for me.
My understanding is that on a covex wheel if the blade is supported by the crown of the wheel just behind the gullet there is less opportunity for the blade to flex at the front (tooth side) of the blade while still allowing any dust to clear away (for the want of a better term) from the gullet as it approaches the lower wheel. Any flex that may occur at the rear of the blade should not matter as it should technically travel in area that has already been cut away by the front (tooth side) of the blade.

As an aside I asked my BS if it had read its own operation manual but it completely ignored me.

Cheers
Rumnut

I agree.
The only thing I need to change it the rear bearing for blade width. The side bearings are always set behind the gullet regardless of blade width. Or blocks as I have.
I also don't get drift when running down a good fence.

Originally Posted by Col

Teeth sizes change, gullet sizes therefore change and blade width changes. You should always readjust the guides to suit the blade regardless. If it aint broke why do people always feel they have to change things.

Col.

I would think that the fact that people are looking at methods to reduce drift would suggest it is broke

Cheers
Rumnut

Originally Posted by Hermit

I'm not trying to change things, I just raised the topic for discussion having seen the video.
It's obvious, though, that some people have benefited from changing to Snodgrass' methods.

And you're right, of course, if it ain't broke, why fix it, but for some people it is broke and they're experiencing drift problems when all else seems OK. This is one more thing that could possibly help cure their problems.

There must be something to this method, even if only for some. I'm sure he's not just saying it for no reason.

Drift occurs for a variety of reasons with some being. Incorrect tension of the blade, set of blade damaged due to incorrect setup, incorrect choice of blade for the task, incorrect feed of cut.

Many users expect the one or two blades they have to perform all tasks but they are not being realistic. In most cases all the user needs to do is ask a bandsaw blade manufacturer like McDivens in Williamstown Vic, which would be the best blade for the saw they have to perform the task required. They will tell you and sell you the blade and for much less than you think. I have a half dozen or so blades hanging on the shed wall which covers most tasks I do. The more you change your blades the faster you get at it and saw setup becomes quick and easy. To get the most out of all of your tools and equipment you need to become familiar with the machine and know the limitations of each and yours. This brings me to the method you are writing about with the bandsaw blade not being centred on the top wheel as it should be. Having the blade off centre means that the blade is always trying to centre itself by moving towards the top of camber or off the tyre if too loose. If the blade tension and thrust bearing is not adjusted correctly the blade can in fact be pushed off the wheel causing damage to machine and operator. The minutes spent setting the correct blade, tension and guides correctly will result in no drift and a safe operator.

Col

Originally Posted by tdrumnut

I would think that the fact that people are looking at methods to reduce drift would suggest it is broke

Cheers
Rumnut

Unfortunately we don't live in an ideal world. Drift happens and, while people will always look for ways to minimize it, there comes a point where the physical limitations of a tensioned steel band mean that we have to live with it.

The exact same setup has been used for well over 100 years with very little change, other than added safety measures, which leads me to believe that, while it is "broke", it's about as "fixed" as we can get it.

I set up my little Chinese 9" bandsaw , to Alex Snodgrass's specs, and discription , from the video.

I had piece of Camphor Laural off cut that had more angles than I care to think about.

this machine had so much drift it has always been a pain to use.

NEW MACHINE the cuts were all straight bar 1 where I hit a hard grain spot and a slight diversion in the cut of 11/2 mm max, for this machine thats straight,.

the machine only uses hobbyist blades , which are very thin and flex everywhere,

While not totally convinced that this is the best system for all band saws , it appears on the short test I have done to work for mine.

I will do some more tests soon.

Jeff
vk4

Originally Posted by vk4

I set up my little Chinese 9" bandsaw , to Alex Snodgrass's specs, and discription , from the video.

I had piece of Camphor Laural off cut that had more angles than I care to think about.

this machine had so much drift it has always been a pain to use.

NEW MACHINE the cuts were all straight bar 1 where I hit a hard grain spot and a slight diversion in the cut of 11/2 mm max, for this machine thats straight,.

the machine only uses hobbyist blades , which are very thin and flex everywhere,

While not totally convinced that this is the best system for all band saws , it appears on the short test I have done to work for mine.

I will do some more tests soon.

Jeff
vk4

Good one Jeff. I'd try it myself if the bandsaw was working.
Very interesting. Out of three that I know have tried it, yourself, _fly_ and tdrumnut, three have had good results.

Great learning thread, with lots of experience like Col's being shared. Thanks guys

Hi Steve - very worthwhile discussing.

For one thing, given a tight metal band round rubber-coated wheels, I assume that under the contact area of the blade on the wheel will be a flattened area - not a single point on a curve - so there's no doubt some leeway to move the blade left and right from the 'centre on centre' arrangement.

Also Snodgrass says (I think) that only the top wheel will run how he suggests and it will be different on the bottom wheel. I am assuming without going out to check it that with the 'centre on centre' arrangement it would be that way for both wheels.

So they may be - I'm sure are - two possible ways to achieve what we want which is a stable dynamical arrangment of two wheels and a metal band that is resistant to being moved away from that arrangment ... like a punching clown that you can push around but comes back to the upright position.

To properly compare the two would need some proposals of experiments that could be duplicated with 'identical' materials under the two different setups.

Eg. Setup a fence each time using the cut halfway by hand method, then cut 20mm, 10mm, 5mm thick slices off of xxx type of wood that is 1", 2", 4" thick by 18" long. Several times.
Then repeat with different woods.
Then report back here.


Paul.