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

Originally Posted by vk4

Hermit,

Glad to see some success ,.

I still think the cut is a bit rough, and should be finer cut marks , although these could be the 3tpi blade.and are a lot finer than the previous tests you have shown.and the fact I am using 4tpi.

So happy to see some light at the end of the tunnel for you, though I still think the saw should go back.

Jeff
vk4

That's the original, rough blade, Jeff. I haven't put the new good one back on yet. (I didn't think I'd be keeping the saw.)

The cut will improve a little with the new blade, but also now I can replace the guides with better ones etc to fine-tune and make it better. Compared to before, this is perfect, believe me. I can make all of the cuts that I need. A little extra sanding isn't too scary.

My budget hasn't increased, so taking this back and buying another low-budget machine elsewhere could well land me in hot water again. For the sake of having a saw to use, I'll keep this one. Better the devil you know than the devil you don't.
I'll buy a bigger better one in a year or two, once I get everything else organised.

It will be interesting to see the difference between that blade cutting 4" vs new blade cutting the same depth.

Good stuff.

Paul.

I concur a great deal learned during this thread.

I will say that when i did my apprenticeship I used a Hafco 14" BS back in the 70's and I only recall it once ever having a blade replaced. Never did I know of any of us going through this procedure not that we were cutting verneer, or for super accurate although it did well for pattern and shapes. I doubt it had the guides we see today.

My BS Bassato 4 has been giving me grief for a while today I had had enough loosened all off, the blade had been running as per Snodgrass suggested. My top guides were readjusted, and the bracket reset a little (no idea how or why it had moved). Table which also had moved off square to the blade 2mm over 150mm. These changes took away the effect Hermit/Steve has shown in his cuts which was on mine becoming worse and not always there. The blade which is supposed to be Bimetal 3tpi from Henry Bros I noticed has one section of blade warp where it wobbles off centre and back.

The blade is not old but has done some heavy work on turning blanks and aussie hardwood.

Steve I look forward to seeing your fixes of the BS

Originally Posted by pmcgee

It will be interesting to see the difference between that blade cutting 4" vs new blade cutting the same depth.

Good stuff.

Paul.

I just did exactly that, cutting the 10mm slice that I needed - no problems, along with a bunch of other cuts in a couple of timbers. It cruised through it all, no excessive screeching, nothing came undone, all cuts were straight and relatively clean without bowing. I know the saw should work better with the blade in the centre, but this is fine.

Notice that the saw cuts are now almost vertical as they should be, too. I don't understand that bit, but don't care.

All other adjustments aside from tracking are exactly the same as I've done from the beginning. Once I got it tracking with the bottom of the gullets in the centre of the wheel, I just did everything else as usual.
Easy to align, too. When the back of the blade is right on the edge of the wheel, the gullet bottoms are exactly centred. (Of course, this means that I can't go up to a wider blade than 1/2", but I didn't plan to.)

I just got more work done in an hour than I've done in weeks.

Originally Posted by wheelinround

I concur a great deal learned during this thread.

I will say that when i did my apprenticeship I used a Hafco 14" BS back in the 70's and I only recall it once ever having a blade replaced. Never did I know of any of us going through this procedure not that we were cutting verneer, or for super accurate although it did well for pattern and shapes. I doubt it had the guides we see today.

My BS Bassato 4 has been giving me grief for a while today I had had enough loosened all off, the blade had been running as per Snodgrass suggested. My top guides were readjusted, and the bracket reset a little (no idea how or why it had moved). Table which also had moved off square to the blade 2mm over 150mm. These changes took away the effect Hermit/Steve has shown in his cuts which was on mine becoming worse and not always there. The blade which is supposed to be Bimetal 3tpi from Henry Bros I noticed has one section of blade warp where it wobbles off centre and back.

The blade is not old but has done some heavy work on turning blanks and aussie hardwood.

Steve I look forward to seeing your fixes of the BS

Interesting.
This Snodgrass guy could start a revolution here.

I have a mate in Sydney, a retired mechanical engineer, who still has a well-fitted out workshop under the house.
If I can work out a way to draw up what I want in the way of a lower guide bracket, he can make it. I have 5mm bearings here that are perfect for the job. If I can get that sorted out, I'll go on to do the top ones. All guides should be bearings, not blocks or bushes/shims, I reckon. Micro-adjustable if he can manage it, too. I'm getting really sick of grub screws and the marks they leave.

So, steve is happy boy as well.
Time for wheel mass production I guess for you.

Originally Posted by _fly_

So, steve is happy boy as well.
Time for wheel mass production I guess for you.

Almost. That's what the 10mm was for, as you guessed.
First, though, I've got to glue in tailshaft and radius rods etc, then make the 3 ice-cream sticks for the steering and put that together. I put them off until the bandsaw was working properly. The steering pivots are done, ebonised and sitting here waiting.

I've got to finish the workbench, too, before I can put too much time into the car. I got one end almost finished today, laminating 4 x 2's into 4 x 4's. It's getting heavy.

Good on you for persisting with it through to this point.

It's a pity there wasn't the know-how/interest/time/whatever at H&F to either tell you how to get the best performance ... or retail a better put together instrument.

Maybe you should let them know your solution - they might be able to help other poor sods

Cheers,
Paul.

Originally Posted by pmcgee

Good on you for persisting with it through to this point.

It's a pity there wasn't the know-how/interest/time/whatever at H&F to either tell you how to get the best performance ... or retail a better put together instrument.

Maybe you should let them know your solution - they might be able to help other poor sods

Cheers,
Paul.

Overall, I'm just pleased to have it working at an acceptable level finally. It's one month to the day since I ordered it.
I will let them know. I was planning to do that tomorrow, although I suspect they'd already know.

When all else fails, this is certainly worth a try. I would have tried it earlier, but was waiting until the bandsaw was working properly. That was never going to happen, until I did it, as it turned out.

I can risk cutting out the bottom of my heart box now, too, so I just marked it out for tomorrow. Have to change to the 1/4" blade for that. Another good test.

Hello,
Like most of you, I tend to set the blade in the centre of the rubber tyre on the top wheel. However, let me show this take on it!
The attached images I just scanned from the owner's manual for our big bandsaw at work, one that have I used, maintained and taught on for nearly 20yrs. Its a Taiwanese one, rebadged Hare and Forbes, although the manual says Chung Kung (Model PBS-600). It is a good solid no-nonsense machine and has given great service for 20yrs. I had an after-market blade guide setup installed some years back, ex Hare and Forbes, although I had an engineer fit it, as there was a major mod needed. In all that time I have set the blade in the centre of the tyre.
The manual has some dodgy illustrations, but the point is clear, the factory recommends the teeth of the blade protrude or overhang the front of the wheel by 3mm. And that a 1mm gap is maintained between the rear guide and the blade.
By my experience I know that with the blade centred (ie, sitting on the crown of the rubber), it is very difficult to prevent the blade touching the rear blade guide, as any pushing of the stock as you cut will push the blade rearwards. And yes, rubbing the blade, creating friction, making sparks, wearing guides etc. To counter that is a fine balancing act of getting the blade slightly forwards of centre, but not running off the wheel.
My supposition then, is that setting the blade as described in this manual would ensure the blade can't get pushed rearwards when cutting, and therefore maintains that 1mm gap from the guide. In essence it is held in place by the camber of the rubber tyre. What I don't quite get is how the blade will stay there without being spat off the front of the wheel! Please note, I haven't actually tried it...

Any comments, apart from what a dodgy, badly scaled drawing?

Cheers


PS second image failed to load, I'll try another format

Originally Posted by Andy Mac

Hello,
Like most of you, I tend to set the blade in the centre of the rubber tyre on the top wheel. However, let me show this take on it!
The attached images I just scanned from the owner's manual for our big bandsaw at work, one that have I used, maintained and taught on for nearly 20yrs. Its a Taiwanese one, rebadged Hare and Forbes, although the manual says Chung Kung (Model PBS-600). It is a good solid no-nonsense machine and has given great service for 20yrs. I had an after-market blade guide setup installed some years back, ex Hare and Forbes, although I had an engineer fit it, as there was a major mod needed. In all that time I have set the blade in the centre of the tyre.
The manual has some dodgy illustrations, but the point is clear, the factory recommends the teeth of the blade protrude or overhang the front of the wheel by 3mm. And that a 1mm gap is maintained between the rear guide and the blade.
By my experience I know that with the blade centred (ie, sitting on the crown of the rubber), it is very difficult to prevent the blade touching the rear blade guide, as any pushing of the stock as you cut will push the blade rearwards. And yes, rubbing the blade, creating friction, making sparks, wearing guides etc. To counter that is a fine balancing act of getting the blade slightly forwards of centre, but not running off the wheel.
My supposition then, is that setting the blade as described in this manual would ensure the blade can't get pushed rearwards when cutting, and therefore maintains that 1mm gap from the guide. In essence it is held in place by the camber of the rubber tyre. What I don't quite get is how the blade will stay there without being spat off the front of the wheel! Please note, I haven't actually tried it...

Any comments, apart from what a dodgy, badly scaled drawing?

Cheers


PS second image failed to load, I'll try another format

Dunno about the rest, but a 1mm gap between blade and thrust bearing?
Wouldn't the blade bow slightly if pushed back that far?
Almost everything I've seen says about the thickness of a playing card, some say even less.

As far as I'm aware, the blade should ride on the thrust bearing during a cut, but not when idle. The lightest of pressure should bring the blade into contact with the thrust bearing, to prevent blade bowing and distortion.

Hi Andy, At least to the question of why the blade isn't kicked off, I can answer. I put some links in my previous post in this thread that explain it. The crowned wheel is what actually holds it there believe it or not. All those old machines driven by flat belts on flangeless pulleys had one crowned pulley. It does seem pretty clear that a big source of wander is bumping the thrust bearing too hard, so your conclusion that it maintains a gap from the thrust bearing might be plausable. In the second link there is a video and in it he mentions some large resaw BS not even having thrust bearings at all, so there is no gap to worry about at all. Actually, Alex Snodgrass mentions the thrust bearing contact as being a contributor to wandering, and the way he explains it, to me it implies a major source...

Originally Posted by Andy Mac

Hello,
Like most of you, I tend to set the blade in the centre of the rubber tyre on the top wheel. However, let me show this take on it!
The attached images I just scanned from the owner's manual for our big bandsaw at work, one that have I used, maintained and taught on for nearly 20yrs. Its a Taiwanese one, rebadged Hare and Forbes, although the manual says Chung Kung (Model PBS-600). It is a good solid no-nonsense machine and has given great service for 20yrs. I had an after-market blade guide setup installed some years back, ex Hare and Forbes, although I had an engineer fit it, as there was a major mod needed. In all that time I have set the blade in the centre of the tyre.
The manual has some dodgy illustrations, but the point is clear, the factory recommends the teeth of the blade protrude or overhang the front of the wheel by 3mm. And that a 1mm gap is maintained between the rear guide and the blade.
By my experience I know that with the blade centred (ie, sitting on the crown of the rubber), it is very difficult to prevent the blade touching the rear blade guide, as any pushing of the stock as you cut will push the blade rearwards. And yes, rubbing the blade, creating friction, making sparks, wearing guides etc. To counter that is a fine balancing act of getting the blade slightly forwards of centre, but not running off the wheel.
My supposition then, is that setting the blade as described in this manual would ensure the blade can't get pushed rearwards when cutting, and therefore maintains that 1mm gap from the guide. In essence it is held in place by the camber of the rubber tyre. What I don't quite get is how the blade will stay there without being spat off the front of the wheel! Please note, I haven't actually tried it...

Any comments, apart from what a dodgy, badly scaled drawing?

Cheers


PS second image failed to load, I'll try another format

Here's the other image showing the gap at the rear of the blade.

Originally Posted by mic-d

Hi Andy, At least to the question of why the blade isn't kicked off, I can answer. I put some links in my previous post in this thread that explain it. The crowned wheel is what actually holds it there believe it or not. All those old machines driven by flat belts on flangeless pulleys had one crowned pulley. It does seem pretty clear that a big source of wander is bumping the thrust bearing too hard, so your conclusion that it maintains a gap from the thrust bearing might be plausable. In the second link there is a video and in it he mentions some large resaw BS not even having thrust bearings at all, so there is no gap to worry about at all. Actually, Alex Snodgrass mentions the thrust bearing contact as being a contributor to wandering, and the way he explains it, to me it implies a major source...

Interesting stuff. Before I changed the blade guides to a bearing type, the rear guide, which was a steel disc running in a brass bushing, would sometimes get seriously worn out by the action of the blade running against it. Sparks would fly and a very sharp burr would form around its perimeter. This suggested tp me that the blade should not be coming into contact with it on a regular basis. However, the notion of NOT having one at all is a bit foreign.... I'll have to process that!