Setting bandsaw blade guides

[OldWood]

I recently bought a 2nd hand Multico BS. I also bought Steve Maskery's DVD's on bandsaws.

The saw guide were solid blocks so I bought the Axi replacement system an with one or two minor hassles fitted them.

One thing I'm having difficulty with is setting the side bearings. Steve uses a bit of paper to set the gap, but what he doesn't say is if the bearings are expected to run all the time or just click round a little as the blade goes passed. Now I can set the guides so that the bearings run all the time, or I can set them a fraction further out so that the blade hits each one randomly about half a dozen times each full circuit. What is correct ? Or perhaps a new good blade runs so true there actually isn't any middle ground as I am seeing.

Not that there is realistically any adjustment for this but what sort of accuracy is expected for the guide raising and lowering mechanism. If this is not truly parallel with the blade, then any guide setting at say the bottom, will not be correct when the guides are at the top. I appreciate this does depend a bit on the quality of the saw, but a ball-park figure for blade deviation would be interesting.

Thanks for any help

Rob

 

[joiner_sim]

I usually tend to set the the side guides so that they are not touching the blade, only enough to see a very small amount of light through the gap between the blade and bearing. Also make sure the bearing is set back from the blade's teeth.

The bearing for the back of the blade should be loose, pull it forward (loose) and set the guide upto the blade. Once the blade is running the back wheel shouldn't spin until you are applying cutting pressure on the blade. The side bearings shouldn't spin that much if at all, personally I think they are just there to help keep the blade straight when cutting sharp curves etc....

 

[Max Power]

Sounds about right joiner sim, thats how I have mine

 

[OPJ]

Steve's 'paper trick' for the side bearings is a good one. But, for the rear thrust bearing, it is often recommended that you create a slightly larger gap from the back of the blade, as much as 1mm - I can't remember exactly what Steve said about setting the thrust bearing on his DVDs?

You basically want the blade to run 'freely' between all the guides when it's not cutting. They should only come in to contact with the back and sides of the blade (never the teeth!) while the saw is under load (cutting). If you've set the bearings using Steve's method and you're still getting a 'tick, tick, tick' as the blade goes around freely then, I reckon the weld on the blade might need a little bit of work - this is demonstrated on Steve's DVD.

Bearings are only there to support the blade during the cut. If you're blades running out of true at all, it could be the tracking or your wheels may not be aligned correctly.

 

[Steve Maskery]

All the above advice is good!

You should not get a "tick, tick, tick". That is indicative of a poor blade (usually at the weld). It's also very common and my current blade does just that. It does not, of itself, make your bandsaw inoperable, merely sub-optimal. Try a good, new, blade. Give Ian John a buzz, he has a good reputation.

As for the back thrust bearing, I can see no benefit at all from leaving a 1mm gap. Simply move the thrust bearing up to the blade (without pushing), lock it off and you are done.

HTH
Steve

 

[jimi43]

I have seen some comment that the side bearings are a bit of a waste of time and that perfectly good guide action can be made with the standard setup of a back thrust bearing and two guide blocks.

Comments on this view appreciated? Steve?

Jim

 

[Jake]

I've had saws with both (first normal blocks and rear bearing, then all bearings, now all solid) and I prefer blocks and solid thrustpads. I would certainly never swap them over for bearings. If a saw came with bearings I would live with them, but I'd rather it was the other way around. They don't look as techy and advanced, but they work just as well if not better (bigger contact area, closer to where it counts). Their simplicity does their image no favours, but it is an advantage in many ways.

 

[OPJ]

As for the back thrust bearing, I can see no benefit at all from leaving a 1mm gap. Simply move the thrust bearing up to the blade (without pushing), lock it off and you are done.

That's interesting, Steve. I've always been taught to set the thrust bearing so it is clear of the blade when you're not cutting to reduce wear, etc. Perhaps it partly depends on the type of bearing you have? On some saws (including yours, I think?), the back of the blade runs on the 'face' of the thrust bearing. On mine and other cheap ones though, they blade runs against the edge, where there is a greater risk it could 'dig in' and create a groove.

1mm does sound a bit excessive; I don't see anything wrong with 0.5mm. It's a little bit like checking blade tension - each to their own method, I suppose.

 

[Steve Maskery]

I don't think we differ Olly. By "up to the back without pushing" I mean pretty much the same as you, I think. You will get unnecessary wear of it is pressed in hard, of course, but just touching is not going to wear it. It should not actually rotate until the wood is fed in

The danger of having a 1mm gap, however, is that if you come to do stopped cuts, you stop pushing when the blade reaches the shoulder (or whatever it is) and then without you even moving, the blade continues to cut another 1mm as it straightens itself up.

Cheers
Steve

 

[paulm]

I've had saws with both (first normal blocks and rear bearing, then all bearings, now all solid) and I prefer blocks and solid thrustpads. I would certainly never swap them over for bearings. If a saw came with bearings I would live with them, but I'd rather it was the other way around. They don't look as techy and advanced, but they work just as well if not better (bigger contact area, closer to where it counts). Their simplicity does their image no favours, but it is an advantage in many ways.

As Jake said, I too have a strong preference for blocks and thrust rods, elegant in their simplicity, totally functional and effective, but I guess each to their own.

Cheers, Paul

 

[Steve Maskery]

There is absolutely nothing wrong with guide blocks that are properly set. But they do wear and need to be dressed from time to time and the potential for heat build-up, if they are a bit tight is greater. Cool Blocks don't have that problem, but they wear at a greater rate.

They are, however, easier and cheaper to replace than bearings.

I agree I would have to have a very good reason for "upgrading". But it's not that blocks are superior, it's that they are perfectly adequate when properly installed.

Cheers
Steve

 

[OldWood]

Thanks guys - it looks as if I'm setting them a little tight. The blade I have is an old but seemingly sharp one - I've got a new blade on order from the local saw doctor, and I'll find out shortly what the difference is.

As far as the ticking is concerned, with the guides set to run freely but close, the bearings are being randomly touched as the blade goes round and this is too frequent to be the weld so I suspect that the gap is just not enough to take up the minor variations in the blade.

There is the other factor that I mentioned and that is the accuracy of the raising mechanism in that it moves independent of the blade. It does require to run totally parallel to the blade over the blade's cutting capacity (in my case 8"), which is quite demanding, or the alignment to the bearings (or even pads - and IMO this is where bearings would be better) will move, and contact with the guides will occur.

Rob

 

[stuartpaul]

I remember reading somewhere about using an oil stone (or similar) against the back of the blade to remove any 'high spots' and also to round over the back edge - gently of course!

Any merit in this?

 

[OldWood]

I remember reading somewhere about using an oil stone (or similar) against the back of the blade to remove any 'high spots' and also to round over the back edge - gently of course!

Any merit in this?

Steve M certainly recommends doing that to take off the sharp corners. There may well be some merit in running on the back a bit prior to that too to give the thrust surface a reasonable chance.

I will admit to being quite intrigued by the concern about the ball type bearings being allowed to run a bit. Isn't that what they are designed to do. And as a mechanical engineer, I do find it even more intriguing in terms of old fashioned engineering that rubbing blocks are used against a moving surface rather than an equal surface that can move with effectively zero friction.

Rob

 

[Steve Maskery]

Thing is, Rob, that in theory (!) the the blade guides don't actually rub at all! There are supposed to clear the blade by the thickness of a piece of paper. But of course, this is only the case for very straight cuts in very accommodating material. As soon as any sideways pressure is applied (to turn direction, for example) the the guides, whatever they are made of, limit the deflection of the blade and then they do, of course, actually rub. But if they are set properly, there should be very little rubbing in normal use on straight cuts.

I do think that bearings are going to be innately "better" than a rubbing block, but not necessarily by so much that it means an upgrade is the best way to spend one's money. Blocks have done a perfectly satisfactory job for a long time and there is no reason why they should not continue to do so. Indeed, well-set blocks will do a better job than poorly-set bearings, I'd say.

It's the set-up that makes the difference, not the materials.

S