Bandsaw issue .. pic's

[Rick Fisher]

Top wheel

http://i335.photobucket.com/albums/m455/jokerbird_photo/Top.jpg

Bottom Wheel

http://i335.photobucket.com/albums/m455/jokerbird_photo/Bottom.jpg


This has been happening lately. I use this saw for ripping lumber..

If I start off with the tires and blade flush, rip only 4 feet of 2" stock.. the blade will be hung off the bottom a bit too much, and the top tire starts to slip out from between the blade and Wheel.

My first thought was that the wheels where not co-planer.. but the blade is not really moving too much.. The tire is actually squeezing out..

So I am a bit confused.. Is it too much tension?

I am getting zero wander on the blade.. the saw cuts straight as an arrow..

[Wilbur Pan]

I think this is a urethane tire issue. On my bandsaw, I had urethane tires, and when I was in the middle of a cut there was a loud bang, and the top wheel tire came shooting out from where the blade exits the top wheel compartment.

When I checked the bottom wheel, the tire was loose as well. I could easily push it back and forth. These tires were much tighter when I first installed them about 2 years ago, and as a hobbyist, I don't think I've been overusing my bandsaw by any means.

I'm replacing them with regular rubber tires. I'm not really trusting urethane tires to maintain their tight fit over time any more, and although the adhesive is a bit of a mess to deal with, I don't want to have to worry about a tire coming off in the middle of a cut again.

[Tony Ward]

Hi, as I am not familiar with urethane tyres, I may not be qualified to comment.

However in my view the two images evidence that blade is not positioned correctly, the blade should always be centred in the middle of both wheels. At the very least in the centre of the top wheel, over the crown of the wheel.

[Bob Wingard]

in my view the two images evidence that blade is not positioned correctly, the blade should always be centred in the middle of both wheels. At the very least in the centre of the top wheel, over the crown of the wheel.

Not necessarily true. Most blades, even brand new have some amount of "drift" that forces you to compensate for it by angling your fence in order to get a straight cut. The "other" method is to run the blade fore or aft of the crown to make it cut straight. This shifting puts a little bit more strain on one edge or the other of the blade, causing it to cut straight without adjusting the fence.

Since the OP said his machine cuts "straight as an arrow", I'm assuming the offset of the blade on the wheels is intentional rather than a mistake.


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[Paul Steiner]

I have had a similiar problem on a delta and on a powermatic. The delta had a tire issue, there was a lump in the tire and it would eventually push the tire off. The powermatic's bottom wheel was warped and would not hold a blade. I replaced the wheel and it now cuts like a champ. How difficult is it to adjust the tracking of the blade? In both of my experiences I had a really hard time getting the blade centered on the wheels.

[Pete Bradley]

Rick,

If your tires are sliding off, they're shot. That looks to be a 18" or bigger, I'd use rubber tires glued on, then trued on the wheel. Bob Vaughan has a "how to" that ships with Carter tires and is available on Taunton's site (though you have to do their "Free 14 day membership" to get it now) or you can look here: http://wiki.owwm.com/CrescentBandSawRestoration3.ashx#BC_-_Installing_New_Tires_1

I use 3M 1300 adhesive which is evil stuff but works well for this operation.

Pete

[Rick Fisher]

The tires are new and are flat..

On this type of saw, the blade teeth hang off the edge of the wheels.

I think this is actually being caused by bad tracking.. I had a new 1" blade with a bad weld and adjusted the tracking trying to get it to run .. The 1" blade went back..

When I let it run idle for a few minutes, the rear wheel on the guides started to spin after a 30 seconds... It appears that the guides where actually keeping the blade on the wheel, it wants to walk off the back.

This is why its a "new problem".. I returned the 1" blade a week ago and didnt get the tracking right again..

Since the top wheel is the one that tilts for tracking, It must create some weird tension on the tire and blade, that the lower wheel doesnt get.

This begs the question.. "what the heck was I doing ... lol.."

The 1" blade had a bad weld. So I fussed setting up the saw for quite a while.. Guess I went overboard ...

[Dan Forman]

The pictures indicate the two wheels are not coplaner. My guess is that if you adjust them so that they are coplaner, with the blade tensioned, the problem will go away. Try it and see, it can't hurt anything. If the wheels are truly coplaner, the tracking knob is unnecessary, the blade will track on it's own. What the tracking knob does is tilt the top wheel in relation to the the bottom, in esscecnce, putting them further out of plane, which forces the blade into a "happy medium" position. So there is force on the blade as well as the tire, as they are working against each other to stay in position. It sounds as if the blade is pulling the tire off the wheel as the two are struggling against each other.

Dan

[Grant Vanbokklen]

The tires are new and are flat..

On this type of saw, the blade teeth hang off the edge of the wheels.

Are those new tires from SCMI?

Looks like you need to make a custom straight edge for getting the wheels coplaner and adjust those adjusting screws on the back of that Italian saw for the lower wheel.

[Rick Fisher]

This saw doesnt lend itself to running a straight edge against both wheels.. I checked it for co-planar as much as I could, using the mounts as indicators..

I did adjust the lower wheel outwards a small amount and the problem is unchanged.

I actually think the upper tire is streched.. I may just put rubber tires on the saw again..

[Rick Fisher]

Are those new tires from SCMI?

Looks like you need to make a custom straight edge for getting the wheels coplaner and adjust those adjusting screws on the back of that Italian saw for the lower wheel.

The tires are aftermarket.. I have lousy success getting parts from SCMI. A root canal is a less irritating procedure.

[Grant Vanbokklen]

This saw doesnt lend itself to running a straight edge against both wheels.. I checked it for co-planar as much as I could, using the mounts as indicators..

I did adjust the lower wheel outwards a small amount and the problem is unchanged.

I actually think the upper tire is streched.. I may just put rubber tires on the saw again..

Are you saying that you tried to get tires from SCMI but that they could not provide them at all?

Just take a piece of plywood and run it on the jointer and cut out where it might hit, like a cutout for the table and such, for your straight edge.

Rick I remember your post of your rebuild of that saw. http://www.sawmillcreek.org/showthread.php?t=96386

It looks like the new tires are putting the teeth of the blade very close to the metal of the wheel. And the old tires held the blade away from the metal of the wheel. If it is a flat tire should it not have a distinct edge on the tire. Does yours? It almost looks with that urethane tire that it is inset and the metal is the edge.

[David Romano]

Rick,
My saw didn't easily lend itself to using a straightedge either, but I did fashion one that worked by edge jointing a 2x4 and notching out the areas that interfered. It works great. Each time I use it, I restraighten it on the jointer, in case it warped since the last time.

In reading yours and others posts, I think that you should go back rubber tires. If your saw as flat tires, keep it that way and hang your teeh over the front edge of both tires. The idea that poor alignment compensated for by crowned wheels is, in my opinion, a convenient excuse for saw manufacturers not designing and assembling the saws well enough. Saws should have the ability to correct for wheel twist and be made well enough that not much alignment is needed by the customer. Crowned wheels a good for narrow blades so the teeth don't dig in, but for "correcting" alignment? The 2 crowns are then competing for control of the blade, causing the saw to vibrate. Your flat tires are the way to go. My Rikon has a nearly flat botton wheel and a very slight crown on the top. I don't adjust the fence for drift. I just track the blade to the center and there is no drift. The saw should not only be co-planar with the blade tensioned, but have no wheel twist either.

After going back to rubber wheels, make yourself a 2x4 straightedge and test the coplanarity vertically and diagonally. Then test for twist by moving the blade forward a few revolutions and making a pencil mark on the top wheel along the back of the blade above the guides. Then rotate the wheel backwards a turn or two and see if the blade still lines up with the pencil mark. If not, it means that the wheels are twisted relative to each other, and this is corrected for with the lower wheel. Asumming you don't have something else wacky, this should solve your problems.

David

[Rick Fisher]

Well.. I dont want to get into a conversation about SCM and parts.. Lets just say that I am looking at a machine of theirs right now and my biggest fear is it needing parts.

I will order up some rubber wheels on Monday.

[Rick Fisher]

What are the chances that this is a summer problem..

The problem has been really bad for the past week. Coincidentally, its been our first hot spell this year..

The saw is in hot garage.

[Greg Crawford]

I own the Rikon 18", and like most bandsaws, the frame gets in the way of a straight edge when trying to check to see if the wheels are co-planer. It has cast iron wheels, so I bought a package of rare earth magnets and stuck a couple of them stacked together to the wheels in several places. My straight edge is aluminum, and I was able to get what I needed.

[Phil Thien]

My Inca bandsaw, where teeth were positioned off the front of the tire, has tires with a hump on the bottom center that fit in a corresponding groove in the wheel. This prevented the tires from slipping around on the wheel like you're showing.

Is friction the only thing keeping your tires on your wheels? Are there no rims or grooves to keep them in place?

[Rick Fisher]

Phil..

I ordered these tires while restoring the saw.. They sat in a box for a few weeks before I tore off the old rubber tires.

There is a groove in the rim, like a T-Track.. Of course these tires dont have that.

They worked fine for the past 9 months.. I had to try them..

Now the top one is slipping.

I think the solution is to get the rubber tires from SCM.

[Dan Forman]

For MiniMax bandsaws, they recommend using a piece of 3/4" plywood, ripped to 12" wide, and long enough to fully span both wheels with the bottom of the plywood resting on the base of the saw (so you don't have to hold it up) to check for coplaner wheels. The idea is you cut out shapes for the table, wheel hubs, and blade, and you can check the wheels while the blade is onthe saw and tensioned. I still think that when they are in proper adjustment, the tire issue will be moot, because there will no longer be lateral forces on them with the wheels coplaner.

Dan

[Wilbur Pan]

The idea that poor alignment compensated for by crowned wheels is, in my opinion, a convenient excuse for saw manufacturers not designing and assembling the saws well enough. Saws should have the ability to correct for wheel twist and be made well enough that not much alignment is needed by the customer.

I think that this is a bit overstated. I also think that it's true that not much alignment should be needed when a machine is delivered. But I also think that using a crowned tire is a perfectly good way to align the blade on a bandsaw. You might as well fault table saw manufacturers for providing set screws to help with trunnion alignment.



What are the chances that this is a summer problem..

The problem has been really bad for the past week. Coincidentally, its been our first hot spell this year..

The saw is in hot garage.

It could completely be a heat issue. Remember, one of the steps in installing a urethane tire is to soak it in hot water.

[Rick Fisher]

Well.. if its a summer problem.. then its a problem..

Either way, I need to put "T" style tires on it.

I emailed SCM today and asked about the tires. I would love to swap the tires without removing the wheels.. sigh..

I think I can do it with the three clamp method.. there is a lot of room inside.