Bandsaw Problems

[mashtun]

Well I more or less inherited an old Craftsman Bandsaw. It has about a 14 inch throat, and it will resaw something about 4 inches high.

The saw has three wheels, one each above and below the table, and A third wheel behind the throat, so the blade forms a triangle of sorts.

The saw has two adjustments that I can see, one is obviously the blade tension which works by pulling the third wheel away from the table.

One seems to adjust the third wheel on it's axis, so it is parellel to the frame of the saw, or towed in to the front or the back of the saw.

I started to play with it yesterday, and noticed that the blade tends to turn to the Left when using it. It does this to the point of Binding the blade. It does this cutting even 1/2 inch cheap HD Plywood.

I tried puting a fence on the table, by clamping a straightedge to it, and then cutting long ways down a piece of Plywood, but the blade turned sideways, and the cut wandered to the left until the saw would not cut, and started to burn the wood.

Note if I let the plywood go with the flow of the blade, it will cut though it until it cuts out the left side of the plywood. The cut is very smooth with no tear out so the blade seems sharp.

I tried playing with the two adjustments, but all I seemed to acompllish was to get it to cut a little striaghter, and to get the blade to fall on the wheels.

I would like to know what the consensis is, is this worth putting any money into?

John

[LCHIEN]

do a search for three- wheel bandsaw here. the general comments are quite negative because the 3-wheel system is so hard to align properly and the blades don't last or track well because of the small radius of the wheels. Its a poor trade off made to get more throat clearance without paying for bigger wheels.

Now stop and think about how many of these you actually see around.

Answer to the bottom line question you post is no.

[gearbuilder]

I would try a different blade. If the tooth set is worn more on one side of the blade it will not cut straight no matter how the guides are set.

Jamie

[SARGE..g-47]

I don't have much experience with a 3 wheeler but.... are the tires worn to a degree that the blade riding on pitted or bumper rubber?

Also slow the feed to a snails pace and see what happens.

And last... how far are the guides above and below the actual stock being cut? If there are guides on a 3 wheeler as again... I am not familar. And Loring's idea of Google to those that have some experience with them would not be a bad idea at all.

[just started]

I have been using a Chiwanese import cheap copy of a band saw like that one for about 30 years and while it certainly isn't great tool it also isn't a P.O.S. either.

To address your specific problem of the blade twisting, the first thing to check is the blade guides. Are they set properly, both top and bottom? Do you have the top guides set to just above the material you are cutting?

The adjustment knobs you mentioned are for blade tension and blade tracking. The tracking adjustment (tilting toe in/out) is to make the band run in the center of the wheels. To adjust, with the safety cover off, turn the wheels BY HAND while adjusting the tracking so the blade runs in the center of the wheels.

Art

P.S. You should put your location in your profile, someone close might be able to help.

[mpc]

Look at the rubber tires on the 3 wheels, assuming each wheel HAS a tire. They should have a "crown" to them - i.e. the center portion should be a tad larger in diameter than the edges. The wheel that tilts (toes in/out as you described) it adjusts the "tracking" of the blade. You adjust this wheel to get the blade to ride centered on the crown... while spinning the wheels by hand with the power cord unplugged.

Once the blade seems "stable" on the crown of the adjustable wheel, eyeball the blade positions on the other two wheels. If it's not centered on those, then:
* the wheels are not "co-planar" which means they are not lined up with each other - one might be closer or futher away from the back of the saw case for example.
* one or more tires are worn so the crowns don't line up right - the crowns should also be coplanar.

Most saws have a way to adjust the wheels to make them coplanar. On 2-wheel bandsaws, the lower wheel (the one that typically is NOT used for the tracking adjustment) is mounted to a metal bar/shaft that is held by 4 screws pinching it from 6, 12, 3, and 9 o'clock positions. By moving the screws in pairs (i.e. 12 "in" and 6 "out") you can tilt the bottom wheel to get it perfectly coplaner with the top wheel. Moving that shaft in/out of the 4 screws allows you to make the wheels "agree" on how far from the case back they should be - the other have of the co-planer story. I don't know what your 3-wheel bandsaw will have; hopefully the wheels have some sort of adjustment. Sometimes inexpensive saws just use shims on either side of the bearings that support the wheels.

For 2-wheel bandsaws it's easy to make a quick tool to check wheels for co-planer: basically a wood stick about the height of the saw and 4 screws: the screws are placed so that they just touch the edges of the wheels (or some "reference" flat spot on them if the edges are unfinished) when the stick is held next to the saw. Use your table saw's fence or some straight edge to make sure the 4 screwheads are perfectly lined up (coplaner) and then hold the stick touching the wheels. If you can't get all 4 screwheads to just touch the wheels then the wheels aren't coplaner. One a 3-wheeled saw getting the top and bottom wheel coplaner is key; the 3rd wheel isn't such a big deal especially if it doesn't have a crown/tire.

Another thing that'll cause blade wandering like you described is using a blade that's too wide for the saw/wheels. A "resaw" blade is a typical wide blade. I'm talking about the distance from the teeth to the back edge of the blade - not the actual thickness of the metal in the blade. A too-wide blade flexes over the wheel crowns and gets distorted too much leading to tracking issues.

Not having the blade guides adjusted correctly also leads to blade twist which then becomes blade wander. The guides on either side of the blade should be positioned:
* just aft of the teeth "gullets" so none of the teeth/blade "set" touches the guides. Bandsaw teeth are bent outwards from the rest of the blade to cut a kerf wider than the blade thickness. You don't want that "set" on the guide blocks/bearings.
* Not quite touching the blade when you hand-spin the wheels or the saw is plugged in an running with nothing being cut. There should be just a hint of space between the guides and the blade... many folks suggest a dollar bill on each side of the blade, then bring the guides in to just touch the dollars.
* The "thrust bearing" behind the blade should also have just a hint of clearance when not cutting anything.
* The same rules apply to the guides below the saw cutting table... many folks forget to check the adjustment on those guides.

If the saw has rollers/bearings for the blade guides (unlikely in an inexpensive saw... those use blocks of low friction material) make sure the bearings are free to rotate. Sawdust gums them up internally. A guide that doesn't spin easily heats the blade and does weird things to the cutting action.

mpc

[guycox]

I had one of those 3 wheeler Sears bandsaws -- it was the most infuriating tool that I have ever owned. I finally decided that it needed a bushing job -- I tossed it in to the bushes and left it...

I'm now the pround owner of a Rikon 14" deluxe bandsaw -- I can now cut up a log section larger than I can actually fit onto my lathe..

[Tom Hintz]

I also would suggest trying a new blade just to be sure. I just touched a nail with a new blade once and it would also "turn" away when cutting from the side that touched the nail. I have had this happen with a bit of metal I didn't see (I think it was a broken off screw in a tree, found it later) and the blade did dthe same thing, turned away from the side that touched the metal.

Trying the blade just eliminates that possiblity before you adjust the machine too much.