Bandsaw tuneup

Just put new tires on an inexpensive bandsaw (14" Chiwanese), and found the upper wheel needed adjusting to an odd tilt.
Apparently the upper/lower wheels are not coplanar, because the band doesn't adjust to center simultaneously on both. I've tentatively identified the offset as 1/4 inch, and there's a joint between the upper casting and lower casting, so I can shim there.
How does this happen? Did the factory mis-grind those castings, or could it have bent somehow in use or transport?
Any words of wisdom before I pull out the big wrenches and do the relatively-major disassembly?
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Certainly it's possible the castings were misground. Bending is unlikely, since cast iron is fairly brittle and more likely to crack.
I would use a long straightedge across both wheels to confirm they're not coplanar. You should be able to get the straightedge to touch at 4 points simultaneously (top and bottom of both wheels). If you can't, adjust the top wheel tilt for the same gap at top & bottom, and that's the offset you're trying to correct.
Rather than seperating the castings, you can probably fix the mis-alignment at the wheel. Sometimes one or both wheels are fixed on their shaft with a setscrew, and you can simply loosen the screw and slide the wheel in or out. In other cases there are washers behind the wheel (sometimes hidden under the hub), and you can take the wheel off and add or remove to get the right alignment.
BTW, it's probably good to check the alignment with the saw tensioned with the blade you typically use. Inevitably there's some flex, so getting it aligned at a typical blade tension is worthwhile.
John
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"whit3rd" wrote in message

While the frame castings could be miss-ground so that the upper section is canted that seems like it would be the least likely scenario. Could it simply be that one or both wheels need to be repositioned on their shafts, and perhaps shimmed, to gain alignment?
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On 10/6/2015 10:22 AM, John Grossbohlin wrote:

A question to ask yourself. Was this a problem before you changed the tires? If not I would suspect the new tire installation.
If the problem was there before, I would think that there is another way to adjust the lower wheel. Many band saws have no upper and lower section/half to adjust so the adjustment must be made at the wheels.
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On Tuesday, October 6, 2015 at 8:31:30 AM UTC-7, Leon wrote:

It seems that low blade tension causes the symptom; I was trying to adjust geometry before adjusting to full blade tension, after removing the blade for the obvious reasons.
A long level used as straightedge does verify the wheels are coplanar now. I'll check for flex at the joint next (clamps, scraps of iron, feeler gages). Dealing with this machine gives me a new appreciation, too, for sheetmetal design; they didn't get all their clearances right.
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On 10/7/2015 5:06 PM, whit3rd wrote:

You should adjust blade tension before adjusting anything else.

I have been down this road. Several years I upgraded from a Craftsman so that I would not have to deal with these type issues. I'm sorry to say that a $1,000. 18" Rikon was not good enough. Inexpensive and or cheaply build band saws are a PIA IMHO. I finally got a Laguna and all those issues are in the past. Laguna is expensive but I believe you are always going to have some issue with a cheaply built band saw. Next best bet would probably be an older model Delta, the ones built in the USA.
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On 10/6/2015 10:22 AM, John Grossbohlin wrote:

A question to ask yourself. Was this a problem before you changed the tires? If not I would suspect the new tire installation.
If the problem was there before, I would think that there is another way to adjust the lower wheel. Many band saws have no upper and lower section/half to adjust so the adjustment must be made at the wheels.
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On 10/6/2015 3:34 AM, whit3rd wrote:

There are those that will tell you coplanar is not necessary. I am not one of those. Once I got my band saw all straightened out, I can use my fence to resaw.
My delta circa 2003 to 2005 I think did not even come close to lining up. I had to remove the pins that register the upper arm.
For me, the drilling of the pins was in a way off space. REALLLLLLLY OFF.
Shim it to get it aligned, and don't look back.
--
Jeff

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