Bandsaw throwing narrow blades off wheels

bobgroh · Post by **bobgroh** » Sat Dec 17, 2011 2:50 pm

For the first time since I've owned this bandsaw, I put a smaller blade on it (normally I have a 1/2" or 3/8" blades that I use) - a 3/16" blade. And, when powered up, the small blade just walked off the wheel(s) in short order. The larger blades work fine. The smaller blade comes off everytime.

Now this bandsaw is an older one - upgraded with new bearings, a new table and cool blocks. I have done an alignment on it and, again with the bigger blades, everything seems to be fine.

I have not run it much but, what little I have run it (again always with a wider blade) it has run fine. I do (now, at least) pull the tension off when I leave it sitting for anytime. The belts are the original types and quite likely the original ones (from probably mid-1980's).

So any ideas on why a small blade would come off and not the bigger ones? Thanks for your ideas and comments.

JPG · Post by **JPG** » Sat Dec 17, 2011 2:56 pm

bobgroh wrote:For the first time since I've owned this bandsaw, I put a smaller blade on it (normally I have a 1/2" or 3/8" blades that I use) - a 3/16" blade. And, when powered up, the small blade just walked off the wheel(s) in short order. The larger blades work fine. The smaller blade comes off everytime.

Now this bandsaw is an older one - upgraded with new bearings, a new table and cool blocks. I have done an alignment on it and, again with the bigger blades, everything seems to be fine.

I have not run it much but, what little I have run it (again always with a wider blade) it has run fine. I do (now, at least) pull the tension off when I leave it sitting for anytime. The belts are the original types and quite likely the original ones (from probably mid-1980's).

So any ideas on why a small blade would come off and not the bigger ones? Thanks for your ideas and comments.

'Coming off' - which wheel(first) and where(inside/outside/front/back. . .)

Back of blade smoothly riding in blade guide(upper left near tension bar)?

Slipping off the tire first? If tire too narrow(on the back side) a narrow blade will slip off tire.

P.S. Blade back straight?

bobgroh · Post by **bobgroh** » Sat Dec 17, 2011 3:34 pm

JPG40504 wrote:'Coming off' - which wheel(first) and where(inside/outside/front/back. . .)

Back of blade smoothly riding in blade guide(upper left near tension bar)?

Slipping off the tire first? If tire too narrow(on the back side) a narrow blade will slip off tire.

P.S. Blade back straight?

answers (such as they are):
1. Seems to come off top wheel first and it is to the 'outside' (if the inside is towards the power head).

2. Back of blade starts out riding in the blade guide (as does the wide blade).

3. Tire(s) pretty much cover the entire wheel with just a 1/16" or so of wheel showing.

4. Blade back straight? I think so. I don't see any obvious 'kinks'.

curtis george · Post by **curtis george** » Sun Dec 18, 2011 3:57 am

This might sound like a dumb question. but are you using the tension gauge build on the bandsaw? I find on my SS band saw, if I over tighten the gauge the blade will come off the wheel like you are saying your machine is doing.

C.A.G.

BigSky · Post by **BigSky** » Sun Dec 18, 2011 8:42 am

Check the upper wheel. It should lean back into the bandsaw on top just a little bit. That cantor is what keeps the blade from walking off the outside of the wheel. The bearings limit how far back it will track.

JPG · Post by **JPG** » Sun Dec 18, 2011 12:39 pm

Check the upper wheel(2). The longer hub side faces in.

billmayo · Post by **billmayo** » Sun Dec 18, 2011 12:45 pm

BigSky wrote:Check the upper wheel. It should lean back into the bandsaw on top just a little bit. That cantor is what keeps the blade from walking off the outside of the wheel. The bearings limit how far back it will track.

A quick work of caution: Do not grap and pushing/pulling on the upper wheel when attempting to tilt the upper wheel. This may warp the upper wheel very easily and cause difficult blade tracking from the warpped upper wheel. I made a jig to assist in straighten these warpped upper wheels. Some upper wheels will develope cracks in the spokes when tilting using the upper wheels. I discard any cracked wheel as I am unsure how safe it will be when being used and under a load.

I remove the upper wheel and use a piece of pipe or deep well socket/extension on the upper wheel axle to tilt it. This may take a few tries to get the tilt to where the blade tracks on the back side of the upper wheel. I use a digital angle indicator to assist me now. Using a straight edge across the upper wheel and extending to the lower wheel to help determine the amount of tilt.

bobgroh · Post by **bobgroh** » Sun Dec 18, 2011 5:22 pm

Thanks to everyone for the ideas. I have been having a very frustrating day getting my new router to work - no, let me rephrase that '....KEEPING my new router from breaking'. I'll get back to the bandsaw and one of the first things to do is to check the 'top wheel tilt' (thanks, Bill, for the warning and words of wisdom on HOW to do the adjustment if needed). As far as the tension is concerned, I am using the builtin tension setter and did appropriately have it set for the narrower blade.

It has NOT been a good couple of days on the wood working front! Trying to get Christmas presents built and just not having good luck. Ugly and discouraging.

bobgroh · Post by **bobgroh** » Mon Dec 19, 2011 10:45 pm

Took a couple of minutes today and pulled the cover off the bandsaw. Laid a straight edge across the rim (very close to the hub) of the bottom wheel and the straight edge lined up nicely (touches) with the bottom of the top wheel. The top of the top wheel was inward (i.e. away from the straight edge) by about 1/4".

This is (if I remember my math) about 1 degree. Is this about right? At least it is in the right direction.

JPG · Post by **JPG** » Mon Dec 19, 2011 11:25 pm

bobgroh wrote:Took a couple of minutes today and pulled the cover off the bandsaw. Laid a straight edge across the rim (very close to the hub) of the bottom wheel and the straight edge lined up nicely (touches) with the bottom of the top wheel. The top of the top wheel was inward (i.e. away from the straight edge) by about 1/4".

This is (if I remember my math) about 1 degree. Is this about right? At least it is in the right direction.

Sounds about right. A straight edge laid against the upper wheel should clear the bottom of the bottom wheel a bit more(maybe a 1/2"). Did you check the upper wheel hub orientation?