bandsaw blade comes off

fixerupper

Well-known Member
I have an older Emerson 64 1/2 metal cutting band saw that's all of 40 years old that has started throwing the blade with more frequency now. The blade stays on fine under no load but when it's cutting the band will lose traction on the driving wheel, the driving wheel will spin in the band and the band will come off. This saw has been almost flawless till maybe a year ago when this would start happening off and on, but lately it will cut for maybe fifteen seconds, maybe less, and like I said the driving wheel will start spinning on the band and the band will come off. A year ago I cleaned up the driving wheel real good and smeared silicone sealer on the wheel surface, trying to create a more or less rubber tire on the wheel. It worked fine till the silicone wore off, then the problem came back. I haven't taken much time to dig into it deeper yet but I did lay a straight edge on the drive wheel and it seems to be aligned OK. The bearing in the top driven band wheel seems to roll free. I took the angle grinder and roughed up the drive wheel to no avail. A thought I had was a little silicone is still on the wheel surface making it slippery, but this problem started before I tried the silicone trick. The band doesn't come off till the wheel starts spinning in the band. Back before this problem started the band would have enough traction on the drive wheel to smoke the V belt if the band caught for some reason. Anyone have an idea of what I could try next?
 
Sounds like the tension is not being applied to
the blade. A mechanical binding, not letting the
full power of the take up spring be applied to
the wheel.

Is the slide free? Not packed with chips? Threads
good in the take up screw? Blade too long,
running out of travel?

Was there ever a rubber tire on the drive wheel?
If the blade aligns with the guide, there
probably wasn't one, but if the guide is 1/8" or
so away from the radius of the drive wheel there
may have been a tire at one time.

Also check for play in the bearings, loose shaft
in the drive wheel, loose gear box mount bolts.
 
(reply to post at 21:02:18 02/04/15) [/quot

All good advice, Steve. The tension is not spring loaded on this one. The tension is directly regulated by how hard I can turn the knob. It doesn't appear to have anything keeping the slide adjustment from tightening the blade enough but will check tomorrow in case I missed something. I've owned this thing since the late 70's and there hasn't been a tire since I've owned it. I did order a tire from Amazon tonight though. I hope it fits. I'll let you know what I find after I check it over.
 
It would be nice to have a stiff spring in the
tensioning screw. It would allow for variations in
wheel runout, blade stretch and expansion as it
heats up. I've seen die springs and belleville
washers used.
 


fixerupper,Does it have an adjustment on the top wheel to adjust it in and out with lilk a couple set screws,or loose bolts?If so like most I've used adjust it so the top of the top wheel tilts away from the teeth a little that will make the bottom of the blade run close to the ridge on the drive wheel.
 
I put a new blade on my old saw yesterday and had the same thing happen. The guide wheels seemed to be to tight. It would saw about half way thru a one inch angle and come off. I found the fines were clogging the guide wheel. Had to be the frost causing them to stick to the wheels. Opened them a tad and it let the blade angle pull in. I re adjusted and it was cutting square and staying on when I quit last night. I have three horizontal band saws and none have tires on the drive wheels. I have two vertical band saws and they both have tires on the drive wheel.
 
I had mine keep losing the blade and I find a bolt
for the plastic pulley cover was to long or pushed
threw the plastic cover making it to long and was
pushing the new blade off. Installed a shorter bolt
and have not had the problem.
 
Have you tried a NEW blade ? When I get one that pops off many times it has a bad or missing tooth and it catches and pops the blade off.
 
I am with steve: If there is no spring on the blade tension what maintains the tension when the blade heats from cutting and expands?
 

Mike I've had times when a broken tooth catches and takes the blade off. For me most times a broken tooth comes from hand feeding thin steel when the saw is in the vertical position. I've tried two new blades to no avail. When I get done with this (dreaded) bookwork this morn I'll pull the bandsaw into the heated shop. It resides in the cold storage room so some of the problem just might be frost. There is no adjustment on the gear box end. The gear box is cast into the main frame. There is aligning adjustment for the top wheel. I'll check the threaded adjustment rod too.
 
What does it have to limit downpressure? Could be your cylinder or spring has gotten too weak. I would definitely pull the guide blocks and reset the alignment on the idler wheel. Then reset the guide roller alignment.
 

I lightened up the down pressure quite a bit by putting tension on the lift spring to no avail there is no cylinder on this one. This evening I'll tear into it. This thing is like almost anything we use in the shop, we don't maintain it like we should. I'm guilty as anyone. I clamp a piece of steel in it, hit the switch and start cutting, grab the cut off piece and walk away how many hundreds of times without thinking about maintenance.
 

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