Band Saw Blade Coming Off Pulley

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ftownroe
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Re: Band Saw Blade Coming Off Pulley

Post by ftownroe » Wed Sep 07, 2011 1:50 pm

I had the same problem with this saw. Check to see if the upper wheel is rubbing against the sliding adjustment block. In my case ( it is a 10+ year old saw) it had worn the block almost down to the threaded shaft. I corrected it by putting a bushing in the hole that bolts the wheel on and and that worked some. I later found that the real problem was that the wheel bearing is pressed into the bore of the wheel and it was not a tight enough fit. Over time the wheel had moved against the adjusting block due to the blade tension and was no longer in alignment. I drove the bearing back into proper position and so far it works OK. I tried to get the adjustment block replacement from Habor Freight, but they no longer support this model.

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JimGlass
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Re: Band Saw Blade Coming Off Pulley

Post by JimGlass » Thu Sep 08, 2011 6:51 am

My 4 x 6 saw is now 11 years old and still running. Use it almost every day. As you can see in the attachment I mounted a simple keeper to prevent the saw blade from jumping off the drive wheel. To replace the saw blade I remove one screw from the keeper and swing it out of the way.

The keeper is not the final solution. First, I figure the blade jumps off the drive wheel because the drive wheel and blade have slippage caused from the saw blade stalling. Several reasons for this slippage.

1) Toward the end of a cut the workpiece being cut tips upward pinching and binding the saw blade just like a brake caliper. Chips and shavings under the cut piece is a common cause.

2) The saw blade lacks enough tension. Dave's idea of a spring in the blade tightening system is a good one. I did this as well.

3) Excesive down pressure.

4) Saw blade tooth pitch is to small. I use a 14 to 18.

5) Be sure to use bi-metal blades

Jim
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sawbladejump.jpg
Tool & Die Maker/Electrician, Retired 2007

So much to learn and so little time.

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stevec
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Location: N.S. Canada

Re: Band Saw Blade Coming Off Pulley

Post by stevec » Thu Sep 08, 2011 6:59 am

Jim, does your keeper tend to get eaten away on a regular basis?
If the piece being cut "tips up" and pinches the blade isn't it being supported to high?

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JimGlass
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Re: Band Saw Blade Coming Off Pulley

Post by JimGlass » Thu Sep 08, 2011 7:07 am

Jim, does your keeper tend to get eaten away on a regular basis?
Nope, same guide been on there for 10 years. There are some signs the blade has made contact with the keeper. My thinking is the blade is not moving when it jumps off the drive wheel.
If the piece being cut "tips up" and pinches the blade isn't it being supported to high?
Yep, the piece being cut never was flat in the saw vise. The last .010 or .020 remaining in the cut works just like a door hinge. While flexable it still has plenty of beef to stop the saw blade.

Example of cut piece having no support at all:

http://smg.photobucket.com/albums/v30/j ... ropend.mp4

A word of caution: It is unwise to leave the 4x 6 saw running while unattended. Since the blade remains on the drive wheel when stalled the electic motor continues to run heating the drive belt beyond the melting point. Happened to me one time. Shop was full of smoke that smelled like car tires burning and the belt was toast.

Another thought on sawing the 3 x3 aluminum. Use plenty of WD40.

Jim
Last edited by JimGlass on Thu Sep 08, 2011 8:42 am, edited 2 times in total.
Tool & Die Maker/Electrician, Retired 2007

So much to learn and so little time.

www.outbackmachineshop.com

stevec
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Re: Band Saw Blade Coming Off Pulley

Post by stevec » Thu Sep 08, 2011 7:14 am

Gottcha Jim.
One caveat against using WD-40 as a cutting fluid/flush, which it is, If the can is handy in the shop it might get used as a lubricant or rust inhibitor which it isn't.

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GadgetBuilder
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Re: Band Saw Blade Coming Off Pulley

Post by GadgetBuilder » Thu Sep 08, 2011 9:33 am

Have you checked to make sure the wheels are co-planar when the blade is tight?

I had to shim mine, see: http://www.gadgetbuilder.com/BandSaw.html#BandsawAlign

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dgoddard
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Re: Band Saw Blade Coming Off Pulley

Post by dgoddard » Sat Sep 24, 2011 11:49 pm

spro wrote:.... Of course the gas can doesn't stay there.......
Very observant spro! :shock: I missed seeing that in the picture and I have a gas can just like that, but I suppose it could contain something else (non flammable we hope) .

And while we are at it, what is that bungie cord doing there :?: If it is being used to increase the down load on the blade that could be problematic as well.

The guide bearings on my enco saw are positioned with both of the bearings that back up the blade being farther from the workpiece than the bearings that run against the sides of the blade. Any comment there?

It might be worth checking the bearings that run on the sides, if one of them is misaligned or badly worn it might be walking the blade away from the back edge bearing and off the wheels.

I have observed that if there is a crack in the blade on the tooth edge that it will cause the blade to be concave on the back edge. This causes the saw arm to bob up and down and the blade to come out of the guide rollers and off the wheels. If it is welded crooked the same thing happens.

When I bought my saw I was advised by someone here not to buy a saw where the guide rollers were supported on a stamped steel arm of the sort shown here. I was told that these cause trouble but I don't remember what that trouble was alleged to be.

The picture raises a few questions, Too bad it is not higher resolution
I never met anybody that I couldn't learn something from.

10 Wheeler Rob
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Re: Band Saw Blade Coming Off Pulley

Post by 10 Wheeler Rob » Sun Sep 25, 2011 4:41 pm

Once in while you get a bum blade too. I did not have much luck with the blades Habor Freight sells, but the Ridgid brand blades sold at Home Depot have given me some very good service for the price. I do look at the weld joint in the package and try to pick the best looking ones at the store. They are not bi-metal, but work on most materials execept some of the stainless steels like 316.

Getting the top wheel and blades aligned made a big difference on my HF saw. Once I got it adjusted, it has behaved well for over 3 years now.

Rob

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mechanicalmagic
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Re: Band Saw Blade Coming Off Pulley

Post by mechanicalmagic » Sun Sep 25, 2011 9:32 pm

10 Wheeler Rob wrote:Getting the top wheel and blades aligned made a big difference on my HF saw. Once I got it adjusted, it has behaved well for over 3 years now.
My HF 4x6 has been going strong since 1999 (I gave it a good tune up then).

Dave J.
Every day I ask myself, "What's the most fun thing to do today."
9x48 BP clone, 12x36 lathe, TIG, MIG, Gas, 3 in 1 sheetmetal.

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