Band Saw Blade Coming Off Pulley

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Phil3
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Band Saw Blade Coming Off Pulley

Post by Phil3 »

I have a cheap HarborFreight bandsaw I bought used and replaced the blade. If the fastest speed is selected, the blade comes off the pulleys after less than a minute of running. I can not seem to make any adjustment to stop this. Ideas?

- Phil
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Davo J
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Re: Band Saw Blade Coming Off Pulley

Post by Davo J »

Hi Phil,
Have you tried adjusting the bearing back that runs on the back of the blade? You have to move to whole bearing unit up the slide both in and out feed ends.
Another thing I can think of is if the top pulley slide adjustment bolts are a bit loose. They are on top on the outside when the saw is down. Mine has 2 bolts their with a plate to allow the top wheel to slide in the adjustment. If this is loose it will allow the wheel to tilt over and the blade comes off.

I would almost guarantee it would be the first one I suggested, but another check you could do since the saw is second hand, is with the blade off check to see if either of the wheels have excessive movement which could mean a bearing is gone.

Dave
Phil3
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Re: Band Saw Blade Coming Off Pulley

Post by Phil3 »

I am not sure I understand what you are saying here. If you are referring to the bearing guide assembly at the opposite end of the motor end that can slide fore and aft, then yes, that is as close as possible to the other bearing guide assembly at the motor end. The bolts for the pulley, but adjustment arrangement makes it impossible to put the two pulleys in parallel. I adjusted things so that the when runnung, with the arm vertical, I could see the blade running around the pulley without any apparent interference with the pully flange. The pully bearing is tight and good.

I am trying to cut a 3" x 3" piece of 6061 aluminum. I noticed that the blade seems to come off if it encounters a snag of any kind. I think the blade may come off if the blade stalls and the pulleys keep spinning. Maybe. I adjusted feed rate to no avail. I finally cut the fpm from 200 to 120 and that definitely helps. You can still see the blade snagging and sometimes it stall and I have to stop it. The blade is definitely really stuck in the aluminum and sometimes takes a fair amount of effort to get it free. I am continuing to cut at 120 fpm, but it is taking a really long time. I don't know what is a proper feed rate to use. Not even sure what proper blade tension is.

- Phil
Last edited by Phil3 on Sun Sep 04, 2011 3:52 pm, edited 1 time in total.
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Harold_V
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Re: Band Saw Blade Coming Off Pulley

Post by Harold_V »

Somewhat off the beaten path, but your comment that the blade hits a "snag" sent up a red flag for me.

Saw blades create a kerf that's wider than the blade, so it can't (shouldn't) hang up. That's true up to the point that you haven't either worn or burned the set off the blade.

Have you examined your blade to determine if it is still functional? Just having teeth isn't enough, as you likely know---the teeth must have the proper configuration and be sharp in order for the blade to perform properly. All it takes is to run the blade too fast, briefly, in the wrong material, to lose all important features.

Unless your saw lacks the necessary power, slowing the blade shouldn't make any difference when sawing aluminum. Can't help but wonder if the blade is trashed.

Harold
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Mr Ron
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Re: Band Saw Blade Coming Off Pulley

Post by Mr Ron »

If the blade comes off when you try to cut, but stays on when not cutting, it sounds like the blade guides are not adjusted properly. The ball bearing at the back of the blade should just touch the back of the blade both above and below the table. The tension should be as tight as you can get it. You pluck the blade with you finger to get a high pitch "ping". What type blade are you using. For 3x3 aluminum, you should be using a coarse tooth blade about 1/2" wide and .025" thick made for cutting metal, not wood. I would recommend a 3 tooth, hook/raker set blade. You won't find this at HF. you will have to go to an industrial supply house and have it welded up to order. Being that it is a HF BS, I question whether cutting 3x3 is not overloading it. Also what is the condition of the rubber bands on the wheels? They should have a crown on them to keep the blade centered.
Mr.Ron from South Mississippi
oldbrock
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Re: Band Saw Blade Coming Off Pulley

Post by oldbrock »

Reading between the lines I would say your blade has too fine a pitch for that thickness of aluminum and your speed should be set to the highest. A little Relton A9 would also help. Peter
Difficult done right away, impossible takes time.
Phil3
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Re: Band Saw Blade Coming Off Pulley

Post by Phil3 »

Harold_V wrote:Somewhat off the beaten path, but your comment that the blade hits a "snag" sent up a red flag for me.

Saw blades create a kerf that's wider than the blade, so it can't (shouldn't) hang up. That's true up to the point that you haven't either worn or burned the set off the blade.

Have you examined your blade to determine if it is still functional? Just having teeth isn't enough, as you likely know---the teeth must have the proper configuration and be sharp in order for the blade to perform properly. All it takes is to run the blade too fast, briefly, in the wrong material, to lose all important features.

Unless your saw lacks the necessary power, slowing the blade shouldn't make any difference when sawing aluminum. Can't help but wonder if the blade is trashed.

Harold
The blade is a new Starrett. I had troubles with it immediately. The only material it has seen is the aluminum piece. I don't know what to look for in the blade to make sure it is servicable. No question, slowing the blade helps. When running, you can heara knock occassionally, and even the arm jiggle a bit. Experience tells me this is the blade almost hanging up, but does not. On one occassion, the blade was so stuck, I had to loosen the stock, lift the arm, and wiggle the blade out of the stock. It was very stuck.

The old blade was worn and hardly cut anything. This is a small saw and wonder how long it should take to cut through 3" x 3" of aluminum. I do not know what to set the feed rate at.

Phil
oldbrock
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Re: Band Saw Blade Coming Off Pulley

Post by oldbrock »

Check your pitch. Should be 8 or 10 but no finer for this thickness of stock. The gullet between the teeth is filling up before the tooth has exited the work and is grabbing on the kerf and galling. Go to top speed. Peter
Difficult done right away, impossible takes time.
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GlennW
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Re: Band Saw Blade Coming Off Pulley

Post by GlennW »

Get some stick wax and wax the blade. Enco Part Number PC505-2034 on sale for $9.95

Hold the wax to the blade while it is running.

It will lubricate the blade and stop the little klinkers from sticking in the gullets, which is what it sounds like is happening.

Relieve a bit of down force on the blade as well and see if that works. I have an old Grainger 4x6 saw that will throw the blade with too much down force and not enough wax when sawing aluminum.

If the blade grabs at all, the drive wheel slips, and oops, the blade comes off.

I've also had a couple of bad blades where the weld was not aligned properly. Clunk, clunk, clunk, every time the weld passed through the cut... :roll:
Glenn

Operating machines is perfectly safe......until you forget how dangerous it really is!
Phil3
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Re: Band Saw Blade Coming Off Pulley

Post by Phil3 »

Glenn Wegman wrote:Get some stick wax and wax the blade. Enco Part Number PC505-2034 on sale for $9.95

Hold the wax to the blade while it is running.

It will lubricate the blade and stop the little klinkers from sticking in the gullets, which is what it sounds like is happening.

Relieve a bit of down force on the blade as well and see if that works. I have an old Grainger 4x6 saw that will throw the blade with too much down force and not enough wax when sawing aluminum.

If the blade grabs at all, the drive wheel slips, and oops, the blade comes off.

I've also had a couple of bad blades where the weld was not aligned properly. Clunk, clunk, clunk, every time the weld passed through the cut... :roll:
That makes sense. Pitch is too fine from what others say for this size of aluminum at 14 teeth per inch. I need different blades for different stock and materials it seems. I get some of that clunking as well, but on a Starrett blade? Photo is attached. Blade is off.

- Phil
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GlennW
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Re: Band Saw Blade Coming Off Pulley

Post by GlennW »

Phil3 wrote: I get some of that clunking as well, but on a Starrett blade?
I've had Do-All blades that were bad.
Glenn

Operating machines is perfectly safe......until you forget how dangerous it really is!
dly31
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Re: Band Saw Blade Coming Off Pulley

Post by dly31 »

Be sure you have the blade about as tight as you can get it with the hand wheel. People who have actually measured the blade tension have said that it is not possible to even get the blade to the optimum tension on these small saws.
Don Young
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