Blades Popping Off (HM126)

[mitchstockdale]

Hey all,

Finally got to do some milling today after the long winter.  Before starting i replaced replaced the drive belt. With a BX 79 as perscribed by the HM126 manual.

I cut one smaller log no problem.  Had a second on the go and was on the second last cut and the head of the saw mill came to a stop half way through.  Gave it a push and the blade popped off.  Got things put back together took a full cut no problem the started on another pass and just touched the wood and the blade popped off again.  Installed the blade again and got two more full cuts and off it came again.

After the last one i threw in the towel for the afternoon...never had any trouble with my mill till today.  

Was wondering if the new belt could be slipping on the blade with water splashing on it ( using water as libricant).  I tried putting water on the belt and rubbing it and it seemed sort of slippery.  Should i rough up the surface of the belt to help grip the blade?

Any thoughts?

[btulloh]

Seems more like tracking or general alignment problem. Go through all the alignment checks and make sure your tension is correct. Water won't cause that. No need to rough up the belt.


When you return the head after the first cut, watch your blade dragging on the cant. After the head is returned and ready to start the next cut check to see that the blade is in the correct position and hasn't moved forward on the wheels.

Is your cut level or does it rise?

[btulloh]

How much water are you running?  Should be a drip per second or so.

Even with a steady stream it shouldn't cause a problem though.

Are you releasing the throttle before dragging the head back?

I don't find it necessary, but you may try raising the head before dragging it back.

[mitchstockdale]

How much water are you running?  Should be a drip per second or so.

Even with a steady stream it shouldn't cause a problem though.

Are you releasing the throttle before dragging the head back?

I don't find it necessary, but you may try raising the head before dragging it back.

I will have to check the blade positioning while cutting next time i am out.  As Far as it being level do you mean length wise or width wise, both ways are fairly close within the lines of the level.

I typically run a trickle of water not a drip.

Yes realeasing the throttle before returning the head ...normally clear the lumber then reset..i have had the blade drag pretty hard on the cant before with no problems.

Will definetly check the tracking again...where do you run your blade? Per the manual 3/8" form the front of the band wheel?

[btulloh]

Around 3/8 give or take a hair.

Level end to end. So the blades not dragging hard. I've had drag pretty hard without affecting it though.

Curiuos about " saw came to stop then the blade popped off when restarting ".  None of that sounds good. Blade should never come to a stop in the cut. Clutch?  Too new. Too much forward pressure?  Not enough tension?

Are your belts sitting proud of the wheels so the blade is riding on the belts and not the wheels?  Sawdust build up on belts?

They say to change both belts at the same time. Not good to run one new, one old, although I've done it.

[donbj]

Any excessive play in your band wheels? With no blade on grab them and see if you can move in and out/up and down etc.

[Crossroads]

When I had that problem with my old lt30, I started looking things over after the second time and found a bad bearing on the drive side. 

[DARRELL1972]

Had similar problem on my lt40 last summer. Was bad bearing on idle blade wheel.

[Woodpecker52]

need to raise the blade up about 1/2 inch before bringing head back seems to help me.

[Chuck White]

Another way to prevent the blade popping off is to disengage the blade when it exits the far end of the log!  ;)  :P

[mitchstockdale]

Around 3/8 give or take a hair.

Level end to end. So the blades not dragging hard. I've had drag pretty hard without affecting it though.

Curiuos about " saw came to stop then the blade popped off when restarting ".  None of that sounds good. Blade should never come to a stop in the cut. Clutch?  Too new. Too much forward pressure?  Not enough tension?

Are your belts sitting proud of the wheels so the blade is riding on the belts and not the wheels?  Sawdust build up on belts?

They say to change both belts at the same time. Not good to run one new, one old, although I've done it.

Ok, I am also setting mine at 3/8.

Bed is level no sags or rises.

The blade never came to a stop.. it was the whole saw head...almost like I was fetched up on something like a piece of bark or wood on the track, I tried to push through it and the blade popped.  At this point I did re-tighten my drive belt cause it must have stretched a bit and had a little more play than when i installed it.

Yes both belts are sitting proud of the wheels about 3/32 to an 1/8.  No sawdust build up clean both belts everytime i change or put a blade back on.

[mitchstockdale]

I am really suspicious of the new drive belt though....this is the only thing that has changed from any other time i have run the mill.

The belt is not from woodland mills I picked it up at NAPA, it is a Gates brand BX79 a fairly rugged belt.

One thing I did notice is it is was more likely to come off while not in the wood....more water staying on the blade?  I did read a post about someone with an HM130 having a similar problem talked about the blade hydro planing... 

I am thinking at this point i will try running things dry and see if I pop a blade. Will check the bearings before I put another blade on but I cant see a bearing being bad since there is limited run time on the mill...maybe  8 days of milling for 5 to 6 hrs.  Maybe this is enough to wear a bearing out...especially if they are made of Chinesium.

[btulloh]

Roger taht.  Checking out the thing that changed before the problem started is certainly a good and rational plan.  

I've used Gates belts before with no problem, but you never know when you might run into a dud.  

You should be able to see something happening prior to the blade coming off if you're watching the guide blocks and bearings.  It's got to be moving in or out and you can see that easily if you watch the guide area.  I always set my bearings so there's a slight gap between them and the blade so they should not be rotating until pressure is applied to the blade in a cut.  That gap will widen if the blade is tracking toward the front.  Is the blade offset the same on both wheels?

It's got to be frustrating.  Things were ok.  Changed the belts.  Not ok now.  Maybe the belt is just goofy.  I like to keep 2 or 3 sets of new belts around at all times.  

I've also had a couple blades that weren't welded correctly - the back of the blade was not straight across at the weld.  Caused tracking problems.

Re stopping in the cut - Hitting a knot will cause this. It sort of goes along with the lower horsepower engine.  I try to feel the knots or keep an eye on them and slow down as I get to them.  

Hopefully you'll get to the bottom of it today and get back to making lumber.  

[mitchstockdale]

Roger taht.  Checking out the thing that changed before the problem started is certainly a good and rational plan.  

I've used Gates belts before with no problem, but you never know when you might run into a dud.  

You should be able to see something happening prior to the blade coming off if you're watching the guide blocks and bearings.  It's got to be moving in or out and you can see that easily if you watch the guide area.  I always set my bearings so there's a slight gap between them and the blade so they should not be rotating until pressure is applied to the blade in a cut.  That gap will widen if the blade is tracking toward the front.  Is the blade offset the same on both wheels?

It's got to be frustrating.  Things were ok.  Changed the belts.  Not ok now.  Maybe the belt is just goofy.  I like to keep 2 or 3 sets of new belts around at all times.  

I've also had a couple blades that weren't welded correctly - the back of the blade was not straight across at the weld.  Caused tracking problems.

Re stopping in the cut - Hitting a knot will cause this. It sort of goes along with the lower horsepower engine.  I try to feel the knots or keep an eye on them and slow down as I get to them.  

Hopefully you'll get to the bottom of it today and get back to making lumber.  

Thanks for your input btulloh.
I hope to try it out this evening, will report back with my findings.

[mitchstockdale]

Another thing I though of is the old drive belt was pretty much flush with the top of the band wheel...the new one is almost and 1/8" proud of the band wheel could this extra little bit of length be causing the blade to be over tightened now when i torque to 25ft-lbs? 

I did have the blade come off twice when i first received the mill and was setting it up. The manual said to torque to 35 ft-lbs but this is incorrect and it was in fact 25ft-lbs.

[Dana Stanley]

My blade was not tracking well and popping off. They had me push the roller guides all the way back when checking the tracking. Sure enough the blade was hitting the guides which made it look like the tracking was all set but it wasn't.

[fishfighter]

My blade was not tracking well and popping off. They had me push the roller guides all the way back when checking the tracking. Sure enough the blade was hitting the guides which made it look like the tracking was all set but it wasn't.

This could be your problem.

[mitchstockdale]

My blade was not tracking well and popping off. They had me push the roller guides all the way back when checking the tracking. Sure enough the blade was hitting the guides which made it look like the tracking was all set but it wasn't.

Good call... I will be sure to do this next time I install a blade.
I set things up last night and spent some time on the tracking and re-installed the blade that kept coming off and it sawed no problem even with the beat up dull blade with no water .  One thing i did do was back the tension off half a turn.  I also checked the bearings they are tight no play.
All appears to be right with the world again...thanks for your input gents.