LT50 popping blades

[Old Greenhorn]

 My last 2 sessions at the mill have been beyond frustrating. I have been breaking blades with a lot less than an hour of time on them, the last one was about 10 minutes work time. In each case there was no solid reason for a break. In one instance the blade was out of the log and I was raising it to gig back when it broke. When I broke the third one today I declared a work stoppage and went off to buck and move logs while I cooled off and thought about it. The I came home to read the manual.
 Before I went back to the mill I checked the last blade I broke. No excessive wear, no gullet cracks, and best I could discern there was about a .005-.007" difference between the right hand set to the left hand set teeth. Also no waves in the few boards I got. Not perfect, but it doesn't explain the breaking. Also, my cuts were pretty much flat but I did see flutter. I am not sure if these are resharps or not, we don't track that real closely, but I have used most blades in this batch as normal with no issues and am now down to 3 or 4 blades left out of 15.
 So after reading and printing out sections of the manual, I went back to the mill armed with some decent measuring tools. I put another blade on and started checking things according to the manual, step by step. I found the movable blade guide is a bit out of whack. When it is all the way in there is zero gap between the back edge of the blade and the flange of the roller guide. When it is full open I have about a 1/16 gap perhaps a tad more. But when it is full closed up, I can rock that arm a bit and I have noticed blade vibes when it is running. This gap between blade back and flange is a tough thing to get in and measure, so I am using my machinist eyes, which are fairly close, but next visit I will try using feeler gages. I also checked the head tilt and that is pretty much right on. 
 I was running out of workable daylight and didn't have wrenches big enough for adjusting the moveable guide assembly anyway, so I headed home and did some further reading.

 My question is: Does this small amount of misalignment and the tiny bit of shake in the moveable guide seem like it's enough to have blades breaking for little or no reason other than that? Or might I have a blade problem?

 Either way, the alignment needs to be done properly and it can be a can of worms. I have long suspected there is not enough down pressure on the inside roller and would like to start there, but if I wind up moving it down, it may change the bottom set point on the Accuset II, so I have to reset that (haven't even looked into that yet), then I have to set to outward roller and check the head tilt again. Before I do any of that, I have to get the blade guide arm running true.

 I am pretty frustrated because I have lost 2 prime days of milling trying to figure out what I know so far. Last night I got another too big order for this time of year and I want to get this all done before the weather closes in within the next couple of weeks. Also, this is a new level of machine care for me on the LT50 and my confidence is not as high as I would like. Any experience folks could share would be helpful. Am I missing something in my evaluation?

[Southside]

First thing that came to mind is the band wheel belts. Change them, if they are letting the band hit the wheel they will break just as you described, been there, done that.

Second, yes you don't want the back of the band rubbing on the guide flange. I run the gap on mine wider than the book calls for, between 1/8" and 1/4". I don't have any issues with cut quality as a result and I don't break bands either.  I would have to go and yank on mine to see how much flex there might be but my gut tells me that isn't your issue. 

[Old Greenhorn]

 Forgot to mention, my first (and easiest) check was the belts. They aren't new, but still holding up and no, the blade doesn't hit the wheels. Still, your experience holds weight, so I will look closer on the next session. Given that there is a holiday tomorrow, not sure if I will get down there. Thanks for that.

[Magicman]

Go through the entire blade guide alignment and ditto the B57's. 

I would want the back of the blade ~1/8th inch+ in front of the flange. 

Is your horizontal tilt correct?

[Bruno of NH]

I would still put new belts on the band wheels
I had that same problem and my belts weren't that old .
New belts and no snapped bands 
Just my 2 cents

[Old Greenhorn]

...

Is your horizontal tilt correct?

Yes, as I said in the OP, the head tilt is per the manual. I did check the belts and there is no contact with the wheels. I do know the guide arm is out of whack and putting the guide flange against the blade back, possibly further, so I am not doing anything until I get the guide arm straightened out.
 Yes, I do hear you one the belts, I may just swap in new ones while I'm at it.

[barbender]

 First, are you certain on the B57 belts? Make sure they are not allowing the blade to contact the wheel. They can look good but mash down enough under the tensioned band to allow contact. Then blades will start a poppin'.

You want that ⅛"-¼" gap between the blade and the flange on the guide. Usually if that is lacking it will cause a bunch gullet cracks though.

I've also had idle side band wheel bearings go bad, and that will break blades too. That is typically accompanied by tracking issues.

[Southside]

When I learned this lesson I thought my belts were fine too. I could not see that the band was hitting the wheel, but once I had new belts on it was obvious that the old ones were toast, and it solved the issue. 

[moodnacreek]

Sounds like it's time for a circle mill.

[barbender]

Because a common maintenance item needs replaced?🤔

[Old Greenhorn]

Sounds like it's time for a circle mill.

NOPE! :D Before I do that I will retire from milling altogether.

[Magicman]

Yes I read "head tilt" which includes both vertical and horizontal tilt.  I was emphasizing "horizontal" because if that is not correct, it will break blades.  Just double checking.

[ladylake]

I found the movable blade guide is a bit out of whack. When it is all the way in there is zero gap

If the back of the blade is too close to the flange you will break blades fast.  I run mine 1/4 inch behind. You might get by with a little closer sawing slow with a high hook angle. You need to get that adjusted the same all the way and out.  Steve

[customsawyer]

You said you broke one blade in just 10 minutes. I have never broken a blade that quickly from an alignment issue. I think you are running some old blades that are all just tired. Get a new box of blades and try one before you start fixing a mill that isn't broken. 

[Crossroads]

Are the bands breaking in the weld or away from the weld? When you look at the fresh break, is any of it discolored? If they're new bands breaking at the weld, someone missed the heat treat. If they're breaking away from the weld and have discoloration in part of the break, that may indicate that they are simply old worn out bands. As customsawyer mentioned, you may want to try a brand new band from a different batch before you pull your hair out and turn your mill upside down trying to fix something that's not broken. If the new band runs, you can go back and do any needed maintenance/tuning just for piece of mind. Best wishes and happy thanksgiving 

[ladylake]

  
 If the back of the blade is rubbing against the flange on the guide wheel its broke and needs adjusting.  Steve

[terrifictimbersllc]

Manual says the idle side blade roller flange should be 1/8" from the blade when the guide arm is 1/2" from both open and closed.

The Accuset adjustment you mention is simple, if it's still the same you just put the blade height at 12 inches ( actual), go into settings,  and do the "set at 12" option.

[stavebuyer]

I know when I ran 1.5" x.055s on my 70 they didn't like to be sharpened more than once or twice. That would be worse on a smaller band wheel. 

[Old Greenhorn]

OK, thank you all. When I get back down there I promise to look at the belts again much more closely and will probably replace them anyway, just because.
 Let me be clear, I am not 'fixing a machine that isn't broken'. I have identified one clear problem which is the moving blade guide alignment. It is way out of whack to the point of binding on or pushing the blade forward. I did not confirm this last detail yet, but I will before adjusting. So yes, there is a clear problem to be fixed (adjusted).
 The blades are not breaking at the weld, no heat marks at the break, nothing unusual. No issues with the first 10 blades in the box at all. I am not going to be quick to blame the blades without making sure the machine is adjusted within spec, and right now it is not. As others have said, a rubbing blade flange is a blade buster, so I need to get that fixed first. If I have to re-set everything in the process, so be it. We have had a few head drift crashes on this machine and possibly a few other things I don't know about.
 The reason for the post was to get others experience with this and see if I should be looking at something else, like the belts as was pointed out. I have precious few milling days left and it's not a lot of fun doing close adjustments in cold weather, so I would like to do this once and get back to work.

[Magicman]

I agree with customersawyer that you probably have some "tired" blades.  Old blades would tend to break more quickly if you have a blade guide alignment issue.

I had an episode with blades breaking on a job in May and found this:  LINK

[Crossroads]

In looking for discoloration in the break, I meant to be looking for oxidation, suggesting the blade had cracks from previous runs. I'm sorry if you thought I was discounting the importance of having the mill adjusted correctly, that wasn't my intent. If the blades are cracked when you put them on the mill, then that is likely the cause of the immediate issue of the blades breaking. With that being said, the adjustment issues that you've found, could quite possibly be the cause of the cracks in the first place. 

[Old Greenhorn]

I get it Jake. I brought some of the blade sections home to my shop where I have a microscope that plugs into my cell phone and gave it a really good look. I used to be an engineer troubleshooting failure problems and did a fair amount of metallurgical work with better equipment. When I found a suspicious area, I would send it off to a lab for cross sectioning, micrographs and chemical analysis. So I have an idea what I am looking at and I am not seeing anything to indicate a problem which tells me it is likely a catastrophic failure caused by other issues. Now the last break I had was doing the first opening cut on a 28" log so the blade guide was open pretty wide. This puts the guide flange in the position where it is pushing against the back of the blade. Hence my strong suspicion that this guide alignment is a leading cause. Besides, it's just 'not right' and I ain't running a machine that ain't right because it's abusive and leads to sloppy work.
 As all the guys who have chimed in here know, these machines are simple, yet they are complex and it takes a while to work through these issues as they come up and learn the machine. I am just over a year into it now, so have quite a way to go. I don't own the machine, but the owner has no time to make lumber and less time for repairs, so he leaves it all to me and my judgement. Truth is, I probably take better care of it because it is not mine and I feel responsible. He had another sawyer a few years ago running his LT40 and that fella was a butcher and his lumber was garbage, so he knows what he is getting now and has zero complaints. Having already found and fixed a couple of other issues with good success, minimal downtime, and improved performance, I am just working my way through this one now. I just wish it was warmer out and I had more daylight. Had to quit at 4:30 yesterday, too dark. I came back to the shop and got more tools together for the next session. Also fixed my 24" Vernier so I can get better measurements which was frozen after 20 years of no usage. ;D
 We'll figure it out.

[barbender]

Simple but complex is a good way to look at these machines. There's not a lot to them mechanically, but when you have to start chasing sawing issues it can get complicated.

When I have blades break from old age/metal fatigue, they typically have gullet cracks but what is really telling is you can fold the blade on itself, and they snap easily (it's actually more of a crumble). I've tried to fold and break new blades that I had metal hits or otherwise destroyed, you can't do it. The metal has too much spring to it. So perhaps you could use my advanced metallurgical testing process if you have another blade break😁

[ladylake]

 

 I get the best blade life with the flange set 1/4" back sawing with a 4° sawing fast.  Even when you get your mill aligned right if you run the blades that have been run with bad adjustment they will still break as they have been damaged.  New one should work fine.  Steve

[moodnacreek]

Sounds like it's time for a circle mill.

NOPE! :D Before I do that I will retire from milling altogether.

Geeze, I thought you liked to cut wood.