LT40 strange out of square problem.

[Dave Shepard]

I've been experiencing a strange out of square problem with my mill. I almost always flip 180° when opening a log, in theory giving me two parallel sides to the cant. Then I flip up 90° and use a framing square off a bed rail to square the cant when making timbers. Whenever my vertical face is square to the bed, and I take a board or slab off the top, I get a square edge. When I have a flat side on the bed rails, and the vertical face is square to the bed, I also get a square top edge. But when I flip the cant a couple of times, it gets out of square eventually. There is no rhyme or reason to it. I checked two of my squares against a big Starrett machinest's square, and also bought a new one for insurance, and they were right on. I've checked my 1/16" tip of the head. Checked all bearings on the head, guide arm, roller guides, spacing of the mast pads and I cannot find anything out of spec. Guide arm is tracking perfectly. Anyone run into this before?

[LeeB]

May be too much clamping force.

[ladylake]

I'd guess it's the 1/16 pull which will vary depending on how hard or soft the wood is and how wide you are cutting.  Steve

[Dave Shepard]

I don't think the clamping force should be a problem. All checks for square are done after clamping. I've never had this problem before, regardless of width or species. The only time I've had a squaring issue is if the 1/16" was not set right.

[Larry]

You might check your moveable guide arm to make sure its not moving the band down (or up) as you decrease the throat opening.

[barbender]

Maybe some slop or wear in the back support pivots, causing them to not be consistent? I'm just guessing.

[Dave Shepard]

Guide arm checked X, Y and Z, all good.

Back supports are good. Also, I'm setting the cant to the bed with a framing square, and not relying on the backstops, although when the mill is cutting right, you can. It's square to the bed before the cut, and after, so it's not being pulled by the force of the saw. The most recent cut is always square. The top will be square to the vertical face, and the vertical face will be square to the bed, meaning the top must be parallel to the bed. But the face against the backstops will not be square to the top, which means that it isn't parallel to the opposite face.

[barbender]

Puzzling, is all I can say.

[Cedarman]

Two things might cause a problem among others.
As you rotate, you might be getting some sawdust left under one side raising the cant slightly.
Another thing is that the cant may be twisting slightly as uneven stresses are released as you saw off material.

[kelLOGg]

Just how much out-of-square are you seeing? A pic of the square on the cant would be helpful.
Bob

[Magicman]

The 1/16" is not necessarily an exact or an engraved in stone measurement.  Your sawmill may be torquing a bit more or less than that amount.  After opening the second face, measure the right against the left sides.  You might use the BGAT or even a yardstick to expand this out so that any difference can be detected and measured.

[mesquite buckeye]

I would definitely ck on the clamping and crud under the cant on the bottom rails. Sometimes after the blade goes into the log the bottom will lift slightly, even if everything looks ok before. We always look under the log anytime we clamp and wipe the rails and pieces of bark chips off the bottom of the cant. If we see light anywhere where the log sits on the rails, there is a problem: rideup, cants flexing from stress, overforce or underforce on the clamp especially with some logs at certain positions. If the bottom sits flat and the saw is cutting flat, all that is left is the log stop adjustments.

[bandmiller2]

Dave, be sure the bed rails are level and well supported by the screw jacks. It doesn't hurt to peek under the cant to check for daylight between cant and rail. Frank C.

[Dave Shepard]

Crud under the cant is not an issue. When I'm cutting timbers, I walk the entire length of the timber checking the bed rails on every turn, no exceptions. Bed rails have been checked for level and support. A necessity with the BX on and not bolted to concrete.

Backstops are not part of the equation. This issue is most present when I have a four sided cant, and the stops are down.

I've checked my squares a couple of different ways, and made proper adjustments to the ones that aren't square anymore. (You fold the tongue around the blade so everyone gets the hint: It's really, really not square anymore!  :D )

Stresses in the log are minimal. I'm sawing white pine, and I have never sawn anything so forgiving. I've split a 15"x15"x47' timber down the middle and it didn't wiggle at all. Nothing. I'm not saying there is never any stress, sometimes splitting a 5"x10"x14' into two 5"x5"s will cause them to bow a little, but for the most part, I'm sawing single boxed heart timbers, often in very clear logs.

1/16" has always worked for me. What is puzzling me is that all specifications are as they have always been after a complete alignment, yet I'm having this strange trouble. When the mill is working properly, you get perfectly square on all four corners timbers. (Hint, if you get a timber that is only square on three corners, adjust square as mentioned above. ;) ) It's almost as if one of the track rollers is fouling up, but I have taken the load off of all the rollers and checked them, and they all feel perfect, they all turn smoothly, no catching or anything. If this problem persists, I think I might change them all out just to eliminate the problem. I'm hesitant to spend the money, as I can't really spare it, but if I can't saw a good timber, then I can't make any money with the mill, either. The mill has 771 hours. Is this in the right hour range to expect a track roller failure? Certainly they can fail at any time, but I didn't think I would see one go with such low hours. The mill head is always tarped when not in use.

I've just had a thought as to eliminating the main mill as the culprit. Tomorrow I'll saw a log on the BX. It will be sort of old school meets new school. Manual clamping and turning with 51 HP CAT and Accuset. Should be weird. ;D

Thanks for all the suggestions.

[Dave Shepard]

To answer one question that I didn't get to. Sometimes the out of square is maybe 1/16" on 8" or 10". I can live with that, especially if there are two opposite corners that are square, although I know the mill is capable of perfectly square timbers time after time. Sometimes the mill is sawing pretty well, and on the last cut throws you a curve ball and it will be 1/4" out. That is a reject if it is a timber for a customer. I can work out of square, but I can't sell them that way. The oddest cut I got was resawing some rejected rafters from one order I had. The rafters were 5"x18". I had a lot of hidden defects in the logs, so I had a lot of rejects that I could cut into something else, or even just blocking. I had one cant that was 8" or 10" thick that I wanted to reduce to 5" thick so I could get a couple of 5"x5" rafters for another project. I cut the cant down to 6", flipped 180° and cut to 5 1/2", then flipped 180° again and cut at 5". This is my way of dealing with what little stresses might be there to keep my cant flat. As usual, I was checking for flatness on the bed. I wasn't checking for square, as all I was after was a wide parallel slab. On the last cut to 5", I immediately saw that the shim cut was tapered left to right. After measuring, I found the slab to be 5" thick at the rail side, and 5 1/4" at the clamp side, with the slab still flat on the bed. I can't explain it. If there was a track roller going bad, I don't think it could just go nuts like that and then go back to behaving. That's too far gone. There are also no signs of odd wear on any of the rollers or the bed rail. ???

[Peter Drouin]

Dave I don't go with the 1/16" thing the cat is heavy. I put the blade right on,  I set it at 12" and make it 12" all the way open . 12" to the tooth tip that turns down to the bed. Set the accuset and go. :D :D

[Dave Shepard]

OK, but that doesn't explain the fact that the 1/16" had always worked for me, and also I am getting a square edge when the timber is flat and square to the mill bed. It's a mystery. :D

[BBTom]

Dave,
You said you have checked all the camlock bearings, but I just want to make certain that you have checked the Bottom ones.  One of those that has a flat spot could cause the problem you are seeing.  Also make certain that one of them is not holding all the weight. 

If they are both good, I am stumped.

[Dave Shepard]

As best I can tell, they are all good. I put a cant hook under the end of the sawhead and lowered it until the weight just came off the bearings. They all turned and I didn't see any flat spots. I'll try it again and inspect all the bearings for flat spots.

Thanks everyone.

[Peter Drouin]

But you said it happed only. When you kept turning and taking wood off. You can be off just a little and it adds up.
When I cut a beam I turn only 90 ° , That's when the square comes out. That's where I adjust it if I have to. The #2 face is where it's all about. :D :D :D

[Magicman]

I do the same Peter.  I can lay the square on the second face opening and adjust if necessary.  (almost never)  From then on, the other three corners will automatically be square.

I rely on the side supports because they can be relied on.

[Dave Shepard]

So on your second face you take the slab off and then check for square from the top to the side against the backstops? My backstops are dead on square, and when working with small cants, they are usually good enough to clamp to and be square to the bed. But working on a 30' long log that is 24" or more on the small end, it's just too much weight to rely on the backstops. I know you can push the backstops out with the two plane clamp on an LT40, and monkeying with a log that weighs two tons or more only exacerbates the problem.

If the mill is working right, flipping 180°gives me two parallel faces and when rotated up, I now have a face that I can square to the bed.

[Magicman]

Dave, my remarks only applied to my situation and I have never sawed a 30' log.  I did not pick up on the fact that you are sawing 30' timbers.  Your market is completely different from mine and obviously a different set of rules apply.

Since you have a bed extension, have you verified that it has not settled or is maybe twisted.

Obviously there is something that you are missing somewhere in your measurements or alignments or else you would not be having a problem.  Maybe back to square one.   :-\

[Peter Drouin]

I take the slab, then 1 or2 boards to get a clean corner then the square. And I do that with 45'ers  :D :D :D 
My back stops are right on too , But I don't trust them, :D :D :D
When I'm cutting beams for a framer, They have to be square. ;D

[5quarter]

Dave...I know you said that clamping is not the problem, but I think it is. It explains all the facets of your trouble. if your backstops are square to the rails, and if the cant is laying flat on all the rails and your blade is running parallel to the rails through the entire cut, you cannot be out of square. When you clamp your cant, it appears to lay flat on the rails, yes? But when you engage the blade and begin sawing, you are putting a lot of lateral force on the cant...esp. with that big cat engine. and the faster you saw, the greater that lateral force becomes. something has changed in the clamping system that it cannot hold some pieces flat to the rails while in the cut. What has changed I have no idea. perhaps the angle of the cleat, perhaps something is bent slightly. But that's definitely a gremlin you need to shoot dead, and quick.

I also agree with Peter...after I open the first face, I rotate 90°. That second cut is the money cut.  ;)