Boards thicker outside then inside

CLL · July 21, 2007, 11:55:49 PM

Lt40, Read all the books and seems like several things can cause it. I'm thinking rails might need adjusting. 60 hours on mill. About 1/8" on 6" board.

Dave Shepard · July 22, 2007, 12:08:48 AM

I would look at your blade guide arm first. I have been doing the alignment on two LT40's this week.

Take a ruler and measure to the bottom of the blade guide arm when it is almost all the way out, and again when it is almost all the way in. If it changes, you need to adjust so that it stays parallel to the bed rail. If this is parallel, measure the height of the band from the bed rail near the inside guide roller, and then next to the outside guide roller, with the guide are almost all the way out. If the readings aren't the same, you need to adjust the deflection of the band so that it is parallel to the bed. I have had to spend some time on the blade guide arm on both of the mills, it makes a big difference if it is not adjusted correctly. I personally doubt the bedrails have moved, there really isn't anywhere for them to wear or bend, unless you drop logs from ten feet up. :D This is just my instinct after spending a bunch of time on alignment this week. Anyone else have any ideas? Let us know how you make out.

Dave

Tom · July 22, 2007, 12:31:30 AM

A square will tell you if your cant is not square. You might be producing a diamond cant and the pressure of the clamp is making the cant rise from the bed of the mill.

It is strange for all boards to be thick on the outside. Usually, once you start cutting, the opposing surfaces will be parallel until you turn the cant or relieve the clamping pressure. Usually it is the first board after turning and the last board of the cant that will show thick and thin to the side.

A diamond cant (Parrallelogram) can be caused by the squaring dogs not being square to the bed or the clamp pushing the cant off of the bed, or something like bark getting between the cant and the bed of the mill.

If your problem occurs when you turn the cant or every last board, you need to check your mill for square. The first place to look is usually the squaring dogs. They take a beating if you are a heavy clamper or if you saw big logs.

To see if your blade is out of square, run the adjustable guide all the way out to expose the maximum of unguided blade as you can. Put the blade over a bunk and measure to the bunk from both the drive side and the idle side. the should be equal. Do this to each bunk in succession until you have checked each bunk.

This will ease your mind that just one isn't out of whack. If they are square, move the blade back over a bunk and move the moveable guide in as you measure the distance to the bunk. If it changes, then your guide needs adjusting. If it is steadily different than the idle side measurement then it might be the bearings in the guides, the bearings in the cam followers or the head horizontal adjustment.

Bibbyman · July 22, 2007, 01:20:08 AM

'Nether simple thing to check. Take the blade tension off, or better yet, remove the blade and check the blade guide rollers to make sure they're mounted tight. With just 60 hours, it could be one or the other has vibrated loose.

That goes for the blade guide arm too. With the blade off, run it in nearly all the way and then lift up and push down on it to see if there is too much movement in it.

Just a force of habit, we check the blade guides about every time we change the blade to make sure they're rolling free and mounted tight. At least Mary does. :

DR Buck · July 22, 2007, 10:09:19 AM

QuotePut the blade over a bunk and measure to the bunk from both the drive side and the idle side. the should be equal.

[/size] ??? ???

Unless you are measuring while the blade is moving (NOT RECOMMENDED) this is not correct for Wood-Mizer. The idle side will be 1/16th higher that the drive side.

I'm not sure what you mean by the "inside" and "outside". Is "inside" up against the back stops? If so, it sounds like the blade guide arm may be pushed up to far. This can happen from banging it into a log or smacking the top of the clamp with the bolt on the bottom of the blade guide. Check the blade alignment section of your manual. :P Follow the directions in order.

Dave Shepard · July 22, 2007, 01:22:51 PM

DRB, in the manual for the mills I am working on, it doesn't say anything about setting the idle side higher by 1/16"th. Is this in newer manuals? I am working on a '92 and a '94. I have the blade parallel to the bunk, and I am getting even board thicknesses right down to the last board. Thanks.

Dave

DR Buck · July 22, 2007, 02:04:14 PM

Don't know when it was changed or the differences between earlier mills and more recent production. Mine is a 2003 LT40 hydraulic.

Here is an excerpt from section 7 of the manual.

Dave Shepard · July 22, 2007, 02:19:41 PM

That is interesting, it is definately not in the older manuals. My question is, what is it going to do when you aren't cutting into a wide cant? That would lead me to believe that you would get an uneven board, especially on a 1x6. Thanks again.

Dave

DR Buck · July 22, 2007, 02:49:01 PM

Dave,

I think for narrower cants like 6", the difference is compensated for by the down-tilt in the adjustable blade guide arm. As you close it up for the narrower cants it deflects the blade down slightly. ??? I think....

CLL · July 22, 2007, 03:52:50 PM

appreciate the help and ideas. Have my first real order and don't want to send 200 4x4's that are lop-sided. Really they are square, you just have to turn thrm a little. :D :D I'll try and adjust in the morning and let you know tomorrow night how it went.

Bibbyman · July 22, 2007, 04:17:12 PM

Quote from: Dave Shepard on July 22, 2007, 01:22:51 PM
DRB, in the manual for the mills I am working on, it doesn't say anything about setting the idle side higher by 1/16"th. Is this in newer manuals? I am working on a '92 and a '94. I have the blade parallel to the bunk, and I am getting even board thicknesses right down to the last board. Thanks.

Dave

I'm sure our 94 LT40 included the instructions for 1/16" higher on the idle side.

Dave Shepard · July 22, 2007, 06:50:19 PM

Bibbyman, my 94 manual doesn't. ???

DR BUCK, the manual wants the blade guide arm to stay perfectly parallel to the bed at all times.

I don't know why my manual differs, but everything is cutting correctly.

Dave

Tom · July 22, 2007, 07:53:21 PM

My manual says for it to be level, as my mind remembers.

There was a time when there was some talk about making the outside be higher to compensate for the torque of the engine. I guess someone believed in it enough to put it in a manual.

I have a hard time with finite adjustments that have a little kentucky windage thrown in. In my mind, if I want the board to be straight, the adjustments have to be straight. Adding 1/16 to one side might compensate for one engine and not the other, or, one set of band wheels and not the others, etc.

My mill was steady as a rock. When all of the adjustments were made and it was square, it cut true.

I guess that you have to go by the manual though. If yours says it has to be uneven, make it uneven. Still, the difference in adjustment gives the 4 post argument that the cantilever moves, some credence, doesn't it.

Bibbyman · July 22, 2007, 08:07:12 PM

Maybe we'll have to wait until Sparks or MartyParsons gets on and votes on 1/16" or not. :

Dan_Shade · July 22, 2007, 08:10:02 PM

at the end of the day, it's a sawmill, not a planer and jointer :D

DR Buck · July 22, 2007, 08:19:48 PM

Quote from: Dan_Shade on July 22, 2007, 08:10:02 PM
at the end of the day, it's a sawmill, not a planer and jointer :D

What he said. ;D

Dave Shepard · July 22, 2007, 09:12:43 PM

Why can't it be both? When everything is right, I can barely see the tooth marks in pine. ;D I agree that chasing the last little bit of accuracy can take a lot of time, but I won't settle for less than the mill is capable of. After all, once the adjustments are done, it will turn out a high level of accuracy for a long time.

Dave

Brucer · July 24, 2007, 12:37:12 AM

The manual for Louis' '96 LT40 (which I ran for a season) mentioned the 1/16" height difference. So did the manuals for my 2005 & 2006 mills. The procedure is to true everything up, getting all the bed rails parallel to the blade. Then tighten the adjusting bolts on the bottom track rollers to tilt the mast and pull the idle side of the blade up 1/16".

The principle is this: when the blade bites into the wood, it will bend the mast toward the log, pulling the idle side of the blade down slightly. Some of the movement is due to slack in the track rollers, some is caused by compressing the plastic guides on the saw head, and some is due to bending of the mast itself (the higher the saw head, the more bending).

There's more bending force when cutting big logs, and that's what the adjustment is designed to compensate for. When you're cutting 6" material, there won't be as much downward movement to the saw head; but a 1/16" discrepency at 24" is only 1/64" at 6". You ain't gonna notice it.

The bottom line for me is this: when my mill is adjusted "according to the book", all my timbers, big or small, are consistently square on all 4 corners. That's what my biggest customer wants, and it's something my competitors can't or won't provide. ;D

jpgreen · July 24, 2007, 12:56:00 AM

My '95 manual notes the 1/16" difference.

ronwood · July 24, 2007, 09:30:57 AM

The 1/16" difference should occur with the outside blade guide roller extend all the way out and measuring the blade height at that point.

Dave Shepard · July 24, 2007, 06:37:43 PM

I found the missing 1/16"th. It was hiding in the mast adjustment section of the alignment book.

Dave

musikwerke · July 25, 2007, 08:17:01 PM

I just finished doing a total restoration of a 1987 LT30 which has taken me the better part of two years. I've replaced everything questionable plus added every upgrade / retrofit kit that Wood-Mizer offers sooo, I've had many, many conversations with the great folks at the main office. On one occasion I had a couple of questions on alignment procedures since the one that came with my High Performance Blade Guides differed from the the one in my original owner's manual. The fellow made it a point to say that the final adjustment (and I had to align the whole mill like it never had been aligned before) is to open the blade guide arm up all the way and set the idle side of the blade 1/16" higher by adjusting the mast tilt. On my mill that equated to turning the mast adjusting nuts 1/12 of a turn clockwise. I agonized over this for a bit but came to the realization that, like another member said, even if the sawhead didn't "torque" or "pull down" when entering the log, with the size logs I'll be sawing I'd never be able to measure the difference.

Dave Shepard · July 25, 2007, 08:24:37 PM

Welcome to the forum musikwerke!

Got any pictures of your mill?

Dave

musikwerke · July 25, 2007, 08:41:33 PM

Thank you Dave. I've been a member for quite a while and have learned more from this site than from any other one thing in my life. I just wanted to finish this project and actually make some decent lumber before I came out the lurking phase. Yes, I have pictures because, if I may brag just a little, the mill not only looks but is better than factory new thanks, primarily, to Wood-Mizer. Let me get the rest of the Summer's projects behind me and I'll make an attempt at posting some pictures.