LT 15 not sawing true on the last cut

Stacy · March 27, 2020, 07:59:33 AM

Hello,
I'm happy to say I found this site and was accepted as a new member. This is my first post!!!!

I have a question pertaining to my LT15 mill. I purchased it new 2 1/2 years ago for my personal use. Since them I have sawed quite a bit of lumber used for new construction and remodeling the old family farm and hundreds of posts and boards for fencing. I live in upstate NY and harvest all of my own oak and pine right off my property. A few weeks ago I noticed the last cut always starts out exactly the thickness I need but the last foot or so is between a 1/4" -3/8" thicker. I was still running the original belts that were showing signs of wear, so I replaced the blade belts and the main drive belt earlier this week. That made no difference. After signing up on this site I did a few searches and seen posts talking about the importance of how straight the bunks are. Yesterday, I strung a string on both sides and made minor adjustments to the bunks. Fired the mill up and sawed a log, the bottom cut was 3/8" thicker on the far end??? I also check the bolts on the rail the head rides on, they were tight. The thing that gets me is it doesn't matter where the log is positioned or how long it is??? Seeing how this is my first experience dealing with an issue I'm really at a loss. To be honest, the amount of adjustments on this thing scares me to death. I would appreciate hearing your thoughts.

Thanks,
Stacy

WDH · March 27, 2020, 08:10:44 AM

Pulling the string was spot on. If you don't have one of the Blade Adjustment Tools, get one and check that the blade is not tilted up and is level to the bed.

Stacy · March 27, 2020, 08:24:12 AM

I do have a blade gauge, I don't know how to use it so I guess i had better hit the books (owner manual) .

YellowHammer · March 27, 2020, 08:27:01 AM

Push your sawhead down over each bed rail and measure the height at each individual bed rail location. If your string or straightedge shows the bed is straight, and then the measurements show the head is at the correct height over each individual bed rail, then the mill bed and head are adjusted correctly.

Then its important to make a cut and replicate the results near the end of the cut. Make a cut 90% down the cant and stop the saw blade in the board, turn everything off, and measure the height of the band above the bed rails again, while it is still in the cant. is it still at the correct height. Is the band climbing? Can you see if its deflecting in the cant? Is the cant still sitting squarely on the bed? Are the clamps letting it move? Is the end of the cant or last board flexing down, drooping lower than the bed rails (very common due to log stress)? Many times cants will have stress and will flex, and if the end is not supported directly by a bed rail, the cant can flex down, making the last board thicker. If the end is on a bed rail, it will make the last board thinner.

As WDH says, check the alignment of the band, its a very critical adjustment. If its tilted up just a hair, it will act like a wing and will climb up. You should be able to detect that the band is physically climbing by measuring its height over the last couple bed rails with the saw turned off and the band still in the log.

Stacy · March 27, 2020, 08:41:55 AM

Thank you so much for the advice. I hope to get out early this afternoon to take some measurements. I will let you all know my findings.

Jim_Rogers · March 27, 2020, 05:45:13 PM

It could be as simple as a dull blade. Sometimes a dull blade will climb up when it pushes off the hard heartwood of the log.

Does it do it with a sharp fresh blade as well?

Log stress can be relieved by sawing one or two boards on one side and then flipping 180° and sawing the other side one or two boards.

Do this until you reach the center most piece. The one that hopefully has the pith in it. This piece will be of the lowest grade of the log and could be junk anyway.

Jim Rogers

Stacy · March 27, 2020, 08:37:30 PM

Well... I got my book out and my blade gauge, spent 2 hours going through the whole alignment process in chapter 7. I did find the blade was tilted 1/8-3/16 of an inch and a couple other areas needing tweaks. Nothing seemed to be more than a few 16th off.

I set a 10' log on and went at it!!!! I made all my cuts then measured the bottom cut and it's still is off. It was pretty much the same as it was before I made the adjustment. I figured out that it starts climbing about 32" from the end of the board, close to 3/8 of an inch thicker.

I do know it isn't a dull blade, I have changed it several times over the past couple months as I have continued to cut. It can't be the logs either, they all came from my property and I have cut thousands of board ft with no issues. This is something that started happening recently.

Stacy · March 27, 2020, 08:41:37 PM

Yellow hammer,

I forgot to mention I did take your advice and checked all the measurements you suggested, everything is true and inline after making slight adjustments.

Klicker · March 28, 2020, 06:48:54 AM

Is the cant supported on the end. I have noticed more then a few pictures on the forum where the cant was just hanging between the benches.

booman · March 28, 2020, 07:02:10 AM

I agree with Jim Rogers that it could be a dull blade. Could you clarify about changing the blade several times over the last two months? A blade could be dulled in seconds if it hits a dirt pocket, metal, or a small pebble lodged in the bark. Are you using a new blade now?

Stacy · March 28, 2020, 07:35:03 AM

I send all my blades back to Woodmizer for sharpening. I've continued to saw even though I'm this issue, I just flip the last cut end for end and make another pass to trim off the thick end. (Its a good thing my wife isn't paying me by my production :D) By continuing to saw I have changed the blade several times. I can install a fresh blade and start out cutting on a clean cant, same issue.

Is it possible I'm not getting the correct set on the blades?

terrifictimbersllc · March 28, 2020, 07:49:26 AM

When it's a beam or cant not the same thickness at each end, usually on my mill its the front end. It is a result of the front end of the mill sinking into the ground a little more than the back end. The cant/beam remains straight but the mill bed sags down at the front, taking the saw head and blade with it. So the blade being lower is the cause of a front end being 1/4 less tall (or wide if I rotated it) than the back end. The distance from the blade to the front bunk is still what it should be but both are lower. In other words when this is happening, the stiff cant/beam is "raised up" off of the front rail. In yet other words, the mill rail and bunks are on long slight curve with the front end being slightly lower.

Without getting complicated or even looking at anything I will run the head to the back end and turn the adjustment of the front outrigger (usually loose) to tighten it, raising the front of the mill a bit. This restores the mill to cutting a stiff cant or beam the same at both ends. On asphalt or an industrial yard where the ground is packed very hard, if I lock the outrigger nuts from turning, the mill will stay straight all day,unless a heavy log knocks it sideways and disturbs the cut. But, for me, maintaining this straightness requires ongoing attention throughout the day with most setups. Lack of it influences board widths, and thicknesses, at their ends.

Not saying it is what you are observing but I would sight the rail(s) by eye when there is such a problem and would expect to see a curve that can be restored to straight by shimming either the front or back of the mill, whichever is where the inaccurate cutting problem exists. Or with the saw head at the back end, put your weight on the front end and watch where the mill contacts the ground-you will probably detect movement there.

YellowHammer · March 28, 2020, 08:00:11 AM

Yes, sometimes, bands can be shipped with no set, improper sharpening, or other problems. Its rare, but does happen. Do you have a different box of bands? If you look down the band, you will be able to see the set of the teeth. They should look the same on either side of the band. if you have a way to measure then, thats better.

Sometimes, a mill can be aligned statically, but moves or gets out of alignment when under load.

In many cases, having a slightly loose blade guide arm can cause problems. If you take the band off and move the arm inboard and outboard, fully extended and fully retracted, grab it with your hand and tug hard on it, and does it move at all? It should be rock solid. Then grab the band roller assembly and rotate it hard with your hand, over and under. Does it move at all? I needs to be rock solid.

Then put the band back on, tension it to normal, and repeat the process except look closely at the band where it exits to guide roller. You can see very or any slight movement by looking at the glint or glare coming off the band. Hand tug and rotate the blade guide arm and look at the band glint and see if it changes which mans the band is being deflected.

Poquo · March 28, 2020, 08:02:54 AM

Is there any sap build up on the blade , that can cause the blade to dive or rise towards the end of the cut .

Stacy · March 28, 2020, 08:17:00 AM

I have this mill set up in a permanent position, 6"-8" of cribbing, on a 24'X24' concrete slab. I seem to have even pressure on all of the legs.

I have had two different shipments of blades over the past couple months. Same cutting issue.

Definitely isn't a sap issue, problem persists with a fresh clean band.

Guide arm is tight as well as the rollers.

stavebuyer · March 28, 2020, 08:21:05 AM

Dull blades, improper set, alignment, tracking usually show up in every cut. Log tension usually shows up more in the final board or cant as the ends or middle rise off the bunks but you will have thick and thin at both ends and middle. If your always getting a thick board at one end and all else appears ok: I agree you need to look at how the mill is supported especially if you have already checked blade to bunk height at every bunk.

SawyerTed · March 28, 2020, 08:49:33 AM

It might be worth parking the head over the area where the end of the cut is then check the bed/bunks for alignment with your string. You might not see the track sag over a low spot because there isn't weight over the area that causes the sag. I'm guessing one end or the other is not supported the same as the rest of the mill

Stacy · March 28, 2020, 09:00:35 AM

It looks like this weekend is going to be a washout, but as soon as I can I'll run the string a second time. I will pay closer attention this time to the potability of weight changing the alignment. I agree that its probably a bunk issue.

The on the drive side of the carriage the head rolls on a aluminum rail bolted to the frame. I have checked all of the bolts for tightness, my question, is this rail adjustable?

GAB · March 28, 2020, 09:37:07 AM

Quote from: Stacy on March 28, 2020, 09:00:35 AM
It looks like this weekend is going to be a washout, but as soon as I can I'll run the string a second time. I will pay closer attention this time to the potability of weight changing the alignment. I agree that its probably a bunk issue.

The on the drive side of the carriage the head rolls on a aluminum rail bolted to the frame. I have checked all of the bolts for tightness, my question, is this rail adjustable?

Stacey:
My experience with an LT15 is ZERO so this may be a bad suggestion or question:
Can you run the test with the string again, then load a decent size log on and run the test again.
That could possibly tell you something.
Gerald

ACman · March 28, 2020, 02:16:31 PM

What bands and what degree are you using ? I have same mill and have not had this issue yet. Have you looked at you blade tensioner and made sure its correct?

Sawmill Man · March 28, 2020, 02:39:01 PM

Dull blades or bad alignment would show up on every cut not just the last one. Mabe the sawhead in its lowest position is riding up on something on the mill frame. If it was stress in the log and he started out with a perfect sized cant he would have thinner boards somewhere to make up for the thick one on the bottom.

aardquark · March 28, 2020, 04:50:50 PM

Consider the possibility that when you are cutting the last board, what remains of the log is more flexible, and thus more susceptible to bending due to stress (or even gravity). It might be interesting to try (with a suitably small log that will fit between the blade and what lies above it on your mill) to cut from the bottom first (when the portion of the log above the blade is much stiffer), see if you notice any difference.

WV Sawmiller · March 28, 2020, 07:07:32 PM

Yeah, that is true if it happens occasionally but if it is happening every time there is an alignment/base/tension/blade issue.

Stacy · March 28, 2020, 07:20:16 PM

Today was a total washout with rain, hopefully tomorrow I can get out between showers.

ACman- I'm anxious to get out to check the blade tension, that's one thing I haven't paid much attention too. Some of the blades I'm using have been sharpen 2 and 3 times, it only makes sense they may be stretched.

Stacy · March 31, 2020, 11:03:58 AM

I'm back with my tail between my legs. :embarassed: I have checked every suggestion you fellas have given me and I still have the same issue, the bottom cut is always 1/4 inch thicker on the far end. I have ran a sting on both sides of the bunk 4 different times with a log and without, it is spot on. As I said before, I send all my blades back to Woodmizer to be reset and sharped. I agree with Sawmill Man, you would think if it was a blade issue it would show on every cut and it doesn't. But, that being said I have ordered some new blades so that theory can be proved right or ruled out.

I'm about ready to tie the white rag on the stick! :(