Unusual "scratches" on the wood with LT70

MobileSawMilSlo · June 20, 2018, 04:32:07 PM

Hi guys

I have one question from my friend which has WM LT70.

From the last week, his LT70 is working very strange. As you would see in pictures below the final cutting result is very bad.

The strange thing is that these bad cuttings apply only on the soft type of wood (spruce), hard one like oak it is OK.
As you would see it below, this unusual "scratches" on the wood are appearing for few inches, then they stop, and appear again and stops etc.

What we have checked (from my side by remote is this):

1) we tested 7 different NEW and also resharpened blades (WM, other, Vortex).
2) we checked guide rollers
3) we checked power belts
4) we checked driven and idle wheel bearings
5) we checked free movement of sawmill head
6) we checked blade tension
7) we checked a guide arms

I was not present with those checkups, but I know, he is very strict and precise man and he double checked everything.

Do you maybe have some other suggestions about what else should we look?

Any advice will be appreciated.

Thank you

Dave Shepard · June 20, 2018, 04:36:34 PM

Going too slow.

MobileSawMilSlo · June 20, 2018, 04:39:29 PM

Hi

I do not think so. He has more than 2500 hours of experience and he knows how to work with it.

Dave Shepard · June 20, 2018, 04:47:51 PM

Electric or gas/diesel? If not electric, I'd check to see that the engine is running at the right rpms. There is some sort of harmonic issue going on, I suspect. Typically, that sort of washboarding is from going too slow, and it's often seen right in the beginning of the cut.

MobileSawMilSlo · June 20, 2018, 04:51:03 PM

Quote from: Dave Shepard on June 20, 2018, 04:47:51 PM
Electric or gas/diesel? If not electric, I'd check to see that the engine is running at the right rpms. There is some sort of harmonic issue going on, I suspect. Typically, that sort of washboarding is from going too slow, and it's often seen right in the beginning of the cut.

Diesel engine. Yes, you are right, we did not check if Kubota is running with full power.

Magicman · June 20, 2018, 06:56:32 PM

Probably harmonics and the cause could be from several sources some of which have already been mentioned. #3 above stated "power belts", and I am unsure whether you/he meant drive belts or bandwheel belts? The drive belt tension needs to be verified to insure that it is not slipping and causing a reduction in the blade speed.

Southside · June 20, 2018, 07:17:29 PM

Has he tried changing the fuel filter? Could be starving for fuel when under a heavy demand.

Darrel · June 20, 2018, 07:30:15 PM

My LT40 does that when I cut too slow.

Magicman · June 20, 2018, 07:50:35 PM

Here is a very similar picture from member @Scottasheppard 's gallery:

I would say that he was entering the face slowly and then speeding up. Nothing really wrong and I have made this pattern many times.

esteadle · June 20, 2018, 07:58:11 PM

Is there sawdust build up on the V-track frame rails? Spruce sawdust is kinda sticky when the sap is running (this time of year), and can build up and lift the head ever so much as it passes. Oak wouldn't be as sticky and probably wouldn't build up the same way.

There was another recent thread here on FF where the V-track frame rails of the saw weren't aligned so well, and causing issues halfway into the cut. After I read that, and went out to saw a couple of times, I noticed this was happening on my mill too, but I don't have segmented tracks (portable mill on continuous rails). So, when I started blowing off the sawdust every couple of boards, I stopped getting weird cuts like this.

POSTON WIDEHEAD · June 20, 2018, 08:03:23 PM

Although lines on a board should be given some attention if its not what your looking for....
I always say its part of a bandmills character like the circle lines from a circle mill.

As long as my boards have a consistent thickness a few lines are not bad.

Scottasheppard · June 20, 2018, 08:22:03 PM

I've only been milling wood for a few months but I've been building furniture full time since 2010 i bought my wood exclusively from David Widehead Poston.. My customers love the saw marks... I've asked the old Goat to put an old blade on the mill... love the character and the $$$

Alberta Wolf · June 21, 2018, 01:38:49 AM

Just maybe it might be the side pitch,It seems to be that some teeth have more than others, my 5 ¢ .That is what I figure ,But I never got set the blade to make sure ,Cause mine does that to.I'm going to check the settings when I can .I never really noted that till now so maybe that is something to look into. :P

LeeB · June 21, 2018, 03:11:09 AM

Not sure if the LT 70 has the blade vibration dampener bolt in the guard above the top of the blade or not. Something to check.

LeeB · June 21, 2018, 03:14:10 AM

WM blade vibration dampening block in Sawmills and Milling

What causes this? in Sawmills and Milling

highleadtimber16 · June 21, 2018, 09:12:29 AM

Have the blade guide rollers been removed and blade checked for levelness on the idle and drive wheels? I had a similar vibration issue and it turned out to be that the carriage rollers were so worn out, the head was wobbling up and down thru the cut, leaving marks.

Chuck White · June 21, 2018, 10:10:35 AM

I find that when I get those marks, that the entry point of the band into the log is always on a curve (round edge of the log) greater than say 45°

Rhodemont · June 21, 2018, 04:10:45 PM

As MM posted "I would say that he was entering the face slowly and then speeding up" I tend to lead into the log slowly with my LT35HD and get that chatter until I turn up the speed and get moving on EWP. The chatter does not happen on oak which I start into even slower. Ross had told me to go ahead and get moving right away but guess I am just unnecessarily concerned the band is going to crumple up against the guide on first contact.

PAmizerman · June 21, 2018, 10:36:47 PM

Does this happen all the time no matter what band he is using? Has he tried a band from a different box?
I had a brand new box of turbos that had bad set from the factory and made the lumber look just like that. I'd try a different box and see if it is still doing it.

tawilson · June 22, 2018, 09:40:43 AM

Quote from: Chuck White on June 21, 2018, 10:10:35 AM
I find that when I get those marks, that the entry point of the band into the log is always on a curve (round edge of the log) greater than say 45°

Sawed this off the top of a cant last night.
I'd say there is steel in Chuck's words of wisdom.

Chuck White · June 22, 2018, 10:44:53 PM

Glad to hear that someone absorbed what I've been saying for...... how long!

Thanks T.A.

Some of the other things members have said are likely to be true too, I'm not arguing that point!

highleadtimber16 · June 23, 2018, 11:22:53 AM

In my experience I've found that it's not so much the curve of the log, but rather the bark. In cedar the stringy bark gets underneath the blade and causes vibration. I debark all my logs, so I no longer have that issue.

LeeB · June 23, 2018, 11:36:18 AM

I can see where the curve of the log could make a difference due to one side of the blade having more teeth biting than the other.

Dave Shepard · June 23, 2018, 12:01:14 PM

There isn't much difference in that regard. How much wider is the log when you drop down 1/8" ? 5" on the top side of the band becomes what, 5 1/4" on the bottom side? I would blame sapwood and bark in that instance. I know Turbo 7s won't cut straight going through narrow sapwood and bark.