Waves and waves

slowzuki · June 02, 2006, 10:29:10 PM

Good evening all. My homebuilt mill has recently been put in service and I have a wave problem.

In dry small softwoods, no prob.

First noticed in a big fresh cut aspen/poplar. Blade dived and dove hard in a 16" wide cut. I had to stop the mill and work it to get out. Wrote it off as a dull blade, yanked the half cut log off the mill to use as a bunk for loading logs.

Cut a few smallish spruce/fir that have been down a year or so and had zero probs on the fresh blade.

Tossed a 16" diameter spruce on the mill and slabed it up ok but when I tried to take the first cut the blade dove and bogged the motor down then eventually rose a bit and bogged the motor. Repeated the cycle for the whole 16 ft cut.

Wasn't a knotty log. Looked at the blade there is a bit of sap on the teeth and gullet area.

I adjusted my movable guide all the way in with no luck.

I have 1/4" down pressure. Running about 800 lbs on the tension arm on the 1 1/4" blade, so 400 lbs across the band.

Guides are aimed very slightly down, maybe I should aim them up?

My 10hp motor doesn't seem to be kicking out the power it had last year, seems really woefully underpowered but I think something is wrong in the wiring, maybe too much voltage drop or something.

Any help would be appreciated.

Brad_S. · June 02, 2006, 10:52:45 PM

You may have a number of issues happening, but to start with, guides shouldn't be "aimed" up or down. Blade should be parallel to the bunks at both the front and back of the blade.

Tom · June 02, 2006, 10:53:38 PM

Your guides should be dead-on straight ahead if that is the direction that you want to cut. Don't angle them up or down. A straight edge clamped to the blade so that it sticks out on the front and back, will detect the slightest up or down in the blade. Measure from one end of the straight edge to a bunk directly beneath it. Then move the head so that the other end of the straight edge is over the same spot and measure the distance form the straight edge to bunk. The measurements need to be the same.

Other things that will cause the blade to dive in the wood are:
Blade speed (slipping belts, low motor RPM, slipping clutch, etc.)
Blade set differently on one side than the other.
Blade set to small.
Blade tension too low.
Gumming of the blade (sawdust on the side of the blade.)

Driving the head of the mill too fast. (if everything is dead-on, even this may not cause the blade to deviate but will rather just kill the motor.}

Cutting fast, cutting wide stock, cutting hard and/or dry woods will all cause a mis-aligned saw to be tempermental.

QuoteRunning about 800 lbs on the tension arm on the 1 1/4" blade, so 400 lbs across the band.

I don't understand this. If you are talking about blade tension, then my opinion is that you are way under tensioned.

That was quick, Brad. Good Show! :D

slowzuki · June 03, 2006, 06:37:13 AM

I will set the guides bang on and crank the tension up, I can go to about 1600 lbs so 800 lbs across the blade (800 top, 800 bottom). I went low because of reading Harolds posts of running low tension.

I guess I should dig out the calipers and clamps and measure. Maybe I'll hook up my water drip with some pinesol too.

woodmills1 · June 03, 2006, 08:10:42 AM

just a tip on pinesol, when I used it with my blade sharpener the bearing in the front of the motor was shaot in a few weeks. It is very good at removing grease

If your mill set up hasent changed then I would suspect blade problems are causing the blade to dive. I have had lots of problems with the few spruce I have cut but these were loaded with multiple small hard knots.

Fla._Deadheader · June 03, 2006, 09:12:38 AM

When I talked about low tension, I was still talking pretty DanG tight :

;D ;D I just don't use any device to measure. Probably not a good idea, but, we cut 24" wide and wider "Heart Pine", which is VERY sappy. I built a bracket on the log side of the fixed blade guide, where we can clamp a small " Platers" wire brush, like a tooth brush, soit wipes the dust and sappy stuff off the blade.

Gotta agree with the other replys, except, crap on the blade will cause all kinds of problems. We use plain water because of the trailer tires. Try a little Pam spray on the blade after each cut, before you tear the mill down. Isolate the problem, instead of causing more. ;) ;D ;D ;D

Good to see the mill is starting to perform for you. I know how much time and frustration you put into it. Feels GOOD, EH ???

D._Frederick · June 03, 2006, 12:47:00 PM

slowzuki

If the 1 1/4 blades you are using are carbon steel, you should tension them to 1000 lbs,( 2000lbs on the band wheels).

Check that blade has correct set, should be 0.022 to 0.025 inches per tooth. Check that the teeth have sharp square corners.

Make sure your guides are set correctly. The roller flange that supports the back of blade should be with 0.025 inches with the blade tensioned and turned by hand.

slowzuki · June 03, 2006, 05:58:43 PM

I will go over everything once it stops raining and crank up my tension. I can't hit 2000 lbs, max is about 1600 lbs but will crank it up.

Thanks for the tips everyone! BTW since it is a new mill these are the first wide boards I have been trying to saw, so I'm really dialing it in for the first time.

Fla._Deadheader · June 03, 2006, 08:40:32 PM

Shouldn't matter. Listen to the blade sing and saw accordingly. Blade could be slowing and you need good hearing to tell.

LeeB · June 03, 2006, 10:38:16 PM

I guess good hearing is a relative thing. I never took care of my hearing when I was younger and now am deaf as a fence post but i can "hear an engine or other machinery juist fine. LeeB

slowzuki · June 06, 2006, 08:14:38 AM

We got out to saw a bunch more last night and adjusted the guides and added more pressure.

The waves are now shallower and don't happen on narrow stuff, but I am getting lots and lots of saw dust left in the cut and it is rubbing the blade body since there is a bit of steam coming out of the cuts. Also the cut is leaving a fuzzy face to the spruce.

Can't seem to go slow enough in the wide cuts either, even only going 5 ft a min or so I can bog the saw down. Last year with the same motor and a bit dryer wood we were flying through the same width cuts.

More tinkering to go. Even so we cut about 200 bdft of 6x6 in 2 hours. Frustrating when the log handling takes almost no time compared to the cutting.

D._Frederick · June 06, 2006, 11:38:00 AM

If you have packed sawdust on the boards, you don't have enough set.

VA-Sawyer · June 06, 2006, 12:19:34 PM

From reading back in the earlier parts of the thread, it sounds like you are using 1.25 X 7/8 pitch blades and sawing 16" wide material. If that is the case and you are getting PACKED sawdust on the cant, then I would say that you have too much set or to be more correct too many teeth. Packed sawdust tends to be the result of the gullet filling up prior to exiting the cut. The tooth is still trying to cut, but there is no room in the gullet for the new sawdust so it is forced past the body of the blade and gets packed against the cant. This can also lead to wave problems as the blade seeks the easiest path and the packed sawdust can push it to one side or the other. Having the gullett fill up will also cause real problems with the speed you can feed the blade. You can try to reduce the amount of set so that there is less material removed and therefor less sawdust produced. There is a practical limit as to how much you can reduce the kerf before you get into true binding against the blade body. This will also cause blade heating problems and look a lot like the current problem except you will tend to have burn marks on the cant from the blade body rubbing. You won't have much packed sawdust either as there isn't any clearance for the sawdust to get between the blade body and the wood.
The really proper solution here is to have bigger teeth with bigger gullets so as to have the needed room for the sawdust. I have a few blades that I sharpen with deeper than normal gullets to help when making wide cuts. I run the set on these down around .018 to keep removed material to a minium. I would like to find some blades with a 1" to 1 1/4" tooth spacing for those wider cuts, but then I would have to make new cams so I could sharpen them.
VA-Sawyer

gmmills · June 06, 2006, 11:20:51 PM

VA has given some great advice. All of which I totally agree with. You may want to try a different blade profile. WM has a 13 deg profile that has a taller tooth, deeper gullet, that works real well in softwoods. I have been using the 13 deg blade this week to saw Poplar. These blades allow faster feed rates, with their deeper gullets and more aggressive hook angle, than WM 10 deg blade when sawing softwoods or easy to cut hardwoods.

Brad_S. · June 07, 2006, 07:36:33 AM

With all due respect to VA-Sawyer and gmmills, I've got to go with D. Fredrick on this one. I run a 1 1/2" blade with a 7/8 pitch and routinely cut 20+" widths. I agree you can get sawdust packed in the cut but I don't consider 16" to be all that wide. Too little set will always pack dust but I have never had burn marks in that situation.
The red flag here for me is the fact that slowzuki is cutting spruce which is nasty sawing anyway you look at it. I normally run a 20 thousandths set for mixed species, but if I know I have spruce coming up, I INCREASE the set to 25 or even 30 thousandths.
Leaving a fuzzy face in spruce is also an indication of a less than perfectly sharp blade, and spruce is unforgiving on blade sharpness. That also will cause waves.

slowzuki · June 07, 2006, 08:05:51 AM

A bit more info from last night, I borrowed a tach and an ammeter.

-My 10 hp motor is NEVER drawing more than 27 amps. It should be drawing 50+ amps when chugging at max load.

-My drive belts are slipping, the tach shows an immediate drop as soon as any load is put on the saw.

-Sawdust is staying packed in, I don't have a setter to increase my set with.

-Every tooth has fibers wrapped over them in the gullet out to the tip, it looks like this build up is what is rubbing on the cut not the actually blade body. I'm going to manually scrub them out this evening, they may be stuck in there from the aspen I sawed earlier.

-I rewired the motor to direct start and the rpm of the motor doesn't seem to drop during the cut now, just belt slippage and smoking hot drive pulley.

:P Going to increase the diameter of the drive pulley to reduce slipage. It will drop blade speed but I can up the lower pulley size later.

D._Frederick · June 07, 2006, 07:15:11 PM

slowzuki

If I remember correctly, you are running 2 "A" size Vee belts. They should be 2 "B" size belts running on pulleys no smaller that 5 inches for a 10 hp motor.

You should have your band speed 4500 to 5000 ft per min., that should get rid of some of your sawing problems.

Larry · June 07, 2006, 08:28:05 PM

I've used the Grainger catalog for a long time to select my belts...If anything they are conservative on there ratings. I would suspect your gonna need cog belts which would be BX or maybe AX iffen ya can find em.

And here is the link.

http://www.grainger.com/Grainger/wwg/catalogPDF.shtml

slowzuki · June 08, 2006, 07:36:58 AM

We have some type of success...

A little work on the belts and have temporarily reduced slippage until I can get some better sheaves.

THE MAJOR PROBLEM WAS:

The cookes guides I have include a bottom grab arm thing. I assume it is to help you install bands but if a blade dives it also catches it before it goes over the back. Well it was a bit too long. When my blades dove, they hit every tooth on the bottom side taking the set out and the edge off.

I only found this after scrubing all the build up off the blade to inspect it.

Solution was to bend the blade catcher back so it can't hit teeth.

After that I tossed on a new blade and even with the motor only pulling part power I went from 10 minutes+ per 10 inch wide 16 foot cut to about 2-3 minutes.

After the change, I could then slice the 6" cants into 2x6's at about 1 minute per 16 ft cut.

So I've got two bands to sharpen and reset now due to that, but at least I found the main problem! 8) 8)

rbarshaw · June 10, 2006, 07:22:16 AM

I had the same problem with Cooks guides and just removed the little blade catch and never had the problem again. I should have realized you were using those guides and could have let you know.

slowzuki · July 28, 2006, 05:04:26 PM

More waves...

Have cut a bunch more lumber, got new big pulleys and the drive belts no longer slip. This has sped my cutting up dramatically, 2x faster or more.

Problem is we are back into some knotty spruce and I'm tearing my hair out. When the cut is wide and I go slow the blade dives, if I go fast it rises. I'm gonna swap blades, add a bit of down pressure on the guides and up the tension and check the guide alignment.

I popped a fir onto the mill and it cut arrow straight at full speed, went back to spruce and all over the map again.

I'll update tomorrow.

treecyclers · July 28, 2006, 07:29:59 PM

For what it's worth, I know that when I get amber waves in my grain, it's usually because I am doing 2 things - too fast in the cut, and dull blade with the wrong pitch for what I am cutting.
I slap a new blade that has the right pitch, and I am cooking with gas once again.
SD

Percy · July 28, 2006, 09:43:31 PM

Quote from: LeeB on June 03, 2006, 10:38:16 PM
I guess good hearing is a relative thing. I never took care of my hearing when I was younger and now am deaf as a fence post but i can "hear an engine or other machinery juist fine. LeeB

Uhhhh Pardon me?? Wassat you said?? :D :D :D

joelmar10 · July 28, 2006, 11:05:07 PM

What about Tim Cook's explanation/cure for diving blades. Any veracity to the importance of the flatness of the body of the blade? and is it more critical depending on the toothset, pitch, and gullet size and/or the particular species?

tcsmpsi · July 31, 2006, 02:19:11 PM

I am new to the bandmill sawing method. But, I am not new to sawing with other methods.
Though my mill sawed fine from the mfr., didn't mean it didn't all need to be checked and squared and leveled to my own satisfaction. One of the areas that notably benefited from fine tuning, was paralleling the band to the bunks between the guides. Though it was ever so little (and may not have been to their measurement/tolerance), the blade running flat to the nth degree, increased the possible sawing speed and took any 'faint lines' out of the lumber.

Of course, the blade running flat is only as good as the bunks all matching it.

It would seem to me, that if the blade was angled either up or down, that would have an effect of sawdust not properly being fed from the cut of the tooth, and would tend to make the tooth grab rather than to cut.