Another wavy cut question

AnthonyW · June 08, 2015, 11:17:18 AM

This weekend I was milling some eastern white pine. I loaded up a monster (to me) 32" diameter 17' long log. I could tell this log would not have any clear wood so I decided at the beginning to cut it into 2x4s. I cut the flitches to be edged and placed on saw horses. I then cut two 4" thick planks and placed them next to the cant. The measurements work out such that when I dropped down 2", I would cut two 2x4s and a 2" plank. With the two 4" planks next to the cant, The saw head was at max width, the blade guard was all the way out and just fit. The cut was very wavy. It hadn't been on the previous pass. I then removed the two 4" planks, dropped 2" and tried again. Smooth and level a cut as I could expect. I then added the two 4" planks back and tried it again. Again a wavy cut. I removed the 4" planks and finished cutting the cant at 2" increments. Every cut came out fine. I cut the 4" planks by themselves and came out smooth. Any thoughts why at 16" it cuts fine and at 24" the cut is wavy?

terrifictimbersllc · June 08, 2015, 12:14:20 PM

Cutting wider widths flat is more challenging than narrower ones. Things that contribute to waviness (less than total sharpness, inadequate drive belt tension, inadequate HP for the feed rate, hard knots in softwood), show up first in waviness at the wider widths.

Because of bark and dirt, keeping the outer wide boards flat when opening up big dirty logs is always challenging.

AnthonyW · June 08, 2015, 12:20:31 PM

Once the cant was made, the blade was changed. The blade was a brand new woodmizer 10 degree. The feed rate was not fast from the start. I could not keep the RPM up (I find it likes to run around 3200 RPM) right from the start without slowing down the feed rate. If available and it fit, would a 1 1/2" blade help?

LeeB · June 08, 2015, 12:38:12 PM

More blade will want more HP to pull it. If it was bogging on you real bad you were losing blade speed and therefor getting the wavy cut. 24 " is a pretty big bite even for a higher HP engine.

AnthonyW · June 08, 2015, 12:44:35 PM

Even with a 8" cut, I can bog the engine down. Especially with the 10 degree blades.

I made the 24" cuts based on engine RPM, maintain 3100-3200 RPM. Knowing the cut was wide, I knew from the start it was going to be a long slow cut. I kept the feed rate as steady as I could.

I even contemplated getting from 4 degree bands, but I don't think I will end up cutting this wide to warrant having a box of them on hand.

Den-Den · June 08, 2015, 02:01:04 PM

If you can bog the engine down in an 8" wide cut; you need more hp or a slower band speed to better utilize the existing hp.

terrifictimbersllc · June 08, 2015, 02:04:06 PM

I didn't know your HP. Even at 42HP I don't take wide flat cuts for granted. When I see I'm going to be making a stack of 16-24" boards, often I'll square up a log to a clean cant a bit oversize with one blade, then put on a freshly sharpened blade (for pine I'll use a 7 degree) to make all the final cuts. Mine are all 045/1.25" Woodmizer blades, I've never used others. Myself I wouldn't expect good results from a 4 degree blade in wide knotty pine unless maybe it were dried out to the point of cracking.

I like to use my Logrite aluminum scaling stick to wipe sawdust off every few cuts in wide material, sometimes every cut with very valuable wood like wide natural edge slabs, it acts as a straightedge scraper, if you will, and I can easily see if the cut is crowned at all or if there are any waves.

Magicman · June 08, 2015, 02:07:29 PM

You were adding 50% more unsupported blade length inside of the wood. When a blade is pushed back, the flat blade has to either stretch or ripple. A new/sharp blade is affected less because it is pushed back less. The flanges on the blade guides stop this rearward movement but they must have the proper horizontal tilt to keep the blade from catching on the flanges and fluttering.

AnthonyW · June 08, 2015, 02:08:50 PM

I would love more HP (only have 15HP Kohler), but I would not want to crank up a heavier engine. I can run the 7 degree bands much better. IMO, because there is less bite or less tendency to take too big of a bite as compared to the 10 degree blades.

My comment on bogging down in an 8" cut was somewhat tongue-in-cheek, it is possible. But I either must really be trying to go too fast or really not paying attention. Other than 2x4 and 2x6, I try not to cut 1x narrower than 8". I just do not find the use for it.

I did some (very expensive) experiments yesterday. Both resulted in killing a blade. The more interesting of the two will get its own thread once I get some photos of the teeth or what is left of them.

AnthonyW · June 08, 2015, 02:09:18 PM

Quote from: Magicman on June 08, 2015, 02:07:29 PM
You were adding 50% more unsupported blade length inside of the wood. When a blade is pushed back, the flat blade has to either stretch or ripple. A new/sharp blade is affected less because it is pushed back less. The flanges on the blade guides stop this rearward movement but they must have the proper horizontal tilt to keep the blade from catching on the flanges and fluttering.

To the best of my ability, it is set per the manual in every aspect.

Magicman · June 08, 2015, 02:34:45 PM

As terrifictimbersllc mentioned above, even with a properly tuned sawmill, sawing wide with a less than sharp blade can cause wavy lumber (when the blade is forced back).

AnthonyW · June 08, 2015, 02:43:29 PM

Quote from: Magicman on June 08, 2015, 02:34:45 PM
As terrifictimbersllc mentioned above, even with a properly tuned sawmill, sawing wide with a less than sharp blade can cause wavy lumber (when the blade is forced back).

Brand spanking new blade. I hope it was sharp when I installed it.

Would changing to a less aggressive blade and keep the RPM would be more effective than changing to a 1.5" blade?

Chuck White · June 08, 2015, 02:46:09 PM

Yesterday I sawed an undesirable 12-14" Spruce "Yard Tree", there were knots about every 4-6" going up the log, so I knew it would produce wavy cuts.

I made the opening cut at my usual sawing speed and man was it wavy.

I dropped 1/2" and about 1/2 to 2/3 the feed speed and it cut just as flat as the bunks on the mill.

I kept this speed and sawed out some beautiful 2x6's.

I was using a freshly sharpened to 8° Wood-Mizer Double Hard blade.

Best advice I can give is use a sharp blade and slow down.

A new, off-the-shelf blade can be dull, due to handling during shipping.

millwright · June 08, 2015, 04:12:10 PM

One thing to check is engine rpm, I have a 15 hp kohler on a little tractor and it is supposed to run at 3600

sandsawmill14 · June 08, 2015, 06:19:46 PM

the 1.5 blades made no/very little difference for me on my b20. i actually like the 1.25 blades better. from what i've heard going to .055 blades helps but have never tried them.

bkaimwood · June 08, 2015, 07:15:37 PM

Bunch of very good points made so far...an 1.5 inch blade will help, but ONLY if you have the HP to turn it...a .055" blade will help, but ONLY if you have the HP to turn it...you wouldn't believe how much going up in .005" blade thickness makes...in terms of power needed to spin it. Next, I wouldn't use anything more than an 8 degree rake on such a log, I run 7's. Lastly, take special note to your dust...it should be heavy not fine, with little kerf marks. Heavy kerf marks and fine powder says feed rate too slow. Many think that tough logs and wavy cuts justify slower feed rates...in many cases, this actually makes it worse...the blade gets warmer, losses tension, and multiplies the problem and confusion. Bottom line, if you have the HP and blade to do so, don't be scared to run it...the worse you'll get is another wavy cut, and eliminate one more thing. If you don't have the HP to do so, and all else fails, maybe its a firewood log. Poop happens. Disclosure statement: this information was derived from experience on both of my diesel bandmills, results may vary from other mills and operators.. I've only been sawing for over a year, but try my best.

AnthonyW · June 08, 2015, 08:02:28 PM

Quote from: millwright on June 08, 2015, 04:12:10 PM
One thing to check is engine rpm, I have a 15 hp kohler on a little tractor and it is supposed to run at 3600

I have a Hardline Tach/Hour meter on the motor. Mostly for the hour meter, but the tach is a nice benefit. That is how I can monitor and quote what RPMs I am running.

AnthonyW · June 08, 2015, 08:09:41 PM

Quote from: bkaimwood on June 08, 2015, 07:15:37 PM
Lastly, take special note to your dust...it should be heavy not fine, with little kerf marks. Heavy kerf marks and fine powder says feed rate too slow.

My father noticed the consistency of the sawdust from my LT25 is very much different than my uncle's. I'm not sure which mill, manufacturer or model he has but I know it is big and diesel powered. His sawdust resembles chips from a dado blade or router table, perhaps the finer chips from a planer. My sawdust when cutting EWP, independent of blade angle, speed, or cutting width, is about the same as course beach sand both in look and feel.

I can easily understand how a thicker blade would take more HP to run. Thicker band = wider kerf = more material to remove = more HP required. Now that I realize my blades are 0.045, I wonder if there is a thinner blade I should be using. Did I see an option for a 0.042?