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Kerf dips at knots, just a dull band?

Started by Dave Shepard, November 30, 2006, 08:11:56 PM

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Dave Shepard

I am going to be doing some sawing for a guy who has an LT40G24, and there seems to be  a little confusion over efficient sawing practices. The current procedure is to open up a log with a duller blade, so it is subjected to the dirt, and then put on a sharp blade and take a few clean up cuts to take the dips out and finish with the sharp blade. Am I nuts, or is this terribly inefficient? It would seem that it wastes time and wood. Shouldn't I just saw until the blade gets dull? I am sawing white pine for siding and flooring. I would be interested to hear what everybody elses approach is to bandlife. Thanks.


Dave
Wood-Mizer LT40HDD51-WR Wireless, Kubota L48, Honda Rincon 650, TJ208 G-S, and a 60"LogRite!

Tom

Use a good blade until it quits performing.

I use old blades for some of my own sawing.  They are missing teeth from being nailed, but they are set properly and sharp as a razor.

Dull blades not only make for a poor cut, they stress the band and cause shortened life, stress the bearings on the band wheels, put excessive pressures on the guides and cause the engine to work hard.  Swapping blades back and forth regularly for every log is a time eater upper.

Tune the saw so that everything is working at its maximum and drive it until something wears out.  Then tune it back up and go again.  That includes blade swapping.

If his logs are that dirty, he needs to address the problem by cleaning the logs, not bulldozing the dirt.

(If he is paying you by the hour then it doesn't matter) :D


SAW MILLER

    I use to tell myself that I ain't gona change that blade already cause I just put it on,but...Now when I am into dirty logs I will put on a sharpy at the first sign of  knot dipping.I don't care If it only sawed one pass..you can't make good footage or good lumber with a dull blade.
  Now..after saying that,If I am going to change real soon,I may take one pass at the next dirty log then change but no way am I putting on a dull blade to open up each log. ::) ::)
LT 40 woodmizer..Massey ferg.240 walker gyp and a canthook

kderby

Good answer sawmiller.

I agree that a sharp blade is an essential source of quality.  The price per board foot sawn per blade is astonishingly low.  In other words,  blades are cheap for what you get from them.

As was just stated by SAW MILLER..."You can not make good footage or good lumber with a dull blade." 

Amen Brother!

KD

Left Coast Chris

Since I don't have a debarker I attempt to let logs sit for four to six weeks to let the bark loosen then use a bar to take the bark off prior to sawing.   It works well on green white oak in hot weather and even fir and walnut.   I do seal the ends of the logs to prevent spliting and keep an eye out for borers.

Regarding the dull blades and a wavy cut........as a sawyer attempting to do good work it is a bad experience that is one to avoid.      I can usually sense the resistance to cutting before it starts to get wavy and change out.  :)

Home built cantilever head, 24 HP honda mill, Case 580D, MF 135 and one Squirel Dog Jack Russel Mix -- Crickett

woodmills1

As stated I think you will find that the blade cost per foot of lumber cut is very low, especially if you sharpen your own.  It is kinda hard to push a dull blade, once it begins to wander there is no telling what it may do next, like take a huge dive on the next pass.  The only time I use one blade for opening and another for finish is if I am making someting like large timbers and have agreed up from to make them as square and nice as possible.
James Mills,Lovely wife,collect old tools,vacuuming fool,36 bdft/hr,oak paper cutter,ebonic yooper rapper nauga seller, Blue Ox? its not fast, 2 cat family, LT70,edger, 375 bd ft/hr, we like Bob,free heat,no oil 12 years,big splitter, baked stuffed lobster, still cuttin the logs dere IAM

Norm

Until I got my own sharpener I was guilty of running blades too long. Not only did the quality suffer but it was also aggravating. Now if I hit a pocket of dirt inside or miss something with the debarker I change to a fresh blade no matter how many bd ft I've sawn. I can sure tell the difference when I run it through the planer too.

treenail

In my experiences, down time from running dull blades , really cuts into the production.  Takes a lot less time and energy to just keep a sharp saw on until it needs changing, and the quality of those first cuts will be an awful lot better too. I sharpen my own saws, and they last a lot better if I don't push them when they are dull
Norwood Lumbermate 2000 sawmill , Ford 4wd tractor,Grimm/Leader maple sugaring equipment, Ford F-350 12' flatbed truck

woodmills1

James Mills,Lovely wife,collect old tools,vacuuming fool,36 bdft/hr,oak paper cutter,ebonic yooper rapper nauga seller, Blue Ox? its not fast, 2 cat family, LT70,edger, 375 bd ft/hr, we like Bob,free heat,no oil 12 years,big splitter, baked stuffed lobster, still cuttin the logs dere IAM

TexasTimbers

When my blade is dull and I hit knots the blade doesn't dip it rises up over it. I didn't know they had a tendency to dip rather than rise, but from reading this thread it seems that way for most others.  ???
Even when I hit a knot below center or under the angle of the knot, it rises. I don't know that I have ever noticed dipping other than waviness in the log itself due to adjustments needed or dull blades.
The oil is all in Texas, but the dipsticks are in D.C.

Dave Shepard

I'm sawing white pine, I don't know what you are sawing, but I am definately getting a dip when I go over the knot. I know it is from dull blades, but I am having a hard time convincing the boss that it makes more sense to just run a blade until it is dull and switch. Right now we are opening up the log with a dull blade and then taking trim cuts with a good blade and making the boards. I'll be able to bring him around when I explain the cost analysis of  1.8 cents a BF for blades and what he's paying  me an hour to change blades and make a large slab heap. I made 500 bf of 5/4 boards 14"-16" wide by 12' long in 4 hours this afternoon. I think I could increase that significantly if I was using good blades the whole time and not making so many cuts just to throw them on the slab pile. I must say it takes some horsepower to spin a 30"+ log that is 12' long without hydraulics. But when I pull on the peavey, somethings gonna move!


Dave
Wood-Mizer LT40HDD51-WR Wireless, Kubota L48, Honda Rincon 650, TJ208 G-S, and a 60"LogRite!

Tony

      Like some I tried to get every bd.ft I could out of each
blade (didn't charge extra for the scalloped design I put in
the board) ;D Now I change blades at the first wobble,
increased efficiency and decreased downtime 8)

      As for the dirty logs.After cleaning what dirt I can off and
making the first cut, I try to keep  the open face toward the
blade. With the TK it is easier to turn the open face away from
the blade and cut dirt again, but a little cant hook workout never
hurt anyone :D ::)   One log, one dirty cut ;D  But I'm still
learning :)             

                                        Tony    8)

TK1600, John Deere 4600 W\frontendloader, Woodmaster718 planer\moulder, Stihl MS461 Stihl 036 & 021 & Echo CS-370
"You cannot invade the mainland United States.  There would be a rifle behind each blade of grass."  Adm. Isoroku Yamamotto ( Japanese

slowzuki

I used to try and push the dull blades too, and you can do it in knot free wood but the fuel use goes up, quality goes down, and swear word use becomes rampant when you have that first monster dive.  In knotty woods the feed speeds drop to a crawl and production is pathetic.

I don't have a sharpener yet but have just been buying new blades to stockpile for sharpening.

derhntr

Dave,

Like you I cut my teeth on white pine, I cut around 12,000 bft this spring. I found many different things effect how the blade cuts, yes I pushed the blade to the max at first. But dull blades were not the only thing that would cause a dip or rise at a knot.

I was using the standard WM 10 degree blades (have not tried the 13's yet) Feed speed had a factor too. To fast and I would get a dip or rise at a knot.  To slow and I would get a wavy cut. I have had dips with brand new blades too.

I talked with a local guy that cuts a fair amount of WP and offered 2 suggestions 1. increase the blade set to .025 and 2. increase blade pressure to 2500 psi. NOTE:(this is above the ranges posted in the WM's owners manual) Try at your own risk. However I tried it and wow what a difference.

I don't know what you are running for lube, but dirty blades effects the cut too. I was running just water and dish soap. After some cuts I would have to turn on the lubemizer full blast just let that clean the blade for a few seconds. Dirty blades cause the band wheel belts to become caked with sawdust and pitch. I cleaned the belts at every blade change.

These are just my experiances with WP. I love the smell of pine and the look of a 24" cant laying on the bed. I have about 6,000 bft of WP to take down, trees up to 28"

Good luck
Brian
2006 Woodmizer LT40HDG28 with command control (I hate walking in sawdust)
US Army National Guard (RET) SFC

WH_Conley

Slowzuki, I did the same thing and would not advise it. It is difficult to store used blades for a long period of time without rust. With the rust on the blade you can not set them accurately, so the first time all you can do is sharpen. Course by then you don't remebmer if a given batch was in rocks or what. Had a guy give me a box of 10 blades a few months back, all I could do was sharpen and put on the mill, some of them never made it through the first log before taking them off. All of that said I wound up 150 used blades before I bought my sharpener and setter and sawed several thousand feet before buying any new blades. The box of new blades I am using on now has been on the mill several times, sharpen easier, set easier(no rust, which makes it harder to get the sap off). All said, if anyone is trying to round enough dull blades to justify buying a sharpening outfit I beleive that it is false economy.

I now run .045 blades, 10 degree hook, .020 to.025 set at 3000PSI. Just as fast as the motor will pull without stalling. Might not work for everyone but in my situation it seems to be the best combination.
Bill

Dave Shepard

Thanks for the insight. After a little convincing, I have been given the go-ahead to do whatever I feel is going to work the best. Now that the boards are piling up he just comes in the mill builiding, smiles, and leaves me alone. I made a little better  count of the footage for Saturday and it was more like 300 feet. Yesterday I cut just under 800 feet in six hours and I also had an 18" square cant and a pile of jacket boards waiting for tomorrow.  I think that wasn't to bad considering material handling is poor the way it is laid out. I did not change any bands. I started with a brand new band and it was still cutting fine when I stopped. I did log-wizard the opening cuts, which I attribute to the long blade life. I also think I could make a lot more boards if I was working with smaller logs. It seems to take forever to get a 32" log squared up, but then it goe very fast once you have it canted out. I also found the winch log turner to be invaluable on these large logs. We use diesel for lube, but I have not really been using it much. The logs are old enough that the bark is falling off and they don't seem to have a lot of pitch in them. If I do see any build up I turn the lube on for 5 seconds and the blade cleans up like new.


Dave
Wood-Mizer LT40HDD51-WR Wireless, Kubota L48, Honda Rincon 650, TJ208 G-S, and a 60"LogRite!

Furby

Quote from: Dave Shepard on December 04, 2006, 06:17:39 PM
I also think I could make a lot more boards if I was working with smaller logs. It seems to take forever to get a 32" log squared up, but then it goe very fast once you have it canted out.
:D
I'll trade ya!


Minnesota_boy

If the logs aren't really dirty and you're getting paid by the board-foot instead of by the hour, skip the log wizzard and replace a band a little sooner and you're likely to end up with plenty more board-feet to justify that extra band sharpening.  Keeping the saw in the wood gets you more production.
I eat a high-fiber diet.  Lots of sawdust!

Dave Shepard

I am getting paid by the hour, so I am trying to get the most footage, but also not blow through a box of bands every day. On this last order I sawed just over a 1000 feet of 5/4 wide (14-18 inch) pine boards before I noticed that it was taking a little more feed pressure to maintain the cutting speed. The cut was still smooth, but I could notice a very slight gap under a straight edge near some of the larger knots, so I put a new band on. After trying to take the top off one of the backstops, (the first one's free, right? :-[), I put the first band back on and sawed out some hemlock. The hemlock sawed out so smooth it almost looked like it had been planed, and this with almost 1200 feet of sawing on the band. I have a stack of flitches to edge tomorrow, and maybe some more hemlock, so I'll see how long I can go before I need to switch. The hemlock also did not seem to need as much power, despite the fact that I could feel the difference of the dull band in the pine. I feel at this point the wizard is a viable step in the sawing process. I only wizard a narrow spot to open the log, so it really only take maybe 20 seconds for each opening cut. That's about a minute a log, it takes a couple minutes just to change a band, so I think it works out OK.

All in all I think I am making out OK, I only have about three days of sawing under my belt, and running this mill feels like I have been doing it forever. I felt a little intimidated at first. I didn't think I'd be able to figure out how to open a log at the right hieght and end up with the right size final board without making a trim cut, but now I can take a couple of boards off the outside and end up with a perfectly sized timber on the last cut. These timbers are going to be great to work with as they are perfectly square on all the corners and are the exact dimension. The timbers I have worked with before you would have to try and pick which two sides seemed square enough and then try to do your layout off of them, but with these I can pick the sides that will give me the best layout.

Thanks to everybody who stops in to give my pointers, it has made milling easier for me. I am definatley hooked, and hope to have my own mill soon.


Dave
Wood-Mizer LT40HDD51-WR Wireless, Kubota L48, Honda Rincon 650, TJ208 G-S, and a 60"LogRite!

derhntr

Dave,

Sounds like you are having a good time sawing. Are you flat sawings your cants top to bottom or are you flipping your cant after a couple cuts? I always seem to have to make a trim cut.  I have started taking 4x4 out of the heart of the cant. I have been making some pretty good boards.

Cutting for my own use I had no number of boards I need to have, so I could cut how ever I liked. We were fixing up a 125 year old barn, The old siding was 12 to 16 inch 4/4 pine. However we had more boards that were in the 8-12 inch range to use for replacements.

I sawed a lot of cants top to bottom to get the widest boards, and the most I could out of each cant. You can make a lot of production that way, but not the best quality. The siding was put up green as they used to in the old days, so we did not have to worry about cupping and warping.

When I got to the #1 logs, I flipped the cants alot to get the best looking/quality boards. Some flips were 180 degrees and some were 90 degrees. I was not cutting for a order so I was not forced in to cutting what the logs did not offer. Each log is different. With all the flips I end up a lot of times with a trim cut. But great looking boards.

Good luck and have fun

Brian


2006 Woodmizer LT40HDG28 with command control (I hate walking in sawdust)
US Army National Guard (RET) SFC

Dave Shepard

Brian, I basically try to get the widest cant I can and also to try and get a few wide flitches out of the opening cuts. I'll give a step by step of how I am sawing.

First, I try to set the log on the mill so that I have the flattest side up, the logs I am sawing sometimes are far from perfectly round. I set the saw at an even 5/4 mark on the scale board and start slabbing until I feel that I have a decent width face, then I flip it 1/4 turn. This face I also start on an even 5/4 mark and take boards until I have a square edge on the two open faces, unless I have to take out to much wood from the ideal cant, then I just get it as close as I can. Flip 1/4 turn. Here I change tactics a little. I take my tape measure and try and decide what even width (i.e. 12" 14" 16" etc.) I can get from the cant. Say it is 14" I then move the scale until one of the 5/4 marks line up with the 14" mark. This way I know that I will end up with exactly 14" in width for my cant. After I get to the 14" I flip it the final time and set the scale so that a 5/4 mark is equal to 0 and then I saw straight to the bottom of the cant. This way you don't end up with any trim cuts. If you wanted to take some 4/4 and 5/4 boards off the outside, you would really have to plan out the exact sequence starting with the third open face. I then stack the flitches on the mill and edge them out to even whole inches. This is a flooring order, so I don't want to end up with ten different widths, so even if I could get say 15", I will make it 14", if there are to many different widths, the installer will have to rip them to more consistent dimension anyway. The logs are from land clearing and construction, so we don't pay for them, we have to haul them off the job anyway, which is what inspired the mill in the first place, so I just make as wide a board as possible and don't worry about flipping them. If there is  a defect I will just edge down to it when I am edging the flithches.

Your are right, I am definately having fun. I have been trying to get my own mill for many years now, so this is a great opportunity to learn on someone elses dime. I have been sawing for only about a week and already I feel very comfortable running this machine. I can't wait for tomorrow!


Dave
Wood-Mizer LT40HDD51-WR Wireless, Kubota L48, Honda Rincon 650, TJ208 G-S, and a 60"LogRite!

Duncan

I have had several problems with snaking of the blade. 

blade related problems:

1. Set
2. Dull

What causes blade related problems?

1. Rocks
2. metal
3. occasionally I will push a blade too long.

Other problems:

1.   Biggest blade tension I run an LT70 and the 51# that was orignially set.  I have run from 65-75 for about the last 400 mill hours and the occasional increase in blade breakage is easily justified by the improvement in cut and blade lifetime.
2.  blade guides must be properly set.

just running the blades from start to finish is the most efficient way to operate your mill.  However I do not have experience with blades less than .055".  I have cut occasionally with a friend's lt40 and would have to recommend that you run the thickest blade that your wheel size will allow.  I have had more problems with 13 degree blades on western red cedar snaking at only 2-300 board feet but have had much better luck with 10 degree blades on that species.  For hardwoods I only use 10 degree.  However I have on severe moments of lazyness left a 13 degree to cut a board and it can get a little hairy cutting white oak because it will occasionally self feed. (:
Kelly

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