another feed rate question:
My daily production is a little on the slow side, i figure my feed rates are slowing me down. I have a tachometer on the saw, I try to keep the tach at around 3550 or so (kohler 25hp). of course as the band dulls, I have to slow down, I may be going too long between blade changes, because when I swap bands, it's always like "wow, this thing is flying and cutting great boards again".
Is it best to push the saw as hard as it will go and still cut straight? or is it best to back off a little?
Saw as fast as the blade will cut and the engine will pull without changing blade speed.
Marty
what should the blade speed be, Marty?
My 24 horse Onan would be comparable . I drove the blade until the motor began to bog a little and then backed off some. That was my rule of thumb to be compensated by wavy grain or knots that required special attention. I listened to the engine, didn't watch a tach. I guess either will work.
As the blade dulls, it finds more resistance and the forward movement must be slowed.
I usually began finding that point at around 600 board feet. That just goes to show how blades changed. when I first started, I would find this point at about 300 to 400 feet.
You can learn a lot by watching the sawdust. It starts off in big chunks and turns toward powder as the blade dulls. Your sawdust pile keeps getting closer and closer. Change blades and you start kicking it out there again.
you lost me, Tom, do you mean if you have the shute up? my sawdust goes down in the same spot regardless (at least from what I've noticed).
I became sensitive to the distance the sawdust left the chute on my 90 mill. Yes it does hit pretty much on the same place, but as the blade dulls, it begins to get into the area where you are walking. Perhaps that isn't a good way to judge on the newer mills. You may still be able to tell about the size of the "curl" on the sawdust. When the blade is new and sharp, the curl is large and intact. When the blade begins to dull, the curl is more scraped away and becomes more powder like. pretty subjective, but it's still something to look for.
I do not know the blade speed to be exact. Tom pretty much explained how I run the saw. I listen, look and feel. On normal density wood you should be getting about 500 to 800 bd/ft per sharpening with a Debarker or logs debarked. With out a debarker you could be 250 to 500 bd/ft per sharpening. So the Debarker pays its dividends quickly. On Ash Hickory Seasoned White Oak etc. the results will and may very. The heavier the blade the faster and longer you will saw. ( Flex Life will be lower but you will get more done in the same amount of time) The thinner the blade the more the blade can move think wavy. but the flex life will be longer. It realy does not effect how sharp the blade is. The thicker blade will cut better when the edge is getting dull.
I go by all the senses there is times I turn the feed rate up and the cuts are :o and there are times I can feel the saw blade change speed and know there are wavy cuts. I will need to pay more attention the the sawdust. Thanks Tom!
Marty
it seems i'm getting a lot of jobs for white oak that's been down since Isabel (whenever that blew through here)!
those hard logs are testing, I suppose!
Thanks guys, i'll pay attention to the sawdust too. I've looked at it before, but couldn't really tell what I was looking at, it all seem pretty fine to me.
If the band saws are similar to circle saws, you will find that different species will give you different types of dust. The harder species usually give finer dust when you have a sharp blade then the softer species.
But, no matter what the species, your dust will get finer as any blade gets dull. The problem with fine dust is that it doesn't fit in gullets as well as coarse dust. The spillage can push a blade.
If you go too slow, its the same as sawing with a dull blade. Your dust will be fine, since you aren't taking as big of a bite. You'll have spillage problems in the gullet.
I have always listened to my saw. It tells me if I'm feeding too fast or if I'm getting dull. I'm pretty sure the same goes for a band saw as with the circle mills.
Hello,
I have no sawing experience but considerable machine design and build experience.
(I have a mill about 2/3 built.) It seems reasonable that I should want panel gauges that tells me "carriage speed" in feet per minute, and "blade speed" in feet per minute. This is easy to do. All it takes is a proximity switch on a shaft feature, gear teeth, sprocket teeth, etc, fed into a scalable electronic rate indicator. Do the current model mills have these features? Also, I think that the amp draw on the carriage motor and on the blade drive motor (assuming electric) should be on gauges on the main operating panel. This kind of instrumentation become how you run a machine, although sounds, sawdust appearance, etc. still count.
eamassey
I'm sure that gauges will help some people to operate the saw. They probably have more worth when doing random tests on blades or configurations.
If I had gauges I would want them to be analog so that I could arrange the needles to all be in a certain configuration when I was at optimum.
Sawing with gauges, though, would be like driving a car and not using the windshield. I think that the more a sawyer gains experience with his machine and isn't thinking about the little individual things, he and it become one. Things happen and you can't rightly tell exactly what happened. You tend to react to your machine and it tells you, by sound and feel, whether it is happy. There is an art here that just happens. It's known to almost all machine operators. Ask a bulldozer operator or a farmer pulling a plow. "I don't know, I just do it", they will probably say.
Since I've been messing with sawmills, folks have always tried to make it a science. They want to push this button, set this knob and get 2x4's. I've never known it to work quite like that. Speeds, production, lumber.... they are all dependent on so many different things. One sawyer will do one thing and another will do something else. Neither are necessarily right, nor are they wrong. It's like painting a picture. Is one artist better than the other? "Usually it boils down to What do you consider better?" Even the log can make a difference and no two sawyers can have the same log.
What one sawyer can give to another is a starting point. From there they develop their own style. You are considered good because what you do works. That doesn't mean that it is the only way to do it.
There have been times that I wished I had gauges. But the times are so few that It would probably be a waste of time for a manufacturer to offer them as standard. Some gauges are necessary. I don't especially like idiot lights for charging or overheat or oil pressure. You really are better off with those kinds of gauges. Tachometers tell you a world of information. hydraulic pressure gauges are nice to have. I'm not so sure that other systems wouldn't be anymore than something to clutter up you mind and would eventually be ignored. :)
With all due respect, IMO, having a battery of gages and meters and whatnot would be way too distracting and may in fact detract from proper sawing rather than aid it. I personally don't care how many feet per second I am sawing or what the blade speed is when I'm sawing. As mentioned, listening to the engine and watching blade performance tells everything you need to know. Sawing by meter readings just doesn't sound efficient.
Edit: Tom posted while I was writing and, as usual, says what I'm thinking in much more eloquent terms! :D
I agree Tom. I saw by ear. The WM mills us a feed speed knob. I can usually guage how sharp the band is by how far I have to turn the knob to achieve the desired feed rate. Guages may help from a diagnostic standpoint, but I don't think I'd use them much once I have run a mill for a while. It's kind of like shifting a truck, you do it by "feel", you pretty much already know what your RPMs are without looking. Ron brings up a good point for bandmills, and that is filling the gullets with sawdust. I have been in a situation on a wide cut when it is better to push the feed a little harder to get a smooth cut. Dull bands are a big problem when you are trying to make a 24" wide cut, this is when things get very wavy for me.
Dave
From a production stand point, Ive learned that as soon as the blade loses its WOW factor (as you put it earlier in this thread :D), I change blades. It means alot more sharpening but production rises in the same amount of given time, even with the extra blade changes factored in... Not what everyone wants to do, but it sure works for me.
On the circle mill, I notice that when my teeth get short from sharpening, they won't stay sharp as long. Some guys will take teeth down as low as they can, but I usually toss them when they start to lose me production. Do bands have the same problem with production and shorter teeth?
As for gauges, I don't have one yet. But, I believe I will put one on that tells me my feed rate, kind of like a speedometer. I do have it that I can now push a button and get a board, hands free. Repetitive motion is pretty tough on sawyers.
What I can now do is push a few buttons and saw straight through a stack and pull boards of different thicknesses down to a target size, all hands free.
QuoteDo bands have the same problem with production and shorter teeth?
Yes, bands suffer drastically from short teeth, but it is a different scenerio. Bands should be gummed out every sharpening or two to keep the gullet deep. This keeps the tooth tall. The problem with bands comes when the operator sharpens only the tooth. That is more common in manual sharpening sessions or when the cam of an automatic sharpener doesn't fit the tooth configuration. Speed and performance are drastically reduced.
After a number of sharpenings the hardened tip also gets sharpened away and the blade won't stay sharp as long.
Can the people with gas or diesel bandmills hear the blade cutting, or is it drowned out? I can hear mine well with the electric power, it gets noisier the duller it gets. There's just a point when it's time to change it. Just from the years I've got a good idea when the noise means check a few teeth & sure enough, they've lost that edge they need. Somewhere [I can't remember though] I read that any tool or blade that cuts wood should be sharpened BEFORE it's dull. Everyone knows how hard you work with a dull chainsaw, or one thats nicked a rock - The same has to apply to the bandmill, sharper is always better.
Yes, you can hear the blade over an internal combustion engine. Maybe not from as far away as an electric, but you can hear it enter the log. It's when you hear nothing or a slight hiss that you know the blade is right.
That's what is great about the mills that you walk alongside. You get all of the senses tickled. :D
Tom, I agree, I wouldn't get a remote mill unless I intended to have a very high production operation (LT70). I like being near the action.
Dave
On my band mill, I have an ammeter on the drive motor that tells me how hard the motor is pulling and a scale on the potentiometer that controlls the feed rate. I keep the current draw at the motors rated current, then reduce the feed rate as the blade gets dull. You can tell pretty close how the blade is holding up.
As usual, Tom is correct. I learned the sawdust size deal when I was cutting a jillion board feet with an Alaska sawmill set up....fine dust equals dull chain...Of course a lot of things are happening at the same time....That's why I enjoy walking with my mill.. I only have a 16 hp Kohler, but I can hear what is going on.... and practice, practice, practice....
final note (from me)on gauges, instrumentation.
Tom, I am a bulldozer owner/operator and a farmer. I have a 54 year old Cat D6 with only oil pressure and temperature gauges. But I also work on other equipment that has so many sensors that it takes a computer to check all the sensors and decide if there is anything going on that is important. The question is always first, what instrumentation will help the operator function in some way, and then, how can it be arranged to not be self-defeating?
If I can ever get sawing, I will post a picture of my control panel--.
I used to saw slow and cautious. A couple of years back Tom mentioned pushing the saw just to the point where the motor was about to bog down -- I figured my wood was different and that wouldn't work for me.
Sometime this spring I realized that when I cut slowly, each tooth would make more cuts going the length of the log (duh). That means the blades would get dull quicker. So I finally took Tom's advice and pushed the cutting speed right up to the max. Whaddaya know - straighter cuts, longer blade life. :)
My first two years cutting, I tried to hear the blade, but all I could hear was the roar of the motor. Then suddenly I began to notice when things were going wrong with a blade. Took me a few weeks before I realized that I could now hear the hiss of a blade cutting smoothly; it was the change in the hiss that was grabbing my attention. So you can hear the blade, once your brain learns to pick it out from the background noise.
And you can definately hear the blade after it hits hardware. >:(
Dave
The blade speed on a 25hp LT40 standard hydraulic is approx. 5330 SFPM. Which means your 158" blade will make approx 405 complete revolutions per minute.
Sparks, what is the pulley sizes on the engine and drive wheel?
also, isn't optimum blade speed a property of the band more so than the saw?
Engine pulley is 4.00" pulley and the pulley it drives is 12.00" pulley.
so the engine RPM should stay above 3200 then? my engine seems to start bogging at 3400... maybe i'm not pushing it hard enough.
I took Suffolk Machinery's advice and up-sized the engine pulley on my 16 HP B & S (LT30) to 4.25" dia. At 3381 engine RPM I'm driving the band wheel 1127 RPM which equals 5601 ft./min. I'm using 1-1/4" X .045" Wood-Mizer blades and the only time my cuts aren't perfect is when I'm feeding too slowly.
Correction to my previous post: My engine RPM is 3181 (or thereabouts).
One way I can tell when my blade starts getting dull is the hydraulic tensioner. As soon as it starts droping and needs more tension seems like the blade is up for a change out.
Also if the tension keeps going up periodicly, and I keep turning it back down, a breakage is on the horizon.
A stable 2000 pounds seems to be the magic point for me.
I wonder if I should up my pulley size? I need a tach to see what's going on.
Seems all are in agreement that blade speed is the secret to feed speed for quality and production. So...why not directly check the blade speed? I'm using a bicycle speedometer, ($10 from Wal-Mart) as suggested by another member some time back to measure blade speed. I've found when the blade in the log, drops below 4,100 SFPM with my mill its going to wave. As the blade dulls my feed slows...but the constant is my blade speed is never allowed to drop below 4,100 SFPM. The bicycle thingy seems to be more accurate than my ear, tachometer, and or voodoo to adjust feed speed. Granted, most times I depend on my ear, but as soon as I hear the engine start to lug I'll glance at the speedometer...quite often when sawing wider than 12".