feed rate

[Dan_Shade]

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? 

[MartyParsons]

Saw as fast as the blade will cut and the engine will pull without changing blade speed.
Marty

[Dan_Shade]

what should the blade speed be, Marty?

[Tom]

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.

[Dan_Shade]

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).

[Tom]

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. 

[MartyParsons]

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   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

[Dan_Shade]

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.

[Ron Wenrich]

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. 

[eamassey]

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   

[Tom]

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. 

[Brad_S.]

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!

[Dave Shepard]

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

[Percy]

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 ), 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.

[Ron Wenrich]

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. 

[Tom]

Do 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.

[LeeB]

After a number of sharpenings the hardened tip also gets sharpened away and the blade won't stay sharp as long.

[mike_van]

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.

[Tom]

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. 

[Dave Shepard]

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