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Author Topic: How the blade cut the log.  (Read 556 times)

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Offline Pabene

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How the blade cut the log.
« on: October 06, 2017, 02:27:45 pm »
How does it work when the blade cut the log?
(I have the opinion, if the cut would be wavy or the surface finish is bad, you have made something wrong by your self.)
When the blade cut the log to boards, it is a cleave operation. Unfortunately there are usually limbs in the log. If the boards are flat sawn the blade will hit the limbs and it has suddenly to cross cut the limbs. Assume the blade has a hook angle of 10°, it performs very good, as long it cleaves the wood. To cross cut the limbs in a good way would need a blade with about 0° or negative hook angle. If the limbs area is, say 25% of the board width, the 10° blade will be very disturbed by the limbs. We have to use a blade with a compromised hook angle, so it can handle both cleave and cross cut. I have used 7° for limby logs. I have never tested the blades with 4°. The 7° blade need a lot more feed force between the limb groups, compared with the 10°, but it will cross cut the limbs aerea in a more acceptable way.
An interesting fact is that if the log would be “star sawn” the blade, just have to cleave all the wood. Why, because all the cut is performed a long the radius, close to the pit. That means the blade will cleave also the limbs. I think you can stay with 10° to !3° hook angle through a star sawing procedure, I will try that next time.
I have 10 hp electrical motor and 1 ½” blade in my mill.

Offline drobertson

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Re: How the blade cut the log.
« Reply #1 on: October 06, 2017, 04:25:42 pm »
Well Pabene, you just said a mouth full, not sure what to make of it, other than I would just let the dust fly? yea knots are or can be a pain in the rear, but a fact that has to be dealt with.  There are many many hook angles for all kinds of wood species and types,, I am so far off on the way I did it it border lines pathetic, but I sharpened my blades at 5° its' where they came out, the lines were off on the scale, but they worked real good, for everything I sawed.  I'm not sure of the cleave, but it has the sound of hacking?  in any case show some pics when you get a chance,,
only have a few chain saws I'm not suppose to use, but will at times, one dog Dolly, pretty good dog, just not sure what for yet,  working on getting the gardening back in order, and kinda thinking on maybe a small bbq bizz,  thinking about it,

Offline Pabene

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Re: How the blade cut the log.
« Reply #2 on: October 08, 2017, 12:45:12 pm »
Drobertson, I am so sorry my English is to poor to explain better. My thread was a try to show what I think is one important thing about milling. My technical dictionary says: “cleave” is to cut the wood the same way as the wedge goes when you are splitting the wood. I think now I also understand “limbs” are the name for the part outside the log and knots are the name for the part inside the log.
Now, to cleave/split a log without knots, in the log band saw, can be performed with an aggressive hook angle 12-13°. That means very low feed force, the blade nearly “feed it self”. That means the blade goes straight through the log and there is no stress in the blade gullets.
If we now would raise the log 90° in the mill and try to “cross cut” “cakes” with the same blade, it will go crazy.
A blade with 4° hook angle would go much better for that case.
If an other log, with knots, would be cut to boards, a big knot inside the log will be cross cut the same way as the "cake".
We can’t change the blade during a cut in the moment you see the knots, you have to select a blade as can handle both cases in an acceptable way.
If you would go for 4°blade, it need a lot more feed force for the cleave/split part.
More feed force results in a lot more stress in the blade gullets and the blade will break soner. To find a good blade for just your logs are important.

Offline drobertson

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Re: How the blade cut the log.
« Reply #3 on: October 08, 2017, 04:32:55 pm »
P, your written english is better than mine buddy, and I surely meant no crossways direction of the conversation.  My thought while reading your post was one of amazement, in regards to your diligence of the study of the cutting action in a weird way resembled a comment I made in another thread on blades.  Wood, as steel, any material being machined for that fact has requirements for optimum performance.  It's my belief, that the thin kerf band manufacturers have worked out a best case scenario in hook angles, relief angles and gullet sizes to accommodate the removed chips.  There really is no one geometry that covers and fits every mill or specie. But many work for the most part in a general way for the average week end warrior.  For those that have their special niches, I'm sure they have found the match to fit.  Your post reminded me of some older tool room days of cutting out single lip cutter with really weird geometry's to get the job done on some heat treated alloyed materials. Getting below an 1/8" cutter, with a flute length that is way past the normal, due to designs of ribs and such, well for those who never will know, its all a pain, good reads from posts  thanks and keep them coming,,   david
only have a few chain saws I'm not suppose to use, but will at times, one dog Dolly, pretty good dog, just not sure what for yet,  working on getting the gardening back in order, and kinda thinking on maybe a small bbq bizz,  thinking about it,

Offline Kbeitz

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Re: How the blade cut the log.
« Reply #4 on: October 08, 2017, 04:55:06 pm »
 

 
Collector and builder of many things.
I have a
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Offline drobertson

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Re: How the blade cut the log.
« Reply #5 on: October 08, 2017, 06:00:25 pm »
K, I know you have to remember the spindle load meters on some of the older production mills, if we stayed in the range then all was good.  Well then, here comes along another fellow from a different shop, different techniques, hauling the rear end you might say,, How?  he, or rather the shop he came from pushed the limits,, it's the same in sawing logs,, find what works, and then do it.. use the tolerances available, while maintaining proper care for the machinery.   Blades, as cutting tools are an expendable item, they are designed for a purpose, which we all have employed,  my thoughts were, and with no disrespect intended, why get into the re-engineering of a tool, unless one plans on redesigning one better?  find what's available and push it to the limit-s that are allowable,
only have a few chain saws I'm not suppose to use, but will at times, one dog Dolly, pretty good dog, just not sure what for yet,  working on getting the gardening back in order, and kinda thinking on maybe a small bbq bizz,  thinking about it,