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Gullet shape

Started by bandmiller2, June 05, 2011, 08:11:53 AM

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bandmiller2

How important is it? The only cam I use on my Cooks cats claw sharpener is the Simonds 3/4"used on 7/8 and1" it makes a deeper gullet that I've had very good luck with.That cam is very close to WM  7/8" gullets.Prehaps I'am a crude old dude but I think even, propper set, and tooth tip sharpness is what carries the mail.I like less than 10 degree hook angle,don't know exactly what mine is now as the grinding wheels wear you get less and less hook,as long as the bands are cutting well I don't mess with it. Frank C.
A man armed with common sense is packing a big piece

ladylake

 Gullet shape, not too important as we can all cut pine at a fast feed rate with a shallow gullet 9* or 10* blade yet when the same blade starts to get wavy at way slower feed rates some blame it on the shallow gullet which doesn't add up.  It's the sharpness, hook angle and set that will make it cut straight in tough wood.   Steve
Timberking B20  18000  hours +  Case75xt grapple + forks+8" snow bucket + dirt bucket   770 Oliver   Lots(too many) of chainsaws, Like the Echo saws and the Stihl and Husky     W5  Case loader   1  trailers  Wright sharpener     Suffolk  setter Volvo MCT125c skid loader

Tom

I'm of a different opinion.  While sharpness is of ultimate importance, tooth shape and gullet depth are a package.

The shape of the gullet does effect the speed of the cut because you can't saw faster than you can get rid of the sawdust, unless you are running a shear.

The transition area at the base of the face of the tooth is important because the band will work harden there if the angle is too sharp.   If the angle is too flat, the sawdust piles up there instead of flowing on into the gullet and could even get tall enough that the tooth quits cutting.  The slope up the back of the tooth gives the tooth strength and defines the height of the tooth.  Short teeth cut slow because their "curls"(sawdust sizes) are limited to the face of the tooth.  The deeper the gullet, the taller the tooth can be (to a point).  If you get the tooth too tall, it loses its strength, too short and it loses its ability to cut deep.   The face of the tooth controls the hook (rake). The softer the wood, the more hook you can run because it can "dig" a curl out of the wood. The gullet has to be able to handle this chip (curl) and expel it.   The harder the wood the less hook you can afford and the tooth begins to scrape rather than dig.   Too much hook and it chatters.  Too little hook and you end up scraping off powder.

The whole package is important.  It's also important that the stone be dressed properly and frequently.  Hook is a result of the attack of the angle of the stone more than the shape of the stone, but the shape of the transition area is totally dependent upon the shape of the stone.

It's my opinion that you should retain as deep a gullet as you can manufacture and not affect the strength of the body of the band.   The tooth and the gullet is where the "rubber meets the road" and not something to be taken lightly.  I don't care whose sawmill you are using, what is the common denominator?  It's the band!  That is the tool that ultimately does the work.  The sawmill is just instrumental in allowing it to do its best.

....and that's all I got to say 'bout that.  ;D :D

smwwoody

Well said Tom.

There is a lot of wisdom in what Tom has said here.

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ladylake

 Explain to me why we can cut pine making a lot of sawdust with a fast feed rate with a shallow gullet and using the same blade cutting hard wood making a lot less sawdust and then blame it on a shallow gullet that is filling up with sawdust that's causing it to cut wavy when if fact there is a lot less sawdust to deal with.  I'll stick with hook angle, set and sharpness unless there is a logical explaination.    Steve
Timberking B20  18000  hours +  Case75xt grapple + forks+8" snow bucket + dirt bucket   770 Oliver   Lots(too many) of chainsaws, Like the Echo saws and the Stihl and Husky     W5  Case loader   1  trailers  Wright sharpener     Suffolk  setter Volvo MCT125c skid loader

Tom

Because there is no one reason that a band doesn't cut straight or fast.  Perhaps you are just such a good sawyer that nothing gets in your way.  You were the one who mentioned the wavy cutting.  I'm glad that you don't experience it.   I don't have all of the answers.  As a matter of fact, I have very few of them.  But, I do have opinions.

You are right that hook angle, set and sharpness is instrumental in straight and fast cutting. A sharp tooth is probably the most important.  But I would think that an experience with a tooth configuration such as found on a wave-set metal cutting band would change your opinion about tooth height and gullet depth.

Banjo picker

Steve why do you say there is less sawdust to deal with--cutting hardwood...A band is going to displace the same amount of area (saw dust) in pine or hardwood...Given as you cut slower in the hardwood the dust may be finer and therefore precived as less but .096 is .096 no matter what you are cutting.  When cutting the softer woods the planets just don't have to align as perfectly as when cutting hickory or ash...Am I missing something?  Tim
Never explain, your friends don't need it, and your enemies won't believe you any way.

ladylake

 When cutting hardwood at a slower speed there is less sawdust to deal with per second or minute.  Tom, I've certainly experienced wavy cutting and that's what make me think the gullet dept doesn't matter much as I've put on brand new 10* blades and couldn't cut straight in wide knotty white oak, took the same blade and sharpened it to 4* and cut perfectly straight 1/4" below the wavy cut with no change in gullet dept. It could be that I got it sharper than factory when sharpening but I think it's the hook angle that makes it cut straight and no I'm no I'm not that good of a sawyer and am sure willing to learn as we should all be. I've certainly learned a lot on here, back when I started sawing  I figured a 13* hook would be best, and thanks too someone on here I ended up at 4* for hard toocut wood. .   Steve  
Timberking B20  18000  hours +  Case75xt grapple + forks+8" snow bucket + dirt bucket   770 Oliver   Lots(too many) of chainsaws, Like the Echo saws and the Stihl and Husky     W5  Case loader   1  trailers  Wright sharpener     Suffolk  setter Volvo MCT125c skid loader

Tom

Well, That's good, Steve.  There is no one-size-fits-all cofiguration.  I'll tell you what though,  13° flew through SYP on my sawmill, though there are times when even it has hard spots that propose problems.  I'm sure that your 4° hook did have something to do with your ability to cut that log straight.

ladylake

 Tom   I agree the softer the the wood the higher the hook angle I can use, I'll be cutting some 30" pine logs 2 weeks from now and you can bet my 10*  new blades will be on my mill for them.   Steve
Timberking B20  18000  hours +  Case75xt grapple + forks+8" snow bucket + dirt bucket   770 Oliver   Lots(too many) of chainsaws, Like the Echo saws and the Stihl and Husky     W5  Case loader   1  trailers  Wright sharpener     Suffolk  setter Volvo MCT125c skid loader

Brian_Rhoad

A slow feed speed with the same blade speed will make fine dust, smaller particles of wood. Fine dust will escape the gullet and get between the blade and the log causing the blade to heat up and not saw correctly.

Softwood sawdust expands more than hardwood sawdust using more space in the gullet.

You need more set in the teeth when sawing softwood due to the wood fibers expanding more than hardwood. If you look closely at softwood the surface has a more fuzzy look than hardwood. This fuzz requires more clearance, set, for the blade.

Gullet depth and shape is just as important as hook angle and sharpness. I had one blade manufacturer tell me the transition from tooth face to gullet, the area at the bottom of the tooth, should be a sharp angle. If the transition is too smooth, the sawdust remains as a curled shaving and does not break into dust particles. This fills the gullet and causes blade heating.

If the gullet is too shallow you need to slow your feed speed. If you feed too slowly you create finer dust, which will spill out of the gullet causing heat.

Every part of the blade has to be correct and work together to saw efficiently.

One thing that is usually not thought abut is what blade flex in the log does to affect the cut process. As the blade is pushed back and bows between the guides it changes the effective hook angle of the teeth. That is one reason wider blades are required for high powered mills to get the best results.

BBTom

Depth of gullet can also be expressed as height of tooth.  I may be alone in my thinking, but I bought some boxes of the 7* .055 blade that I sent back because of my inability to get them to cut straight.  Mind you, I cut alot of old dry white oak, cherry and whatever logs.  When the logs lay for a couple years, they are very difficult to cut.  My guess is that the length of the tooth gave it enough leverage to "follow" the grain in the dry logs I was cutting at the time.

My normal blade is a 4* .055 that I sharpen using a 4* profile wheel with a 7* hook on the grinder motor.  I also set them a bit wider at .028-.030.  This combination seems to stay sharp longer and saw straighter for me with the type of sawing I do.  I am not suggesting that it will work for anyone else, just that after playing with the different configurations over the 5200 hours on my LT40 super, it works for me.

I do not pretend to be a sawdust flow technician, so I just had to experiment to see what works.

I do love to take a 13* blade to a stack of fresh cut pine and strap up the dust chute so I can watch the curls fly 40 feet or so while running the forward speed almost wide open. I just don't get to do that very often in this part of the country.





2001 LT40HDD42RA with lubemizer, debarker, laser, accuset. Retired, but building a new shop and home in Missouri.

bandmiller2

BB,I'd say good straight boards are vindication of your sharpening method,good product and good production tell the story on any mill. Frank C.
A man armed with common sense is packing a big piece

Magicman

No argument that the teeth do the actual cutting.  Their pitch, set, etc. is different for different wood species/hardness.

It is still the gullet that transports the sawdust.  It's shape/depth is also a designed to allow the band to efficiently and effectively do it's job.

The band is a system combining the two.
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