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Resharpeing Bandsaw Blades

Started by Firebass, November 18, 2007, 07:46:04 PM

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Firebass

I have a question for those of you that sharpen your own bandsaw blades.    I have a bunch of 3/4" wide,  metal cutting bandsaw blades they are 6 to 4 teeth per inch variable Pitch.   These are the best Bi-metal blades on the market.  I have in the past tossed over a 100 blades because they get dull.  My question is would a sharpener that is used to sharpen sawmill blades work for these?  And how log does it take to sharpen a  small portable sawmill blade?  These metal cutting blades run about $40.00 each. 

Thanks
Firebass

Tom

The same type of sharpener would work, but you would have to match the cam to the pitch and find a stone narrow enough to fit in the gullet.  The rest is just mechanics.

Firebass

Oh that sound good ;D

What is a good brand that is commonly used?

Tom

Woodmizer makes a good one.

Dino makes one that is probably 3 or 4 in popularity with sawmillers, but they work and might be just the ticket for odd blades. (I think it works without a cam)   Baker sells them.  Click on their logo on the left and go to Products.  Then give Tom Stout or Adam a call.

Furby

Um, variable pitch in the same blade?

Dan_Shade

if it's variable pitch, it would probably take some pretty expensive/fancy sharpening equipment.  a woodmizer type sharpener wouldn't work with a variable pitch blade, I don't think.
Woodmizer LT40HDG25 / Stihl 066 alaskan
lots of dull bands and chains

There's a fine line between turning firewood into beautiful things and beautiful things into firewood.

Furby

It would, you would simply have to figure out what the pattern is and count each tooth to follow the pattern.
Then change your sharpener setup to the next pitch and go around again.
And so on.
Probly not worth it. ;)
I'd look at the blades and see if you can figure out the pattern and how many different pitches there are.

pineywoods

Wouldn't be hard to fabricate a cam for the woodmizer sharpener that would handle that. And narrow grinding wheels are readily available. At least on mine, which is a 95 model. Newer ones may be different. Back before woodmizer came out with the doublehard blades,we used to break a lot of blades. I'd grind the broken ends square and take them to a shop which had a resistance welder, weld them back and grind off the weld. This left the spacing between the teeth at the weld a little short,  1/8 inch or more. The woodmizer sharpener never noticed, worked fine.
1995 Wood Mizer LT 40, Liquid cooled kawasaki,homebuilt hydraulics. Homebuilt solar dry kiln.  Woodmaster 718 planner, Kubota M4700 with homemade forks and winch, stihl  028, 029, Ms390
100k bd ft club.Charter member of The Grumpy old Men

Firebass

Yes Variable Pitch.   When cutting through 4" or 6" 4140 steel bar these blades work allot better than standard 4 or 6 pitch blades.  What it does is smooth out any harmonics that cause chatter.  Would that be any use in wood? 


Tom

It's been tried, but other than the sales hype there hasn't been any positive feedback. 

kderby

This might be a good thread to ask about "good enough." 

First an example, the raker on a chain saw chain has an important function.  However, I sharpen a "few" times before I file the rakers.  Thus the rakers are not at peak performance but they are "good enough" for a significant portion of the chain's life.

I have been interested in sharpening the four thousandths of an inch of the bandsaw blade that cuts the wood while ignoring the tooth set and gullet depth.  The resulting tooth profile would not be perfect.  Why would it not be good enough.

If I were cutting iron with $40 dollar blades I would look at the opportunity to resharpen the blade and regain function rather than perfection....to a point ;D

I do accept the concept that blade cost is not a large factor in the production of lumber.  I understand that some people use the blade once and toss it.  I send mine off to be sharpened.  I would like touch them up and use them "twice" before they got shipped to the re-sharp.

Thanks for your comments.

KD

Brad_S.

IMO, good enough is a relative thing that pretty much only you can answer. If you are cutting straight lumber, removing most of the sawdust as opposed to packing it and doing so at a speed you are satisfied with, then your close enough would be good enough.
That said, from my experience, I find that the only time I can get away without re-setting is when I sharpen a blade I had previously set for softwood and next intend to use for hardwood. Without enough set, the blade packs sawdust and wanders on me. Sharpening the tooth face only and not deepening the gullet means you are shortening the tooth height, so you would have to slow down feed speed which means production falls. I would also think if you only ground the gullet occasionally, you would have to remove a fair amount of metal and risk removing the temper from the steel, thereby shortening blade life, but that is just a guess on my part.
"Life is what happens to you while you're busy making other plans." J. Lennon

Tom

I agree with Brad. 

Grinding the gullet, called gumming out, has been determined to increase blade life by eliminating micro cracks.  I'll have to believe the manufacturers on that because my eyes aren't good enough to see them.   Gumming out has a main function of providing tooth height.  If your tooth is too short, the gullet fills with sawdust too quickly and the tooth quits cutting along with other maladies that occur with gullet spillage.   I was always told that a tooth height of at least 3/16" be maintained.  Some of these new blades use a really tall tooth, but that is engineering to be done at the factory. (measured from the tip to the transition curve)  Very tall teeth impose a lot of stress at the transition point of the tooth and gullet and can cause blade failure.  While you can experiment with it, it behooves you to understand the stresses on the blade when you change tooth configuration.  It's not all about how good the band cuts, but longevity as well.

Larry

Found a pic of a variable pitch in my gallery.



I use them a lot and have re-sharpened a couple...something I don't recommend.
Larry, making useful and beautiful things out of the most environmental friendly material on the planet.

We need to insure our customers understand the importance of our craft.

Kelvin

My biggest change in getting my blades up to like new specs was dealing with "set"  However if your question is, as long as i might throw them out after one use, how could i make them last longer, you could make some things work.  I've seen a fellow chuck a flat stone on a drill and attach it to a long board he pivots off the ground to keep it more square to the teeth.  Just kiss the front of the tooth a bit and you can get quite a bit more out of a blade.  I've discovered a low tech way of going farther with a blade that has hit metal.  my woodmizer double hards are often okay after hitting a couple of nails, but a small piece of steel is usually curled up on the tooth causing problems.  I have often hand filed these teeth to remove the steel, and gone a little farther and touched up the tooth.  It can be done like a chainsaw blade with a dremel tool. 

As it has been stated, if you don't grind your gullets you won't get too far with the blades, but you can extend some sharpness for awhile with some touch ups.  I'm always touching up my planer and jointer knives while they are in the machine.  People who pull them when they are dull are crazy.  I can get 3x's the life out of one sharpening by honing them in place.  On a band blade usally other things give out eventuall, like set.  I like figuring out what is good enough and going with it.
KP

Furby

Quote from: Kelvin on November 19, 2007, 08:38:23 PM
I've discovered a low tech way of going farther with a blade that has hit metal.  my woodmizer double hards are often okay after hitting a couple of nails, but a small piece of steel is usually curled up on the tooth causing problems.  I have often hand filed these teeth to remove the steel, and gone a little farther and touched up the tooth. 

As was posted earlier in this thread and many, many times elsewhere in the forum, a pocket knife will peel those curls off in less then a minute.
I will sometimes keep cutting a cant with 8d nails in it and just take a knife or other piece of scrap metal and clean the blade after each board if it's only going to be a few cuts and I know the lumber isn't going to get planned.
I've also just kept cutting and not worried about taking the curls off either. :)

Dan_Shade

Woodmizer LT40HDG25 / Stihl 066 alaskan
lots of dull bands and chains

There's a fine line between turning firewood into beautiful things and beautiful things into firewood.

Furby


Dan_Shade

Woodmizer LT40HDG25 / Stihl 066 alaskan
lots of dull bands and chains

There's a fine line between turning firewood into beautiful things and beautiful things into firewood.

Furby

Same difference eh? :D :D :D
Was it loud? ::)

shopteacher

I have a Wardwell bandsaw sharpener that has a variable cam that can be set to match any blade according to the patent information. It has automatic feed with double paws to assure positive advancement of the blade and uses grinding wheels from 1/6" to ?  There were discs upto 5/32" in the machine when I go it. Looks like it can sharpen anywhere from 1/4' to about 6' wide bands. Quite an impressive machine. I haven't been able to find a manual for it , but the description to the patent office is very descriptive of it function and use.  I'm thinking of putting it up for sale and will add a picture as soon as I can figure out how to do it again.
Proud owner of a LT40HDSE25, Corley Circle mill, JD 450C, JD 8875, MF 1240E
Tilt Bed Truck  and well equipted wood shop.

ely

brad s and tom are both correct in my opinon. i also do like furby does and remove the curl with my knife after i hit metal.

when i first started with my sawmill, i thought i could get by and make the bands good enough by myself with more than crude methods. after all my attemps proved futile i  then purchased the cat claw sharpener.

i just thought a brand new band cut good. i now think the bands cut best after the first or second sharpening. just like my new chains on the saws. at any rate i could not get any satisfaction out of the bands when i was trying to sharpen them by hand.

when my dad got his WM he acquired 20 or so bands that had been discarded by the previous owner. all these bands and the bands that were being used on the mill were sharpened by hand on an old woodmizer sharpener, i guess because the guy could not figure out how to run the sharpener. i was amazed at how good a job the guy had done when grinding the bands by hand. they were very close to correct. i know he could not use the sharpener because he seen us set it up and use it once and he said" so thats how that things works"
so i guess there is some folks out there that just can do things the hard way and it works for them.

i also do like kelvin and hone my blades on the planer machine in between sharpenings.

Gilman

Steve,
I have a WM band sharpener if you want to try one out.  You'd have to make a cam though.  I think it was Furby that mentioned you could skip 2 teeth to match the variable pitch.  If the blades are one tooth short of a full set, the tooth indexer would skip to the next pitch each full pass. 

The big mills use variale pitch blades, cuts down on harmonics like someone else mentioned.
WM LT70, WM 40 Super, WM  '89 40HD
Cat throwing champion 1996, 1997, 1999. (retired)

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