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Blade set vs. Blade Angle vs. HP vs. Cut Quality vs. Blade Life...

Started by Ljohnsaw, October 03, 2018, 12:58:32 PM

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Ljohnsaw

I did some searchs but it didn't turn up much.  I use WM 184" 7°, .042" bands with a 18hp gas engine.  I now have (the remains) of two boxes - about 26 or 27 blades left.  I sent one box out to a local WM reseller for sharpening and was a little disappointed.  It took 2 weeks (I dropped off and picked up) and they lasted a little less then the new blades - didn't seem as sharp. 

So I made a sharpener from a radial arm saw.  I could only fit a 3/4" stone on the arbor (7/8" tooth spacing) so the profile I shaped the stone does not cut the backside of the tooth, just the face and the gullet.  While I matched the angle of the tooth with the stone, I think the angle was altered a little (less angle).  What I found is the blades cut faster and seem sharper/last longer.  But I may be just imagining it. ::)  I made a set remover and a dual tooth setter but have not used them yet.  I've done 2 sharpenings on my bands so far.  Takes me about 12-15 minutes per blade just to sharpen (210 teeth).

So the question(s) - For reference, I'm cutting pine and cedar anywhere from 16" to 34" diameter:

I see a recommended set of .020 - .025 and a hook angle of 7° to 10° depending on species.  Is there a correlation or recommendation between the set and the angle?  For a given HP, can you go more set with less angle?  Should you?

Is there a correlation between hook angle and blade life?

I think I read the more set the more HP needed, correct? (makes sense to me)  And the same for hook angle, the greater the angle (more aggressive), the more HP needed?

And then quality of cut - does having more or less set alter the quality of the cut (cause or prevent waves)?

Likewise, does more or less angle alter the quality of cut?  My sawdust is not flour fine - more like sugar - NOT like chainsaw.

Right now I'm concentrating on using sharp blades (duh) for more consistent cuts but I'm wondering if affecting any of the blade parameters would be worthwhile in keeping the blades sharper for longer or allow a dulling blade to cut better.

I think that covers it. TIY
John Sawicky

Just North-East of Sacramento...

SkyTrak 9038, Ford 545D FEL, Davis Little Monster backhoe, Case 16+4 Trencher, Home Built 42" capacity/36" cut Bandmill up to 54' long - using it all to build a timber frame cabin.

mike_belben

In machining, the pointier you make a cutting tooth, the more agressive it will cut but the sooner itll chip and dull the edge.  So these tend to be for light pressure, high speed passes on softer metals.  If you want to make it rain blue steel chips from a slow spindle, the cutter needs to have blunter tip angles and big meaty shoulders to back them up so they dont snap off. 

In metal cutting circle saws, the set or tooth insert width makes clearance so that the body of the blade doesnt heat up on the edges of the kerf.  A narrow set will run hotter than a wide one due to friction. 

I dont know a thing about bandsawing wood, but i assume these two properties have some carryover from the metal cutting world.  Forgive me if that isnt true
Praise The Lord

SeaPickle

Hello lJohnSaw! Hope I can help!
Tooth setting provides side clearance for the band while it is within the cut. Depending on what you are cutting, you may want different sets. Do not go beyond 0.005" runout with teeth or you will see marking on your product.
If you are not hitting the back of your tooth during grinding, do NOT keep hacking into your hook face! This will lead to hollow backs, and washboard! Your quality of cut depends on the tooth geometry, gullet capacity vs feed speed, and the likelihood of the tooth flexing while in the cut. This is also dependent on the lubrications of the blade.
Yes, the hook angle will dictate the HP needed due to the depth of cut. But also the back angle of the tooth and the tangential and radial angles you are running. I'd recommend checking your SHARPNESS angle. It's the hook and back (clearance) angle. Modifying either one of these will dictate your HP needed. Excess set will also require more HP but also reduce recovery. Excess or too much hook angle will also require more HP from the motor and therefore more resources (gas/diesel) required per board foot recovered.

Ljohnsaw

Thanks.  I wouldn't say I'm hacking the tooth face.  From what I've read, I should expect about 3 to 5 sharpening on a blade before it breaks due to metal fatigue.  I am just kissing the tooth face enough to leave a burr on the edge and kissing the gullet.  Probably taking .0005 off.  I watch the (big) shinny tip before the hit and it disappears.  I've only had to grind one blade because of a good, solid metal hit.  The re-sharp folks would probably have tossed it so no loss if it didn't work - and it did so I'm ahead of the game.

I know tooth set is to provide clearance, just wondering what the effect is if too much (blade wander?, more hp required?, more (or less) sawdust let on the board?) vs. too little (heat build up and subsequent loss of tension and then blade wander?) etc.
John Sawicky

Just North-East of Sacramento...

SkyTrak 9038, Ford 545D FEL, Davis Little Monster backhoe, Case 16+4 Trencher, Home Built 42" capacity/36" cut Bandmill up to 54' long - using it all to build a timber frame cabin.

SeaPickle

Since tooth set defines your kerf, the larger the set, the more sawdust you are placing in the gullet of the tooth each time it travels through the cant/log. when the gullet gets too full, the sawdust spills out the side, causing friction with the blade and creating heat. This can lead to loss of tension withing the body of the blade.
Furthermore, the more set you place, the more careful you have to be to make sure that the set is equal on both sides. Unequal set will cause the blade to snake to the side with more side clearance because its biting more on that side. In addition, since the saw tends to want to "dive" out of the cut by nature (which is why we place lead in our guides), if the set is greater towards the outside of the cut, the saw will snake even more.
A good way to tell if your gullet is overfed is if you see sawdust spilling out the back of the blade during the cut.
Hope this helps!
Edit: more set also equals less recovery!

Silverfoxfintry

Sorry if I am hyjacking this post.
My Son David and I are overhauling an old 1995 Forester Jacko mill. Things are progressing well, we have replaced all the carriage and post rollers along with the hydraulic feed motor and chain.
I am having problems with the NEW blade "diving" in the cut.
After checking everything, and I mean everything. I noticed that the NDE blade support roller was wider than the DE roller. It was removing some of the set from the lower teeth on the blade. Am I correct in thinking that this will cause the blade to "dive" into the wood. It formed a distinct repeating pattern with a pitch of about 24". Falling and then rising in the cut.
I suspect that at the lowest point the blade tension was forcing the blade back up. This pattern repeated on the next cut.
I have removed the roller and machined it to match the other roller. It was very hard, I had to use a ceramic tip cutter to machine it. The cuttings were so hot they were combusting in the swarf tray on my Lathe.
I will refit the roller and try another new blade.
Do you think I am correct?
Any help appreciated.
On

John Bartley

My experience:

A sharp blade with less than enough set will cause waves in the board face.  I find this to be worse in knotty woods where the wood hardness changes from clear to knotty sections.

A dull blade with the correct set will not cause waves but will cut slowly.

A sharp blade with the correct set will cut straight and fast.

A blade with too much angle (hook) will cut faster but last a shorter time before going dull.  (this I think is due to the reduced material at the tip for dissipating heat).

A blade with too little hook will still cut well, but slower than optimum in soft woods and at a decent speed in hard woods.

Because I cut mostly Spruce, Tamarack, Cedar I use a 10' hook angle and about 0.028 set.

I have minimum 10+ sharpenings on most of my bands and probably 15 or more on some.  They are about ten years old and are starting to break.  It's time to replace them.  I think they have lasted so well because I am the only person who touches them ... I sharpen, I set and I cut.  When I sharpen I remove "just" enough material to make them sharp without bluing the tooth.

Anyway ... that's all I got and that's from a hobby sawyer.

cheers
Kioti DK35HSE w/loader & forks
Champion 25hp band mill, 20' bed
Stihl MS361
Stihl 026

JRWoodchuck

John what mill are you running? How big are the band wheels? How many HP? Diesel or Gas? What blades? Green wood or dead? 
Home built bandsaw mill still trying find the owners manual!

John Bartley

I am running a manual mill, an SMG Champion, Wheel diameter ...19"?, 25hp Kohler carburetted, 30" x 21'.  I am using Hakansson silicon bands.
Kioti DK35HSE w/loader & forks
Champion 25hp band mill, 20' bed
Stihl MS361
Stihl 026

YellowHammer

Others have made lots of good points, but the main thing is, chisel sharp teeth, adequate set, consistent set, grind the gullets to remove gullet cracks and extend band life, don't burn the teeth, and oh, did I mention, SHARP teeth and consistent set?

So what the my idea of sharp?  Here are a few pictures of a band I sharpened. First two pic are of an incompletely sharpened band.  Incorrectly formed corners, slightly burned tips.  Oops.


 



 

It looked sharp, but wasn't. Notice how the corners of the tips are rounded, show a little glint?  Round corners don't cut.  Think of the front of a tooth as a chisel, where full clean cuts are made as long as the teeth are sharp all the way to each corner, as in this picture.  

Next picture.  This baby will cut.  Notice the slight hollow grind, I had to spend a little time getting the wheel right in the center of the tooth face, for awhile, it had been slightly off to the side creating a lopsided grind.  There are a few burrs but they will come off he first pass

<<


As far as set, I like the basic angles and distances of the WM bands, but the main thing to good looking boards is absolute consistency of set.  One or two badly set teeth and the wood goes from "wow, that's a sweet looking cut" to " Well, what do you expect? It's called rough sawn for a reason."

YellowHammerisms:

Take steps to save steps.

If it won't roll, its not a log; it's still a tree.  Sawmills cut logs, not trees.

Kiln drying wood: When the cookies are burned, they're burned, and you can't fix them.

Sawing is fun for the first couple million boards.

Be smarter than the sawdust

terrifictimbersllc

Nice pictures.

Hey guys if you haven't tried, this is what you can see with a 10x hand lens.  Blade isn't cutting right will usually look like first 2 pics above.
DJ Hoover, Terrific Timbers LLC,  Mystic CT Woodmizer Million Board Foot Club member. 2019 LT70 Super Wide 55 Yanmar,  LogRite fetching arch, WM BMS250 sharpener/BMT250 setter.  2001 F350 7.3L PSD 6 spd manual ZF 4x4 Crew Cab Long Bed

Ljohnsaw

John Sawicky

Just North-East of Sacramento...

SkyTrak 9038, Ford 545D FEL, Davis Little Monster backhoe, Case 16+4 Trencher, Home Built 42" capacity/36" cut Bandmill up to 54' long - using it all to build a timber frame cabin.

YellowHammer

I use the $20 ear canal and eye flashlight magnifier available at any local drugstore or Wal Mart.  

If you want to really see what your band teeth look like, zoom in with one of these.  You may be surprised.  
YellowHammerisms:

Take steps to save steps.

If it won't roll, its not a log; it's still a tree.  Sawmills cut logs, not trees.

Kiln drying wood: When the cookies are burned, they're burned, and you can't fix them.

Sawing is fun for the first couple million boards.

Be smarter than the sawdust

doc henderson

Hello guys.  You may still want to get a loop or otoscope, but you may want to look with your phone camera.  We do this for lacerations before and after repair to communicate with the plastic surgeon.  It is amazing when we use the finest (smallest) suture on a child's face and you blow up that pic on a good camera,  The thread looks like a cable on a bridge and any imperfection in the repair can be seen.  I will try this but had not thought about it for blade eval until reading this thread and seeing the pics.  you can get Macro lenses to add to a camera phone as well to get more detail.  It also works well if a model/serial number on equipment is in a tough to see location, or if it is faded like the old alum. plates on an engine. often the photo will pick up impressions and color you cannot see.
Timber king 2000, 277c track loader, PJ 32 foot gooseneck, 1976 F700 state dump truck, JD 850 tractor.  2007 Chevy 3500HD dually, home built log splitter 18 horse 28 gpm with 5 inch cylinder and 32 inch split range with conveyor powered by a 12 volt tarp motor

Ljohnsaw

OK, so I'm kicking this up to the top again.  I'm seriously considering buying the BMS25 sharpener from WM.  My blades (.042 x 1¼ x 184; 9°) have morphed down to probably 4° with my radial arm saw grinder setup.  The reason for 9° is that WM only offers 9° or 10° in the 184" length and the lady on the order desk said the 9° would work better for my HP and wood (pine & cedar).  I *think* I get better performance from the lower angle.  The BMS25 comes with a 10/30 cam.  I tried emailing WM but get a canned response to call my local dealer because of Covid!?!  What I want do do is substitute the appropriate cam for my needs and not have to spend the extra $40 to have a unusable cam just sitting on the shelf.

So, back to one of my original questions - HP vs. Hook angle.  In the back of my mind (unable to uncover with the Search function), I recall that 4° would be better for a "low powered" machine such as mine (18hp).  Perhaps a few of you out there have tried 4° - comments?  I think Tom (OGH) is using 4°now?

The alternative cams available are 4°/32°, 7°/34°, 7°/39° (Turbo 7), 7°/47° (Turbo 747), or 9°/29°.

Also, there is another thread that @Old Greenhorn started last November BMS25 Anybody? Doesn't anyone have one yet?  I'm wondering if you can tip the grinder head to tweak the tooth angle a little bit.  Say I want to go to 5° or 6° on the 4° cam.  I'm assuming the face of the tooth is shaped by the side of the grind wheel.  Or would that mess up the back side of the tooth as the wheel raises too slow.
John Sawicky

Just North-East of Sacramento...

SkyTrak 9038, Ford 545D FEL, Davis Little Monster backhoe, Case 16+4 Trencher, Home Built 42" capacity/36" cut Bandmill up to 54' long - using it all to build a timber frame cabin.

Old Greenhorn

I can't speak to tweaking the angle because I don't have the machine. But yeah, I did switch to 4° blades and am very pleased with the results and will stick with them for sure. It just turns out to be a better general purpose blade for my small machine.
 It's interesting now that I am running the LT50. He has boxes of blades and I can't read ANY of the faded out labels on the boxes to know what I am running. They look like double hard 7° blades, but I can't be sure. I'd like to try some different blades on that machine with the big HP on all this pine I am milling. My sense is that the low angle blades tolerate dirt a little better also, but that is just a hunch or feeling with no evidence to support it.
I don't know if WM has the 4° setup for this machine yet though. They did not when I started that other thread and I have not gone back to check.
 If you do buy this machine I want to hear all about it.
Tom Lindtveit, Woodsman Forest Products
Oscar 328 Band Mill, Husky 350, 450, 562, & 372 (Clone), Mule 3010, and too many hand tools. :) Retired and trying to make a living to stay that way. NYLT Certified.
OK, maybe I'm the woodcutter now.
I work with wood, There is a rumor I might be a woodworker.

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