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Author Topic: Bandmill Blades Breaking  (Read 44868 times)

Offline HaroldCR - AKA Fla.-Deadheader

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Bandmill Blades Breaking
« on: February 01, 2016, 09:16:27 AM »

 This might be rehashing old info and ideas, but, it seems to be a constant subject.

 It seems that WoodMizer is one company in particular that sets the blade tension really high/tight/whatever you choose to call it. Among other things, it results in loosing pressure in the hydraulic tensioner over time.

 We built a homebrew version of WoodMizer design, using trailer wheels/tires. Believe me, we never put the strain on our blades that WM recommends. We cut many thousands of bd/ft of sand laced river recovered Cypress, along with SYP, Live Oak, (harder than any Oak-Hickory y\all are used to cutting), along with several species of Tropical hardwoods, again, harder than y'all cut.

 Choice of blades varies greatly, but, we chose the Swedish Steel blades, Munksforsager, and they cut everything we tried. We cut as smooth and accurate lumber as any mill out there.

 My theory is, a lot of sawyers run their blades under too much tension. I also believe proper tuning of the mill will allow less tension to be required.

 When someone buys a mill, they follow instructions which might appear a little foggy to the buyer. Building a mill, you become one with the mill, and recognize any intricacies with the parts/setup required to properly adjust everything to it's finite potential.

 Lately, as I more frequent the forum, I still read posts about blades breaking, especially at the weld. We used to eventually grind the blades down to where the gullets would chatter on the guide rollers. We broke less than 5 blades total, and 3 of those were from jamming and straightening out the kinks.

 I am nearly finished with building another WM type design using motorcycle alloy wheels. Having no access to a metal lathe or similar precision tools, this will be a unique situation, to say the least. 

  I already bought some Munks blades. They are still very reasonably priced. I bought a few for a local saw team to try, and, I just bought more for them, because they were AMAZED at how much better/longer lasting they are, compared to what is sold down here. I need to get them to sharpen their own blades, because here, they just set and grind away, wearing down blades WAY too quickly.

 Another local had problems with his blades wandering in the cut. I went to his house and watched him sharpen a blade. I stopped him before he got to the tenth tooth. I changed his tooth angle a little, and ground his cutting wheel to a slightly more rounded gullet, (another reason for blade s breaking, that sharp squared area at the beginning of the gullet) and sharpened the blade. Then, he went to the mill and he started sawing. Less than 3 steps into the cut, he turned and had a large smile on his face. The mill was practically sawing by itself. He is waiting for new blades from me, right now.

  Hopefully, my crate will be here by the end of February, so I can get to logging and sawing of our plantation trees, and taking orders for Munks blades and building sharpeners.

 Anyone that wants to add to this thread with ideas and experience, feel free, though, keep it civil. The idea of this thread is to enlighten newer sawyers especially, that ALL info may not be right for your mill, according to the manufacturers specs.

 I am NOT a mechanical engineer, trained machinist, rocket scientist or anything other than one that pays particular attention to detail. I firmly believe this is most of the problems that develop into excessive blade breakage.

 Harold
 

 

 

Offline furu

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Re: Bandmill Blades Breaking
« Reply #1 on: February 01, 2016, 02:29:42 PM »
Harold
What kind of tension are you running?  More precisely how many tensile pounds or newtons in your part of the world are you using? If you have/use a tension meter.

I know that TK recently upped a bit, their recommended tension on their blades (measured on their pressure gauge which is not a tensiometer).
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Offline HaroldCR - AKA Fla.-Deadheader

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Re: Bandmill Blades Breaking
« Reply #2 on: February 01, 2016, 06:27:48 PM »

 We used a 3/8" ratchet that tightened the tension bolt, until it got tight, then, engaged the drive belt and watched where the blade ran on the guide rollers. We could change the tracking of the blade with more or less pressure on the blade tension bolt.

 Also, we ran on the middle tread rib on the tires, and, that had a little give, also, being a rubber strip.

 I just don't see all that much tension being necessary.

 More than anything 1/8 to 3/16 down pressure on the blade guides will hold the blade steady, IF you set and sharpen correctly. I can't imaging solid block type blade guides not causing problems heating the blade from friction.

Offline bandmiller2

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Re: Bandmill Blades Breaking
« Reply #3 on: February 01, 2016, 07:30:49 PM »
Harold, I agree with you on excessive band tension. I built my bandmill about 12 years ago and have never had a band break. Too much tension is an attempt to force the band to cut straight and it doesn't work, its sharp and proper even set that cuts straight. I ran a WM LT-70 for a couple of years for a friend usually after the third sharpening, Bam band breaks and we all jump. My own mill with much less tension I get at least a dozen sharpenings. Frank C.

Offline backwoods sawyer

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Re: Bandmill Blades Breaking
« Reply #4 on: February 01, 2016, 08:53:52 PM »
Here is what I have.
Been running wm blades, for the most part, for ten years now I have been getting multiple sharpening out of the saws until the last four boxes. This last box 7 have broke on the first run with one still on the mill and one still in the box.  I have been saving the ones that look like they can be welded for a slow day.
When all this started WM belts started separating so I changed over to the orange rubber belts, the saws continued to brake and eat up the orange belts, so went back to wm belts, lost a drive belt to a broken saw the other day.
Checked mill for vibration all checks passed!!!


For several years now I have run 80 psi in the air bag style tensioner, up from 60 psi in the manual.

The saws are not all cracked up like a vibration issue they just brake so my thought is that the source of the metal for the wm bands may not be the same mix as it was before the down turn in the economy, same thing with the glue used to hold the outer layer of the belts, less or different glue.   

Time for me to try new brands and see if that resolves it, but trying new saws is a hit and miss process I find Suffolk's to be to soft and not hold set and Cooks to be to hard and they don't carry .055.

Offline HaroldCR - AKA Fla.-Deadheader

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Re: Bandmill Blades Breaking
« Reply #5 on: February 01, 2016, 10:01:14 PM »
I assume you have a WM mill ? Why do you use .055 blades ? They will definitely fatigue at the weakest spot, likely at the weld.

 I don't agree with the 19" wheels on most mills. I find it very difficult to find 21-22" V belt pulleys, but, 19" is very common. I believe this is why 19" wheels are so commonly used.

 The mill we built had a 23" outer diameter at the tire circumference.

 Why not contact Kenne-saw & supply Co. at 877-420-9235 and tell them your problem. They usually send a free blade to try. I would drop to .041-.042 and reduce the tension back to 60 and see how you get along. We constantly got 10 or more sharpenings from each blade.

 I had Suffolk blades and we broke several of them. They are too soft for our use.

 

Offline mountainlake

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Re: Bandmill Blades Breaking
« Reply #6 on: February 02, 2016, 05:30:41 AM »
  I've heard of others breaking WM blades a lot lately , maybe they got a bad batch of steel or switched suppliers.  I've been running Simonds for years with real good results but maybe 5 years ago they got a bad batch that never made more than 1 sharpening, seems like they were too brittle. I run my tension a little less than what TK recommends.   Steve

Offline backwoods sawyer

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Re: Bandmill Blades Breaking
« Reply #7 on: February 03, 2016, 07:53:00 PM »
I am running a wm LT-70 (the first 70 built) with 24" belted wheels powered by a Kabota 42 hp with turbo.
replaced the wheels a few years ago after the steel wheels developed cracks thru the balance holes.
I prefer the steel wheels ;)

The saws have not been braking at the welds

As for .055 it is for the beam strength-faster cuts using more of the horse power
have tried thinner saws but for sawing anything other then cedar they did not perform as well for me.

 
will make a call in the morning



Offline HaroldCR - AKA Fla.-Deadheader

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Re: Bandmill Blades Breaking
« Reply #8 on: February 04, 2016, 08:14:31 AM »
 That diameter should not cause breakage from flexing, I would think ?
 What is the recommended PSI of the blade tension? What width blade do you use?
 Curious what rake angle you run?

 We cut the occasional " fat lightered " Old growth Long Leaf Yellow Pine, from the original devastating logging of the virgin timber, that we found river diving. THAT stuff is something else. I bought 2- 1.5" .055 WM blades and changed the gullet shape and more tooth set to saw that stuff, using them on the 1.25" roller guides. Had to flood the water on, or, use Pam cooking spray, because of the very sticky sap.

 Keep us up to date on what you try and the results. Could be very interesting.

Offline backwoods sawyer

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Re: Bandmill Blades Breaking
« Reply #9 on: February 04, 2016, 10:08:24 PM »
1.5 x .055 x 184" *10

Got a box of saws ordered today,
His comment was you cant get to much farther apart for shipping, never the less even with the extra for shipping the total was almost $50 less.
Look forward to giving them a spin.

Offline HaroldCR - AKA Fla.-Deadheader

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Re: Bandmill Blades Breaking
« Reply #10 on: February 05, 2016, 06:57:05 AM »

  :o Didn't expect you to buy any without a free try out. My confidence in them is still high for you to like them. Try them with less tension. I just don't like fiddle string tight.

 In a post wayyy back, Kirk said he liked them, but, the price went up so high he quit using them. ???

 Just got word my crate will be delayed another week before pick up, so, that puts me receiving it in early-mid March  ::) ::)

Online Kirk Allen

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Re: Bandmill Blades Breaking
« Reply #11 on: February 05, 2016, 08:50:09 AM »
I would still use them if they had the same profile as the WM set up because I can use my CBN grinder to sharpen them but since they are different I dont have the time or patience to do one tooth at a time manually
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Offline Stevem

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Re: Bandmill Blades Breaking
« Reply #12 on: February 05, 2016, 10:50:48 AM »
Is Kenne the only place to but the Munk blades in the USA?
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Offline HaroldCR - AKA Fla.-Deadheader

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Re: Bandmill Blades Breaking
« Reply #13 on: February 05, 2016, 12:56:51 PM »

 There is a place in Michigan somewhere. Don't remember the company.

 I've had nothing but excellent service from Kenne-saw.

Offline red oaks lumber

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Re: Bandmill Blades Breaking
« Reply #14 on: February 06, 2016, 04:25:22 PM »
i don't get past the second sharpening before the band breaks. i'm not terribly concerned about breakage,to me it;s the cost of doing business.
your band should never break in the weld.just sayin 8) i run 1 1/2 x .55 x 196  mostly turbo 7's but will run others depending the conditions.i went from 80 psi to 90 psi in frozen wood my sawing speed has gone back to over 75 fpm all the while holding a flat cut.
 i think the biggest culprit in band breakage is over flexing on smaller wheels and under feeding the band allowing the band to build heat,which will start to temper the blade.i don't run a debarker and my wood sadly is quite dirty,i change bands every 2 hours which is around 1,200 -1,400 b.f per band which for me is exceptible.
  the best way to keep from breaking bands... don't saw  ;D
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Offline bandmiller2

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Re: Bandmill Blades Breaking
« Reply #15 on: February 06, 2016, 08:14:30 PM »
Another factor not mentioned is running the bands too long between sharpening, that tends to stretch the gullets especially high HP mills. My mill has Browning 19.5" wheels and as I've said never broke a band am get around 12 sharpenings. My bands start out 1 1/2" when they reach 1 1/4" they start to wonder, by that time they have cut so much lumber I feel I got full measure pressed down and running over. Frank C.

Offline bandmiller2

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Re: Bandmill Blades Breaking
« Reply #16 on: February 07, 2016, 06:06:26 AM »
A band, in a way, is like a chain each gullet is like a link. When your pulling that band through a 24" log that's a lot of strain on a gullet, especially if dull, add that to too fast a feed and you have a snapper. My band mill is powered with a Baldor 15hp. three phase motor it just gets warm to the touch not even hot I could cut faster but everything works well and I loathed to change things. Frank C.

Offline HaroldCR - AKA Fla.-Deadheader

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Re: Bandmill Blades Breaking
« Reply #17 on: February 07, 2016, 06:58:59 AM »
 Have to agree with Bandmiller2. Still, we cut many 32-36" logs and was constantly pulling the governor on the Honda 24HP engine. I used to run the engine as hard as it would stand and the logs were really impregnated with sand. This is what impressed me most about the Munks. They still cut reasonably well in the sandy conditions.

 Gullet grinding is very important, although many light sharpenings are certainly better than heavier grinding.

 On matching the profiles on different blades, we found that changing the square part of the WM 1.5" blade gullet made no difference to performance. Like anything, I believe a squared corner will start to fatigue sooner than a rounded corner. Experience has shown a score line in glass, a deep scratch in thin metal, a cut thread on a bolt, etc., will fatigue or break easier than clean smooth metal.

 Like Bandmiller2, once something suits me, I prefer to not mess with changing things, unless I can be convinced that change will better whatever my project may be.

Offline backwoods sawyer

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Re: Bandmill Blades Breaking
« Reply #18 on: February 08, 2016, 12:04:42 AM »
I find that when I have ran dull saws to long it generally has cracks forming in a multiple gullets at the sametime.
A clean brake on new saws leads me to look for something else.

Offline bandmiller2

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Re: Bandmill Blades Breaking
« Reply #19 on: February 08, 2016, 05:29:31 AM »
It would be an interesting experiment for you fellas that get early breakage to try less tension, a little slower feed, and pulling the bands off a little sooner and see if it has much of an effect on band life. Frank C.

Offline furu

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Re: Bandmill Blades Breaking
« Reply #20 on: February 08, 2016, 02:09:14 PM »
As has been posted, contact with the metal rim on a belted wheel can cause an increase in blade breakage itself.
  
I know my drive wheel belt is getting a little thin and I need to replace it but the TK video shows it to be such a PITA that I have not yet done it due to the perception of how long it will take me the first time I do it (until I develop a good technique).  The idler wheel belt is worn as well but is in much better shape.  

I keep watch on the metal edge to see if there is any shiny spot that would indicate blade contact but none found yet.  There is a small/tiny edge still on the rubber (not much though) above the metal edge.  

The story behind how my belts are so worn in the number of hours on the mill is rather "funny" given the point of of this thread which is reducing blade tension to help reduce breakage.

I was sawing an initial log one morning and just about 3/4 of the way down the first cut I saw a large amount of "steam" (white/grayish in color) emanating from the area of the blade exiting the cut and the drive wheel enclosure.  I had seen what looked like small amounts of smoke before in the outer initial cuts of a log and after some research elsewhere decided it was steam from the wood moisture and the weather conditions (temperature/dew-point spread).  

Having seen it before I did not grasp quickly enough that this was a lot more "steam" than I was used to seeing.  As I realized that this was different than what I had seen previously and started to slow the cut, the blade came off the wheels, having been pushed off the belted wheels due to inadequate blade tension at full speed about 15 feet into the cut.  

I had failed to check tension before I started to mill that morning.  

I had left the blade on the mill the previous night since I was going to saw first thing the next morning but I always backed off tension before stopping for the day/evening.  My failure to check blade tension/tighten-up the tension to the recommended spec allowed the belted wheels to spin inside the band and while the band was spinning and cutting, the slippage did an amazing amount of wear on the belt in one 20 foot (actual only about 15 ft before the blade came off) cut.  Stupid me.  Lesson learned.  Of course I had to cut the blade to get it out of the mill and cut which really annoyed me as it had been put on brand new the previous day shortly before I stopped for the day.  Probably had less than 50 linear feet of log cut on that blade.

Never would have thought that a black rubber belt would put out that light a color of smoke but it did.
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Offline HaroldCR - AKA Fla.-Deadheader

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Re: Bandmill Blades Breaking
« Reply #21 on: February 08, 2016, 03:37:12 PM »
 
Quote
Of course I had to cut the blade to get it out of the mill

 This is the one fault I have with 4 post mills. A couple of times we had a belt come off, from not paying enough attention, and we simply gig back the carriage on the WM style mill we built, after removing the wheel covers, and put the blade right back on the wheels and continued sawing.

 We built ours with a remote feed system, ( same as the one I am building now) so, I never throttled down, just bumped the sawhead up and gig back, instead of dragging the blade back through the cut, like a lot of guys do.

Offline furu

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Re: Bandmill Blades Breaking
« Reply #22 on: February 08, 2016, 04:10:05 PM »
Oh if the blade had just been sitting there the 4 post head would not have been an issue at all.  I could have put it back on but it was a bit more than that as it came off the wheels.  

Don't quite grasp the "bumped the sawhead up and gig back" language  can you explain it?
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Offline HaroldCR - AKA Fla.-Deadheader

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Re: Bandmill Blades Breaking
« Reply #23 on: February 08, 2016, 05:01:35 PM »
A lot of guys stop the blade from turning and drag (gig) the sawhead back through the cut they just made.

 I don't stop the blade, just raise (bump) the sawhead above the top board and drag (gig) the sawhead back to me. I don't chase the sawhead all day long. I have remote control motor that does that.

 We had a few blades run off, when using Suffolk blades and they broke regularly. If it was not broken, we would just put it back on. Our drive belt was inside the sawhead shroud and we replaced it one time in all the 1000's of bd/ft we cut.

Offline furu

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Re: Bandmill Blades Breaking
« Reply #24 on: February 08, 2016, 05:19:12 PM »
I presume then that you finish the cut after you reinstalled the blade.  It would be rather challenging to raise the head if the blade was still in the cut when you put it back on the wheels.  I must have misinterpreted the order of events.

I also rarely stop the blade when I am returning the head to the start point for the next cut.  Only if I am going to re-position the log and or cant.
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Offline HaroldCR - AKA Fla.-Deadheader

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Re: Bandmill Blades Breaking
« Reply #25 on: February 08, 2016, 05:51:15 PM »
Quote
I presume then that you finish the cut after you reinstalled the blade.

 Correct

Offline Tom the Sawyer

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Re: Bandmill Blades Breaking
« Reply #26 on: February 09, 2016, 11:00:27 PM »
My mill (Timberking B-20) has never thrown a belt.  Broken blades have gouged a chunk out a few times but I have never had to stop and replace a belt - just changed it later during my normal maintenance.  I never return the saw head with the blade in the previous cut, I raise it at leaset 1/2" above the top of the board and then bring it back.  The B-20 really flies coming (gigging) back.  I have knocked the blade off of the wheels, either by not raising it high enough before gigging back  >:(, or by trying to back out of a cut for some reason (hitting a spot on the log too wide to pass without trimming, hitting something in the log) with the blade turning.  Knowing that, I normally will stop the blade engine, wedge the board up and then back it out.  :-[

Having never thrown a belt is probably because the TK mills use a tight-fitting belt (B56 for the B-20).  Some other mills use a loose-fitting belt, like a B57.  I have heard they are much easier to change but sometimes get sawdust under the belt.  Tight-fitting belts can be a pain to change, even after watching the video.  The video shows them changing a belt while the wheel is off the mill, clamped in a vise.  I change mine on the mill.  It seems to take three hands but a couple of small C-clamps and two old screwdrivers get it done for me. 

I accidentally ordered the wrong belts the last time.  I ordered BX56 instead of B56.  The "X" denotes a cogged belt but I decided to try them.  They have been working fine and, they were significantly easier to install.  I normally get about 75 hours on a set of belts.  I think they have been on there at least that long.

FYI, I run about 1/4" in front of the flanges on the guide wheels with 1/4" below tangent.  I am running the updated guide wheels from TK that have a grease zerk built in.  This is an improvement that TK came up with, years after my mill model went out of production.   ;D
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Offline bandmiller2

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Re: Bandmill Blades Breaking
« Reply #27 on: February 10, 2016, 06:15:22 AM »
I too run tight belts, and believe they are less prone to damage. Some like flat top, myself I like a slight crown, they seem to work ether way. Putting the belts in hot water and using soap helps as does a couple of old butter knives. Its the same as mounting a tight tire on a rim. Frank C.

Offline Stevem

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Re: Bandmill Blades Breaking
« Reply #28 on: February 10, 2016, 10:04:57 AM »

Quote
The video shows them changing a belt while the wheel is off the mill, clamped in a vise.  I change mine on the mill.  It seems to take three hands but a couple of small C-clamps and two old screwdrivers get it done for me. 

I too looked at the TK video on belt changing and am prone to try and change the belts on the mill (when I get the mill and when a belt needs changed).
Was questioning why they didn't use soapy water to help ease the belt on.  Used all the time in changing tires!

And if you take the wheel off, to put it back on you are supposed to use a torque wrench to get the proper tightness.  Another tool to lug around!

Looks like I'm going to have to buy a whole set of tools for the TK :'(.  The Lucas came with most every tool I need. :) :)
Stevem
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Offline furu

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Re: Bandmill Blades Breaking
« Reply #29 on: February 10, 2016, 10:16:42 AM »
Any decision on delivery?
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Offline Tom the Sawyer

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Re: Bandmill Blades Breaking
« Reply #30 on: February 10, 2016, 01:10:53 PM »
Stevem,

Your mill will be much easier to work on, with the swing away doors and nothing in front of the wheels.  My B-20 has a 2x2 vertical post in front of the wheel.  For me, it was much easier than taking the wheels off.  I have tried the hot water method but the stove is about 200' from the mill.   :)  I do use soap to lubricate the belt but the cogged belts were significantly easier to install. 

I bought extra tools when I got my mill, but only because I would be milling on the road and didn't want to be switching tool boxes all of the time.  I can only think of two 'tools' I bought to work on the mill that wouldn't be in most people's toolboxes.  One was a Cook's blade leveling device (a straight edge that clamps to the blade to make sure the blade is level to the mill bed.  The other was a V-belt tension gauge, which probably should have been in my toolbox, but I had never bought one.
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Offline Stevem

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Re: Bandmill Blades Breaking
« Reply #31 on: February 12, 2016, 07:41:50 PM »
Checked with TK, mill is due here the first week in March.  I am excited.  Been sawing at a local (zombie) mill for custom orders and seeing where the band mill will (I hope) make my life easier.  Sawing mostly smaller oaks that the Lucas just doesn't do well with.

On the changing the belts:  TKs video shows beating the hub nut off with a hammer and 16" crescent but to reinstall they spec a torque of 150 ftlb.  Cant see caring around a precision wrench in the cab of my pickup that is seldom used.

Figuring on a tool box like an old ammo box to carry with the mill, all "new" tools or duplicates of my present tool stock.  But that's as I go to see what I need.  Already bought a torpedo level as per TK suggestion.

Belt tension gauge?  What's that for?  TK directions says to just line up the dots on the tensioner  spring housing/barrel?  What would you tension it to? Is there a spec somewhere?

Stevem
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Offline Tom the Sawyer

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Re: Bandmill Blades Breaking
« Reply #32 on: February 12, 2016, 08:34:25 PM »
I wouldn't beat on any fastening device, except a nail, with a hammer.  It should only take 151 ftlbs to take it off :)
I would think you could change your belts without removing the wheel.  That is the way I do it and it is probably easier on the newer mills.  Hopefully, someone with that model will chime in.

I have found it very handy to have a toolbox on close to the mill, with an extra set of tools just for the mill.  I actually found a poly tool box at Tractor Supply that fit nicely between the frame rails.  I have one in front of the operator's station that has lubes, tools for pulling nails, chalk, and my PPE.  I mounted another one at the front end of the mill and it contains a first aid kit, fire extinguisher, and PPE for clients/helpers (dust masks, ear muffs, ear plugs, eye protection, goggles, and gloves - I'd hate for someone not to be able to tote boards because they left their gloves at home. :) ).

The blade tension gauge is built into the saw head.  The tool I was referring to is a spring loaded tool to check for proper tension on the drive belt.  There is a formula, I don't have it memorized, for the number of belts and the distance between the pulley centers, etc.  You put a straight edge across the pulley tangent and use the tool to deflect the belt a specific distance - it shows how much pressure it took.  I have the proper tension for my mill written down, I'm sure you could call Jason and he could tell you the proper tension for your mill/engine combination off the top of his head.  I use a 2' magnetic level for setting up my mill, although I have considered mounting a couple of permanent level vials, like I have seen on RVs.
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Offline furu

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Re: Bandmill Blades Breaking
« Reply #33 on: February 12, 2016, 10:11:33 PM »
Earlier in this thread I asked about the actual tension that folks were using on their blade in actual pounds of tension after Harold recommended a lower blade tension than a lot of folks use.
Never saw a response as to the actual real tension on the blade. I decided that I would do some measurements on my mill and post some numbers.
It seems that each manufacturer has their own method of tensioning the blade and thus it is a challenge to do an apples to apples instead of an apples to oranges type of comparison.
Backwoods sawyer points this out in how WM has a different style tensioner and "good tension" is at 80 psi on that style tensioner. TK uses a gauge in which the tension is set properly at 1200-1400 psi readings.  No real way to actually figure out who has more tension or less or what is excessive with all the different methods for setting said tension.

For several years now I have run 80 psi in the air bag style tensioner, up from 60 psi in the manual.
 

Cooks has different measuring setting device from either WM or TK.

Since I have a TK mill, I think in TK terms which is in reality nothing other than a base line for that specific  brand mill.
TK for example previously recommended that you tension the blade by:
“Turn the blade tensioner until the gauge reads 1,200 pounds.”
 
A little over a year ago they modified their recommendation to:  
Turn the blade tensioner until the gauge reads 1,300-1,500 pounds for 1-1/4” blades and 1,800-2,000 pounds for 1-1/2” blades.”

Cooks has some recommendation for "real" tension on saw blades.  I quote their recommendations:

Standard tension settings for:
1 to 1.5 inch blades         16000-17000 lbs
1.5 inch blades                 17000-18000 lbs
1.5 x .050 or .055 blades      18000-20000  lbs
2 inch                                        18000-22000  lbs

Higher settings (Faster cutting less longevity)
1-1.5 inch                                   18500-20000 lbs
2 inch                                         19000-23000 lbs

I collected data on my TK mill to see what the TK recommendations resulted in "real" blade tension and also I was curious as to how linear the tension increase was as I increased the gauge psi on the TK tension device.  See picture/graph and note that it is a rather linear increase.  Well there is no picture as for some reason after I upload the picture it says unable to access)  It is a near straight line  with the Mill gauge reading on the x-axis and the Tensiometer reading on the y-axis)

Mill gauge psi      Tensiometer (measured using a Lenox tensiometer)
500                            2600
750                            7500
1000                        12400
1100                        14000
1200                        16000
1300                        18000
1350                        18750
1400                        19400
1450                        20800
1500                        22500

TK’s new recommendations falls in line with the higher setting that Cooks recommend on blade tension and their older/previous recommendation matches up with the bottom of the Cook’s recommended standard tension setting.

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Offline backwoods sawyer

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Re: Bandmill Blades Breaking
« Reply #34 on: February 12, 2016, 11:24:58 PM »
Made a few test cuts at lower tensions today with a new out of the box saw. air bag had 60 psi so I started at 65, then 70, it wandered, in cedar 75 was was cutting ok, but had to go back up to 80 in Doug fir.

Offline Tom the Sawyer

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Re: Bandmill Blades Breaking
« Reply #35 on: February 12, 2016, 11:28:46 PM »
furu,

Thanks for doing the research and for all of the details.  My B-20's manual also said 1200 lbs., although I would watch the blade for flutter while I was tensioning it and modified the tension to reduce flutter.  I have found that, for woods like cedar, hackberry and walnut, it cuts just fine at 1100 lbs.  For woods like oak, locust, hedge or mulberry, I'll raise it back up to 1250 lbs., give or take.
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Offline HaroldCR - AKA Fla.-Deadheader

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Re: Bandmill Blades Breaking
« Reply #36 on: February 13, 2016, 07:05:51 AM »

 Good info, maybe.  ::) A story my Dad told me years ago, when he was a Kaiser-Frazer dealership mechanic.

 Oil pressure gauges read 5-8 Psi on engine oil, so, factory guy had the faces changed to read 15+ PSI, so customers were satisfied.  ::)

 Nothing to really do with Furu's excellent info, though. On another forum, a member clamped a sliding caliper to his blade, on the mill, and at whatever the recommended setting was supposed to be, he actually stretched the blade a few thousandths.  ???

 My starting of this thread was to give some insight to those that had problems with excessive blade breakage. Maybe someone can do some research on bearing life at those high pressure settings. Once a mill is sold, manufacturers need to sell parts to help cash flow, same as car dealerships.

 

 

 

Offline furu

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Re: Bandmill Blades Breaking
« Reply #37 on: February 13, 2016, 09:04:39 AM »
We used a 3/8" ratchet that tightened the tension bolt, until it got tight, then, engaged the drive belt and watched where the blade ran on the guide rollers. We could change the tracking of the blade with more or less pressure on the blade tension bolt.
 Also, we ran on the middle tread rib on the tires, and, that had a little give, also, being a rubber strip.
 I just don't see all that much tension being necessary.
 More than anything 1/8 to 3/16 down pressure on the blade guides will hold the blade steady, IF you set and sharpen correctly. I can't imaging solid block type blade guides not causing problems heating the blade from friction.

I remember from Tim Cook's excellent discussion of and about his mills the criticism that he leveled against some mill design that did not have anything other than brute force tensioning of the blade.  His video certainly left the impression that Cook's was against any tensionning device that did not have "give" in it to absorb shocks and stretching effects.

From your description it appears that you tension and set tracking with the same tension bolt. ???
We could change the tracking of the blade with more or less pressure on the blade tension bolt.
Interesting design.  

The problem that I see with setting tension with a ratchet is consistency.  Of course you do it each time so you have a consistent feel.  But what if the threads are a little stiff from corrosion, piece of dirt or sawdust or easier due to grease.  What if you use a different size ratchet one day as your other one was misplaced.  One mill manufacturer tried to eliminate that variable by using a torque wrench to set blade tension.  That at least removes one of many variables but many still exist.
The thing is without actually measuring the blade tension with a tensiometer none of us know what our different mills techniques for setting blade tension actually result in.  If the blade does not flutter or it thrums at some level when tight is all dependent upon the one who is doing it.  It would be interesting to actually get a group of sawyers together without any additional aids and have us set our blades tension and then measure the actual real tension that we are running.  Might surprise us a lot.

I do know in my case that I have a large data point for not running tension too low (but what is too low).  I had my drive wheel turning inside the blade wearing down the belt and did it in an amazingly short period of time.  Without the tension being high enough the engine was driving the wheel and the energy could not be transferred to the blade due to lack of blade tension thus it slipped big time and wore a belt very quickly.
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Integrity is doing the right thing when no one else will ever even know.

Offline mountainlake

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Re: Bandmill Blades Breaking
« Reply #38 on: February 13, 2016, 10:13:56 AM »
Made a few test cuts at lower tensions today with a new out of the box saw. air bag had 60 psi so I started at 65, then 70, it wandered, in cedar 75 was was cutting ok, but had to go back up to 80 in Doug fir.


 It would be interesting to know what tension you are getting on a Lennox tension meter at different air bag pressures. I like the idea of a air bag tensioner which should have good give compared to a hyd tensioner.   Steve

Offline HaroldCR - AKA Fla.-Deadheader

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Re: Bandmill Blades Breaking
« Reply #39 on: February 13, 2016, 12:03:12 PM »
 When you build a mill from scratch, you learn a lot. We built a lot of adjustment devices in the design. When I showed my son a brochure, and said we were going to build one, he gave me that "look".  ;D He is an excellent welder and fabricator and still thought I was nutz.

 As I stated previously, we ended up using Munks blades and they are as accurate blade after blade, as anything we tried before. The company has no dog in the hunt for selling machines and parts like mill manufacturers. WM sells their own brand of blade and makes money with resharps. They have a stake in how they teach their customers.

 My point is, a 19" band wheel is stressing the blade in the tight radius. They have NO give at the wheels.

 We used trailer hubs and tires. The rubber tire HAS give, so shock absorption is a non issue. We use Cooks roller blade guide system. Works well with lots of adjustment capability.  We don't "stretch" our blades, the tires allow for knots, clumps of bark, and, if paying attention, you "hear-feel when something is going wrong and shut down to investigate.

 Cooks recommend their blade roller, to take the curved "set" out of a used blade, after using on hard "steel" wheels. I don't know anything about Cooks mills. We could not afford to buy a mill at the time we needed one. After several years, Cooks, WM, TK ,etc are still in business, so, I believe they make good equipment.

 As far as "pre set", we still watch the blade as we run up the RPM's, and, if it runs a little toward or away from the roller guide flanges, we adjust accordingly.  We run our mill by "feel" watching how it performs, like operating a bull dozer. There are no levels or other handy devices on dozers. You climb on, do the deed and watch how it comes out, adjusting as needed. Actually, we have 2 adjustment bolts, one for tension, the other for blade travel on the guide rollers.

 At an agri show, in Moultrie, Georgia, Dave Mann, head honcho for Wood Mizer, heard me discussing how I changed one of their features when we built our mill. He was talking to a crowd, and, as we turned to leave, he asked us to hang on a minute. He had guessed we were the ones that built an open sided cantilevered mill, like WM's. I was ready to hear about copyright infringements, as we had heard from many people, because we copied the WM design. Actually, he was interested in what we said and asked several questions about what and why we built the cantilever design. I told him, and, he wished us good luck with the mill.

 I bought a used Peterson Swing blade mill for down here, to cut BIG-hard logs. I had asked a lot of questions on another forum, and got feedback from Peterson when I talked about building a swing mill. I was even invited to visit their factory, in New Zealand, by one of the owners, and was told I would have access to their "design-research" room. Apparently, they like free thinkers that try different ideas.

 My son took over the sawing when I moved down here, but, he just didn't catch on to the whole reading the log, getting the most out of it, and, he was working alone. Our mill was set up for 2 people system as I did the sawing and Ed did the heavy work.  Kirk and Buzz actually saw the mill in action.

 If this comes across as bragging, or, being an expert, it is NOT my intention. I just call 'em as I see 'em, and always try to help anyone that asks questions. I just pay close attention and keep the blade in the log, rather than worry about a few pounds of blade tension. All my concerns were worked out on the build(s) of 2 mills. I was told by many people that we could not build a functioning mill and we could NEVER keep a blade from running off a mill.

 Have y'all read the thread where I taught a complete stranger, online, how to sharpen blades AND change the profile? Sawmill Squaw was the student and she is married to a hard headed guy. She did what I explained and her husband bragged all over their area of how she did a better job than the ones they tried at getting their blades sharpened. She simply paid attention and asked questions, same as y'all here.

 This is why I asked for input and to keep things civil. Blade tension is not some magic trick. Just find what works for YOU and keep doing it.  ;D

Offline red oaks lumber

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Re: Bandmill Blades Breaking
« Reply #40 on: February 13, 2016, 05:47:29 PM »
well written harold  !!!
follow your heart, the rest will happen

Offline HaroldCR - AKA Fla.-Deadheader

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Re: Bandmill Blades Breaking
« Reply #41 on: February 13, 2016, 06:00:50 PM »

 Thank you. I sometimes get carried away with my comments.  ::) ::) ;D

Offline HaroldCR - AKA Fla.-Deadheader

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Re: Bandmill Blades Breaking
« Reply #42 on: February 20, 2016, 07:40:16 AM »
See if this works. The dreaded band blade tensioner.

 NOPE


Offline furu

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Re: Bandmill Blades Breaking
« Reply #43 on: February 22, 2016, 07:04:29 PM »

I collected data on my TK mill to see what the TK recommendations resulted in "real" blade tension and also I was curious as to how linear the tension increase was as I increased the gauge psi on the TK tension device.  See picture/graph and note that it is a rather linear increase.  Well there is no picture as for some reason after I upload the picture it says unable to access)  It is a near straight line  with the Mill gauge reading on the x-axis and the Tensiometer reading on the y-axis)

Mill gauge psi      Tensiometer (measured using a Lenox tensiometer)
500                            2600
750                            7500
1000                        12400
1100                        14000
1200                        16000
1300                        18000
1350                        18750
1400                        19400
1450                        20800
1500                        22500

TK’s new recommendations falls in line with the higher setting that Cooks recommend on blade tension and their older/previous recommendation matches up with the bottom of the Cook’s recommended standard tension setting.

Now I can include the graph of the data since Kirk got the photo upload working again.  (Thanks Kirk)

I am now able to include the graph of the linearity of the blade tension vs the blade gauge on the TK.  While there is some minor bobble in the data  it is not much and is pretty straight.  (I was in a hurry, the light was low and I am certain I could have done a more accurate job of data collection)
The vertical axis is the Tensiometer reading and the horizontal axis is the mill tension gauge.

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Integrity is not just doing the right thing when no one is looking.
Integrity is doing the right thing when no one else will ever even know.

Offline bandmiller2

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Re: Bandmill Blades Breaking
« Reply #44 on: February 23, 2016, 06:52:01 AM »
As far as mill tension data goes that's about as predictable as you can get. Furu, have you ever tried clamping a Vernier caliper to the band and then tensioning it, would be interesting to compare it to that tension meter. (at least for us poor folks) Frank C.

Offline furu

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Re: Bandmill Blades Breaking
« Reply #45 on: February 23, 2016, 08:36:52 PM »
I can try it but I am not certain what I would use to do the clamp that would work without being too cumbersome and heavy.  Most all my clamps are welding clamps.  The caliper  prongs are all sloped as well. 

I can take a look but I am in the middle of planting season and I have a lot of seedlings to plant and protect from the infamous Aplodontia rufa.  I will get back on that but please don't turn blue holding your breath.
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Offline red oaks lumber

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Re: Bandmill Blades Breaking
« Reply #46 on: February 24, 2016, 07:33:24 AM »
are you guy's suggesting the band stretches in lenght as it tightens? i know it will when it heats up.
follow your heart, the rest will happen

Offline HaroldCR - AKA Fla.-Deadheader

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Re: Bandmill Blades Breaking
« Reply #47 on: February 24, 2016, 07:46:11 AM »
 Yep, if you tighten it enough. That's why I don't like solid steel or 19" wheels and V belts. Once they are smashed into the pulley groove, then what ???

 One day, I need to visit my Buddy with the wide band mill blades, over 6" wide, and see if they get curved from running over steel wheels. His sharpener is so worn out, the whole advance mechanism jumps around and his tooth tips are tungsten or something and they don't use any liquid cooling. ??  Y'all should see the sparks fly out of that thing when they sharpen.

 Where is that guy that ordered some Munks blades a couple 3 weeks ago? Looking to see if he proves me wrong about them.

Offline bandmiller2

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Re: Bandmill Blades Breaking
« Reply #48 on: February 24, 2016, 07:40:03 PM »
Furu, where are you located mate, up here in Ma. we still have snow piles. I've never tried it but they say if calipers are clamped on a band and then tensioned you can read the stretch. Probably a couple of vice grips would do the deed. My band mill just has a heavy compression spring, I just collapse it and don't have any idea how much tension. Its been OK for the last 15 years so it must be close. Frank C.

Offline backwoods sawyer

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Re: Bandmill Blades Breaking
« Reply #49 on: February 24, 2016, 10:54:13 PM »
On the munksfor saws I have only ran three of the saws, noticed a wave with the first one, changed guides wave went away. Have not broke a saw out of this batch, however I was just milling soft redwood and the saws were changed mainly do to milling dirty logs.

Offline HaroldCR - AKA Fla.-Deadheader

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Re: Bandmill Blades Breaking
« Reply #50 on: February 25, 2016, 06:22:39 AM »

 Thanks for the response. Are you running the same tension as you were previously ?

Offline backwoods sawyer

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Re: Bandmill Blades Breaking
« Reply #51 on: February 25, 2016, 10:48:29 PM »
i tried a lower tension but went back to where I was

Offline backwoods sawyer

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Re: Bandmill Blades Breaking
« Reply #52 on: March 08, 2016, 11:33:33 PM »
First three saws out of the box made it to the sharpening room but 4-5 and 6 all broke, #7 found the hook end of a lag bolt twice.

Offline HaroldCR - AKA Fla.-Deadheader

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Re: Bandmill Blades Breaking
« Reply #53 on: March 09, 2016, 07:06:09 AM »

 That's not very encouraging. With the amount of blades that are breaking, it sure seems that something is amiss with the tuning of the mill, perhaps ??  Don't have any ideas to help. I still believe excess tension is involved.

 I have a photo of a very large, ugly Live Oak, which is one of the densest woods ( Cannon balls would not break or penetrate the hull) and we cut it up no different than any other hardwoods we encountered .

 This may be tough to figure out.

Offline kelLOGg

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Re: Bandmill Blades Breaking
« Reply #54 on: December 20, 2020, 08:26:36 AM »
I'm very late to the party and I hope this adds something helpful to this old discussion.

When suppliers of bands provide the stress (lbs/sqin) to be applied to their bands, those of us (who have spring tensioners and no gauge to tell us when we have reached this recommended tension) need more information. Proper stress can be obtained by measuring the stretch (strain, in engineering language) when tension is applied to the band and plugging it into the equation below.
 
Stress(or tension in lbs/sqin) = E(modulus of elasticity in lbs/sqin)  X Strain (dimensionless quantity)
where E=30,000,000 lbs/sqin  for tool steel.

Strain can be measured by opening calipers to a specified length and clamping to the band with small c-clamps and tensioning the band. How much tension depends on the band thickness and width. I run Kasco 4 degree, 1.25”, 0.045” thick bands so I contacted Cutting Edge and was told 20,000 lbs/sqin was a recommended value.

Strain=20,000/30,000,000 or 0.000667 is the strain value.

Strain is defined as the change in length of the band as it is stretched divided by its original length, so if I open the caliper to, say, 5.5 inches, the right amount of stretch in the band is 5.5 X 0.000667 or 0.0037 in. So I tension the band until the caliper reads 5.5 +0.0037 or 5.5037” and I should have 20,000 psi on my band. This should remove the guess work in tensioning a band and give better band life.

I have just learned all this information so I have high hopes that my band life will increase as well as yours.
 
Apparently, of equal importance as band tension is that the band back does not contact the flange on the roller guide except during extreme sawing conditions. I had to push my roller guides back a bit as Tom the Sawyer does.
« Last Edit: December 21, 2020, 04:16:15 AM by kelLOGg »