Author Topic: Bandmill Blades Breaking (Read 46782 times)

HaroldCR - AKA Fla.-Deadheader · « **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

furu · « **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).

HaroldCR - AKA Fla.-Deadheader · « **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.

bandmiller2 · « **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.

backwoods sawyer · « **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.

HaroldCR - AKA Fla.-Deadheader · « **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.

mountainlake · « **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

backwoods sawyer · « **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

HaroldCR - AKA Fla.-Deadheader · « **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.

backwoods sawyer · « **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.

HaroldCR - AKA Fla.-Deadheader · « **Reply #10 on:** February 05, 2016, 06:57:05 AM »

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

Kirk Allen · « **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

Stevem · « **Reply #12 on:** February 05, 2016, 10:50:48 AM »

Is Kenne the only place to but the Munk blades in the USA?

HaroldCR - AKA Fla.-Deadheader · « **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.

red oaks lumber · « **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

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

bandmiller2 · « **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.

bandmiller2 · « **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.

HaroldCR - AKA Fla.-Deadheader · « **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.

backwoods sawyer · « **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.

bandmiller2 · « **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.

furu · « **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.

HaroldCR - AKA Fla.-Deadheader · « **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.

furu · « **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?

HaroldCR - AKA Fla.-Deadheader · « **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.

furu · « **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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Author Topic: Bandmill Blades Breaking (Read 46782 times)