Chestnut

Another Broken Bandsaw Blade

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Well laguna said they would replace it. The guy that I've been emailing told me he has been using this blade on his 1412 for a long time with out issue. Maybe i'm just unlucky 3 times. This wouldn't be the first time that I've had poor luck with a product but i always ask politely for a fix and usually get some help. 

He mentioned in his email to start tension at 3/8" on the gauge and use the deflection method to dial it in from there. That doesn't seem like much tension at all. He also mentioned to monitor the blade tension during period of high usage stating that temperature can effect tension, i just don't see it impacting the tension enough to cause breaks.

Just received notification of shipment. So it was replaced. Guess i'll get to try this again and maybe make a few changes on operation on my end. Thanks @HuxleyWood for the great information. Where in the H E double hockey stick did you learn all of that?

Edited by Chestnut
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2 hours ago, Chestnut said:

Well laguna said they would replace it. The guy that I've been emailing told me he has been using this blade on his 1412 for a long time with out issue. Maybe i'm just unlucky 3 times. This wouldn't be the first time that I've had poor luck with a product but i always ask politely for a fix and usually get some help. 

He mentioned in his email to start tension at 3/8" on the gauge and use the deflection method to dial it in from there. That doesn't seem like much tension at all. He also mentioned to monitor the blade tension during period of high usage stating that temperature can effect tension, i just don't see it impacting the tension enough to cause breaks.

Just received notification of shipment. So it was replaced. Guess i'll get to try this again and maybe make a few changes on operation on my end. Thanks @HuxleyWood for the great information. Where in the H E double hockey stick did you learn all of that?

Curious did you go to a 1/2" on the replacement?

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1 hour ago, pkinneb said:

Curious did you go to a 1/2" on the replacement?

The replacement that Laguna is sending is a direct replacement so 3/4". I bought my own replacement which is a 1/2". My plan is to run the 1/2" and keep the 3/4" around for a rainy day or something.

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3 hours ago, Chestnut said:

Well laguna said they would replace it. The guy that I've been emailing told me he has been using this blade on his 1412 for a long time with out issue. Maybe i'm just unlucky 3 times. This wouldn't be the first time that I've had poor luck with a product but i always ask politely for a fix and usually get some help. 

He mentioned in his email to start tension at 3/8" on the gauge and use the deflection method to dial it in from there. That doesn't seem like much tension at all. He also mentioned to monitor the blade tension during period of high usage stating that temperature can effect tension, i just don't see it impacting the tension enough to cause breaks.

Just received notification of shipment. So it was replaced. Guess i'll get to try this again and maybe make a few changes on operation on my end. Thanks @HuxleyWood for the great information. Where in the H E double hockey stick did you learn all of that?

 

First I am glad they are taking care of you, they should considering they market the blade with their 14" saws.  I searched the forums to see if I had been missing more reports of fatigue cracks in the RK and saw about the number I remember.  Either they are being underreported or it doesn't seem to be a widespread pattern problem.  I do think it is fairly dubious to recommend them for 14" wheels but they do run a fairly ductile high silicon steel backer.  I would love to know the surface roughness in those gullets and I have a sneaking suspicion that some stock is getting through with too high of a RA/RZ  and providing nucleation points for cracks in some stock.  This could be intermittent but one guy that got three bad ones seems to indicate otherwise unless they were bought at or near the same time.  

 

I won't get between a manufacturer and customer regarding tension other than to say IMO their suggesting is way low for the best cut quality HOWEVER they may be fully aware of this but have determined it is needed for longevity and one must give up some of the cut quality the RK is capable of to run them on a 14" wheel.  This is now on my list of conversations to be had at IWF.  In the past, I have been able to get a couple of the Laguna reps to be frank with me via the wink and nod.  The idea of reduced tension for longevity hadn't really occurred to me normally you would not recommend tooling that can't be optimized on a particular machine but there may be a cost/benefit analysis going on.  In any event I would love to hear how lower tension (if you choose to follow their directions) works out, both in cut quality (hand feeding you might not notice a difference) and longevity.  

 

Let's consider the heat issue as it affects tension.  I have actually collected some data on this.  My methodology (very simplistic) was to measure the temperature of the blade backer (roughly the middle so slightly behind the gullets) above and below the cut to determine an average temperature change above ambient (tension set at ambient) for the blade.  The cuts were ~16" resaws in walnut using a sharp 1.25" Trimaster with a constant feedrate of 8fpm (using a feeder) the temperature delta and then average increase was calculated from the temp at the end of each 75" cut.  This seemed to be about the highest duty a hobby saw will see and the temperature dropped very quickly during the time I was moving and refeeding the board.  The highest delta to ambient I was able to obtain from the average blade temp from above and below the cut was ~94C.  We will simply use 100C as our average max temp rise.  Using the linear thermal expansion of steel and the 115" blade length on the 14BX that would correspond to a .138" increase in length divided by 2 and the spring would be allowed to expand .069" or just over 1/16".   If you knew the spring rate of the tension spring you could actually calculate the psi difference in strain but I think most will agree (assuming my data is reasonably accurate and somewhat universal) the decrease in tension during hobby use of these saws will be very minimal.  I recognize there are a ton of variables here but I am pretty comfortable saying unless a blade is unusually long, and the spring has a very high spring rate (none of these are the case with any of the saws we are likely to encounter) the heat related change in tension would not be a significant issue.  My hypothesis is that on a vertical bandsaw in hobby use the thermal expansion of the blade is not enough to cause a significant decrease in tension on the blade or at least enough to cause a significant difference in cut quality.  

I am just a someone that bandsaws have been a hobby within a hobby for 25 years or so and not afraid to experiment and read academic papers on a subject where information is otherwise limited or contradictory.  There is quite a bit of peer-reviewed work on bandsaws and blades, while the vertical bandsaw is all but dead in industry bandmills are alive and flourishing.  Just think how much the wood flooring industry has grown in the US in the last 20 years.  

 

Good luck, I hope this one works out for you.  The RK is a great resawing blade.  

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1 hour ago, drzaius said:

Wow, what a great thread this has turned into. Thanks to all for the info presented.

Amen to that.  I love this stuff.

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20 hours ago, HuxleyWood said:

I would love to know the surface roughness in those gullets and I have a sneaking suspicion that some stock is getting through with too high of a RA/RZ  and providing nucleation points for cracks in some stock.

I still have the blade laguna doens't ever want the broken ones back. If you would like i could provide you with a small chunk. I should try making a marking knife out of the blade i wonder if that would work very well.

20 hours ago, HuxleyWood said:

This is now on my list of conversations to be had at IWF. 

International weightlifting federation? :DIf you have that conversation please come back and share what you find. I'm curious as well if they design the blade to be purposefully ran at lower tensions to manage the smaller diameter wheels on the 14" saws. The mechanics of materials knowledge i have is conflicting with this but they never taught us in depth metallurgical stuff just basic material mechanics. This just gave me anxiety from remembering Mohr's circle... man i look back at some of the stuff i had to learn in school and wonder how in the hell i did it.

20 hours ago, HuxleyWood said:

 If you knew the spring rate of the tension spring you could actually calculate the psi difference in strain but I think most will agree (assuming my data is reasonably accurate and somewhat universal) the decrease in tension during hobby use of these saws will be very minimal

So just assuming that the spring takes 0.5" of compression to achieve the force necessary to tension the blade ~400 lbs. 0.05" of thermal expansion would decrease the tension force by 40 lbs or roughly 10%. So the tension would go from 20,000 lbs to 18,000 lbs. Significant but you'd assume there is enough of a fudge factor that 10% wouldn't make the difference between lasting 4 years of 6 months.

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12 minutes ago, Chestnut said:

International weightlifting federation?

International Woodworking Fair its in Atlanta later this month. Its an awesome show if you ever get a chance to go.

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35 minutes ago, pkinneb said:

International Woodworking Fair its in Atlanta later this month. Its an awesome show if you ever get a chance to go.

I know but the thought of a bunch of weight lifters talking about bandsaw blades makes me laugh. It's also the firs thing that pops up when you google IWF. I think the 3rd is the IWF we're interested in. I'd love to go but Atlanta in august? .... :unsure: MN in august is hot enough for this guy.

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Just now, Chestnut said:

I know but the thought of a bunch of weight lifters talking about bandsaw blades makes me laugh. It's also the firs thing that pops up when you google IWF. I think the 3rd is the IWF we're interested in. I'd love to go but Atlanta in august? .... :unsure: MN in august is hot enough for this guy.

I'm with you but woodworkers are cheap it doesn't get cheaper than Aug in Atlanta or Las Vegas in July for AWFS next year LOL...having said that I got a great deal on my Hammer a3/31 At AWFS by buying the floor demo there...seriously considering an upgrade so will be attending the 2019 show to see if I can pull off the same thing next year...and yes last time it was 109 avg for the 3 days we were there, even my wife said that was to hot to sit in the pool LOL

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I feel like a moron. The laguna guy told me that the tension gauge in the 1412 and 14BX series saws is a magnet that is movable. So once you find your desired tension for a given blade you can move the gauge to arrive back at your tension quickly. Here is my gauge sitting on the table of my bandsaw.

726659225138426320.thumb.jpg.459106d78eb87659eec1c894b0cd4746.jpg

Also i got a carbide blade into day from Highland Woodworking. There were metal filings in the protective case as well as 2 teeth missing. Should i contact them over that or just call it water under the bridge? I'm going on the record and saying i have the worst luck with bandsaw blades.

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2 minutes ago, Tom King said:

no choice but to call over teeth missing

This really cramps my style i need to get these parts cut tonight..... hope they don't mind cause they aren't open to call.

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DSC_1700-01.jpeg

DSC_1701-01.jpeg

Broken teeth above and cut quality compared to the resaw king. It's better than a bi-metal blade but hot dang that resaw king is one fine cutting blade. It is appropriately named.

DSC_1702-01.jpeg

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First, thanks for the offer of a piece of the blade but I have no access to anything that will test surface hardness on something that narrow.  

Not sure if I have ever seen a smaller saw spring with a 800lb spring rate, but they could exist.

I am also not sure who makes Highlands carbide blades but it looks like a Sterling made by Diamond saw, they have that matte finish.  In any event, you should not have to deal with a blade missing teeth since A you paid for all the teeth and B it may signal more issues.  I have occasionally lost teeth on carbide blades, I just crush them off so I know nothing is protruding past the kerf (unlikely) or bit of remaining carbide don't come off and foul other teeth.  I use the same formula as for circular blade as long as I have 90% of the teeth I use it.  Just looking at the cut quality I would say the blade has more issues than just the missing teeth, the may just be a symptom of a bigger problem.  The Highland blade is a 4TPI TCG so it should cut very similar to a Trimaster 3-4 TPI blade which is also a TCG.   The RK's grind has more shear surface and will leave a slightly better cut, but ti should not be that much better than a properly ground TCG.  That cut quality from the Highland blade looks like it was made by a blade with set that the set was all screwed up no carbide blade should ever look that bad.   

You have my sympathy and nomination for the worst bandsaw blade luck.  

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6 hours ago, HuxleyWood said:

Not sure if I have ever seen a smaller saw spring with a 800lb spring rate, but they could exist.

It has to be a somewhat decent spring rate you'd need around 600 lbs to tension a 3/4" blade and there isn't much more than an inch of travel on the spring. I don't think it nearly compresses all the way when tight so i just took a stab at 800 lbs. I would be curious to know but i doubt if i asked laguna they'd tell me, if they know even. Some engineer in the back knows off the top of his head probably. Can probably rattle off the spring rates for each of their saws.

14 minutes ago, Tom King said:

One of those ridges is from the missing tooth.

Yeah your probably right. I did get my parts resawn cleaned up and tenons made so it lasted long enough for what i needed last night.

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Update:
The make of the blades for Highland wood working determined that the blade i was sent was in fact defective so I'll be getting a replacement blade from them as well. This brings my total of carbide tipped band saw blades to 7. I don't think I've bought that many regular saw blades.

 

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That's a lot of blades for sure, but it is also a bit of a testament to buying quality blades in the first place.  Break a $20 blade and you have zero chance at getting it replaced for free, even if it is days after purchase...even if you have TWO of them break.  DAMHIK.  Nearly caused Highland WW to lose all business from me, if I didn't like the Woodslicer so much it would have.

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1 hour ago, wdwerker said:

Save that damaged blade for a backup or for risky cuts.

They might want it back, the blade company not highland WW, but i'll have a Resaw king and the 1/2" carbide tipped at my disposal.

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Replacement blade from highland Woodworking is out for delivery in San Jaun Puerto Rico .... :blink:  I swear i have the worst bandsaw blade luck. People should bet against me.

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1 hour ago, Chestnut said:

Replacement blade from highland Woodworking is out for delivery in San Jaun Puerto Rico .... :blink:  I swear i have the worst bandsaw blade luck. People should bet against me.

Well look at the bright side...you can't break it if its on vacation in Puerto Rico :ph34r:

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On 8/6/2018 at 10:20 AM, bleedinblue said:

 if I didn't like the Woodslicer so much it would have.

 

Be aware Spectrum Supply and Iturra Designs sell the same Atlanta Sharptech black stock as the Kerf Master and Bladerunner for much less money.

 

I said I would ask about the tensioning suggestings the OP got from Laguna at IWF, however, Laguna didn't have a single bandsaw there (almost everything was CNC machines except for 3 other items).  None of the guys knew much about the blades (all CNC all day) and I didn't see Torben any of the times I walked by, so no new info.  

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