And then it went BANG
#21
John, just for reference, I have sharpened my CT twice already. If yours can be fixed, it has lots of life yet.

Regards from Perth

Derek
Articles on furniture building, shop made tools and tool reviews at www.inthewoodshop.com
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#22
that does not look like a good weld to me.  Shouldn't break at the weld anyway.  Next to it, yes, but not at the weld itself.
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#23
(03-15-2018, 10:45 PM)Tapper Wrote: Nice going - at least you have the ball rolling. Good luck and let us know how Lenox responds.

Doug

I got an Email back last evening saying that if I shipped it to them they would "examine and reweld it".  I had neglected to tell him in my first email that many of the teeth had been damaged when it went from 4500 fpm to 0 in about a millisecond.  I sent him that bit of info. late last evening; haven't heard anything yet today.  

Eric, I agree.  Looks like a bad weld.  

Oh, I didn't buy the blade directly from Lennox.  I bought it from Spectrum Supply.  Great prices; now we'll see how their CS responds.  

So, assuming the worst and they don't give me a new CT blade, or a large discount on one, I likely won't be buying another right away.  I love how it cuts but can't justify the price for so few sq. ft/$.  For those of you who do much resawing in stuff up to 12" thick, what blades do you like?  I'm talking high use here, as in 1000's of square feet.  I don't mind resharpening a carbon or bi-metal blade.  Most important to me is a smooth cut and a fast feed rate, exactly what the CT excelled at.  So what do you like?  

John
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#24
How much does that blade cost, John? BTW, I think I'd go ahead and send it to them for evaluation, cause and effect. Surely they can deduce that if the weld failed (looks like it did) it would follow there is a strong possibility that teeth could be damaged.

Doug
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#25
(03-16-2018, 09:59 AM)Tapper Wrote: How much does that blade cost, John? BTW, I think I'd go ahead and send it to them for evaluation, cause and effect. Surely they can deduce that if the weld failed (looks like it did) it would follow there is a strong possibility that teeth could be damaged.

Doug

I offered to send it to them as requested, but was hoping to hear back now that they know the blade can't be saved before doing so.  

I paid about $160 for the blade, including shipping.  I see now that it costs about $135 plus shipping, so still likely cheaper than when I bought the first one.  Still, I can buy carbon steel blades for less than $30 and bi-metal for less than $75 and they can be resharpened w/o special skill or tooling.  I know Derek said he's sharpened his CT, but I wouldn't attempt it knowing Connecticut Saw will do it for less than $50.  

John
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#26
I've used the highland woodworking woodslicer variable tpi blade which cuts down on noise. And I've heard the timberwolf silicon steel blades are nice. If your CT blade isn't salvageable it could be sectioned and used for a nice bowsaw 
Big Grin
Alex
Final Assembly Quality Inspector for the manufacture of custom vintage sport biplanes
[Image: 07-15-28-122_512.gif]
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#27
(03-16-2018, 11:55 AM)jteneyck Wrote: I offered to send it to them as requested, but was hoping to hear back now that they know the blade can't be saved before doing so.  

I paid about $160 for the blade, including shipping.  I see now that it costs about $135 plus shipping, so still likely cheaper than when I bought the first one.  Still, I can buy carbon steel blades for less than $30 and bi-metal for less than $75 and they can be resharpened w/o special skill or tooling.  I know Derek said he's sharpened his CT, but I wouldn't attempt it knowing Connecticut Saw will do it for less than $50.  

John

I suppose the issue becomes the durability of carbon steel and bi-metal blades + their cost of sharpening, versus the obvious benefits of a carbide tipped blade that can be resharpened at least a couple of times. I know you do quite a bit of resawing on your big Griz bandsaw; seems that carbide would be the way to go, assuming (there's that word again) that a regular carbide blade will perform as advertised. They seem to have a pretty good track record overall.

Doug
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#28
Can they replace a short section and make it good?

looked harder at the picture of the failure.  It shows the signs of a fatigue crack, which doesn't really absolve the weld at all.

I'm not a fractography expert, but I have stared at a lot of fracture surfaces under high magnification. 
The crack started at the gullet.  It was in plane strain for a while, which is less ductile and the fracture surface is pretty flat.  About halfway through, it translates to plain stress, which is more ductile.  You can see a rough area at about 45 degrees.  This would be "cup and cone" if it wasn't flat. That doesn't last too long before rupture. Which is also at about 45 degrees, but notably different angle than the plain stress region, and the surface is smoother. In the plain strain part of the fracture surface, it may be sharp right at the surface of the blade.  This area is in plain stress because of the free surface.

I would have to put it under a microscope to tell more, but I guess the initiation site is pretty messed up by cycles after the crack started.
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#29
(03-17-2018, 11:27 AM)EricU Wrote: Can they replace a short section and make it good?

looked harder at the picture of the failure.  It shows the signs of a fatigue crack, which doesn't really absolve the weld at all.

I'm not a fractography expert, but I have stared at a lot of fracture surfaces under high magnification. 
The crack started at the gullet.  It was in plane strain for a while, which is less ductile and the fracture surface is pretty flat.  About halfway through, it translates to plain stress, which is more ductile.  You can see a rough area at about 45 degrees.  This would be "cup and cone" if it wasn't flat. That doesn't last too long before rupture. Which is also at about 45 degrees, but notably different angle than the plain stress region, and the surface is smoother. In the plain strain part of the fracture surface, it may be sharp right at the surface of the blade.  This area is in plain stress because of the free surface.

I would have to put it under a microscope to tell more, but I guess the initiation site is pretty messed up by cycles after the crack started.

Nice forensics! So when the saw started the "thump thump thump" noise the blade was already in mid-failure. I can't count how many times this noise has saved me from continuing to use a blade until it snaps. As soon as it starts thumping I stop the saw (or perhaps finish my cut if I'm feeling bold
Big Grin) and examine the gullets. Almost every time I can find the stress crack and take the blade off before things go boom. Usually it's not at the weld but somewhere else. Hope they treat you right and get you another CT for a good price.
Alex
Final Assembly Quality Inspector for the manufacture of custom vintage sport biplanes
[Image: 07-15-28-122_512.gif]
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#30
(03-17-2018, 12:21 PM)alanealane Wrote: Nice forensics! So when the saw started the "thump thump thump" noise the blade was already in mid-failure. I can't count how many times this noise has saved me from continuing to use a blade until it snaps. As soon as it starts thumping I stop the saw (or perhaps finish my cut if I'm feeling bold
Big Grin) and examine the gullets. Almost every time I can find the stress crack and take the blade off before things go boom. Usually it's not at the weld but somewhere else. Hope they treat you right and get you another CT for a good price.

Yep, I should have stopped when I started hearing the thump-thump-thump.  

Monday, I'm going to send them the blade.  I never did hear back from the guy on Friday, but I figure they won't do anything w/o looking at it in person.  As for saving this blade, there are teeth chipped and missing all around the band; I think it's a lost cause.  We'll see.  

John
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