Woodnet Forums
Help me understand how by bandsaw blade brok e - Printable Version

+- Woodnet Forums (https://www.forums.woodnet.net)
+-- Thread: Help me understand how by bandsaw blade brok e (/showthread.php?tid=7335708)

Pages: 1 2


Help me understand how by bandsaw blade brok e - Alaric - 12-20-2017

I had finished a cut and then stopped the bandsaw.  The blade was still coasting to a stop when I turned the saw back on.  Pop! The blade instantly broke.  

1/2" blade on a Laguna 14" saw.  The blade is about six months old, probably less than ten minutes of running time on it.  It was about 50° in the shop. Blade tension indicator showed it was right for a 1/2" blade.


RE: Help me understand how by bandsaw blade brok e - Stwood_ - 12-20-2017

Look at the ends. See if you can see the weld. The weld may have broke.
Also it could have been from stress. Though I question that as it was a fairly new blade.
They will stress crack, then snap suddenly. Sometimes they will crack only halfway through, and start wobbling a bit, not tracking correctly, then break.


RE: Help me understand how by bandsaw blade brok e - chips ahoy - 12-20-2017

May have been caused by the fact that you didn't let it come to a full stop before turning it back on.Just a wild guess.

Mel


RE: Help me understand how by bandsaw blade brok e - Wild Turkey - 12-20-2017

Is there slack in your drive belt?   That could allow for a "jerk" when you powered it back up that could stress the weld, etc.


RE: Help me understand how by bandsaw blade brok e - Alaric - 12-21-2017

(12-20-2017, 08:56 PM)Wild Turkey Wrote: Is there slack in your drive belt?   That could allow for a "jerk" when you powered it back up that could stress the weld, etc.

I didn't think of slack in the drive belt.  I'll check.  Since the blade was under tension I knew there wasn't any slack in the blade.


RE: Help me understand how by bandsaw blade brok e - daddo - 12-21-2017

It amazes me blades last as long as they do since the blade is bent and straightened twice every complete revolution.

At one per second, that's 1,200 bends in 10 minutes.

Metal doesn't like to bend as much when it gets colder- perhaps that has sometime to do with it? 50 isn't that cold though.


RE: Help me understand how by bandsaw blade brok e - SteveS - 12-21-2017

Either a cheap band or one at the end of its fatigue life.


RE: Help me understand how by bandsaw blade brok e - tnff - 12-22-2017

My guess is since the wheels were still spinning, their built up momentum, rather than absorbing the start up shock, actually increased it by letting the motor start at a much higher speed.  So all that shock went right into the blade rather than the wheels and the dynamic impulse was too great.


RE: Help me understand how by bandsaw blade brok e - Arlin Eastman - 12-27-2017

(12-20-2017, 07:26 PM)Stwood_ Wrote: Look at the ends. See if you can see the weld. The weld may have broke.
Also it could have been from stress. Though I question that as it was a fairly new blade.
They will stress crack, then snap suddenly. Sometimes they will crack only halfway through, and start wobbling a bit, not tracking correctly, then break.

Having used them a ton in the sheetmetal and machine shop that is a big factor of most of the breaking or the weld was on done very well and our bandsaw had it's own spot welder.

Back in the middle 80's I made a suggestion of using a stone on the back of the blades to round off the edges to keep stress cracks from happening and they gave me $500 for the Idea and save the AF a lot of money.

Here is what I use now and put a rare earth magnet on the back so it will stick to the Bandsaw which makes it handy


https://www.amazon.com/Olson-AC70013-Blade-Finishing-Stone/dp/B003A07FNM


I bought two and gave one to a friend.

Just turn on the bandsaw and hold the stone at a 45 to start and then start moving your hand around the blade and it will take only a few moments to do one side make sure you do both of the sides. 

Once done it no longer needs to be done if you take if off.


One more thing as to why it might have broken is if you always leave the tension on the blade and it will stress the blade if it is run and kept that way.

Also do not forget that you can sharpen the blades if it is less then 8tpi.  I use my Drumel and some diamond bits to sharpen them with and I got them from here.  They will last a LONG long time


http://www.grizzly.com/products/Mini-Diamond-Burr-20-pc-Set-1-8-Shank/D2471?utm_campaign=zPage&utm_source=grizzly.com


RE: Help me understand how by bandsaw blade brok e - Alaric - 12-27-2017

Wow, thanks for the tip Arlin. I didn't know about the bandsaw stones.

I don't leave the blade under tension. When I first got my Laguna saw I realized I'd be prone to leaving the tension on, or worse, starting the saw with the tension off. So I fashioned a cord and plug holder that I secured to the tension lever. To get the plug off I have to turn the tension lever. To put it away I have to release the tension lever. Haven't forgotten once since then.