# Sparks on bandsaw



## richgreer (Dec 25, 2009)

I'm using a 1/4" blade on my bandsaw and trying to cut a curve with a radius of 3.75". I'm cutting through 6" of white oak. I'm getting some sparks from the blade. I've never seen this before.

Is this normal? If not, what could be the cause?

In advance of your responses let me say that I believe I have the right tension on the blade (20,000 lbs./square inch) based on my tension gauge (not the indicator on the side of my bandsaw).

All advice is appreciated.


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## blackcherry (Dec 7, 2007)

The blade teeth were hitting the guide bearing, to tight a turn in such a thick piece. You may need to set the guide bearing back a bit more…BC


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## BigTiny (Jun 29, 2010)

Might also be mineral deposits in the wood.


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## TimKane2 (Jan 30, 2011)

Having no experience, and essentially no knowledge of band saws except they cut stuff, 20,000lb/square inch sounds like an insane amount of force. That is a normal tension?


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## wchips (Dec 11, 2009)

could be sand on the wood or embedded in it


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## greasemonkeyredneck (Aug 14, 2010)

My old Craftsman 12" has guide blocks on each side of the blade. If I cut too tight a radius in wood, according to the thickness, the blade teeth sometimes will contact the guide blocks in a way to throw sparks.


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## richgreer (Dec 25, 2009)

In response to TimKane2 - - I've read from several sources that 20,000 per square inch is right. You need to realize that a 1/4" blade has a cross section that is a very small percentage of a square inch. My calculations say that it is about .55% of a square inch. That implies a total pull on the blade of 110 lbs. That sounds reasonable to me.


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## bubinga (Feb 5, 2011)

Where exactly are the sparks originating from?

I saw sparks one time, when the blade broke and flew off, not fun
Actually had that happen with mineral deposits.


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## gfadvm (Jan 13, 2011)

I had sparks when my lower thrust bearing siezed.They obviously were below the table but the upper thrust bearing siezing would generate sparks above the table.I studied all the blade tensioning advice and use the 1/4" deflection and or the flutter technique.These have both been effective and simple to perform.You should be able to cut a much tighter radius with a 1/4" blade so I dont think that is the problem.I routinely cut 1" diameter circles with my 1/4" blade.


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## Popsnsons (Mar 28, 2010)

Rich,

I had sparks come from the guide blocks. But when I run a Carter Stabilizer with my 1/4" blade the standard guides and bearings, both top and botttom, are not used and the operation is much smoother.


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## Dusty56 (Apr 20, 2008)

Hi Rich ,My first thoughts were mineral content or foreign objects , but you don't mention if the sparks are before entering or when exiting the wood , but I'll assume they're up top because it would be impossible to see below the table while slicing. That would leave blade contact with the guides or bearings and not much else that I can think of.
Sorry.


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## Maddhatter (Aug 9, 2008)

Rich, have to agree with Dusty 56, with out knowing where the sparks came from it is hard to provide a recommendaton. most likely I would check the lower guide blocks as they can come out of adjustment and because they are below the table, you may not have noticed.

Hope all goes well. good luck and safe sawdust.


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## SteveMI (May 19, 2009)

My band saw started making sparks at times and I found that one of the bearings had siezed. When cutting straight it was fine, but when trying to cut any kind of curve the blade contacted the bearing and caused the sparks. I changed the bearing and sparks went away.

Steve.


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## Jenine (Sep 6, 2013)

Mine just started doing this and the bearings are fine. Brand new blade. Saw and bearings are only a few weeks old. Pretty sure the problem is the cheap sandpaper I just used …? I think it is leaving bits behind. Damn Harbor Freight…


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## Jenine (Sep 6, 2013)

Just want to confirm my hypothesis above. I tried the other piece of stock I sanded with the HF sandpaper and it also sparked. So, I vaccumed the stock, then brushed it with a stiff nylon brush and vacuumed again. Finally, I wiped with mineral spirits. Now they aren't sparking anymore 

Bad harbor freight. #liveandlearn


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