Sparks on bandsaw

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Forum topic by richgreer posted 04-20-2011 12:48 AM 7669 views 0 times favorited 14 replies Add to Favorites Watch
View richgreer's profile


4541 posts in 4127 days

04-20-2011 12:48 AM

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.

-- Rich, Cedar Rapids, IA - I'm a woodworker. I don't create beauty, I reveal it.

14 replies so far

View blackcherry's profile


3345 posts in 4876 days

#1 posted 04-20-2011 12:58 AM

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

View BigTiny's profile


1703 posts in 3941 days

#2 posted 04-20-2011 01:12 AM

Might also be mineral deposits in the wood.

-- The nicer the nice, the higher the price!

View TimKane2's profile


9 posts in 3726 days

#3 posted 04-20-2011 03:57 AM

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?

View wchips's profile


314 posts in 4141 days

#4 posted 04-20-2011 04:05 AM

could be sand on the wood or embedded in it

-- wchips

View William's profile


9950 posts in 3895 days

#5 posted 04-20-2011 04:13 AM

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.


View richgreer's profile


4541 posts in 4127 days

#6 posted 04-20-2011 04:16 AM

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.

-- Rich, Cedar Rapids, IA - I'm a woodworker. I don't create beauty, I reveal it.

View bubinga's profile


864 posts in 3720 days

#7 posted 04-20-2011 04:17 AM

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.

-- E J ------- Always Keep a Firm Grip on Your Tool

View gfadvm's profile


14940 posts in 3743 days

#8 posted 04-20-2011 04:43 AM

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.

-- " I'll try to be nicer, if you'll try to be smarter" gfadvm

View Popsnsons's profile


450 posts in 4034 days

#9 posted 04-20-2011 04:51 AM


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.

-- Pops ~ In So Cal...

View Dusty56's profile


11863 posts in 4741 days

#10 posted 04-21-2011 01:03 AM

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.

-- I'm absolutely positive that I couldn't be more uncertain!

View Maddhatter's profile


127 posts in 4630 days

#11 posted 04-21-2011 02:17 AM

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.

-- Norm (AKA - The Maddhatter), Middletown DE

View SteveMI's profile


1167 posts in 4347 days

#12 posted 04-21-2011 04:05 AM

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.


View Jenine's profile


148 posts in 2776 days

#13 posted 09-29-2015 05:22 PM

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… ;)

-- - Montana sucks. Tell your friends.

View Jenine's profile


148 posts in 2776 days

#14 posted 09-29-2015 07:18 PM

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

-- - Montana sucks. Tell your friends.

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