# Preventing finger joint blow out?



## BFG-Cabs (May 7, 2019)

I build Fender style guitar speaker cabs that require 1/4" finger joints. I built a jig from Shop notes and the jig works great but what I am fighting is backside blow out.





















All the wood used is #2 Pine that is KD and good quality and produces little blade slag. I keep the blade clean 

So my delemia is that the side that is facing the fence seem to blow out at the top creating chips, to some point this is OK as the original fender cabs had it some what but would like to clean it up some

Is this issue being caused by the blade or zero clearance area on the jig?


You can see the chipout on the board on the right side as opposed to the front of the board that hits the blade first.


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## Steve Neul (Sep 2, 2011)

The jig being zero clearance is as good as it gets. The blade being clean or not wouldn't cause that. Either the blade isn't sharp enough or you are making the cuts too fast. Another thing that might help is if you would put masking tape on the face of the wood. Sometimes that is just enough to prevent blowout when you have a blade that isn't quite sharp enough.


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## BFG-Cabs (May 7, 2019)

Not sure why the images are not showing up??? Trying again and adding links

http://www.yetisnowbikes.com/bfg/PG1.JPG










http://www.yetisnowbikes.com/bfg/PG4.JPG










http://www.yetisnowbikes.com/bfg/BFG-Fender-HotRod-1x12-6.png










http://www.yetisnowbikes.com/bfg/BFG-Fender-HotRod-1x12-8.png


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## difalkner (Nov 27, 2011)

They're showing for me, fwiw.

David


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## TomCT2 (May 16, 2014)

my bet is the "Backing Insert" Part F shown in step(?) 10 has been nibbled too high. it's effectively not zero clearance at the top, only on the sides.

the break out splinters have no support as the blade moves through - a less likely option is the workpiece is moving away from the fence.


have you considered jigging it so you always cut from the outside to the inside? thus putting any breakout on the invisible inside?


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## BFG-Cabs (May 7, 2019)

TomCT2 said:


> my bet is the "Backing Insert" Part F shown in step(?) 10 has been nibbled too high. it's effectively not zero clearance at the top, only on the sides.
> 
> the break out splinters have no support as the blade moves through - a less likely option is the workpiece is moving away from the fence.
> 
> ...


Hmm makes sense that the top is not supported and the height has changed.....I will need to try and set the height and then drop in a new Zero clearance plate that will be to the right height

The Zero clearance that in in there now does sit a hair slightly recessed.



Also you bring up a good point that this also might be user induced....not keeping the board stable and rushing....

Ill have to check it out


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