Preventing finger joint blow out? - Woodworking Talk - Woodworkers Forum
 
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post #1 of 6 Old 05-07-2019, 09:55 AM Thread Starter
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Question Preventing finger joint blow out?

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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Last edited by BFG-Cabs; 05-07-2019 at 10:50 AM. Reason: Images not showing up
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post #2 of 6 Old 05-07-2019, 10:05 AM
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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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post #3 of 6 Old 05-07-2019, 10:45 AM Thread Starter
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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...Rod-1x12-6.png



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


Last edited by BFG-Cabs; 05-07-2019 at 10:48 AM.
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post #4 of 6 Old 05-07-2019, 10:56 AM
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post #5 of 6 Old 05-07-2019, 12:47 PM
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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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post #6 of 6 Old 05-07-2019, 01:25 PM Thread Starter
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Quote:
Originally Posted by TomCT2 View Post
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?
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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