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So I have started building guitar cabs and feel like Im chasing my tail. This has been an issue with 2 different dado stacks. The cabs are built out of #2 Pine and I am currently using a new Freud SD208S 8'' Dado Set

Use a gig that I built following ShopNotes-62 and cut on a Ridgid-3650 Table Saw. The back side of the pieces always get tear out. I Pine is flat and is sitting flat against the fence. You can see in the pic that the font side cuts are nice and clean. Its not a huge issue but just taking extra time to have to fill and sand.
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Thoughts?
 

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the slot cut by the dado in the backing fence is too high.
that allows tear out - as there is nothing 'backing up' the top edge.
 

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Thanks for your response, rear plate is replaceable and I have changed it out several times and still get the tear out. I use a blank and the height is set for each new set of cabs that I finger joint. (Does not look it in the pics but it is flush)

Maybe try and make the plate sit slightly proud of the fence or maybe time to re-make the gig?

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Not sure, but looks like the sacrificial panel isn't as thick as the plywood on either side, so there will be a small gap behind the work piece.

Maybe use layers of masking tape behind it to bring it flush.
 

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Not sure, but looks like the sacrificial panel isn't as thick as the plywood on either side, so there will be a small gap behind the work piece.

Maybe use layers of masking tape behind it to bring it flush.
Ya Ill confirm again but pretty sure that it is sitting flush. Might even try to make it a hair proud. Ill update
 

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the shadow lines demonstrate is is not proud, and it is not flush.
which is why you're getting the break out. there is no zero-clearance support behind the finger cut.
 

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If you look closely the particle board does not have a clean slot. I agree the insert doesn’t look flush.

Particle board isn‘t the best fence material for this. I suggest one solid fence of MDF, no insert. I usually double stick a piece of 1/4 when I need one.

That said, clamping the board against the fence is a good idea just in case there’s any bow in the board.
 

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I like the design with the sacrificial insert as a backer. I'm not sure what you are using as a material for it, but I would try solid hardwood with the grain running like the workpiece. Hard maple works for me. I've seen ash used also. This gives the stiffest possible support behind the bottom of the cut.
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Mostly I make these end grain cuts on a shaper like this slot and tenon joint about 1 3/4" deep. This backer is maple.
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Dr. Roberts has a good suggestion about clamping the workpiece tight against the backer. Occasionally glazing bars for divided lite windows are too short to run the sticking molding after the end grain copes are cut. I cope these, after the sticking is run in a longer piece, in a hardwood cradle that conform closely to the molding profile and clamp them tight into it.
 

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I cut lots of finger joints on figured hardwood for guitar speaker & head cabs - I use an 1/8 plywood backer that is fresh cut for the current height of the finger. I also clamp both sides to eliminate movement caused by vibration and to flatten out the piece being cut.



I get it if you want to follow 'But that's the way they did it' but with today's modern glues the need for maximizing glue surface area isn't needed. You could cut 1/2 or 3/4 fingers and reduce the cut time. The other option if you are covering with tolex would be a dab of thick CA and a squirt of accelerant.

Please showcase your work in the projects section.

Russ
 

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I cut lots of finger joints on figured hardwood for guitar speaker & head cabs - I use an 1/8 plywood backer that is fresh cut for the current height of the finger. I also clamp both sides to eliminate movement caused by vibration and to flatten out the piece being cut.



I get it if you want to follow 'But that's the way they did it' but with today's modern glues the need for maximizing glue surface area isn't needed. You could cut 1/2 or 3/4 fingers and reduce the cut time. The other option if you are covering with tolex would be a dab of thick CA and a squirt of accelerant.

Please showcase your work in the projects section.

Russ
Russ - your sled looks interesting. I’m planning to build one this summer and looking for some ideas. Would you mind posting some additional pictures of it?

Is the plywood backer Baltic Birch or some other hardwood plywood?
 

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Russ - your sled looks interesting. I’m planning to build one this summer and looking for some ideas. Would you mind posting some additional pictures of it?

Is the plywood backer Baltic Birch or some other hardwood plywood?
Hi Tom,

I'll post in the jigs forum so I won't hijack this thread.

Russ
 

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i agree with Paul, the sacrificial backer degrades after every cut. you may get a few cuts out of it, but if you keep checking the backside of your cut, you will see more and more tearout as you go. the fix it can be as simple as laying a thin strip of wood there for every board, and slide it along as you go as Paul said.
 
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