# Incra I-jig and tear out problems with walnut



## Jeffreaux2 (Jun 17, 2013)

I'm using a 3/8" dado blade to cut box joints in 3/4" thick walnut. I'm getting awful tear out at the blade exit. Anyone have ideas to avoid? The jig has a 1/4" mdf backer board to provide zero clearance.


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## gfadvm (Jan 13, 2011)

Jeff, I posted a comment on your other thread but forgot to ask what dado set you were using? My Freud box cutter set works MUCH better than my previous cheapo dado set.

That mdf backer board will need to be changed reasonably often as it the kerf will widen with repeated cuts and allow tearout.


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## Momcanfixit (Sep 19, 2012)

Was thinking the same thing as Andy.

Love love love my iBox jig. Had minimal tearout even on plywood using my Freud set.


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## Jeffreaux2 (Jun 17, 2013)

Hey guys. Thanks for replying.

I am using a Freud 8" stacked dado set. Would i be better off replacing the mdf backer board with something stouter?? I have some mahogany that i had resawed to 5/16 thick or i have some poplar or red oak that I could mill to size.


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## Momcanfixit (Sep 19, 2012)

http://www.finewoodworking.com/how-to/article/eliminate-tearout-with-tape.aspx

Jeff, I've not used tape for box joints, but I don't see why it would hurt to try. Only other thought I had was this - to double check that your iBox was set up properly. If I remember correctly, you can actually set up the backer board the wrong way and end up with a larger hole than needed behind the cut.

Good luck, let us know how you make out with it.


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## NiteWalker (May 7, 2011)

If a fresh area of mdf still allows for tearout, I'd go for the stouter material.
Also, try a slower feed rate.


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## Gene01 (Jan 5, 2009)

Like Sandra, I love the IBox. My dado set is an 8" Tenryu. While it's a great set, it did leave "bat wings". After the outer blades were re shaped, I now get flat cuts with no tear out. 
I do not believe that any dado set, or any saw blade, for that matter, is as true as it can be direct from the manufacturer. There may be exceptions. I just haven't stumbled across any. So, it's always best to have them trued by a expert. Don't get me wrong, my saw blades (all Tenryu) await that process until their first sharpening. I'd wager that if you were to have your dado blades sharpened and trued, you would be amazed at the difference.


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## bigblockyeti (Sep 9, 2013)

Stouter material surely wouldn't hurt, the nice thing about MDF is the consistency of the wood, the bad: As the blade is pushing/shearing the last fibers of the walnut out of the cut and into the MDF it's possible the tiny sawdust particle that make up the MDF are being abraded away allowing the problem to get worse over time. How tight are you able to hold the walnut against the MDF right where the cut is being made?


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## MrRon (Jul 9, 2009)

The first thing that comes to mind is; Are you cutting with the grain parallel to the blade (as in rip)? If you are cutting the orher way, the tearout will be terrible. I assume the former.


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## Jeffreaux2 (Jun 17, 2013)

Thanks for all of the replies.

- I had to replace the start switch on my saw so I had taken. Few days off. In that time I brought my Dado set to a sharpener. $8.70.

- I have some magogany that i plan to use between my stock and the mdf backer board.

- I am cutting with the grain. Not across.

- I tried using masking tape but it didnt help.

- Sandra- are you saing the backer board itself can be installed backwards or are you referring to the rear blade guard??

- I will hopefully find time to get back on this project very soon.

Thanks again for the tips. Ill report back here and tell you all how it goes.


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## Momcanfixit (Sep 19, 2012)

Jeff,

Each of the backer boards has a smaller hole on one side and a larger on the other. I had them mixed up during assembly and the larger hole was the exit point for the blade instead of the smaller. Hope that makes sense.


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## Woodmaster1 (Apr 26, 2011)

I use this homemade jig it seems to work fine. I got the plans from shopnotes and made some modifications.


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## MrRon (Jul 9, 2009)

Jeffreaux, I would question the quality of sharpening for $8.70. Is your set carbide? The reason why I ask is the chippers have to be .015" below the outside cutters for a clean, flat bottom cut I don't think the sharpener did this $8.70 sounds much too cheap for a good job. I use a Freud box joint blade set and get great cuts.


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## Jeffreaux2 (Jun 17, 2013)

We will see how well the sharpening went. He has done well on my planer blades and router bits.


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## Jeffreaux2 (Jun 17, 2013)

Well I am back to work on this. the dado set cuts as good as it ever did, however while waiting for the new switch for my saw I elected to buy the box joint blades that so many of you use.

The result is great looking joints. thanks so much for the helpful replies.


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## Jeffreaux2 (Jun 17, 2013)

.


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## gfadvm (Jan 13, 2011)

I KNEW you would like the box joint blades! Keep em clean (I use Simple Green-purple) and they will stay sharp for a LONG time. Enjoy!

By the way those joints look perfect.


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## NiteWalker (May 7, 2011)

Nice box joints. 

One of those box joint sets is on my wish list.


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## Woodbum (Jan 3, 2010)

Jeff: I found that I need to change the backer board position to a fresh one after each set of box joints or in the middle of a set if cutting a bunch of wide stock to prevent tearout. Like Andy said before, the successive passes of the blades through the gap will widen it ever so slightly, not providing good backup. This method works great with the Freud box joint set and with my Forrest Dado King set. Your last set of joints look great. I do go through a lot of backer material, but Masonite is cheap and worth the investment for splinter free joints.


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