Tear-out with Incra I-Box

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Forum topic by Jofa posted 07-27-2015 09:30 PM 1287 views 0 times favorited 6 replies Add to Favorites Watch
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272 posts in 1863 days

07-27-2015 09:30 PM

Hey guys.

I’ve been using my Incra I-Box quite a bit and I like it very much. However, I’m finding that I’m getting tear-out on soft woods like pine.

I’ve fine-tuned the system so that my joints are aligned very well but the tear-out is an issue.

I made a supply of back plates out of 1/4” MDF but I’m finding that the tear-out is actually breaking through it. Should I possibly use 1/4” ply?

-- Thank you Lord for the passion and ability to make things from your creation.

6 replies so far

View Fred Hargis's profile

Fred Hargis

4999 posts in 2518 days

#1 posted 07-27-2015 09:32 PM

You can, it will work fine. Is this on a table saw (?), maybe it’s time to check the blade.

-- Our village hasn't lost it's idiot, he was elected to congress.

View Jofa's profile


272 posts in 1863 days

#2 posted 07-27-2015 09:45 PM

Thanks Fred.

Yes, I’m using a Freud Diablo dado set. I really hope it isn’t the blade(s) as I haven’t used it daily or anything. It should still be sharp. Plus, the cuts on the way into each joint and on the edges are very clean. It’s just the way out.

-- Thank you Lord for the passion and ability to make things from your creation.

View ksSlim's profile


1276 posts in 2915 days

#3 posted 07-27-2015 11:28 PM

I’ve been using 3/8” Borg ply for a backer board.
Seemed to stop the blowout.

-- Sawdust and shavings are therapeutic

View CharleyL's profile


222 posts in 3389 days

#4 posted 07-27-2015 11:56 PM

Try some 1/4 birch ply for backer boards. Also try moving the jig much slower over the saw blade. If pushed too fast the chip removal will be too aggressive and blow through the backer. I get the best box joints by using the Freud SBOX8 blade set on my Unisaw but I also use a Freud adjustable dado blade with very good results. They are designed to provide very square 1/4 and 3/8 joints with a minimum of tear-out. Moving the jig slower should make a huge difference.


View DocSavage45's profile


8589 posts in 2867 days

#5 posted 07-28-2015 01:21 AM

Does tear tout occur without the Incra jig? Is this a wobble dado or the shim type. Any problems with tear out outside of this situation? Was this always a problem? That would help the problem solving.

-- Cau Haus Designs, Thomas J. Tieffenbacher

View Jofa's profile


272 posts in 1863 days

#6 posted 07-28-2015 04:55 PM

Hey everyone. Thanks for the replies.

@ Doc: I haven’t tried the dado without the jig (but I will). It’s a shim type (actually, it’s the Freud SBOX8)
It seems to have been an issue from the start

@ Charley and Slim: I’m going to try some different backer boards but I’ll also slow down. I’m using an old Craftsman (Atlas Press) table saw from like the 40’s (newer motor however) and it may not be powerful enough for the speed I’m going. I’m going to try tonight and see if I get similar results after slowing down.

-- Thank you Lord for the passion and ability to make things from your creation.

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