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Incra I-jig and tear out problems with walnut

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Forum topic by Jeffreaux2 posted 10-02-2013 03:42 AM 1088 views 0 times favorited 18 replies Add to Favorites Watch
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Jeffreaux2

17 posts in 491 days


10-02-2013 03:42 AM

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.

-- Regards, Jeff


18 replies so far

View gfadvm's profile

gfadvm

11226 posts in 1376 days


#1 posted 10-03-2013 01:28 AM

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.

-- " I'll try to be nicer, if you'll try to be smarter" gfadvm

View Sandra's profile

Sandra

4618 posts in 761 days


#2 posted 10-03-2013 01:32 AM

Was thinking the same thing as Andy.

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

-- No, I don't want to buy the pink hammer.

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Jeffreaux2

17 posts in 491 days


#3 posted 10-03-2013 05:47 AM

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.

-- Regards, Jeff

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Sandra

4618 posts in 761 days


#4 posted 10-03-2013 09:45 AM

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.

-- No, I don't want to buy the pink hammer.

View NiteWalker's profile

NiteWalker

2710 posts in 1263 days


#5 posted 10-03-2013 10:05 AM

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

-- He who dies with the most tools... dies with the emptiest wallet.

View Gene Howe's profile

Gene Howe

5768 posts in 2115 days


#6 posted 10-03-2013 12:42 PM

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.

-- Gene 'The true soldier fights not because he hates what is in front of him, but because he loves what is behind him.' G. K. Chesterton

View bigblockyeti's profile

bigblockyeti

1659 posts in 407 days


#7 posted 10-03-2013 01:17 PM

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?

View MrRon's profile

MrRon

2859 posts in 1930 days


#8 posted 10-03-2013 10:32 PM

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.

View Jeffreaux2's profile

Jeffreaux2

17 posts in 491 days


#9 posted 10-05-2013 03:17 AM

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.

-- Regards, Jeff

View Sandra's profile

Sandra

4618 posts in 761 days


#10 posted 10-05-2013 12:41 PM

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.

-- No, I don't want to buy the pink hammer.

View Woodmaster1's profile

Woodmaster1

498 posts in 1273 days


#11 posted 10-05-2013 03:49 PM

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

View MrRon's profile

MrRon

2859 posts in 1930 days


#12 posted 10-05-2013 07:26 PM

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

17 posts in 491 days


#13 posted 10-06-2013 02:50 AM

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

-- Regards, Jeff

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Jeffreaux2

17 posts in 491 days


#14 posted 10-14-2013 12:08 PM

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.

-- Regards, Jeff

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Jeffreaux2

17 posts in 491 days


#15 posted 10-14-2013 12:18 PM

.

-- Regards, Jeff

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