Incra Box Jig Question

Robert166

robert166
Senior User
I checked and double checked all the settings on my box jig to be absolutely sure nothing was wrong. Then did a test cut, everything fit exactly like I wanted. But.... if this makes a difference, the test cut was with the wood grain. The project piece was to be cut against the grain, I didn’t think it would make a difference, but it did. But I can not figure out why. I would think a box joint is the same regardless of which way it is cut, right? But nope it is much tighter, way to tight.
 

Mike Davis

Mike
Corporate Member
Some wood is softer in the long grain, maybe it is compressing more easily in that direction.

But, Wood is not as strong in the cross direction, the joints may fail over time.
 

Robert166

robert166
Senior User
Yes same wood, oak. I always cut a piece for my test cut for the joints. And it is not green, had it for several years inside the shop. Just seems strange, next one I make have the test cut against the grain. I do realize it is not a strong joint, but for the project it needs to be that way for looks.
 

Jeff

Jeff
Corporate Member
I don't understand some of the terms in this discussion. How is a box joint cut any other way besides with the grain?

1. " the long grain"
2. "with the wood grain."

I doubt that a weaker joint will make a difference over time once it's glued up. I've made a few box joints but don't understand how it applies to my box. This look like both joints were cut with the wood grain.

Screen Shot 2020-06-29 at 9.25.58 AM.png


This is a red oak "berry box".
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Robert166

robert166
Senior User
Okay, pictures when I get home, :)pictures are better. I will have a pic of the test cut piece, then of the project cut piece. That should help in explaining my box joint issue.
 

Robert166

robert166
Senior User
Same piece of wood, just cut with grain and against grain, one fits together nicely, the other will not without the use of a hammer. I know how to fix it, trying to understand why I have to. Perhaps the only answer is cut against the grain with a wider clearance.

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Robert166

robert166
Senior User
This is what I am making, post office banks and I like the joints as shown here. Kinda look like bricks.
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Robert166

robert166
Senior User
Sorry for all the pictures, last one. Here is the same piece that would not fit, turned the micro-adjustment knob about a 1/3 of a turn and this was the result.
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Alan in Little Washington

Alan Schaffter
Corporate Member
Unless the wood is wet or soft and compressible- the fitness of the fingers should be the same regardless of the orientation of the grain if the jig is properly set and used. The difference between a good fitting joint and one that is too loose or too tight can be as little as .004" or less!

Are you sure you rotated the micro knob 1/3 of a rotation. If the first joint was close, making 1/3 of a rotation is probably too much! It should only require rotation of a few dots. (each dot is .001" )

FYI, Cross-grain fingers are very weak and can easily snap off if you aren't careful, plus you need a very sharp blade and good backer or you will have a lot of tearout.

How did you cut the fingers- TS or router? By the appearance of the fingers in your photo, especially the really flat bottom and lack of "ears" typical left by the trimmer blades of many dado blades like the Forrest Dado King, it looks like you used a router table. If you use a router table, you must hold the stock firmly or better yet clamp it against the fence because the rotation of the bit adds a lot of side force and can cause the stock to move sideways very slightly. Also, the miter bar must be properly adjusted to the miter slot or the entire jig can shift sideways.

I am the inventor of the I-Box.
 

Robert166

robert166
Senior User
Alan,
I will not argue with the inventor, like I said trying to understand why. I am using a table saw and the blades are Oshlun 1/4 & 3/8 finger joint set. I did measure the “fingers” of each cut.
I enjoy using the IBox, I have 2 of them, and any fairly confident I have it set correctly.
A third of a turn was not correct, apologies I was incorrect, after I took the photo, I realized it was a bit, just a smidge loose, but still a decent fit with a little friction as the joints fit together.
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Jeff

Jeff
Corporate Member
Robert, thanks for the pictures and explanations. Maybe cross grain or with the grain orientation doesn't make any difference and you simply had to make the micro-adjustment to the iBox jig.

Here are some postal banks that I found. Do you have the doors for the banks?


 

patlaw

Mike
Corporate Member
Even after Phil S. helped me with the iBox, I was not able to get good results using a router. I'm holding onto it in case I ever decide to try it on my table saw, for which I don't have a dado blade, cartridge, and throat plate. It's a creative piece of equipment, but it's not working well for me.
 

Alan in Little Washington

Alan Schaffter
Corporate Member
Wow, two IBOXes! I only have 1 and a half (mostly a pile of parts! - a production model and a pre-production model with tons of extra holes in it an mostly disassembled :rolleyes:) I'll bet you have made more box joints in the past few years than I have. :(

The only thing I can add is the compressability factor of your stock- your joint with fingers parallel to the direction of the grain may have been near perfect, but off by just a few thou making it tight but still able to be assembled. That would not likely be the case with a joint having fingers perpendicular to the grain. Wood can compresses (and expands/contracts seasonally) across the grain but hardly at all in the direction of the grain.

Since you are an experienced user I'm sure you don't make any of the common errors, e.g. forgetting to lock the mechanism before cutting, forgetting to unlock the mechanism before adjusting finger size or adjusting micro, then briefly unlocking and locking again (mechanism will jump!), etc., etc. FYI, my initial design did not have micro- I was confident it didn't need it if care was used during adjustment. Chris Taylor at INCRA wisely thought otherwise. ;) We struggled to add micro to the design until I a light when on in my head and I came up with a simple but elegant method. I had a few other improvements that didn't affect performance but came about after the design was finalized so never incorporated, e.g. totally acrylic (vs MDF) blade and dust guard with dust collection port, quick cam mechanism lock, etc.

I don't drop by here often, but will respond to PMs if you or anyone has IBOX (or Lock Miter Master) questions.
 

Alan in Little Washington

Alan Schaffter
Corporate Member
Even after Phil S. helped me with the iBox, I was not able to get good results using a router. I'm holding onto it in case I ever decide to try it on my table saw, for which I don't have a dado blade, cartridge, and throat plate. It's a creative piece of equipment, but it's not working well for me.
You need to be careful when using the IBOX on a router table for the reasons I mentioned above. That said, Perry McDaniel (the INCRA guy in the IBOX video) sent me a short video years ago showing him using the IBOX on a router table to make a special joint. He didn't use the small furniture clamp suggested by INCRA to hold the stock and was only wearing "gripper" gloves while he held the stock firmly with his hands. I also suspect his router bit was new or just extremely sharp. But anyway, he was litterally flying- cutting a joint at about three times my normal speed- the result- the fit of the joint was perfect. So, it can be done, but like most woodworking processes it takes careful setup, sharp tooling, and proper use.
 

Mike Davis

Mike
Corporate Member
The only thing I can add is the compressability factor of your stock- your joint with fingers parallel to the direction of the grain may have been near perfect, but off by just a few thou making it tight but still able to be assembled. That would not likely be the case with a joint having fingers perpendicular to the grain. Wood can compresses (and expands/contracts seasonally) across the grain but hardly at all in the direction of the grain.
This was my thought but expressed so much more clearly by Alan.
 

Robert166

robert166
Senior User
Even after Phil S. helped me with the iBox, I was not able to get good results using a router. I'm holding onto it in case I ever decide to try it on my table saw, for which I don't have a dado blade, cartridge, and throat plate. It's a creative piece of equipment, but it's not working well for me.
Mike,
In the beginning for me, there was a learning curve, but after understanding the basic set up it has been a breeze to use. I have watched the YouTube vids several times, and some of the things that are very important (in my opinion) were not stressed enough for new users. The IBox is very accurate and easy to use, once it is dialed in, correctly. Like any other tool it must be set correctly. It is not what I call a finicky tool, there is room for error and you still can produce a decent joint. The ability to adjust the fit is what makes this tool stand out.

I have not tried it on a router table. Routers not my strong suit, tool wise.

I had a few other improvements that didn't affect performance but came about after the design was finalized so never incorporated, e.g. totally acrylic (vs MDF) blade and dust guard with dust collection port, quick cam mechanism lock, etc.
Dust guard and dust collection port, that would be a nice feature! Heck all of those improvements would be nice to have!
 

Robert166

robert166
Senior User
Robert, thanks for the pictures and explanations. Maybe cross-grain or with the grain orientation doesn't make any difference and you simply had to make the micro-adjustment to the iBox jig.

Here are some postal banks that I found. Do you have the doors for the banks?

Jeff,
I bought some off eBay, the large style door. Do you have a contact for some nice ones?

$35.00 for a bank? Wow, that is cheap! Doors cost me about $10 apiece then factor in the wood and time, I couldn't and wouldn't do it for $35.
 

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