Incra ibox jig

[stacey martin]

I bought one a year ago and just getting around to using it. I'm having some issues with it or my stacked blade. It's a no name brand I bought along time ago has worked ok. I set up the jig made some test runs on scraps. It came out good as far as spacing but was to tight to go together unless you hammered it. I back off on the pin setting got it to fit nice but I was getting a little sliver of wood at the end when I was finished and took a little off of the other board. 4" wide doing 1/2 pins. I got to measuring with my calipers and the pins are not consistent in width on the board. Any where from .498 to .494 they did fit together fine and I would leave it this way but I need to get rid of the little sliver. I'm thinking I need to re-adjust the blade width. Anyone have another idea I need to look at?
Thanks Stacey

[Alan Schaffter]

Stacey, first, I assume the sliver you are referring to is the last finger. The width of the last finger is a function of the board or dado width, not the I-Box (or any box joint jig). Remember, dado width may not be the sum of the published thicknesses of the stacked trimmers and chippers. Many companies like Forest grind their dado blade tip a tad undersized and require shims. You can waste a lot of time trying to adjust the dado thickness so you end up with a full last finger (whole integer number of fingers/slots), but that is nearly impossible. If you want all pins to be full size it is much easier to just rip all the boards and remove the "orphan" (sliver) once the fingers on all boards have been cut. Ensure you place the correct edges of all boards against the rip fence! If the width of the boards is important to you or critical to the design, read the manual or watch the video to see how to use your I-BOX to make a center-keyed box joint- it drives the sliver to the center of each set of fingers so you end up with a center finger that is a tad wider than the others- it will be nearly impossible to see.

There are a number of possible causes for pin variances, the biggest being user technique- cutting too fast or pushing the jig to the left or right while cutting. Failure to lock the mechanism can cause this problem as can a loose miter bar.

As far as your initial cuts, it would help if I knew- were you using a standard stacked dado, a wobble dado (you can't use one of those), or two blade reversible dado (like the Freud Box Joint blade- you must be careful using that type of dado)? Did you follow the initial assembly/setup, calibration and guide pin setting procedures precisely? They are three separate operations. Did you remember to lock and unlock the mechanism when required?

When the fingers were too tight you said you "backed off on the pin setting", what did you actually do, what knob did you turn?? Did you unlock the mechanism first?

If you followed the assembly/setup, calibration and pin setting procedures correctly it is still possible to get a joint that is a tad tight- if set correctly, the I-BOX may make a joint that may not allow for glue or extra spacing, and you may end up with a fit that is what I call "too perfect"- it is just a tad too tight. If assembly/setup, calibration and pin setting were done correctly, it is easily to adjust the fit of the pins:

First unlock the mechanism. If you don't, you can damage the positioning engine or cause a bad setting when you unlock the mechanism later. Then, prevent the red knob from turning while you rotate the silver "micro" knob just a few tic marks counterclockwise (lefty loosey, righty tighty). Doing anything else can cause problems.

FYI, I do not work for INCRA, but I licensed the design to them. Send me a PM if you have any questions.

[Ben Rivel]

^^^^^ WOW, yes that would be the man to talk to!

[Cliff Polubinsky]

Alan,

What is it you need to be careful about with the 2 blade box joint blades like the Freud?

Cliff

[Alan Schaffter]

Alan,

What is it you need to be careful about with the 2 blade box joint blades like the Freud?

Cliff

I designed the I-BOX mechanism so that it is calibrated against the teeth of the trimmer blade of a standard dado set that you install first- against the arbor flange. Regardless of how thick or thin you ultimately make the dado stack, the teeth on that arbor flange trimmer NEVER change position in relation to the miter slot and hence the I-BOX. The big advantage of this is, unless you mess with the micro, have your dado blade sharpened, or buy a new one, once calibrated the I-BOX theoretically will always stay calibrated to that dado set and shouldn't need recalibration regardless of finger size settings.

The issue, though relatively small, with the two blade box joint sets is that the carbide teeth are off-set slightly to one side of each blade disk. To change the dado width, typically between 1/4" and 3/8" (Freud SB08), you swap the position of the blades on the arbor (see drawing below) which causes the offset to be on opposite side of the stack (both inside or both outside). That will change the distance from the arbor flange teeth to the miter slot, put the I-BOX out of calibration, and prevent you from making a joint without recalibration. This means that whenever you change finger sizes with a two-blade box joint set, you must recalibrate the I-BOX.

It isn't a big deal and is much the same as using the I-BOX on a router table. It is just something you need to be aware of. (FYI, that is why you can't use the I-BOX with a wobble dado)

[Ben Rivel]

I designed the I-BOX mechanism so that it is calibrated against the teeth of the trimmer blade of a standard dado set that you install first- against the arbor flange. Regardless of how thick or thin you ultimately make the dado stack, the teeth on that arbor flange trimmer NEVER change position in relation to the miter slot and hence the I-BOX. The big advantage of this is, unless you mess with the micro, have your dado blade sharpened, or buy a new one, once calibrated the I-BOX theoretically will always stay calibrated to that dado set and shouldn't need recalibration regardless of finger size settings.

The issue, though relatively small, with the two blade box joint sets is that the carbide teeth are off-set slightly to one side of each blade disk. To change the dado width, typically between 1/4" and 3/8" (Freud SB08), you swap the position of the blades on the arbor (see drawing below) which causes the offset to be on opposite side of the stack (both inside or both outside). That will change the distance from the arbor flange teeth to the miter slot, put the I-BOX out of calibration, and prevent you from making a joint without recalibration. This means that whenever you change finger sizes with a two-blade box joint set, you must recalibrate the I-BOX.

It isn't a big deal and is much the same as using the I-BOX on a router table. It is just something you need to be aware of. (FYI, that is why you can't use the I-BOX with a wobble dado)

Interesting. This makes sense and I imagine it would be the same issue if the Forrest Finger Joint Sets (LINK and LINK) were used.

That being the case, what is the best way to get a truly flat cut when using the I-Box jig? I have a Forrest Dado King dado set and the outer blades in the stack have bevels and create the "dog-eared" effect in the groove when cutting a dado. I havent tried them yet but wouldnt that show up and look terrible in a finger or box joint?

Would the best option be to just use a single flat top ground 1/8" kerf blade like the Forrest Woodworker II "1 OD ground (LINK)? Or is calibrating the I-Box jig for a Finger Joint Set a better option as those will hog out more material than an 1/8" kerf blade?

[Alan Schaffter]

Interesting. This makes sense and I imagine it would be the same issue if the Forrest Finger Joint Sets (LINK and LINK) were used.

That being the case, what is the best way to get a truly flat cut when using the I-Box jig? I have a Forrest Dado King dado set and the outer blades in the stack have bevels and create the "dog-eared" effect in the groove when cutting a dado. I havent tried them yet but wouldnt that show up and look terrible in a finger or box joint?

Would the best option be to just use a single flat top ground 1/8" kerf blade like the Forrest Woodworker II "1 OD ground (LINK)? Or is calibrating the I-Box jig for a Finger Joint Set a better option as those will hog out more material than an 1/8" kerf blade?

I frankly don't feel the "dog ears" are objectionable. They really are pretty small, and get even smaller after the moisture in the glue causes the wood to expand during assembly. For most woods the surface across the bottom of each finger socket made with a good blade like the F. Dado King disappear when the joint is clamped. But if you really want smooth sockets try a Dado King with a flat grind (stock or special order from Forrest?) or get an Infinity flat bottom dado set. As to calibrating- you seldom change finger sizes on a project and calibration is such a quick and simple process- why I called it "kiss calibration" which is not only what you do but a takeoff of "KISS"- Keep it Simple Stupid.