Review: INCRA I-BOX Jig for Box Joints

Along with dovetails joints, box joints are one of the strongest and most attractive joints you can make but they require absolute accuracy and traditionally involve test cut after test cut until you get it right. That all changes with the INCRA I-BOX Jig for Box Joints. Incra are renowned for the incredible micro-adjustability of their products (you only have to look at something like their LS25WFNCSYS 25-inch Range Positioner to see what I mean) and that’s exactly what you need when making box joints – absolute accuracy plus easy repeatability.

One of the challenges of using a typical finger joint jig (commercial or shop-made) is properly setting the distance between the cutter and indexing pins. The accuracy of this relationship is critical, since it is what determines the fit of the joint. If spaced too widely, the joint will be overtight; too close and you’ll have gaps. That’s where the Incra I-BOX comes in.

The system consists of the the main heavy-duty aluminum I-BOX fence which attaches to Incra’s excellent GlideLOCK™ Miter Bar Assembly (the same as used in their high-end miter gauges like the INCRA Miter1000/HD Miter Gauge).  Two stock ledges attach to the front of the fence which accommodate stock up to 1-1/4″ thick. A front and rear cutter/blade guard provide protection and there’s a clear acrylic chip deflector that mounts to the front guard.

So far, so good, but the heart of the system is the I-BOX pin plate positioning mechanism which sits inside the main fence. On the end of this you have a calibration wheel for calibrating the pin plates to the cutter/blade and the micrometer adjustment wheel for adjusting the size of the joints.

To ensure accurate positioning, the dual-pitch lead screw of the micrometer moves the two indexing pins in phase with each other and relative to the cutter. No measuring or trial-and-error fitting is required.

Priced at $145.99, the INCRA I-BOX Jig for Box Joints is expensive compared to other box joint jigs such as the Woodhaven 4555 Box Joint Jig but the Incra is in an altogether different league in terms of accuracy and safety. No other box joint jig comes close.

Once you’ve set up the INCRA I-BOX jig, it’s extremely easy to use and make perfect joints but you’ve got to set it up properly in the first place. Most people, especially if you’ve been woodworking for a while, don’t tend to read the instructions, they skim them at best. That’s just not going to work here. The settings are simple but there’s a lot to remember, so you must read the instructions or, even better watch the excellent setup DVD that comes with the jig.

The video below shows how easy it is to use the INCRA I-BOX, both to setup and use. Most of the work is on the table saw but it works just the same on the router table.

Just watching the video and seeing how easy it is to make beautiful joints makes you want one. The Incra I-BOX Jig retails at $145.99. 

After you’ve put the INCRA I-BOX Jig together, one test cut is all you need, using the I-BOX pin plate positioning mechanism, which is the heart of the system. Incra call this one-time kiss calibration and it works like this:

1. Loosen the top locking knob and zero the pin plates to the cutter/blade using the outer (silver) adjustment knob.
2. Then turn the inner (red) adjustment knob to adjust the pin plates to fit the test cut you’ve made in your stock – this simultaneously sets the all-important distance between the pin plates and the blade as well as the width of the cut.
3. Tighten the locking knob and you’re ready to go – after this one-time you simply adjust the pin plates to any size joint you want.

The only time you need to re-calibrate the jig is when using a different diameter cutter.

The Incra I-BOX has a number of useful features in addition to its amazing accuracy and ease of use:

The INCRA I-BOX Jig is a well-made, extremely accurate micro-adjustable box joint jig with the quality and attention to detail that characterizes all of Incra’s precision woodworking products. With its emphasis on micro-adjustable precision and accuracy, easy repeatability and hugely improved safety features the INCRA I-BOX Jig excels. There is no other box joint jig like it on the market.