Rockler - Cross Lap Jig #56372 (Rating: 5)

I used this jig to create an egg crate style return air grill (project here) and it worked flawlessly. I have used shop made jigs in the past for box joints but the adjustable fingers on this jig intrigued me. I have never used the Incra I-Box jig but they look to operate similarly.

The jig comes in a sturdy box and is packaged well with a block of Styrofoam included to prevent shifting of contents. The parts are in two separate bags. The wood components in one bag and the adjustable key mechanism, knobs and hardware are in another. The included knobs are Rockler's rubber coated easy to grip and I found them nice to use. I may be looking to use them on future shop projects. The adjustable key mechanism while made of plastic feels to be plenty strong enough for the purpose. The keys themselves are steel ~0.10" thick. The mechanism is smooth with little play in the movement. Out of the box I did have to adjust the nut to remove backlash. I also added a small amount of teflon lube behind the nut and knob to reduce friction. Four flat head wood screws were included, I assume to mount the key mechanism to a board with no t-slot; this was not identified in the instructions. The wood fence pieces are melamine coated MDF. The piece to attach to the miter gauge is 10" and the sliding fence is 22" long. As the fence gets chewed up you can cut off and move the key mechanism down or cut a new fence using the guidance in the instruction manual. I already own the T-slot router bit so I will likely cut a new one from 3/4 MDF.

In order to use the jig it needs to be mounted to a miter gauge. I chose to use my Incra but it should mount to any gauge with mounting holes. There is no hardware included to attach since the need will be different depending on your miter gauge. I used some 3/4" sheet metal screws I had on hand since MDF does not do well with tapered wood screws. The 10" piece is attached to the miter gauge and the 22" fence simply attaches with T-bolt hardware. The instructions indicate to cut a 1" wide 1/2" notch in the bottom of the fence at a specific location to accommodate the key mechanism. I cut per directions but in hindsight would have only cut it slightly wider than needed for the project if I had to do it again. Due to my spacing the wide notch left my cuts partially unsupported which could cause tearout. The notch could always be made wider as the project requires. The key mechanism is attached to the fence T-slot using a metal plate and a couple of flat head machine screws. You will need to slip the plate in the slot and line up the screws as the keys will not let the mechanism slide in from the end.

The jig is designed for use on a table saw with dado blade at the width of material being joined. After cutting the first notch in a piece it will be placed over the keys which need to be adjusted to width using the knob at the end. Adjust keys to be snug in the notch but not overly tight. Lock the keys with the knob on top of the mechanism. To create the desired spacing the location of the keys needs to be adjusted using the knobs/T-bolts attaching the two fence pieces together. Then it is a simple operation of placing the previous cut notch on the keys, make the cut and repeat.

My Impression:
Although the jig is intended for the table saw I see no reason it would not work just as well on a router table with a miter slot. The key mechanism could be added to a sled or any other jig/fixture using a t-slot or screws. I believe the jig will make a nice box joint jig. As a test I ran some quick 1/4" box joint. Since I had the dado adjusted to a perfect 1/4" I laid a 1/4" brass setup bar along the dado teeth and slid the jig fence so the keys were aligned to the 1/4" spacing. Cutting fingers on some scrap wood left a perfect finger joint. This will most likely be how I use the jig in the future. The jig as delivered can accommodate 1/4" through 1" notches spacing would be limited by the length of the fence. I found I could set the keys at ~1-1/2" but the mechanism needs to be taken out beyond the length of the adjustment screw to get there.

While Rockler's jigs can be a bit expensive when you look at what they are I am pleased with this one. I was able to purchase using the current 15% off coupon which brought the price to below $30. For the time it would have taken to make something and the flexibility to use for box joints in the future I am very satisfied with the purchase.