MPOWER Tools is a British company that has developed a unique line of woodworking accessories, including marking and measuring tools, a sharpening system, a vacuum clamping system, and a rather unique routing system designed to produce accurate grooves, dados, mortises, arcs, and circles, and to facilitate edge routing and trimming. I’ve had the opportunity of using this new routing system – the CRB7 MK3 – over a two week period. It’s a jig I wish that I would have had access to years ago. What I particularly like about the CRB7 is that it replaces the need for several separate jigs, a real boon for anyone working in a small shop. And, with fewer jigs, there aren’t as many bits and pieces to mislay.
The CRB7: (A) base plate, (B) 5/16″ and 9/32″ guide rods (only 1 set shown), (C) 25/64″ compass rods, (D) scale, (E) handle, (F) mortise pillars, (G) pivot hub, (H) pivot pin, (I) lock bars, (J) anti-tilt leg
The CRB7 consists of a base plate (A) on which is attached an aluminum bridge that supports a pair of steel guide rods (B) to which the router is attached. The 3/16″ x 6-1/2″ x 11-1/4″ base plate is made of a rigid, durable, thermoplastic. The thermoplastic base plate is ultra smooth, so that the CRB7 easily glides over wood surfaces.
You also get two pillars (F) for routing mortises; a pivot pin (H) to rout circles from as small as 3/4″ up to 8-13/16″; and a pivot hub (G) used in conjunction with a pair of compass rods (C) to rout arcs and circles up to a 25″ radius. A pair of lock bars (I) are handy when joining the two compass rods, while a large handle (E) and an anti-tile leg (J) help you to stabilize the CRB7 in use.
While you could use some of the features of the CRB7 with a stationary router, you’ll want to use it with a plunge router in order to take full advantage of what the jig has to offer. I tried it with a mid-sized 2-1/4 HP Milwaukee (#5616-24), but found it more comfortable, and equally effective, using a compact 1-1/4 HP Porter Cable (#450PK).
Mounting a router on the CRB7 is pretty easy – the steps are clearly laid out in the supplied instruction manual. The CRB7 comes with two sets of guide rods that fit standard 5/16″ and 9/32″ mounting holes found on a wide range of routers. Because it only takes about 5 seconds to remove or install a router onto the CRB7 there’s no need to have the router specifically dedicated for the jig.
The micro-adjust wheel
What I especially like about the CRB7 is the micro-adjust wheel, which enables you to precisely locate the router bit where you want it to go. You make coarse adjustments by loosening the guide rod locking nuts on your router, and then positioning the router. You then lock one of the guide locking nuts, and fine tune the bit position using the micro-adjust wheel. There are red registration lines on both the stationary arm of the adjuster (what M-Power refers to as the bridge) and the rotating wheel. Each full rotation of the wheel moves the router 5/100″ (.05″) forward or backwards. After going through this process a couple of times I found that it was very quick to precisely line up the router bit.
Don’t tilt during edge routing
As you can see in the photo above, when using the CRB7 for edge routing all the weight will be on one side of the jig. You’ll need to keep constant pressure on the opposite side of the jig to prevent it from tilting, which can happen very easily. While you can mount the round handle onto the jig (left photo above), I found easier, quicker and just as effective to grasp onto the bridge (right photo above).
Routing with a clamp guide
I found that the quickest way to rout grooves is using a clamp guide (or any straight edge) attached to the work surface. For deep grooves it’s safest to make several incremental passes at increasing depth of cut rather than hogging out the full depth at once.
If you wanted to make consistently spaced grooves then make and attach a batten to the CRB7 sized to fit snugly into the first groove, adjust the router to the desired spacing, and rout the subsequent grooves. Easy peasy.
Mortising pillars installed
A pair of mortising pillars converts the CRB7 into a mortising jig. As installed in the photo above, you can rout mortises on material from 3/4″ up to 4-7/8″. By installing the pillars in the alternate positions (red arrows), you can rout mortises in stock up to 8-5/8″ thick. Again, you’ll want to make multiple passes at increasing depths rather than hogging out the full mortise at once.
Use battens when mortising narrow stock
As you can see in the photo above, mortising on narrow stock means that only a narrow band of the base plate actually connects with your work piece. It’s better if you take the time to clamp battens to the sides of the stock. This will provide a wider bearing surface for the base plate, considerably reducing the likelihood of ruining the mortise by inadvertently tilting the router in use.
Small circle routing with the pivot pin
Converting the CRB7 to a small circle (or arc) cutting jig takes less than a minute. You simply attach the supplied pivot pin to the base plate. Drill a 1/4″ hole at the center of your circle, adjust the distance, and you’re good to go. Optionally, you can use a #6 screw in place of the pivot pin. There are several locations on the base plate where you can attach the pivot pin (or screw). This enables you to rout circles with a radius as small as 3/4″ up to 8-13/16″. While this is a feature I won’t likely use often, it’s nice to have should the need arise.
The pivot pin conveniently stores in a magnetized cavity on the bridge – which I particularly like because it’s darn small and likely to ‘wander’ off.
Large circle routing with the pivot hub and compass rods
For large circles and arcs the CRB7 comes with a pivot hub – that you attach with a screw onto your work surface – and a pair of compass rods that connect the pivot hub to the base plate. Assembly takes all of a minute, and you can rout arcs up to a 25″ radius and circles up to a 50″ diameter. That covers the full range of arcs and circles I’m likely to use.
The optional flush trimming attachment
There are two accessories available for the CRB7. I found the Flush Trimming Attachment to be the most useful. Essentially it’s a separate plate that slips onto the CRB7 base plate and lifts the base plate 1/4″ above the work surface. It comes with a roller bearing that you attach to the base plate. This creates a consistent distance between the bottom of the cutter and the work surface. You simply need to adjust the router cutter so that it rests a hair’s breath above the top of the work surface (I use a sheet of paper to set the bit height), and then rout the edging flush with the work surface.
I’ve found this attachment indefensible for trimming solid edge banding, though you could use it for iron-on banding and for leveling dowels. It works like a gem.
Optional edge guide
The optional Edge Guide attachment is useful when you need to rout grooves or mortises within 7-1/2″ of the edge of a work piece. It can mount to end of the base plate, as shown above, or onto either long side of the base plate. Using the micro-adjust wheel you can fine tune grooves without having to switch router bits.
I’ve only been using the CRB7 for a couple of weeks, but I can already see how convenient and versatile it is. The jig is well made, and surprisingly quick and easy to convert from one application to another. If you do a lot of router work, then I think you’ll find this jig a welcome addition to your router accessory arsenal. Highly recommended.
- 3/16″ x 6-1/2″ x 11-1/4″ base plate
- Made of thermoplastic, steel, and aluminum
- Accommodates routers that use 9/32″” and 5/16″ guide rods
- Micro-adjust feature
- Rout arcs/circles up to 50″
- Rout circles, arcs, mortises, dados, grooves, and rabbets; profile edges; flush trim edge banding and dowels.
- Includes: Offset handle, anti-tilt leg, pivot pin, mortise pillars, compass pivot hub, two 9/32″” and two 5/16″ guide rods, lock bars, self-adhesive rule, instruction booklet