…or tenon and housing dado trimmer par excellence.
I say Paul’s because I developed it to work so effectively. Many routers are highly effective at perfecting a chiselled out housing or dado joint and the faces of tenons. They have been used for such for centuries now. The idea is of course that they span the two sides of a recess and the cutter skims off the irregularities to take the final pass down to exact depth. On wide recesses or on tenons, one side of the router plane often finds no support and dips to one side, gouging into the bottom of the recess or tenon cheek and thus depriving us of our goal toward perfection. With a wide housing dado such as the ones in my aprons and the underside of my well board, even fairly large routers don’t fully span the width and so our work can be compromised. I retrofitted one of my routers with a ¼” aluminium plate that lengthened the sole and I may post on this some day because it so transforms the tool, but today I want to show you a tool I make to task as needed. It actually takes no more than three minutes to make and the results in my finished work are always stunning. This tool perfects both tenons and housing dadoes.
Paul’s perfect router is Paul’s because of the extended length of the sole and the calculated angle of presentation of the cutting (chisel) iron in relation to the wood to be worked.
I want my tenons to be surface skimmed so that they perfectly align centrally to the length of my rail. Any discrepancy here will result in ill-fitting shoulders, a misaligned tenon and worse still a twisted frame. This tool aid eliminates this altogether. By extending the length of the body of wood I can hold one side to the length of the rail and then swivel the business end to task. It’s easy to adjust position throughout to negotiate grain and knots as you work too. The same tool will be used for the large housing dadoes yet to be formed in the aprons and well board.
I chose a piece of wood 1” thick by 3” wide and 20” long. That’s my suggestion for you, but go with what you have as this is not critical. The important thing here is the angle of the bevel of your chisel. Typically this will be 30-degrees. I add a few degrees; 3-5-degrees and not usually any more, so that the cutting edge is not compromised by the heel of the bevel riding the wood and causing the tool to rise up as I thrust the router into the wood. Dead simple.
I bored 6” from the end of the wood and 5/8” in from the top edge corner.
First I ran a parallel line 5/8″ in from one edge to guide me and then measured 6″ along from one end for cross hairs for the point of my auger bit.
If you have a helper they can hold the protractor at the right angle or they can site you in as they hold the bevel of the chisel on the wood to show you the angle you need to bore at. Either way will work fine. Bore through the wood at 33-35-degrees, making sure you sight as squarely as possible to the length of your billet. This will ensure the cutting edge is parallel to the sole when you tap the chisel through. In this case we are using a ½” chisel and so the hole I bore is 3/8”, that way the edges of the chisel ‘bite’ into the walls of the angled hole. I anchored my piece to the new bench top so that the hole area overhangs the top and I can bore through freely. I am using a brace and bit but you can use a drill/driver and regular 3/8” twist drill if that’s what you have. They are more difficult to start at this lower angle, but if you begin drilling in a more upright angle and then drop the angle to present the bit to gain the correct angle it will work fine.
Don’t worry if there is any breakout on the underside, as this has no consequence on the work in hand.
To get the right depth, or near to, mark your depth of cut onto the edge of a piece of wood and tap until the chisel protrudes through to where you need it as shown. For trimming tenons, tap through and test on the actual work. The idea is to take of small increments in depth and by tapping the chisel handle you can get the exact depth you want. To retract the chisel and lessen the depth, tap the back, upper corner with the hammer. It is trial and error but surprisingly quick and accurate with a little practice.
The underside of the sole often breaks out when the chisel is driven through, but this again has no consequence on the work in hand. Simply chisel away any unevenness with a second chisel.
Here is the new tool in action on housing dado and tenon.