JOINING MITRE EDGING TO TOP PLATE:
The sides and edges must be prepared to accept the edging and these must be absolutely true and fair.
On the table saw, reverse the top plate, taking off 1/32nd or less on each edge until a true fair edge is attained. Follow the same procedure with the longitudinal mitred edge piece.
With respect to the ends of the top plate, these are a tad more tricky due to the width and length (table saw) and I am reluctant to use the mitre saw for something requiring absolute accuracy. I will therefore use the router with a high quality aluminum fence. The fence is secured to the end of the work bench utilizing spacers the same thickness as the top plate. A 3rd clamp is used to create pressure between the aluminum fence and the top plate, to ensure that the latter remains immobile.
Use a good quality set square to ensure the fence is absolutely perpendicular with the longitudinal edge of the top plate.
In conjunction with a suitable carbide tipped straight bit, work from left to right, make small cuts and use a piece of painter's tape at the end in an attempt to reduce tear out.
The 3 ends/edges are now prepared for fastening the 3 1/2 inch mitred edging.
Begin with the mitred longitudinal.
The length of the wide top plate is 50 3/8 inches and remembering the 45 degree angled ends of same require an additional 3 1/2 inches of length for each end. The total length of the mitre strip should be marginally over 57 5/8 inch (57 3/4 inch) allow an equal overlap at each end of approx. 3 9/16 inch.
Scribe line at intersection of two work pieces (photo 3028)
Use the scribed line and the end of the top plate to reference the edge of Dowelmax.
Set the extended distance gauge to 9 5/8 inch.
Align and clamp Dowelmax to the scribed line, drill through 3 & 4, install the extended distance gauge in the last bore and align Dowelmax to the end of the extended distance gauge rod, drill 1 & 2, repeat process along work piece until last setting, and drill 3 & 4 (photo 3029).
Follow the same procedure with the wide top plate, beginning at the left edge (check mark), drill through guides 3 & 4, continue with the same procedure as for the mitred trim.
Before dry fitting the trim and top plate, remove both scribed lines at junction with top plate and trim. Dry fit using approximately 50% of the dowels and close joint to ensure proper fit before reapplying scribe marks at each corner.
With this type of mitred trim, I like to reinforce the mitre connection with one or two dowels (one would probably suffice). Normally when we join a mitre joint using Dowelmax, the device is set with the guides absolutely perpendicular to the mitre surface. However as a consequence of the axis of the dowels on the edges and ends, this is not possible. In other words some of the dowels would be set at an angle of 90 degrees, whereas the mitre joint would be set at 45 degrees. We have therefore to align the mitre dowels in the same axis as the routed end trim (see diagrams a & b).
Implement two procedures prior to drilling, (1) ensure routed trim ends are perfectly perpendicular to the longitudinal axis of the rail, (2) scribe a line coinciding with the original scribed line.
Reference Dowelmax to the inner edge of the rail, and also to the top. Drill through guide #3 and using the 45 degree scribed line, ensure depth of the drill hole is approximately 1 inch past that 45 degree line.
The next step is to follow a similar procedure for the end routed trim. Install check marks at the rear faces and ends/edges. Reference Dowelmax to rear end and upper face. Clamp and drill. Set distance gauge to 3 1/2 inches, align Dowelmax with rod and drill guide #1. Move distance gauge along, align rod with Dowelmax and drill through guide #3.
Reference to the top and rear edge of the top plate and perform the same reference and drilling procedures.
At this juncture, my 3/8 drill required to be sharpened. A quick method for setting the proper depth, the drill is inserted and rotated until the scribed line. Align the screw to the scribed line. Tighten both screws.
Following drilling, dry fit the assembly, following which, Dowelmax is clamped to the routed rail with the block firmly against the top plate, and again referencing from the top.
Once all the bores have been drilled to accept the 3 routed rails, the next step is to cut the 4 mitres. Begin with the longitudinal routed rail, install 3 dowels (ends and centre) dry fit to top plate, scribe 2 marks on longitudinal routed rail to correspond to the ends of the top plate. Use these marks as a guide for the mitres.
Before proceeding, perform test cuts and adjust mitre gauge to attain perfect 45 degree angle.
Make several passes, constantly dry fitting to ensure inner corner of mitre aligns with end of top plate.
Remove any dowels from the short routed end rails, then cut mitre on rail, short of the finish point (approximately 3/8 to 1/2 inch). Adjust angle if cut until a perfect match with the longitudinal 45 degree mitre is achieved.
Maintain mitre gauge setting and with great care, making several passes, until perfect alignment has been achieved.