Mitre Joint with Offset Shoulder Construction

I like the mitre joint look but also the tenon-mortise strength and wondered if a mitre joint with offset shoulder could merge the benefits of both. I wanted a joint that could be machined for accuracy et repeatability as well as doesn't need specialised head cutters. A single rough saw blade allows for the following joint but need much time and care than common methods.

Overview


Rails hold the tenon and stile the mortise. I started on the spindle moulder clearing one third of the whole depth on the rails and two thirds on the stiles. After locking the tenoning guard on the sliding table and the suitable fence, I adjusted the mitre gauge at 45° and cut the bevels step by step about a half of the blade kerf each passes then sanded the shoulders to get a flat surface.

Mitre Clearing


I formed the offset shoulder with the mitre gauge at a 90° angle and a first kerf on the spindle moulder then cleared with another cut on the table saw. That last cut was a bit fiddly and I avoided to remove too much material for further adjustment.

Offset Shoulder Clearing


Then machined the stile mortises flush to the bottom cheek and slightly moved back just in case of I would change my mind and mould the inner side. Here as often, the table attachments made the operation easier.

Mortising


The tenons were sawed related to the mortises dimensions and I made dry assemblies until satisfactory bevel and back joints and tenon mortise fitting. However rails with their tenons tended to slightly lift at their outer side probably due to the big contact surface of the cheeks.

Tenons


Machining the groove raised an issue and stiles required a dropping-on operation. I had never performed such cut on the table saw but the shallow cut let me think that I could groove safely with suitable arrangements. I set up a convenient right blade guard with a scrap of wood screwed on the two carriage hold-downs. If something went wrong my fingers could not reach the teeth. I clamped a front stop on the fence plate and a back stop at the rear table. The back workpiece leaning against the front stop I lowered the wood until the bottom side contacted the table and kept the stock downward applying pressure firstly before the blade then after as soon as I could while using the depressed handle push stick until the front stopped against the rear stop. Of course such operation can be safely performed on the spindle moulder mostly due to the fence back-stops aiming dropping-on operations.

Groove


The coved raised panel could now be slid into the frame grooves and it remained to shape the coved applied moulding then assemble the panels. The strength of the joint surprised me so much that I said to myself I would keep that technique in mind for possible further needs.

Frame