Thankyou for the address. They did have a getstart.pdf but it did'nt include anything for a finger bit similar to mine.
However, without needing to revert to a full frontal lobotomy I now see how to jig up for this finger router bit to make 180 deg butt joints in lengths of timber.
The router bit consists of a top bearing, 5 No. thin 3.3mm gauge TCT cutters (consisting of two 0.6mm shoulders & a 2.1mm deep tip) & 1 No. bottom thicker cutter (consisting of one 0.6mm shoulder & a 5.5mm deep tip), the underside of the bottom cutter being parallel to the base plate of the host router. There is 1.9mm clearance space between TCT's. The total router bit base cutting depth is 32.3mm. On a 35mm thick timber, this leaves 2.7mm, the depth of one 2.1mm tip & one 0.6mm shoulder
The router use is given as suitable for a max thickness of wood of 35mm (9.5mm min). Thus, for a 15mm thick pine ogee skirting board:-
A first cut is made in the first skirting in a face down attitude, with the router depth set for the skirting board face to be level with the router bit base. A gash timber guide 20mm deep (35 - 15mm) is clamped to the top of the skirting board, in line with the butt joint end, to reach the router bit top bearing which provides the depth of cut stop. This cut, at the base of the router bit, provides a 5.5mm tip rebate on the face of the skirting board & circa 1 1/2 No. 2.1mm tip groves forming 2 No. thin fingers for the joint.
The second cut in the adjoining skirting is made in a face up attitude with the 20mm gash timber guide clamped to the bottom of the skirting board, the router depth is increased by 2.7mm. This cut, at the top of the router bit, provides 2 No. 2.1mm tip groves forming 1 No. thick & 2 No. thin fingers for the joint.
Q.E.D. (quod erat demonstrandum or quite easily done?)