Yes, the Leigh Super FMT does appear to be a well designed, well manufactured, and well documented jig. I got everything set up in less than an hour and, so far, have spent about three hours experimenting with it.
So far, I have had some good results and some puzzling results. Just about an hour ago I managed to produce a tenon which was mis-shaped:
[ ERROR: SPECIFIED ATTACHMENT MISSING ]
and, for the life of me, I can't figure out what I did wrong.
From the photo you posted it appears (I could be wrong here) that you are clamping your tenon workpiece horizontally, not vertically. All tenon stock should be clamped vertically. See the procedure below. It is also possible that the table is not clamped and that is moving slightly when you route the tenon. Check that it is clamped firmly. Hope this helps. I have been presenting seminars at Lee Valley in Ottawa for several years on the Leigh Jigs and this sort of thing happens from time to time if one forgets to ensure the table is clamped properly after centering it over the stock.
1. Install appropriate bit in router
2. Install joint guide
3. Mark outside surfaces of mortise and tenon stock
4. Adjust table to its centre position
5. Install fence off centre by about 1/2 the width of the tenon stock. Ensure it is 90 degrees vertical.
• Mark the length of the tenon on the work piece.
• Clamp tenon stock vertically against the fence and touching the retractable sight.
• Turn the left guide pin clockwise until it stops, the raise it two full turns.
• The left guide pin steers the router bit around the guide to form the tenon.
• Move the router in a clockwise direction to begin (a climb rout) to produce a clean shoulder, then counter-clockwise to complete the tenon, ensuring the guide pin rides against the joint guide all around.
• Before removing the router or tenon work piece, confirm the tenon is properly routed.