I use the bandsaw ...now.
Yes, that's a problem holding the long board and making a cut... and it depends on the length of the tenon. A RAS with a dado set will allow you to see the progress from above AND the long board will rest nicely along the back fence. On a table saw, unless you have made an auxiliary miter fence which extends the face, it will be difficult to keep the board in constant registration... it will what to wobble unless clamped down Then you can use a stop block either on the rip fence or on the extended fence on the miter gauge.
I now use the bandsaw with2 different fence stops, one for the length of the tenon, the other for the depth of the shoulder cut. All your boards must be identical in dimension and a practice piece or two will make certain yuu have the tenon the correct width and centered.
Now for a question.
Which boards are you attempting to make the tenons on?
The table top ends..?
Or the apron ends ...?
The process would be different IF the top is all ready glued up.
The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)
Last edited by woodnthings; 08-15-2017 at 10:46 AM.