Join Date: Jan 2019
Location: Central North Carolina
Floating tenons that are made on the table saw and finished to thickness with a planer gets my vote if you are on a budget. Cut the mortises with a plunge router and the desired diameter of up spiral router bit.
Make the mortises using a router and edge guide, or a more elaborate shop made jig for holding the work piece and guiding the router bit. A friend of mine made a jig from cabinet plywood by roughly copying my FMT jig, but he installed stops for the mortise length and a slide to guide the router. He has been having great success with this jig and using floating tenons as I suggest here. I explained why I have an FMT Pro jig, but it isn't necessary if you go the floating tenon route as I explained here. Your M&T joints will be just as strong and almost as easy to make by going the "floating tenon" way. It doesn't require expensive tooling and most likely you already have what you need. If you don't have a planer, just a more careful table saw setup for tenon thickness and a good belt sander can make acceptably good floating tenon stock. It might just take a little longer.
If you plunge cut the mortise with a spiral bit, your plunge router, and an edge guide, do so in many overlapping plunges and then go back to clean out the remaining wood and smooth the mortise sides to the bit dimension, Let the bit diameter determine the width of your mortise. Use a planer to fit the floating tenon stock to the exact thickness needed for the mortise and then cut the floating tenons to length and width out of this material as you need them. Don't worry about the half round mortise ends. Just cut the tenon size to fit the length of the flat sides of the mortise. The strength of the joint is all in how well the flat sides of the tenon fit the flat sides of the mortise and the glue used. The unused 1/2 round mortise ends are a good place for the excess glue to go. The tenon gains almost no extra strength by being rounded to fit these ends closely. The joint needs to dry fit together without the need for a hammer, but not so loose that it falls apart on it's own. Anywhere in that region of thickness will produce a great joint. Use a good wood glue like Titebond or Franklin and you will never have a joint failure. I like Titebond II, but use whatever you prefer. I don't like Gorilla Glue because it isn't as strong and the foaming as it dries makes a huge clean-up mess. I use Titebond because it cleans with just water, until it dries, and then becomes water resistant.
A tip - If any glue squeezes out of the joint, leave it alone until it partially sets up and becomes a bit rubbery, unless it runs. If it does run, a significantly wet paper towel will remove the runs if you act quickly, but be certain to not leave any on the wood surface or it will affect your finishing steps. Then, when the glue in the joint is partially set up, a plastic soda straw end can be pressed against the joint and form to the shape of the joint (usually 90 deg). As you push the open end of the straw along the joint, the excess glue will be collected into the straw. A pair of scissors will shorten the straw and leave a fresh end to scoop the glue from the next joint. Repeat this as often as necessary to clean up all of the glue joints in your project. It is very rare that I need more than one straw for each glue-up.