In laying out a 3/8″ tenon on 3/4″ wood I convert 3/4″ to 48/64″ and divide by 2 to get my center of  24/64″. I then draw a line 12/64s” on either side of the center line and this leaves me with an 3/8″ center tenon. I use a similar procedure for cutting mortises. Is there an easier way to do this? Also, it would seem easier to use a 1/4″ tenon and mortise with a 1/4″ tongue and grove and  slott cutting router bits. Is a 1/4″ mortise tenon considered strong enough for making 3/4″ furniture joinery?