Hi,,,,I am making my 1st scarf joint. I am using 3/4 inch stock and want to resaw it to 5/8 inch to fit the depth of the tuners. When do I cut the thickness?,,,,before or after I make the angled cut for the scarf joint?
It depends on tools you have available as to best method. I run a full board of 3/4 through a desktop plainer to get my 5/8 and cut that into a bunch of head stock. However, you can go ahead and cut your scarf and take your down your head stock piece down by sanding or whatever means available to you. I find it much easier to reduce thickness when they are separate and it looks cleaner. Plenty of Youtube vids on scarf jigs.
I glue the joint then measure 5/8 (or 1/8 from the top) and make the cut with a band saw. Then clean the top of the cut with a file and sandpaper. You really can just rasp the 1/8 off. Be sure to take it off the top so the tuners have the flat surface to mount.