One way to attach a scythe grip is to use a hanger bolt (I've seen them at all the hardware stores near me, including the big box stores). A hanger bolt is like a wood screw combined with a bolt. The screw end goes into the end of the grip, and the bolt end goes through a hole in the snath and is attached with a nut. I've used this method for making adjustable one-grip snaths.
The grip is recessed into the snath to prevent it from turning. The recess is about 3/16" deep and needs to be flat at the bottom with two vertical sides, to fit snugly with the grip. Once the recess location is marked onto the snath, the material can be removed using a hand saw (even a hacksaw) and a chisel (or knife). First cut the two vertical sides down to the base lines, and then make a bunch of cuts (down to the base lines) crowded together between the two side cuts. Then use a chisel or knife to remove what's left, smoothing the bottom of the recess. A hole is then drilled into the center of the recess for the hanger bolt.
The end of the grip needs to be flat, with two flat sides at this bottom end, sized to fit snugly into the snath recess. While fitted together, a pilot hole should be drilled into the grip, to make sure the location and alignment of the hole are correct. Remove the grip and if necessary, finish drilling the pilot hole for the screw end of the hanger bolt. Then put some glue (preferably epoxy) into the hole before screwing the hanger bolt into the grip.
The hanger bolt has no head, so how do you turn the screw to install it in the grip? Two methods: (1) put two nuts on the end of the hanger bolt and with two wrenches, lock them together (turning in opposite directions to tighten them forcefully) and then the end nut can be turned like the head of a bolt; or (2) simply use a vise-grip wrench to clamp tightly onto the middle section of the hanger bolt, taking care not to damage the threads at either end of the hanger bolt, and turn the locked vise-grip wrench to spin the screw. (The vise-grip wrench will damage the middle section of the hanger bolt, but it's not a problem because this section of the hanger bolt doesn't extend beyond the snath when the grip is installed.)
Once the glue dries, the hanger bolt will be permanently installed in the grip, and now the grip can be attached securely using a nut, washer, and lock washer.
One advantage of this method is that more than one recess can be put on the snath to make the grip adjustable. Alexander Vido (of ScytheWorks) has sold one-grip snaths having two grip positions, one for field mowing and one for trimming. I made a one-grip snath for teaching beginners, which has five recesses along the midsection of the snath, to fit a range of user heights from 4'6" to 6'6" (the five recesses correspond to approximate heights of 4'6", 5'0", 5'6", 6'0", and 6'6"). The same blade cannot be used for this range of heights, however, due to the difference in tang steepness that would be required by taller and shorter users.
When swinging the scythe, it shouldn't be difficult to make sure that the nut end of the hanger bolt doesn't hit your leg. For my adjustable snath with five grip positions, I initially used a wing nut on the hanger bolt, and the extra protrusion did cause some problems when I used a certain stance or trimming technique, so I went back to putting a regular nut on the hanger bolt.
