I like the look of the spanner bolts on T-152. I didn't own a metal
lathe when took on this project, so I went to my trusty hardware store
and bought some 3/8" stove bolts ("A", at left). 1/2"
bolts will give a bigger head if you want.
B) I chucked them upside down in my drill press and, while the bolt was turning, filed off the grade numbers and galvanized surface so they would take bluing or Parkerizing.
C) I turned them right side up and center punched, then drilled a 13/64" hole for a 1/4" - 20 tap. There is a convenient square shoulder on a stove bolt that holds it nicely while tapping. After tapping the holes I cut the heads off the shanks.
D) I threaded one end of a 1/4" rod (you can save time and buy threaded rod) and then I screwed the heads on upside down and clamped them in a vise in preparation for drilling the small tightening holes. For a spacer I used the bushing I later used for the trigger roller. Once the hole was started I removed the spacer. (I tried drilling from the arched top of the bolts with predictable messy results. Drill from the back)
I threaded my own rod because I could, but dies are expensive. Threaded rod is cheap and will work fine. To get the smooth top bolt I simply screwed on a bolt head about a half turn shy of flush and then welded it in place. I chucked it up again and filed as in "B", above, left.
The bottom heads I left open. I drilled a 1/4" hole in the top bracket so the rod would pass through, but I drilled a 13/64" hole in the bottom bracket and tapped it 1/4" X 20. That way the nut is a lock nut, and keeps the whole bolt assembly from turning so the top holes stay neatly in line.
Here (left) is a variation. A long 1/2" carriage bolt (I use a 12" bolt to get the long shoulder needed) is altered by removing the square shoulder with a metal lathe, cutting the bolt to length, then drilling and tapping a 1/4" hole in the bottom. A second, short carriage bolt is turned to 1/4" and threaded. This drawing shows the resin handle with an Allen screw keeping the handle from rotating. To see more details on making this type of bolt, click here.