Decided to make at least one vang using a Dubro 2157 4-40 full threaded turnbuckle.
Generally I think anyone who does make their own vangs puts a left hand thread in an aluminum tube, but a couple years ago I made one by putting a left hand thread in a Sullivan 4-40 gold-n-clevis. I did not remember how I did that, but I decided maybe I had drilled the clevis out with a 3/32 drill bit and then threaded it with a LH thread cutter.
That worked very well today. It takes a bit of care and slow going to make sure the cutter does not break. I just put the tap in a vise and kept working the clevis back and forth.
After the thread is cut, the tool is still pretty tight in the hole - difficult to spin it out of the clevis - but the turnbuckle has a perfect fit.
I had limited luck at putting a left hand thread in a brass tube. It is easier with the clevis sincne it is not solid - has a split in the barrel.
Scott