V-serrated two-piece grips for tension testing

[Ingenuity]

I have to load test (in the field) some old (40+ years old) high-tensile post-tensioning components to a force not to exceed 33 kips (about 150 kN).

The post-tensioning element is made up of 7-wires to form a 1/2" nominal diameter strand, of 270 ksi tensile capacity. Outer six-wires are spirally laid around the central king wire.

The strand is held in a barrel chuck, with a two-piece wedge. The barrel chuck has an OD of 2.5", and is about 1.5" long. The barrel chuck looks like this:

To test the assembly I have to grip the 2.5" OD chuck barrel, using a collet, with two-piece wedges custom made to fit over the 2.5" OD barrel.

The collet setup is like the following:

The last time I made up this arrangement was back in 2009 and the manufacturing company that did the collet wedge manufacturing/hardening is no longer in business, so I have little info on the collet wedge coarseness, material type, treatment etc.

My questions are:

1. Are v-serrated "teeth" to the two-part collet wedges best to be fine (like 25 threads per inch) or course like 8 threads per inch for the 2.5" dia barrel chuck?

2. What is the best material to make the wedges? AISI 4140?

3. What heat treatment of the wedges is appropriate? I was thinking Q&T with hardness of Rc 60?
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Thanks in advance.