If anything, machine the blank very slightle undersize, (in this case say 0.010&quot so as to truncate the thread to prevent root / crest intereference. This is assuming that the thread to be cut is a male one. If female, machine slightly oversize, for the same reason.

Somewhere in my Apprentice Notes there is a formula to to calculate by how much the thread should be truncated.

Found it!

For WHITFORM threads truncation should remove (0.160083 x Pitch) from the crest of the thread, which looks like 0.020" for 8 tpi. So I was erring on the side of caution, above.

Truncated dia of SCREW = Nominal Dia – 0.1478 / TPI (1.835" in this case)

Truncated dia of NUT = Nominal (Core) Dia + 0.1478 / TPI

BUT allowance needs to be made for the truncation when setting depth of cut, so maybe the depth of cut on a 1.875 x 8 TPI thread would then become 0.060" ( If the blank were not truncated, the tool would make contact at 1.875", but the truncation has removed 0.020" already, so the tool should only be fed in 0.060" to achieve a full depth of thread.

Howard