If all else fails, you can make a bespoke one to clamp the FTI to the stem on your your Mag Base column

After all, we are supposed to be Engineers, with the ability and facilities to make things!

(Two small pieces of square bar, each with two drillings (Reamed holes would be best ) at right angles to each other. On one piece sized to suit the column on the Mag Base, and to suit the DTI stem on the other, with a common sized drilling, to suit the clamp screw.

The only other operation is to slit each block across the clamp screw drilling, so that tightening the clamp screw closes the slit.

If you cannot make a knurled knob for clamping, an Allen capscrew and nut will do the job.

It may be a hybrid, clamping to a metric column, to hold an Imperial stem DTI.

"C'est brusque, mais ca marche"

SO WHAT?

It will do the job that you require.

Or if the hole in one part matches the Mag Base column and the other is oversize for the DTI stem, turn up a sleeve to match the stem to the hole, and split it.longitudinally.

Howard

Edited By Howard Lewis on 23/06/2021 15:12:31

I would trust a Starrett quarter-inch to be a true quarter-inch, unlike some of the what-the-'eck diameters on some of my bought stand clamps and bars.

Nevertheless there seems a Law – it must have someone's name on it – that when you need assemble a set of commercially-made fittings that are nominally compatible… they aren't.

I became so fed up one afternoon trying to mount a DTI and stand on my large lathe I spent the rest of the time making assorted rods to fit my Imperially-dimensioned instruments to the somewhere-handy, bought parts made to Elbonian Standard rather than French Revolutionary, mm.