Barton sheet lead track slider - thread size

[Slocumotion]

Track is 1" wide (near as damn it, 0.946" if that makes any difference) Locking wing bolt thread is 0.243" diameter, but does not seem to be 1/4" UNF. Any suggestions?

 

[macd]

M6?

 

[Slocumotion]

No. Should have said - M6 has right pitch but very loose fit.
Thanks though.

 

[lw395]

0BA?