Logan 200 Lathe Spindle Threads Ground Flat

[AmericanMachinist]

Hello,

I purchased a Logan 200 lathe from the 1950s (?) that is in immaculate condition. It essentially looks new. One oddity is that the front or first ~2/3 of the threads on the head stock spindle are ground flat, with maybe 1/4 or so of their full depth remaining. The grind is so clean and uniform that I assumed this was intentional, perhaps to make threading of chucks easier, with the full threads at the rear to provide additional grip.

However I'm not seeing similarly-ground spindles in images on the web. Is this something that Logan did at some point? I'll add images when I can.

Thank you!

 

[MontanaLon]

Pretty good chance is was done by a prior owner to "correct" damage from a cross threaded chuck or face plate. I can't see any good reason to do this unless there was damage.

If the threads still hold and everything lines up on the register, it shouldn't cause any issues for working in a home shop. Really it is only the fit of the last threads and the register that matter in holding everything together when spinning "forward". It may affect the amount of holding power if you turn in reverse but that is something you should approach with caution anyway.