Lathe spindle nose configuration On traditional engine lathes, the spindle nose end commonly has which thread arrangement for mounting chucks and faceplates?

Introduction / Context:
Spindle noses provide standardized interfaces for mounting chucks, faceplates, and drive plates. Older and many general-purpose lathes employ threaded spindle noses, while more modern heavy-duty machines often use camlock or long-taper key fittings.

Given Data / Assumptions:

• Conventional engine lathe.
• No camlock or A-type short taper specification implied.
• Question focuses on the traditional threaded style.

Concept / Approach:
In the threaded spindle nose system, the male thread is on the spindle nose (external), and mating female thread is on the chuck backplate. This allows easy mounting/removal while a register fits for concentricity.

Step-by-Step Solution:
Identify traditional spindle nose style: externally threaded spindle.Recognize mating backplate with internal threads.Select the corresponding option.

Verification / Alternative check:
Lathe manuals and standards show common nose threads (e.g., 1.5 in–8 TPI, M68×6) with external spindle threads.

Why Other Options Are Wrong:
Internal threads exist on the backplate, not the spindle. Tapered threads are uncommon for this purpose. Smooth noses are used with camlock/taper systems, not for threaded mounting.

Common Pitfalls:
Confusing spindle nose types across different standards; always verify the specific nose standard when selecting chucks.

Final Answer:
External screw threads