Turbo Wood Lathes FAQ: Tailstock Quill and Lead Screw Thread Specifications

Turbo T40 Thread Specification: 5/8-11UNC-L

This refers to the quill and lead screw threads on the Turbo T40 model. Here's what each part of this thread spec means:

• 5/8 – This is the major diameter of the thread, meaning the thread is 5/8 inch (0.625”) wide.

• 11 – This stands for 11 threads per inch (TPI), describing how tightly spaced the threads are.

• UNC – This is the Unified National Coarse thread series, which is a U.S. standard commonly used for strong, general-purpose fasteners.

• L – This means the threads are left-hand. That’s important! A left-hand thread tightens counterclockwise and loosens clockwise, the opposite of a standard thread.

Why Left-Hand Threads?
Left-hand threads are used in areas where the regular operation of the lathe (such as spindle or tailstock movement) might loosen a standard right-hand thread. Using a left-hand thread prevents accidental loosening due to rotation direction.

Turbo T60S Thread Specification: 3/4-10UNC-L

The Turbo T60S uses a slightly larger and more robust thread:

• 3/4 – The major diameter is 3/4 inch (0.75”), making it thicker and stronger than the T40’s lead screw.

• 10 – This means 10 threads per inch, which are a bit farther apart than those on the T40.

• UNC – Again, this is the Unified National Coarse standard.

• L – This is also a left-hand thread, for the same reasons mentioned above.

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