- Joined
- Jan 31, 2012
- Messages
- 212
I am now the proud owner of a Starrett #6 screw pitch gauge.
On each blade, there are 2 values:
- the TPI
- a decimal number that seems to be 2x the value called "Depth of Sharp V-Thread" in the Machinist handbook.
e.g. 20 TPI - book: 0.04330 x 2 = .08660 - the blade shows .086
24 TPI - 0.03608 x 2 = .07216 - .072
etc.
The Depth (or Height) of Sharp V-Thread is the difference between the root and the crest if the threads were cut perfectly sharp and straight.
What is the practical purpose of that indication on the gauge? Why is it 2x the value above?
On each blade, there are 2 values:
- the TPI
- a decimal number that seems to be 2x the value called "Depth of Sharp V-Thread" in the Machinist handbook.
e.g. 20 TPI - book: 0.04330 x 2 = .08660 - the blade shows .086
24 TPI - 0.03608 x 2 = .07216 - .072
etc.
The Depth (or Height) of Sharp V-Thread is the difference between the root and the crest if the threads were cut perfectly sharp and straight.
What is the practical purpose of that indication on the gauge? Why is it 2x the value above?