- Joined
- Feb 1, 2015
- Messages
- 9,516
Yesterday, I had to thread some 5/16" stainless rod and did not have a chart of thread depths handy. This morning, I decided to make one based on the definition of unified National thread geometry. The external thread geometry consists of a 60o vee shape with the top of the vee truncated to a width of P/8 where P is the thread pitch and the bottom truncated with a radius which is tangent with thread at a distance of P/4 along the thread face from the bottom of the vee.
If using a threading tool ground to a sharp point and advancing the tool using the compound, the distance along the thread face from the major diameter to the bottom of the vee is P -1/8 * P = 7/8 * P = .875 * P. If the compound is set at an angle of 29.5o, the distance is slightly less or .995025 * 7/8 * P = .87065 * P.
If a tool is ground to conform to the specification (i.e., with a radius), the distance traversed by the compound will be less yet and equal to .79167 for a 30o compound angle and .78773 for a 29.5o compound angle.
The chart gives the compound distance for a 29.5o compound angle setting for cutting the standard UNC, UNF, and UNEF threads.
Bob
Note the chart was removed due to an error. A corrected chart is shown in a following post.
If using a threading tool ground to a sharp point and advancing the tool using the compound, the distance along the thread face from the major diameter to the bottom of the vee is P -1/8 * P = 7/8 * P = .875 * P. If the compound is set at an angle of 29.5o, the distance is slightly less or .995025 * 7/8 * P = .87065 * P.
If a tool is ground to conform to the specification (i.e., with a radius), the distance traversed by the compound will be less yet and equal to .79167 for a 30o compound angle and .78773 for a 29.5o compound angle.
The chart gives the compound distance for a 29.5o compound angle setting for cutting the standard UNC, UNF, and UNEF threads.
Bob
Note the chart was removed due to an error. A corrected chart is shown in a following post.
Last edited: