If the threads are to extend to the bottom of a blind hole, the intermediate ( plug ) tap will be used to cut threads until the point of the tap reaches bottom, after which a bottoming tap will be used to finish the hole.
22.
For example, pieces of shot may be placed between the wood pieces to produce indentations when the pieces are clamped together; after the clamp is released, the indentations indicate the center points for drilling . " Dowel centers " are simple and inexpensive tools for aligning opposing blind holes.
23.
I would like to know the methods for checking the cone angle of a blind hole . please help me in this regard . i would like to know the methods to check with gauges . we can very well check in a countour or by cutting and checking in a profile projector . please let me know if you have any other methods . thank you.
