Chapter IV: =screw-Threads.=

=Screw Threads=, the various forms of 85
The pitch of 85
Self-locking 85
The Whitworth 86
The United States standard 86
The Common V 86
The requirements of 86
Tools for cutting 87
Variation of pitch from hardening 87
The wear of thread-cutting tools 88
Methods of producing 88
Alteration of shape of, from the wear of the tools they are cut
by 89
=Screw Thread Cutting Tools.= The wear of the tap and the die 89
Improved form of chaser to equalize the wear 90
Form of, to eliminate the effects of the wear in altering the
fit 90
Originating standard angles for 91
Standard micrometer gauge for the United States standard screw
thread 91
Standard plug and collar gauges for 91
Producing gauges for 92
Table of United States standard for bolts and nuts 93
Table of standard for the V-thread 93
United States standard for gas and steam pipes 93
Taper for standard pipe threads 95
Tables of the pitches and diameters at root of thread, of the
Whitworth thread 95
Table of Whitworth's screw threads for gas, water, and
hydraulic piping 96
Whitworth's standard gauges for watch and instrument makers 96
Screw-cutting hand tools 96
=Thread-Cutting Tools.= American and English forms of stocks
and dies 97
Adjustable or jamb dies 98
The friction of jamb dies 98
The sizes of hobs that should be used on jamb dies 99
Cutting right or left-hand thread with either single, double,
or treble threads with the same dies 99
Hobs for hobbing or threading dies 100
Various forms of stocks with dies adjustable to take up the
wear 101
Dies for gas and steam pipes 101
=Thread-Cutting Tool Taps.= The general forms of taps 102
Reducing the friction of 102
Giving clearance to 102
The friction of taper 103
Improved forms of 103
Professor J. E. Sweet's form of tap 104
Adjustable standard 104
The various shapes of flutes employed on taps 105
The number of flutes a tap should have 105
Demonstration that a tap should have four cutting edges rather
than three 106
The position of the square or driving end, with relation to the
cutting edges 106
Taper taps for blacksmiths 106
Collapsing taps for use in tapping machines 107
Collapsing tap for use in a screw machine 107
The alteration of pitch that occurs in hardening 108
Gauging the pitch after the hardening 108
Correcting the errors of pitch caused by the hardening 109
For lead 109
Elliptical in cross section 109
For very straight holes 109
Tap wrenches solid and adjustable 110
=Thread-Cutting.= Tapping 110
Appliances for tapping standard work 111