CHAPTER VII.

=DETAILS IN LATHE CONSTRUCTION.=

=Live Spindle= of a lathe, the fit of 157 With coned journals 157 Methods of taking up the end motion of 158 Arranging the swing frame for the change gears 158 Taking up the wear of the back bearing 158 The wear of the front bearing of 158 =The Taper= for the live centre 159 =Methods= of removing the lathe centres 159 =Tapers= for the live centres 159 =Methods= of removing the dead centre 159 =Driving Cone=, arranging the steps of 159 Requirements of proportioning the steps of 159 Rules for proportioning the diameters of the steps of, when the two pulleys are exactly alike and are connected by an open belt 159 to 161 When the two pulleys are unlike 161 to 164 =Back Gear=, methods of throwing in and out 165 =Conveying= motion to the lead screw 165 =Attaching= the swing frame 166 =Feed Gear.= Arrangement for cutting worm threads or tangent screws 167 =Feed Motion= for reversing the direction of tool traverse in screw cutting 168 For lathe aprons 168 =Slide Rest=, weighted elevated 168 Double tool holder for 169 Gibbed elevating 169 =Examples= of feed motions 170 =Feed Regulators= for screw cutting 171 The star feed 172 =Ratchet Feeds= 173 =Tool Holding= devices, the various kinds of 173 =Tool Rest= swiveling 174 =Tool Holder= for compound slide rests 174 For octagon boring tools 175 =Lathe Lead and Feed Screws= 175 Lead screws, supporting, long 176 Position of the feed nut 177 Form of threads of lead screws 177 The effect the form of thread has in causing the nut to lock properly or improperly 177 Example of a lead screw with a pitch of three threads per inch 177 Example of a lead screw with five threads per inch 178 Example with a lead screw of five threads per inch 179 Device for correcting the errors of pitch of 179 =Table= for finding the change wheels for screw cutting when the teeth in the change wheels advance by four 180 For finding the change wheels when the teeth in the wheels advance by six 180 Constructing a table to cut fractional threads on any lathe 181 Finding the change wheels necessary to enable the lathe to cut threads of any given pitches 181 Finding the change wheels necessary to cut fractional pitches 181 =Determining= the pitches of the teeth for change wheels 182 =Lathe Shears= or beds 182 Advantages and disadvantages of, with raised V-guide-ways 182 Examples of various forms of 183 =Lathe Shears= with one V and one flat side 183 Methods of ribbing 184 The arrangement of the legs of 184 =Lathe Tailblock= 185 With rapid spindle motion 185 With rapid fastenings and releasing devices 185 The wear of the spindles of 185 Spindles, the various methods of locking 186 Testing, various methods of 187