Facing Between Centers Unit 51

Objectives Set up workpiece for machining between centers Set up workpiece to face the ends Face workpiece to exact length

To Set Up Cutting Tool for Machining Move toolpost to left-hand side of T-slot in compound rest Mount toolholder in toolpost so setscrew in toolholder approximately 1in. beyond toolpost Insert the proper cutting tool into toolholder Have toolbit extend .500 in beyond toolholder Never more than twice its thickness

Set cutting-tool point to center height Tighten toolholder setscrew with only two-finger pressure on wrench to hold toolbit in toolholder Careful tightening setscrew – too tight, break toolbit Set cutting-tool point to center height Tighten toolpost securely to prevent it from moving during cut

To Mount Work Between Centers: Using Revolving Tailstock Center Check live center by holding piece of chalk close it it while revolving Not true – chalk will mark only high spot If not true, remove live center from headstock and clean tapers on center and headstock spindle Replace center and check for trueness

Adjust tailstock spindle until extends about 2. 50 to 3 in Adjust tailstock spindle until extends about 2.50 to 3 in. beyond tailstock Mount revolving center into tailstock spindle Loosen tailstock clamp nut or lever Place lathe dog on end of work with tail pointing to the left Place end of work with lathe dog on live center and slide tailstock toward headstock until dead center supports other end of work

Tighten tailstock clamp nut or lever Adjust tail of dog in slot of driveplate and tighten lathe dog screw Tighten tailstock handwheel using thumb and finger pressure only to snug up work between centers Tighten tailstock spindle clamp Move carriage to farthest position (left-hand end) of cut and revolve lathe spindle by hand

To Mount Work Between Centers: Using a Dead Center Follow steps 1-4 of revolving center method Mount dead center in tailstock spindle and then check center alignment Place dog on end of work and lubricate the dead center hole Mount work between centers and tighten tailstock lamp nut or lever

Adjust tail of dog in driveplate and tighten setscrew Turn driveplate until slot is in horizontal position Hold tail of dog up in slot and tighten tailstock handwheel Turn handwheel backward until tail of dog just drops and tighten tailstock spindle clamp Check center tension of work. There should be no end play

Facing Between Centers Facing – operation of machining ends of workpiece square with its axis Lathe centers must be in line Purposes of facing Provide true, flat surface, square with axis of work Provide accurate surface from which to take measurements To cut work to required length

To Face Work Between Centers Move toolpost to left-hand side of compound rest and set right-hand facing toolbit to height of lathe center point Clean lathe and work center and mount work between centers Use half-center in tailstock if available Set facing toolbit pointing left Point must be closest to work and space must be left along the side

Set lathe to correct speed for diameter and type of material being cut Start lathe and bring toolbit close to center of work Move carriage to left until small cut started Using apron handwheel Feed cutting tool out by turning crossfeed handle and cut from center outward Repeat 5-7 until work cut to correct length

Facing the Workpiece to an Accurate Length Compound rest graduated micrometer collars may be used Compound rest set to 30º (to the cross-slide) Side movement of cutting tool always half the amount of the compound feed