Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. PowerPoint to accompany Krar Gill Smid Technology of Machine Tools 6 th Edition Drilling, Boring, Reaming, and Tapping Unit 58

58-2 Objectives Drill small- and large-diameter holes in a lathe Ream holes to an accurate size and good surface finish Bore a hole to within.001-in. (0.02-mm) accuracy Use a tap to produce an internal thread that is concentric with the outside diameter

58-3

58-4 To Spot and Drill Work in a Chuck Spotting ensures drill will start in center of work Spotting tool used to make shallow, V- shaped hole in center of work –Provides guide for drill to follow Most cases hole spotted quickly using center drill –Extreme accuracy use spotting toolbit

58-5 Procedure To Spot and Drill Work in a Chuck 1.Mount work true in chuck 2.Set lathe to proper speed for type of material 3.Check tailstock and make sure in line 4.Spot hole with center drill or spotting tool

Mount twist drill in tailstock spindle, drill chuck, or drill holder 6.Start lathe and drill to desired depth, applying cutting fluid frequently 7.To gage depth of hole, use graduations on tailstock spindle, or measure depth with steel rule 8.Withdraw drill frequently to remove chips and measure depth of hole Always ease force on feed as drill breaks through work

58-7 Boring Operation of enlarging and truing drilled or cored hole with single-point cutting tool Can produce special-diameter holes May be drilled in lathe, but not accurate –Drill become dull or hit hard spot and wander –Reamer will follow drilled hole and be off For reamed hole to be straight and true –Drill, bore and then ream

58-8 To Bore Work in a Chuck 1.Mount work in chuck; face, spot, and drill hole approximately.060 in undersize 2.Select boring bar as large as possible and have it extend beyond holder only enough to clear depth of hole to be bored 3.Mount boring bar holder in toolpost on left-hand side of compound rest 4.Set boring toolbit to center

Set lathe to proper speed and select medium feed 6.Start lathe and bring boring tool into contact with inside diameter of hole 7.Take light trial cut.250 in. long at right- hand end of work 8.Stop lathe and measure hole diameter with telescopic gage or inside micrometer 9.Determine amount of material to be removed from hole 0.10 to 0.20 in. for a finish cut

Set depth of cut for half amount of metal to be removed 11.Start lathe and take roughing cut Slow lathe speed and increase feed if chatter 12.Stop lathe and bring boring tool out of hole without moving crossfeed handle 13.Set depth of finish cut and bore hole to size Fine feed recommended for good surface finish

58-11 Reaming Quickly obtain accurately sized hole and produce good surface finish May be performed after hole drilled and bored

58-12 Procedure to Ream Work in a Lathe 1.Mount work in chuck; face, spot, and drill hole to size Holes under.500 in – drill.015 in. undersize Holes over.500 in. – drill.030 in. undersize Holes true – bored.010 in. undersize 2.Mount reamer in drill chuck or drill holder Holes.625 in and larger, fasten lathe dog near reamer shank and support tail

Set lathe to approximately half drilling speed 4.Bring reamer close to hole and lock tailstock in position 5.Start lathe, apply cutting fluid to reamer and slowly geed it into drilled or bored hole with tailstock handwheel 6.Occasionally remove reamer from hole to clear chips from flutes and apply cutting fluid

Once hole reamed, stop lathe and remove reamer from hole Caution: Never turn lathe spindle or reamer backward for any reason. This will damage reamer! 7.Clean reamer and store in carefully to prevent it from being nicked or damaged

58-15 Tapping One method of producing an internal thread on a lathe Tap aligned by placing point of lathe dead center in chuck end of tap to guide while tap turned by tap wrench When tapping hole in lathe, lock spindle and turn tap by hand

58-16 To Tap a Hole in a Lathe 1.Mount work in chuck; face and center drill 2.Select proper tap drill for tap to be used 3.Set lathe to proper speed 4.Drill with tap drill to required depth Use cutting fluid if required 5.Chamfer edge of hole slightly larger than tap diameter

Stop lathe and lock spindle, or put lathe in its lowest speed 7.Place taper tap in hole and support shank with tailstock center 8.With suitable wrench, turn tap, keeping dead center snug into shank of tap by turning tailstock handwheel 9.Apply cutting fluid while tapping hole 10.Back off tap frequently to break the chip 11.Remove taper tap and finish tapping hole with plug or bottoming tap

58-18 Grinding on a Lathe May do cylindrical and internal grinding –Toolpost mounted on lathe used for cylindrical and taper grinding –Internal attachment permits grinding of straight and tapered holes Should be done on lathe only when no other machine available Work rotates in opposite direction to grinding wheel so lathe must be equipped with reversing switch

58-19 To Grind a Lathe Center 1.Remove chuck or driveplate from spindle 2.Mount lathe center in headstock spindle 3.Set slow spindle speed 4.Swing compound rest to 30º with centerline 5.Protect ways of lathe with cloth or canvas and place pan of water below lathe center

Mount toolpost grinder and adjust center of grinding spindle to center height 7.Mount proper grinding wheel; true and dress 8.Start lathe, with spindle revolving in reverse 9.Start grinder and adjust grinding wheel until it sparks lightly against revolving center 10.Lock carriage in this position

Feed grinding wheel in.001 in. using crossfeed handle 12.Move grinder along face of center using compound rest feed 13.Check angle of center using center gage, and adjust compound rest if necessary 14.Finish-grind center Polish center with abrasive cloth at high spindle speed if high finish desired