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Drilling, Boring, Reaming, and Tapping

Session 11

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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 start for drill to follow

• Most cases hole spotted quickly using center drill

• Extreme accuracy use spotting/ chamfering toolbit

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Spotting Work in a Chuck1. 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

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1. Mount twist drill in tailstock spindle, drill chuck, or drill holder

2. Start lathe and set for proper RPM for workpiece and cutting tool

3. With tailstock spindle handle, move drill tip to end of part. Note reading on tailstock spindle.

4. Drill to desired depth, applying cutting fluid frequently

Drilling Work in a Chuck

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5. To gage depth of hole, use graduations on tailstock spindle, or measure depth with steel rule

6. Withdraw drill frequently to break and/or remove chips and measure depth of hole

7. If hole is through, always ease force on feed as drill breaks through work

Spotting Work in a Chuck

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Boring

• Operation of enlarging and truing drilled or cored hole with single-point cutting tool

• For producing 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

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To Bore Work in a Chuck1. 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

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4. Set boring toolbit on center5. Set lathe to proper speed and select

medium feed6. Start lathe and bring boring tool into

contact with inside diameter of hole7. Take light trial cut .250 inch long at

right-hand end of work8. Stop lathe and measure hole diameter

with telescopic gage or inside micrometer

Boring Work in a Chuck

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9. Determine amount of material to be removed from hole

• 0.10 to 0.20 in. for a finish cut

10.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

Boring Work in a Chuck

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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

13.Check hole diameter

Boring Work in a Chuck

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Reaming

• Quickly obtain accurately sized hole and produce good surface finish

• May be performed after hole drilled and bored

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Reaming Work on a Lathe1. 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

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3. 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

Reaming Work on a Lathe

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6. Occasionally remove reamer from hole to clear chips from flutes and apply cutting fluid

7. 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!

Reaming Work on a Lathe

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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

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To Tap a Hole in a Lathe1. 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

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6. 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

To Tap a Hole in a Lathe

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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

To Tap a Hole in a Lathe

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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

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Grinding 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

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6. 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

Grinding a Lathe Center

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10.Lock carriage in this position

11.Feed grinding wheel in .001 in. using crossfeed handle

12.Move grinder along face of center using compound rest feed at a steady pace

Grinding a Lathe Center

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11.Check angle of center using center gage, and adjust compound rest if necessary

12.Finish-grind center• Polish center with abrasive cloth at high

spindle speed if high finish desired

Grinding a Lathe Center