Drilling Holes - Skilled Trades Math On-line

Drilling Holes
Session 11
Drill Press Safety
1. Do not operate before understanding
operation including how to stop
2. Always were approved safety glasses
3. Never attempt to hold work by hand
4. Keep your head back from revolving
5. As drill begins to break through work,
ease up on drill pressure
Drill Press Safety
6. Always remove burrs from drilled hole
with file or deburring tool
7. Never leave chuck key in drill chuck
8. Never attempt to grab work that may
have caught in drill
Stop machine first
9. Always keep floor around drill press
clean and free of tools, chips, and oil
Drilling Hints
1. Treat cutting tools with care
2. Always examine condition of drill
point before use – do not use dull
3. Make sure drill point angle correct for
type of material to be drilled
4. Set correct revolutions per minute for
size of drill and workpiece material
Drilling Hints
5. Set up work so drill will not cut into
machine as it breaks through
6. Work should always be clamped
7. End of workpiece farthest from hole
should be placed on left-hand side of
table so it will not swing toward
Drilling Hints
9. Use shortest drill Always clean
tapered drill shank, sleeve, and
machine spindle before inserting drill
10. length possible and/or hold it short in
10. Good practice to start each hole with
center drill
Provides guide for drill to follow
Drilling Hints
11. Thin workpieces should be clamped
to hardwood block for drilling
12. Chips from each flute should be
shape; if blue during drilling, check
drill point condition
13. Drill squeak usually indicates dull drill
Drilling Hints
14. When increased pressure must be
applied during drilling, reason
usually dull drill or chip caught in
hole between drill and work
Determining Size of a Drill
• Good practice to always check drill for
size before drilling
• Checking for size
• Drill gage
• Micrometer
• Most accurate
• Check measurement across margin of drill
Spotting Hole Location With
a Spotting Drill
• Chisel end on drill wider than centerpunch mark on work
• Spot center-punch mark with spotting drill
Small point on spotting drill will accurately follow
center-punch mark and provide guide for larger drill
Spotting Hole Location
With a Spotting Drill
Mount small-size spotting drill
Mount work in vise
Set drill speed to 1500 r/min
Bring point of spotting drill into centerpunch mark and allow work to center
itself with drill point
5. Continue drill until proper diameter has
been produced
6. Spot all holes to be drilled
Spotting Hole
Drilling Work Held in a Vise
1. Spot hole location with spotting drill
2. Mount correct-size drill in drill chuck
3. Set drill press to proper speed for size
of drill and type of material to be
4. Fasten clamp or stop on left side of
5. Mount work on parallels in drill vise
and tighten it securely
Drilling Work Held in a Vise
6. With vise against table stop, locate
spotted hole under center of drill
7. Start drill press spindle and begin to
Holes up to ½ in. – hold vise against
Holes over ½ in. – Clamp vise to table
Drill until full drill point into work
With drill revolving, deep drill point in work
and tighten clamp holding vise
Drilling Work Held in a Vise
8. Raise drill occasionally to break the
9. Apply cutting fluid during drilling
10. Ease up on drilling pressure as drill
starts to break through workpiece
Drilling to a Layout
1. Clean and coat surface with layout dye
2. Locate position of hole from
two machined edges of
workpiece and scribe lines
3. Lightly prick-punch where two lines
4. Check accuracy of punch mark
Drilling to a Layout
5. Spot drill work to just beyond depth of
drill point
6. Mount proper size drill in machine and
drill hole to depth
Drilling With Large Drills
• Drills increase in size; thickness of web
also increases to give drill strength
• Thicker web, thicker point of drill
• Thick web won’t follow center-punch mark
• Two methods to overcome poor cutting
action of thick web on large drills
• Web is thinned
• Lead, or pilot, hole is drilled
Pilot Holes
Drill pilot hole diameter which is
slightly larger than thickness of web
Care must be taken to drill pilot hole
on center
Pilot hole then followed with larger drill
Problems when pilot hole too large
Cause chattering
Drill hole out-of-round
Spoil top (mouth) of hole
Drilling with Pilot Holes
1. Check print and select proper drill
2. Measure thickness of web at point
Select pilot drill with diameter slightly
larger than web thickness
3. Mount workpiece on table
4. Adjust height and position of table so
drill chuck can be removed and larger
drill placed in spindle after pilot hole
drilled and lock table
Drilling with Pilot Holes
5. Place center drill in drill chuck, set
proper spindle speed, accurately drill
center hole
6. Using proper-size pilot drill, drill pilot
7. Shut off machine, leaving pilot drill in
8. Clamp work securely to table
9. Raise drill spindle, remove drill and
Drilling with Pilot Holes
10. Clean taper shank of drill and spindle
11. Mount large drill in spindle
12. Set spindle speed, feed and drill hole to
required depth
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