Drilling
1. General Indications:
Drill
bits: Regular, new high-speed steel twist drills, or new carbide-tipped
drills are suitable for drilling holes in PALSUN sheets of various
thicknesses, as long as they are sharpened well. They are used mainly
for bores up to 12 mm(1/2 “) diameter.
Larger holes may be drilled by flat, chisel edged drill blades with a triangular
cutting tip, similar to those used in woodworking, kept always very
sharp.Rake angle should be about 5° to avoid side friction. They are
used mainly for bores from 12 to 20mm (1/2 “ to 13/16 “).
Commercially available cutting cups or circle cutters of several types can be used for performing large round apertures.
Speed: Decrease the drill’s speed as hole diameter and / or sheet thickness
gets larger. Drilling speed may vary due to actual conditions.
Feed rate: May vary due to actual conditions.
Table 15: Drilling Speed and Feed Rate Change in Accordance with Bore Diameter
Hole Diameter |
Drill Speed |
Feed Rate |
in. |
mm |
in. |
rpm |
mm/rev |
in./rev |
1/8 |
3 |
0.12 |
1500-1800 |
0.03-0.07 |
0.012-0.028 |
1/4 |
6 |
0.24 |
800-1500 |
0.03-0.07 |
0.012-0.028 |
13/32 |
10 |
0.4 |
500-1000 |
0.01-0.07 |
0.004-0.028 |
19/32 |
15 |
0.6 |
350-700 |
0.07 |
0.028 |
25/32 |
20 |
0.8 |
250-350 |
0.07 |
0.028 |
Table 15: Recommended Drill Bit Configurations
| Clearance Angle |
5 – 15° |
| Rake Angle γ° |
0 – 10° |
| Drill Tip Angle β° |
110 – 150° |
| Helix Angle α° |
30° |
| Cutting Velocity |
15 – 30 m/min (49 - 98 ft/min.) |
2. Drilling tips and recommendations
Location: Locate holes no closer to the edges than 2 – 2.5 times the diameter of the pertinent hole, with a 10mm (0.4 in.) minimum.
Precision: It is imperative to keep the sheet (or stack of sheets) firmly clamped
to a stable workbench (or a similar base) to avoid fluttering during
drilling.
Cooling: Usually cooling is not required with regular drills.
However,
in cases of deep drilling, like putting perpendicular holes through the
sheet’s edge, or when drilling through a stack of sheets, cooling both
the drill bit and the vicinity of the hole with a jet of compressed air
is a good practice.
It is also recommended, when drilling deep
holes, to stop frequently, pull the drill out and clear the hole from
swarf and debris with compressed air.
Preventing internal stresses: Producing a clean, smooth bore, keeping heat buildup to the minimum, by
the procedure described above, prevents excessive heat buildup,
meltdown and gumming of the drilling dust and debris, and possible
seizure of the bit. It also prevents undue internal stresses at the
vicinity of the hole.
Honing and polishing the edge of the hole by
mechanical or chemical means contributes to keeping the sheet
stress-free, preventing cracking.
Mantainig the edge: Carbide tipped twist drill bits are preferable for long or continuous
production runs. They are more durable and improve the edge quality.
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