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.