This blog post discusses drilling holes in Polycarbonate sheet. It identifies many of the best practices to drill high quality holes without causing stress in the sheet, which could lead to part failure.
- Standard 118º high speed steel twist drill bits can be used with polycarbonate. The drill bit should be sharp. Grinding a 10º back clearance at the cutting tip will help eliminate friction and prevent gumming. Dub off the rake angle to 0º o that the drill scrapes rather than digs the material.
- Always support the polycarbonate sheet from the back and clamp the sheet in place to avoid vibration.
- Any type of fabrication generates localized heat. Localized heat induces stress in the area and stress in plastics results in part failure. When drilling, always use coolant at the source. Water can be used, but compressed air is recommended. Do not use cutting oils as they may cause crazing (spider cracking) around the hole
- Peck drill to avoid heat generation (stress).
- Remove chips from the hole frequently to avoid build up.
- Feed rate and speeds should be:
| Hole Diameter | Feed Rate (in/rev) | Drill speed (rpm) |
| 1/8″ | 0.001 | 1750 |
| 1/4″ | 0.002 | 1500 |
| 1/2″ | 0.004 | 500 |
- Holes should not be drilled closer to the edge than 1.5 – 2.0 times the diameter of the hole. If your hole is 1/4″ diameter, then the bottom edge of the hole should be a minimum to 3/8″ to 1/2″ from the edge of the sheet.
- Polycarbonate expands and contracts with temperature. Always oversize your holes to accommodate for this thermal expansion and contraction, which can cause the holes to crack or the polycarbonate sheet to bend. Note: Maximum growth comes at the ends of the sheets and is less in the center holes. If you are having issues with buckling around the holes, consider using slot holes.
- Use rubber grommets so that the polycarbonate can expand and contract without chipping or cracking. Rubber grommets also help reduce vibration that can cause chipping and cracking around the hole.
- Never torque down too tightly on the polycarbonate. Always allow the polycarbonate to expand and contract with temperature.
For information, we have written other blog posts that cover thermal expansion and contraction of polycarbonate sheet.
For more information on working with polycarbonate sheet, contact Liz Grimes – Technical Director HighLine Polycarbonate. Tel: 215-872-3532 or email: lgrimes@highlinepc.com