Working with ACRYLITE®
Working with ACRYLITE®
Procedures and equipment for drilling ACRYLITE® Resist sheet
ACRYLITE® Resist acrylic sheet can be fabricated using the same machinery that is used on ACRYLITE® Premium (FF) acrylic sheet. Fabrication techniques are nearly the same. Minor modifications may be necessary due to the sheet's unique properties. Its greater impact resistance and special formulation require special care in certain machining operations. In general, equipment should be stable, vibration free and show a minimal amount of tool wobble (run-out). For best results, follow the recommendations below and refer to the information prepared for ACRYLITE® Premium (FF) sheet for additional information.
Because ACRYLITE® Resist sheet is not as stiff as unmodified acrylic sheet, it has a tendency to lift off the machining table when the drill bit exits the hole. To compensate, clamping devices need to be placed as close as possible to the hole being drilled, carefully allowing for clearance of the rotating spindle and cutter. Several hold-downs may be required to firmly hold thinner stock flat to the machining table. Wherever possible, ACRYLITE® Resist sheet should be drilled on stationary equipment. Portable electric hand drills should only be used as a final option and for small diameter holes only.
ACRYLITE® Resist sheet drills cleanly with high-speed steel “modified for plastic” twist drills. On large diameter holes, it is recommended to pilot drill first before enlarging the hole to the final dimension. Adjust speed and feed rates so that a controlled chip is produced with no melting of the plastic. Continuous chips are not readily produced when drilling ACRYLITE® Resist sheet, nor are they required for excellent drilled-hole finishes. Rotational speeds in the 500-1000 rpm range, combined with feed rates in the 3-12 in/min range will usually give good results. Standard twist drills can also produce satisfactory holes in ACRYLITE® Resist sheet. To avoid sheet notching, securely clamp the material to the machine table and apply slow entry and exit feeds. Proper backing material such as plywood or another piece of acrylic should be used when drilling. The backing material will help prevent chipping of the bottom surface. When drilling stacks of sheet, it is a good idea to utilize a coolant such as water or kerosene. This will minimize heat build up and create cleanly drilled holes.
Spade bits with side spurs (i.e. IRWIN 2000 Speedbores) produce satisfactory holes in ACRYLITE® Resist sheet. The drilling is done in two steps with reduced machine speed for large diameter bits. Step one: Drill one face of the sheet to lightly score the perimeter of the hole. Step two: Flip the material and complete drilling from the opposite face of the sheet. CAUTION: The original Speedbores, without side spurs, are NOT recommended.
Circle cutters can be used for cutting large diameter holes in ACRYLITE® Resist sheet. Sharp cutters along with multiple hold-down devices are essential. A single clamping device is inadequate for circle cutters; should the cutter grab, the sheet can pivot and dangerously kick-out towards the operator. For thinner gauge material (.098" and thinner), lightly score the perimeter of the hole from one face and then flip the material to complete drilling from the opposite face of the sheet. This practice will eliminate notching on the edges and grabs, to which thinner stock is prone.
Hole saws also produce acceptable holes in ACRYLITE® Resist sheet. Although less smooth than other hold cutting techniques, best results are achieved with sharp hole saws tipped with carbide. Because of the high friction produced by these cutting tools, a coolant solution of detergent and water or kerosene will help to minimize melting of the material.
Countersinking in ACRYLITE® Resist sheet is best done with a non-fluted (Weldon) countersink design. The large land of this cutter combined with the oblique hole forming the cutting edge of the tool, results in a controlled cut with little chatter and plenty of chip clearance. Pilot drilling is necessary when using this countersink design. The pilot hole should be oversized with reference to the shank of the fastener.