Routing and Shaping, Turning, Drilling, Scraping, and Filing Acrylic sheet

Acrylic Sheet can be machined with standard woodworking routers in much the same way as wood. You'll find many uses for portable hand routers and small table routers. Use them to cut patterns into edges or larger holes out of pieces of acrylic sheet.

For best results, use single-fluted bits for inside circle routing and double-fluted bits for edge routing.

Routers are designed to operate at high speeds. 10,000 to 20,000 rpm is recommended for an acrylic sheet. And because routing speeds are so high, the vibration must be carefully avoided. Even small vibrations can cause crazing and fractures in the acrylic sheet during routing.

Turning

Turning is the only practical way to produce the most rounded cross-sectioned parts, such as knobs, furniture legs, and vases. Acrylic sheet can be turned on almost any type of lathe.

Bits designed especially for cutting acrylic are available. But most high-speed tool bits with a zero-degree or slightly negative rake will work very well. The rake must be maintained at 0° to -4° for satisfactory results. Clearance angles should be from 5° to 10°. Use a turning speed approximately ten times faster than for wood. It would be best to get a continuous ship from an acrylic sheet.

Drilling

Any hand or power drill may be used for drilling an acrylic sheet. A stationary drill press is the preferred tool because it gives better control and greater accuracy. But a drill press won't be applicable in all instances, and with a little care, proper technique, and a correctly-ground drill bit, you can get good results with an ordinary hand drill.

For best results, use a drill designed specifically for acrylics.

Regular twist drills can be used, but the cutting edges must be modified to prevent the blade from grabbing and fracturing the plastic. Acrylic sheet is relatively soft. Your drill should have an edge that cuts with a scraping action. To obtain this, you can modify your drill bit by grinding small "flats" onto both cutting edges with a medium or fine-grit grinding wheel or a pocket stone. The flats can be parallel to the length of the drill and about 1/32" (1 mm) wide. The tip angle should be between 60° and 90°.

For the best possible finish inside the hole, use a drill with smooth, polished, slow spiral flutes, which will clear the hole of all shavings without marring or melting the walls.

If the drill is correctly sharpened and operated at the proper speed, two continuous spiral chips or ribbons will emerge from the hole.

When drilling a hole three times deeper than the diameter of the drill, a lubricant or coolant should be used. This will help remove chips, dissipate heat, and improve the finish of the hole. Rough, irregular, or fuzzy holes can lead to cracking and breaking months after the pieces has been completed.

Scraping

Many techniques used to cut acrylic sheet can leave a rough edge that is usually unsuitable either as a finished edge or to join to another piece of acrylic. It is necessary to smooth and square the edge of the sheet. You can do this using several different techniques, depending on the desired finish.

The first step, and perhaps the easiest technique, is scraping. A scraper can be almost any piece of metal with a sharp, flat edge. The back of a hacksaw blade, a knife blade, or a tool steel blank is ideal. Whatever tool you use must have a sharp, square edge.

Filing

It is easy to file an acrylic sheet to a surface ready for final polishing. The filing, however, must be done correctly and carefully.

Almost any commercial file can be used. But the quality of the finish will depend on your choice of file coarseness. A 10" to 12" (250 to 300 mm) smooth-cut file is recommended for filing edges and removing tool marks. Other files-half rounds, rat tail, triangular files, and even small jewelers' files are good for smoothing the insides of holes, cutting grooves and notches, or finishing detail.

File in only one direction. Keep the teeth flat on the surface of the acrylic sheet, but let the file slide at an angle to prevent the teeth from cutting unwanted grooves in your work.

Always keep your files clean and sharp. Wire brush them often to prevent the teeth from filling up. And don't use your acrylic files for working metal or other materials that might dull the teeth.

For small work, try clamping the file in a vise and rubbing your work across the file.