Correct Way to Cut Plexiglass Circles

Plexiglass, also known as acrylic glass, is a versatile transparent thermoplastic often used as a glass substitute due to its lightweight and shatter-resistant properties. While plexiglass sheets can be cut into various shapes, circular cuts require precision and the right tools to get a clean edge.

Cutting a perfect circle in a plexiglass sheet can seem daunting to DIYers but is quite straightforward with some basic guidelines.

Cutting Plexiglass Circles

When working with plexiglass circles, the key things to keep in mind are:

• Marking an accurate cutting line
• Choosing the right blade for clean cuts
• Securing the plexiglass properly to prevent unwanted movement
• Making smooth, circular cuts without cracking or chipping

Follow these four central steps correctly, and you'll be able to cut uniform plexiglass circles every time. Pay close attention to blade control and plexiglass positioning, as rushing through cuts can ruin the final product.

Marking the Cutting Line

Before starting any plexiglass circle cut, the first step is marking an accurate cutting line. Place the plexiglass sheet on a flat work surface and determine the desired circle size.

Use a compass to draw the circular cutting line, marking pivotal measurements like the radius and diameter. Alternatively, use a pre-made circular template if cutting multiple plexiglass pieces of the same dimensions.

Make sure to account for the blade thickness when marking the cut line. For example, if using a 1/16-inch blade, draw the circle line 1/16-inch inside the finished circle's edges.

Choosing the Right Blade

The next vital step is selecting an appropriate blade for the plexiglass thickness. For 1/16 to 1/8-inch sheets, a standard utility knife or razor blade works well. Moving up to 1/4 or 1/2-inch plexiglass calls for more robust tools like table saws, jigsaws, or band saws.

Well-sharpened blades are essential for smooth cuts without edge chipping. Carbide-tipped blades last the longest, but high-speed steel also cuts plexiglass cleanly. Ensure the blade has more teeth per inch for reduced material shattering when cutting.

Securing the Plexiglass

Holding the plexiglass sheet stationary is paramount for precision circle cuts. Small pieces can be secured directly to the workbench using clamps. For larger sheets, sandwich the plexiglass between two rigid plywood sheets screwed or clamped together.

The plywood backing helps reinforce the plexiglass to prevent vibrations and slippage when cutting. Make sure to align the circular cut line visible between the plyboards before fixing them to the work surface.

Making Smooth Circular Cuts

With the round cut line marked and plexiglass secured, start cutting slowly along the circular path using gentle pressure. Ensure the blade engages the scrap side first at a 90-degree angle. Cutting too quickly risks cracks and an uneven cut.

For curved cuts, guide the blade incrementally along the line, pivoting the sheet as you go. Lifting and realigning helps steer clear of tight corners. Stop occasionally to cool hot blade teeth preventing damage. Finally, trim and finish any rough spots with a file or sandpaper.

Tools for Cutting Circular Plexiglass

Choosing the right tool for cutting plexiglass circles depends on the material thickness and diameter. Here are the most common options:

Utility Knives

A standard utility knife with breakaway blades works for thinner plexiglass up to 1/8 inches thick. Mark the cut path first, then score the line before snapping off the circular piece. Long cuts may require repositioning the plexiglass as you go.

Jigsaws

For plexiglass between 1/4- and 1/2-inches thick, a jigsaw with fine-tooth blade gives nice rounded cuts. Jigsaws handle curves well, especially when backing the sheet with rigid plywood. Take care not to twist the blade when cutting or you'll crack the plastic.

Band Saws

Band saws utilize long, flexible rotating blades to cut gentle curves in thicker plexiglass. They require a bit more skill but provide very precise, smooth circular cuts. Use ample blade lubrication and slow feed rates for best control on the plexiglass.

Table Saws

Table saws fitted with acrylic cutting blades make quick work of circular cuts in thick plexiglass sheets. Adjust the blade height carefully to avoid chip-out and employ various fences/guides for angled rounded cuts. Letting the blade teeth cool periodically gives a cleaner edge.

Measuring and Marking the Plexiglass

Proper measurement and line marking are imperative first steps to accurately size and cut plexiglass circles. Planning the cuts well makes the actual blade work much simpler. Consider using:

A Template

For mass cutting multiple plexiglass circles of the same dimensions, create a durable circular template to trace onto the sheets. Use thick plywood or plastic to cut an exact circle outline you can mark off each new plexiglass piece before cutting the same sized rounds.

Marking the Center Point

When not using a template, identify the plexiglass sheet's center point first. Measure and make perpendicular tick marks across the midlines of the plexiglass. Connect the intersecting ticks with a dot, noting the exact circle's center point for the next steps.

Drawing the Cutting Line

Finally, use a compass aligned to the desired circle radius from the central axis tick point. Lock the compass at the appropriate radius length, then rotate it through a full circular rotation while holding the point steady on the center mark. This scribes a near-perfect circle ready for cutting.

Cutting Tips and Techniques

When executing circular cuts, knowledge of a few plexiglass-specific cutting best practices helps ensure high quality edges:

Clamping the Plexiglass

Workbench-mounted clamps like C-clamps or vise grips hold plexiglass sheets stationary when cutting. Use rubber or wood pads on clamp faces to protect sheet surfaces and prevent slippage. Over-tightening risks damaging the plastic.

Controlling Blade Speed

Rushing blade cuts causes cracks, chips, and poor edges. Maintain consistent smooth blade speeds based on material thickness. Thicker plexiglass requires slower feed rates for cleaner cuts. Listen for high-pitched squeaking indicating the blade is moving too quickly through the plastic.

Cooling the Blade

Frictional heat generated by cutting plexiglass dulls blade teeth faster. Regularly lift the blade free while cutting to force cool, clean air across the teeth. Flushing debris also helps restore sharpness for better ongoing cut quality.

Finishing Rough Edges

Despite best efforts, minor blade chatter or wobble spots may remain along the cut. Lightly dress these areas using fine-grit sanding sponges/blocks to smooth ripples for an even edge. Take care not to round over the adjacent intact areas of the cut line.

Common Cutting Mistakes

While cutting round shapes in plexiglass sheets avoid these common errors:

Rushing the Cut

Attempting to cut too quickly or forcefully stresses the plexiglass and dulls blade tips leading to fractures or poor cut quality. Ease into rounded cuts gradually, letting the tool do the work by nibbling away material.