In this tutorial we'll show you how to cut acrylic without it cracking or melting, the right tools to use for cutting acrylic sheets, and how to use them to cut out the shapes and designs you need for your projects. You'll also find a step-by-step guide to cutting acrylic to size and preventing the sheets from cracking or melting along the way. The same techniques can be used for cutting Perspex or any other type of acrylic material.
Cutting acrylic to size at home isn't difficult. With a few simple tools, a bit of patience, and a few tips and tricks to avoid the most common mistakes, you can create all sorts of structures, enclosures and displays for your home or business. And if you don't have a workshop, it's an easy job to do outdoors — you can do it all in the garden or on a balcony.
How Does Acrylic Crack or Melt When Cut?
Acrylic can fail in two ways during the cutting process. Here we look at both problems, and how to solve them.
Cracking is a stress problem. If you apply stress to the acrylic then inevitably it will crack. This can be caused by a variety of things, including an unsupported sheet of acrylic, vibration whilst cutting, or an aggressive cutting blade that grabs at the acrylic rather than cutting smoothly through it.
Melting is a heat problem. As you cut acrylic sheets with power tools, friction from the blade can heat the sheet and start to burn it. Since acrylic has a very low melting point, the material can soften quickly and then re-fuse to the back of the cut (behind the blade) as you continue to cut. This produces a terrible edge with a gooey, welded type of finish. You need to cut acrylic sheets with your power tools in a steady feed — fast enough to clear the cut, but slow enough to avoid chipping the edge of the sheet.
It really is not that difficult to cut acrylic without any problems, once you understand the two main causes of cracked or melted edges in the first place.
Start with the right thickness
First off, check the thickness of your acrylic sheets, as different tools are required to cut different thicknesses of acrylic. A 2mm sheet of cast acrylic can be scored and snapped in seconds but bends and flexes alarmingly if left unsupported over any distance. On the other hand, a 10mm thick sheet of cast acrylic is as rigid as a piece of timber and can be held in place with minimal support over large distances, but requires more power and a fine-toothed blade to cut through.
Before you even cut your first sheet of acrylic, you need to ensure that you have the correct thickness for your particular task. In our blog post on what thickness acrylic you need we have outlined the required thickness for various tasks, from cutting out templates for craft to making an aquarium.
Cast or extruded — does it matter for cutting?
Cast or extruded acrylic? It matters a lot. The two types of acrylic machine very differently, and using the wrong technique on the wrong material is behind a surprising number of ruined cuts.
Cast acrylic has a higher molecular weight than extruded acrylic, making it the more stable of the two when it comes to heat. This is why it is better to use for sawing, routing, sanding and in particular laser cutting, as it vaporises well and leaves a crisp, frosted edge.
It's worth reading up on our guide to cast acrylic vs extruded acrylic, which looks at the two types of acrylic in detail and outlines why cast acrylic is the preferred choice of professionals everywhere when it comes to cutting acrylic with precision — especially laser cutting.
The best tools for cutting acrylic
Match the tool to the thickness and the cut you need.
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Scoring knife (score and snap) — For very thin sheet material (up to 3mm), and straight cuts only. An acrylic scoring tool is used by scoring along a steel straightedge; five to ten passes will make a groove deep enough to be snapped over a bench edge or dowel. Cheap, and uses no heat.
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Jigsaw — As jigsaws are flexible, they're ideal for cutting out shapes or curved cuts in thicker acrylic sheets. Use a fine-toothed blade (preferably a plastic or metal cutting blade) and work at a steady, moderate pace. The shoe of the jigsaw should be kept flat on the surface of the acrylic at all times, and only as much pressure as required to cut should be applied — do not force the blade.
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Circular saw or table saw — These tools are very suitable for cutting long, straight sections in thicker sheets of acrylic. The circular saw will have a fine-toothed blade (about 60–80T) with a triple-chip grind that is made for cutting non-ferrous metals and plastics. Feed slowly and consistently to achieve a high-quality cut. A table saw is even better, if you have a sturdy fence. For the cleanest cut of all, though, you'll want a router or CNC.
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Router or CNC — The smoothest cut available, and ideal for creating intricate shapes and models. You will require the appropriate cutting bit for acrylic and a guide to ensure that your work is kept to exacting standards. High-quality cut-to-size panels are typically cut using such machinery.
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Laser cutter — These cutters produce the cleanest cut of all, leaving cut-to-size material that can be drilled and finished with no need for sanding down rough edges. They're ideal for cutting precise and detailed shapes. Unfortunately, laser cutters are usually found in large workshops and maker spaces. For domestic use, scoring knives and saws are more practical, alongside cut-to-size acrylic ordered online.
When scoring, keep the protective film on the surface of the acrylic as much as possible and draw your score lines on it with a fine marker. The sheet can then be cut through the film using the scoring tool and straightedge, and the film will come off cleanly in one piece, saving lots of time removing scraps afterwards.
How to cut acrylic step by step
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Measure and mark. Mark your cut line on the protective film with a fine marker. Double-check it — acrylic offcuts can't be re-joined.
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Support the sheet. The acrylic sheet should be supported by a solid surface during cutting, with the cut line just off the edge of the surface. A sacrificial cutting board is recommended to stop the acrylic sheet flexing and chipping during cutting.
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Keep the film on. Cut straight through it. Don't peel the film back to take a peek as you are cutting, as this will create scratches on the surface of the acrylic before the cut is even completed.
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Set the right speed. For power tools such as jigsaws and circular saws, run at a moderate, consistent speed. If you go too fast you risk chipping the edge of the sheet, and if you go too slow you risk melting it.
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Feed steadily and don't stop. Get the blade up to speed before it meets the workpiece, then continue straight through at a steady pace. Never stop sawing in the middle of a cut, as this will weld the edge together.
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Let it cool, then check. Run a finger (carefully) along the edge — a clean cut should feel smooth, not gummy or ridged.
Finishing the edges
You will find that sawn edges of acrylic are matt and can be rough. If this is going to be hidden then it's best to leave it. If, however, the edge is going to be visible — such as with models and other decorative items — then the edge can be sanded. Use wet-and-dry sandpaper, starting at about 180 grit and working your way up to a fine 600 grit. The sandpaper should be kept wet while sanding to prevent scratching the acrylic. For really smooth edges, such as those needed for display models, the edge can be buffed. Alternatively, the edge can be flame polished. Be careful when using this method, as it is very easy to over-polish and end up with a rounded edge — it's best to practise on an offcut first.
Common mistakes to avoid
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Using a coarse wood blade to cut acrylic. Such blades have very aggressive teeth that will grab hold of the acrylic and cause it to crack. Fine-toothed blades are better suited to cutting acrylic and will produce a better cut.
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Cutting too slowly, or stopping the tool in the workpiece. Either one causes a melted, welded edge.
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Peeling the film off early. This can cause scratches to the surface of the acrylic before you have completed the cut.
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Not clamping or supporting the sheet. Flex and vibration crack acrylic and chip the exit edge.
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Drilling with standard bits. For drilling in acrylic, ordinary twist drill bits can cause severe cracking of the material. Use specially designed plastic bits, drill at low speed, and back the hole with scrap material to minimise this type of damage.
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Cutting too close to an edge or corner. This is the one place where acrylic is least flexible and therefore most prone to cracking — so always leave a larger tolerance at the cut lines than you would with wood.
When it's worth ordering cut to size
For a single straight cut in a small amount of thin sheet, doing it yourself is fine. After that, the maths often points to buying cut to size. Factor in the price of the correct blade, the offcuts (created even with the best of care), and the inevitable crack at the very edge of the sheet caused by sawing right to the edge in the final part of the cut.
Our cuts are accurate to ±1mm on professional machinery, so there's no waste for you to deal with and nothing left to chance. If you would rather we cut your acrylic than risk a crack on the final cut of expensive material, we can do it for you — just order your acrylic cut to size.
Frequently asked questions
Can you cut acrylic with a Stanley knife? Thin sheets of acrylic can be scored with a sharp utility knife and then snapped to size. There are also specialised scoring tools for cutting acrylic, which have a unique hooked blade. These tools make a deeper, cleaner cut in the acrylic and provide a much better snap line.
What blade should I use to cut acrylic? Acrylic cutting blades are rated by the number of points per linear inch, or TPI, typically expressed as a range (e.g. 10–14 TPI jigsaw blades). Cutting quality is also improved by specialised grind styles, such as a triple-chip grind. The most effective blade for cutting cast acrylic is usually a fine-toothed blade designed for plastics or non-ferrous metals (such as aluminium or brass). For circular saws and table saws we recommend blades in the 60–80 tooth range, while for jigsaws we typically look for blades of around 10–14 TPI.
Can you cut acrylic with scissors? Not cleanly — scissors apply uneven stress and will easily crack or craze the sheet. Acrylic of any thickness is far better scored using an acrylic scoring tool, which has a hooked blade that cuts a deeper, cleaner groove than a utility knife. The line made from snapping the scored acrylic is also far superior, and gives a neater finish.
How do you cut acrylic without it cracking? Support the sheet with clamps or other means close to the cut line. Use a fine-tooth blade, keep the protective film on, and cut at a steady, even pace. Cracking is caused by vibration, an unsupported sheet, or a blade that is too aggressive.
Does acrylic melt when you cut it? As you are cutting the acrylic sheet with a saw, the friction can cause the acrylic to melt, and then re-solidify once you stop. This can lead to a welded edge, which is unacceptable. To prevent the acrylic from melting, make sure you are cutting it at a consistent feed speed.
Written by the team at Mitlee Plastics — specialists in premium cast acrylic sheet, cut to size and delivered across the UK.
