Short answer: Acrylic makes a good machine guard where the job is keeping chips, coolant, dust, and fingers away from moving parts while you watch the work. Use 1/4 in. for most guards and 3/8 in. for large panels. Where a part, tool, or workpiece could be thrown at the guard, use polycarbonate instead: it takes roughly 30 times the impact before breaking.
Is acrylic the right material for your guard?
Start with the honest question, because it matters more than thickness. Acrylic is clear, stiff, scratch-resistant for a plastic, and holds its clarity for years. It's anywhere from 2 to 20 times tougher than ordinary glass of the same thickness, depending on maker and test. But when it does fail, it cracks into sharp pieces rather than bending.
So split guards into two groups:
- Acrylic is a good fit for chip and splash shields on drill presses, sanders, and lathes run at modest speeds; coolant splash panels; dust hoods; belt and pulley covers you want to see through; viewing windows in cabinets; and finger guards on light-duty equipment.
- Use polycarbonate anywhere a broken bit, a flying workpiece, a grinding wheel fragment, or a kicked-back board could hit the guard: CNC mill enclosures, lathe chuck shields at high speed, saw blade guards, and anything on a production line. Polycarbonate is roughly 30 times more impact-resistant than acrylic and bends instead of shattering. It scratches more easily, and that's a fair trade.
If you're not sure which group your machine is in, treat it as the second. A guard required by a safety program or inspector should follow the machine maker's guidance and your workplace rules; ask your safety officer. Read more on acrylic vs polycarbonate.
What thickness to choose
| Guard size | Thickness | Notes |
|---|---|---|
| Up to 12 × 12 in. | 3/16 in. | Small splash shields and covers |
| 12 to 24 in. on a side | 1/4 in. | The usual choice; stiff and easy to drill |
| Over 24 in., or unsupported edges | 3/8 in. | Less flex when bumped or wiped |
| Viewing window in a steel door | 1/4 to 3/8 in. | Clamp in a frame with a gasket |
Clear cast sheet machines and drills more cleanly than extruded, so we suggest it for guards with lots of holes or slots.
Mounting holes and hardware
Most guards fail at the holes, not in the middle. A few rules keep them whole:
- Keep holes at least twice the sheet thickness from any edge, and 1/2 in. is better.
- Drill holes 1/16 in. larger than the bolt so the panel can expand and move. Acrylic grows about 0.00004 in. per inch per °F.
- Use washers or a backing strip on both sides to spread clamping force, and don't overtighten.
- Slot holes on panels longer than 24 in. so they can float.
We drill and countersink to your drawing, and we can tap threads in 1/4 in. and thicker sheet for light screws. For a hinged flip-up guard, a 90° bent lip along one edge gives you a stiff handle and a place to mount the hinge; we can line bend acrylic up to 1/4 in. thick. If you're drilling your own, see how to drill acrylic without cracking.
Caution: keep acrylic away from heat sources. Its continuous service limit is about 160 to 180 °F (71 to 82 °C), and it's combustible: once lit, it burns rapidly. Don't use it as a spark shield on a grinder or near welding or torch work.
Chemicals and coolant
Water-based coolants and most cutting oils are fine. Solvents, brake cleaner, acetone, and some degreasers will craze or crack acrylic, especially around stressed holes. If your guard will be wiped down with solvents, polycarbonate has the same weakness, so ask us about other options or keep solvents off the panel. Clean acrylic guards with mild soap and water.
How we make it
Send a sketch with the outside size, hole positions, and any cutouts for spindles or hoses. We laser cut or route the panel, drill and countersink the holes, and finish the edges. Machined edges are a good choice for guards: clean, square, and less glossy than laser edges, so they don't catch light in your eyes. Simple rectangles go straight through the instant quote; anything with cutouts can go through upload a drawing.
Questions
Is acrylic or polycarbonate better for a machine guard?
Polycarbonate is better wherever something could be thrown at the guard, because it bends instead of breaking. Acrylic is better for chip and splash shields and viewing panels where clarity and scratch resistance matter more than impact.
How thick should a clear guard be?
1/4 in. for most guards up to about 24 in. on a side, 3/8 in. for larger panels or ones with unsupported edges. Thinner 3/16 in. works for small covers.
Will coolant damage an acrylic guard?
Water-based coolants and most cutting oils won't. Solvents like acetone, brake cleaner, and strong degreasers can craze it, especially near drilled holes.