Last week I read a “how-to” where it said to use a dull razor blade to scratch and cut plastic sheet materials. I suppose I can see where that recommendation came from, but it’s wrong. For scoring plastic sheet goods for hand-separation, nothing beats a plastic scoring knife.
Clarification: the “score and snap” method can only be used to create controlled breaks in certain plastic materials, such as acrylic, styrene, and construction laminates. Many plastic materials cannot be scored and snapped and must be cut using other means. If in doubt, check with your plastics supplier.
Here’s how scoring a plastic sheet works:
- Lay out your cut line.
- Use a straightedge and scoring knife to cut a narrow and shallow groove in thin plastic sheet materials (e.g. 1/8″ acrylic). (Thicker plastic sheets might need to be cut via other means.)
- Make multiple passes to deepen the groove if needed.
- Place the plastic sheet, groove-side up, over a hard edge, such as a tabletop, with the groove slightly beyond the edge.
- Optional: Clamp a flat block over the sheet, preferably with a hard edge as well
- Bend the overhang with a quick and even motion.
- *SNAP*. The groove will deepen as a crack propagate throughout the thickness of the sheet, separating it into two pieces with straight and relatively clean edges.
The process is similar as with cutting glass, but with plastic it’s usually okay to make multiple passes with the scoring knife.
Scoring can be accomplished with utility knife blades and other such instruments, but a scoring blade is really the best way to do it.
There are three main types of plastic scoring knives:
- Fixed-blade utility knife
- Retractable knife
There might be slight design differences, but scoring knives – at least all the ones I’ve used – all feature triangular blades with strong points. You might see sharpened edges, but it’s the flat inside of the pointed blade that is mainly used for scoring.
The flat sharpened edges are used for deburring or cleaning up of freshly separated edges.
Disposable Plastic Scoring Knife
You can generally find these inexpensive scoring knives at plastic supply centers. The blades are a little on the thin side, but they’re cheap and widely available.
Buy Now(via Tap Plastics)
Fixed-Blade Plastic Scoring Knife
Stanley’s 10-519 fixed blade scoring knife comes with a standard non-retractable fixed-blade knife with a 11-942 plastic scoring blade. The design actually works great, but the combo is hard to find and replacement blades even harder. There is a relatively new identical-looking Stanley Bostitch version, but I haven’t tried it yet.
I keep mine in its original plastic-covered retail display card since the blade is quite sharp and sticks out with no form of protection. Just something to keep in mind.
Buy Now(Stanley Bostitch 10-133 Knife via Amazon)
Buy Now(Bostitch 11-101 Blade via Amazon)
If you already have a fixed-blade knife, Stanley blades can be secured in the same way as regular utility knife blades.
Some fixed-blade knives are one-piece designs, such as the Hyde 45730 (via Amazon).
Retractable Plastic Scoring Knife
Retractable plastic scoring knives, such as this Olfa PC-L, are a good compromise between rigidity and convenience. Replacement blades are widely available, and Stanley now makes a new knife handle (model STHT10192) that is compatible with Olfa PB-800 replacement blades.
Buy Now(via Amazon)
You have the marketplace pretty well covered. Hyde and Red Devil also have ones.
Another HD one comes from Fletcher-Terry:
They also make a much less expensive model and a more automated machine that you often see in big-box stores
Fletcher Terry also makes a scoring anvil that snaps the two pieces in half. Works great for smaller pieces that don’t merit the overhang method.
Thanks ToolGuyd! Your timing couldn’t be better, I am going to have to cut some lexan for a project and I was tying to figure out a better way of cutting it. The last time I used my dremel and didn’t like the results. I just bought a Olfa scoring knife to help me with my project. Keep up the good work.
A different option for thicker sheets is to cut the sheet goods on a table saw with a blade designed for the purpose – 2 that come to mind are the Freud LU94m010 and the Forrest NM10601100.
If you happen to have a 4-1/2 inch trim saw (like my old Rockwell Porter Cable 9314) then this blade works remarkable well:
I have used TCG non-ferrous blades on plastic materials with no problem in the past (Freud 10″ TK706, but no longer available). I believe a slow bandsaw should work well too.
In my experience this type of tool works well on Acrylic (Plexiglass) and other hard plastics but very poorly to not at all on Polycarbonate (Lexan) and softer plastics. If the plastic is not prone to brittle fracture it will not snap cleanly.
For Lexan you are far better off using appropriate blades in either a circular saw or a reciprocating type saw. blades such as these from Bosch should give good results http://www.amazon.com/home-improvement/dp/B0000223FX
Actually, Bosch now has a line of plastic-specific jig saw blades.
It is true that the score-and-snap method works best on harder plastic materials. I have added clarification about this at the top of the post, thanks for the reminder!
Thanks everybody for the information, I just ordered some Bosch reciprocating blades to help me cut the lexan.
Correct that, I meant Bosch jig saw blades. Thanks again.
Very well thought out and 100% accurate, I ‘ve been cutting sheeting and plastics at home for over10 yrs and have used this exact methodology!!! ?? also what helps to maintain a perfect edge is using tape where you plan to score and snap it, with a piece of wood or whatever is at hand to put on the very edge ????
How do you cut – hundreds of plastic boards of the same size – do you recommend outsourcing for machine cut?
Depending on the size and what the products will be used for, outsourcing will probably be the best option. Or, if you will need this done very regularly, buying a laser cutter or CNC machine.
I am constantly looking for a better cutter or method as I fabricate sheet plastic cages for my critters. Any help with cutters or help with surplus sheeting clear and in 2 ft wide strips would be greatly appreciated——–currently I am making about 1000 cages.
I’m sorry, but it sounds like you need to contact a plastic materials supplier, and possibly look into light fabrication equipment. The cutting volume you describe is above my level of familiarity.