Got some about 1/4" thick perspex to cut, not sure whih way to tackle it. Don't fancy score & snap, it would be ouch if one broke where not wanted. I could use circular saw, jigsaw or soldering gun with melt/cut tip, but all strike me as lousy options. The circular would likely shatter it, jigsaw even worse so, and the melty thing would take forever. What do you reckon? I've got around 4m of cuts to do.
Whatever you do, do it very slowly and with a sharp blade, as acrylic melts easily and makes a real mess of the blade, not to mention the work piece. It's somewhat resilient, and it's not likely to crack as long as it's held firmly. Pouring water on the cutting point would allow slightly faster working, if that's practical.
I have used a jigsaw, very carefully after the first tests. Today I would probably use a bandsaw if size permitted, with a very slow feed, backing off to clear swarf frequently.
There's quite a lot on the Net about it.
The last time I cut a lot of perspex (during this summer) to glaze a greenhouse I had a lot of success with a hand tenon saw This one
The cutting edge of saw blade was used fairly flat to the surface of the perspex and once the cut was started at any one time 80-90% of the length of the blade was cutting the perspex. The angle of the blade was such that it only two layers of card were cut through. It helps to have a second pair of hands to GENTLY hold the waste side of the perspex at the end of the cut. If on your own as you get towards half way, and onwards, it helps to tape the cut you have already made so as you reach the end the waste doesn't twist away and snap off the corner in a direction you don't want.
Before I used the tape method over the cut I did have one failure where the waste side twisted slightly and the perspex cracked.
We used to make guitar scratchplates from perspex with a multi-bladed spindle cutter and a very low speed feed. There was quite a lot of wastage but with the shape of the guitar scratchplate there would have been quite a lot of waste anyway.
Nick
Working with Perspex, is some kinda S&M.
You can drill into the edge of 0.220" sheet and use #2 screws to make plastic boxes (without using solvent glue), but if you do that, the pilot hole for your tap, will always "drill crooked". The tip of the drill bit deflects to one side, every time. If you send the tap into the material, the tap will bind, so you cannot afford to tap the entire length of the drilled hole. You cut the #2 screws down, so only
3/8" goes into the sheet, and then the method works OK.If I had a band saw, that's what I'd use. Probably all the tools I normally use here, have been fouled with melted plastic at least once. Of all the miserable choices I've got, I'd probably use the hack saw. My jig saw wouldn't cut a true enough edge, for any purpose. (Glued edges require really "true" cuts. Amateurs like me, need not apply. All you have to see, is what kind of edge the master machinist at work can put on materials like that, to get some idea how far out of your league you are.)
And if you foul drill bits, clean them as soon as they foul. Don't declare "to hell with it" and drill until the bit is chock full of plastic. It can take 20 minutes, if you're a cowboy and don't stop on first sign of trouble, to clean the plastic out of a totally clogged bit.
You just can't be aggressive. You might make a cut. Then go upstairs and play with the cat for a bit. Go down and do a bit more. Take another break and make coffee. And so on. Working in plastic is always a rate-limited process.
For drilling holes, if you just select a 0.25" drill and start drilling, you can crack the sheet. And especially if two holes are "within spitting distance" of one another. You can work your way up through the drill index, one size at a time, as an approach. Or you can accelerate the process, using these to "get close", and then use the final regular drill bit size, to get the hole you really wanted. These still clog, but, you need fewer drill bit changes, to get a finished hole.
[Picture] Taper drill bits
I have watched an experienced technician making very clean cuts on perspex but struggled to do so on exactly the same equipment (lathe and end mill). Flooding the work with coolant is essential. Very sharp tools are essential. Fixing the workpiece as rigidly as possible is also important. Large pieces change shape as they are machined because of the internal stress in the material which gets partly relieved as it is cut away. So yes, taking a break regularly to allow the material to settle is helpful. Any significant heating is a disaster. John
What kind of finish do you need on the cuts?
Straight cuts, or curves / shapes / following a path etc?
Perfectly smooth, & perpendicular, or can you cope with a bit of roughness, not perfectly square?
If I were going for "good enough" (say cutting out something that would have its edges hidden in a frame), then a metal cutting blade in a good quality jigsaw running at a slow speed. Possibly with some compressed air directed at the cut to cool it.
If I wanted "perfect", then a 6mm straight fluted cutter in a router at a fairly high spindle speed (~24K rpm). Take shallow passes, and use feed rates similar to those in wood.
For something perfect, then on something 6mm thick polishing the cut with different grades of abrasive paper can remove the saw marks and/or straighten/square up a cut.
Also flame polishing
I have had good results doing the following on a table saw, YMMV:
Cut with (TCT, ideally) circular saw blade, leaving perhaps 2-3 mm too much.
The cut will be partially melted, with a ridge, chipping and a poor finish. Allow the material to cool for several minutes. Take a second cut with a very low feed rate, so that the cut material is less than the width of the blade.
Thomas Prufer
I've had some sucess in cutting up 3mm perspex sheet with a router - this is counter-intuitive, as the router cutter speed is probably the hightest of all the tools I use, but it works, and cuts cleanly. Perhaps at high cutting speed the perspex chips are cut and thrown before they have time to melt.
This method works for straight line cuts. Clamp the perspex flat to a sacrificial piece of MDF or similar, with a steel strip above the perspex included as a guide for the router. Use a small (1\8th inch) TCT cutter, and take multiple shallow cuts until you are through to the MDF.
You will gret a slightly rough edged straight cut, which can be improved with abrasive paper, and if needed polished with the usual methods.
Good luck!
Charles F
It's not been done yet. Cuts are straight lines, reducing sheets to required sizes. Any roughness can be cleaned up with sander & flame. I'm leaning toward circular saw.
Probably not a lot of use to you, but we use a laser cutter for such things. They are pretty impressive, there might be a company near that will cut it for you for a price.
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