Cutting plexiglas

rvieceli

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Feb 4, 2008
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Just pulled a nice big chunk of 9mm plexiglas out of a roll off at the mall.  [big grin]

Thinking about making a router base and a jig or two. What is the best way to cut and machine this stuff?

[member=25351]rst[/member] and [member=74278]Packard[/member] suggestions? Will I be able to do it without buying a bunch of stuff?

Thanks

Ron
 
To my Imperial-measurement mind that is 0.354” thick.

1/8” up to about 0.200” thick you can score deeply and snap.  I have a wall mounted glass/mat/plexiglass cutter that will score that deeply enough to snap.  I never tried that on thicker material.

I’ve also cut plastics by using a high-tooth-count all steel plywood blade mounted in reverse. This makes exceptionally clean cuts on thinner materials. These blades are extremely cheap.  Amazon shows an Irwin 10” blade with 180 teeth for $7.00.

You don’t need or want carbide for this.  The plastic does not seem to dull the blade very quickly.

When I mounted the blades the “correct” direction, I experienced edge shattering.  Reversing the blade cured that.

The blades are cheap enough that you can try it out.  I have never cut anything as thick as 9mm (plastic).

Flame polishing will make quick work of smoothing the cut edges.  There is a small learning curve, but a couple of quick trials should get you competence. 

There are plenty of videos online for flame polishing.  A heat gun will work also (but slower). 

When I still worked, and the company had a full tool room facility, I could get plexiglass machined on a milling machine.  The same type of bit in a router would melt the edges. 

You can use a router to skim off very small amounts of material if you move the router fairly quickly.  But it is really spinning way too fast for plastic.

What is the application?  Just curious.
 
You can remove a few thousandths of an inch on a cut with a router. But I would probably resort to using a sander for that purpose. Sandpaper removes plastic pretty well.

I’ve used a random orbital sander to make “privacy glass” from plexiglas. With 400 grit or finer you end up with a translucent piece.  But only use new and unused sanding discs.  A small particle of foreign matter will scratch the hell out of the finish.
 
I cut it a lot, using a blade intended for solid surface material. They are fairly high tooth count (72), carbide teeth, triple chip grind, with -5 degree rake. The ones from Festool, for plastics, that work with a TS55 just fine too. It just depends on how you want to go about it.
I have no problem cutting it on a table saw, if the protective paper is still on it. If that has been removed, I would rather use the TS55. That reduces the chance of scratching, since you are not sliding the piece in the saw.

The worst part is usually drilling. A hand drill wants to grab/snag as it breaks through the back side and the piece has a tendency to lift up at that point, when using a drill press. This action can be reduced/eliminated by slightly dulling the cutting edges of the drill bit. Just a couple of swipes with a hand stone is good enough. This is also best-practice when drilling brass, it does the same thing.
In machinist circles, this is called "brassing off" a drill bit.

A fair percentage of the acrylic panels that I cut have "things" trapped between layers, so flame polishing is out of the question. I polish those with the RO90, ordinary sandpapers up to p500. Then I switch to some foam discs that go to p2500. After that, Novis plastic polish with a felt disc.
 
I have cut 1/8" or a little thicker quite a few times with the TS55.  I run at speed 2 or 3 and move the saw right along. Nice cut, no issues. Make sure the entire sheet is fully supported. Place it on top of another sheet of something sacrificial. 

Seth
 
I have cut both acrylic and polycarbonate with both table saw and jig saw. 
Its pretty soft and will cut without much difficulty.
I don't recall chipping being a problem, but melting is.
Don't go too slow with a fine blade.  Move as quickly as practical to avoid melting the plastic onto your blade.
 
Hey Ron, just last week I was sawing some 3 mm acrylic for shelf liners on wire shelf storage for under the sink. I used the TSC along with the Festool aluminum blade because you want to have a zero to negative rake on the teeth so that it doesn't self-feed. That's the reason why reversing a regular blade in the saw kind of works...but it does make a hellacious sound.

You'll need to drill some holes for the router bases and the drill bits should have a point angle of 60º-90º otherwise cracking & chipping can be an issue.
Tap Plastic, Toolstoday & E Plastic all offer drill bits for acrylic.
https://www.tapplastics.com/product/supplies_tools/plastic_tools_supplies/tap_plasdrill_bits/161-https://www.toolstoday.com/high-speed-steel-drill-bit-for-plastic.htmlhttps://www.eplastics.com/accessories/plastic-tools/drill-bits

If you have a Drill Doctor you could also alter the geometry of the drill bits if you need a special size.

Finally, this is the cheat sheet I use for acrylic fabrication. There's just a ton of information inside from cutting with a jig saw to wet sanding.
https://minplastics.com/wp-content/uploads/2018/06/Acrylic-Working-with-Acrylic-PLEXIGLAS®.pdf
 
A solid surface blade works pretty good in a table saw.  For not-straight cuts, I use an o-flute bit in the Shaper Origin, with the speed down to 4 and autocut speed turned up 5-10 ipm faster than default, whatever speed that is.  Moving fast.  Jigsaws always seem to shatter the edge.
 
You might also consider phenolic sheets.  There are many grades.  Extremely strong and dimensionally stable.  Easily machined.  But not clear. 

They used these sheets to produce welding fixtures and tooling in the company where I used to work. 

At one time you would see router mounting plates made from this material.  It has been supplanted by aluminum.

Here is some information on phenolic sheets:
https://www.piedmontplastics.com/blog/phenolic-sheet-explained

 
WastedP said:
The link is wonky because of the "®", but copying and pasting it took me to a document that will probably change my life.  Thanks.

Ya thanks for that...the link needs to include ®.pdf in it but I can't seem to add it to the address, however if I copy & paste rather than clicking the link, then the Plexiglas cheat sheet comes up.
 
I use aluminum cutting blades in all my saws, portable or stationary, the geometry is so similar that it is irrelevant for plastics up to .5".  If you rout, use a straight blade not a spiral.  Specialty plastics drill have a 90 degree straight geometry and sizes up to .5" are cheap, regular metal cutting blades will grab and cause cracks in acrylics.  Always made screw holding holes slightly oversize as plastics will grow with humidity and heat.  Large holes in acrylic should always be sanded to prevent craze runs later. And this is my condensed plastic fabrication over view.  Happy making!
 
Thanks again. I have an aluminum blade for the table saw I'll try.

Basically, I was on my way to the post office the other day and since Bed Bath and Beyond closed our store, there was a 30 yard roll off parked in front. Sticking out of the top was most of a 3 x 4 foot section of around 9mm plexiglas that they used for the cough/sneeze guard at the registers.

Not being too shy to do a bit of dumpster diving, I scaled the corner and wrestled it out and threw it in the back of the Jeep. So I don't have a cost basis for this find.  [big grin]

Ron
 
Plastics are insanely expensive right now, I have an order that required 24pc 18" x 24" of 1/4" clear acrylic.  I did not check with my distributor as I had enough cutoffs, but online pricing was $32.00 @ and up not including shipping.  Also need 48 pcs of 2" x 2" x1/8" aluminum...can't wait to see that pricing.  I used to buy 10 S/S 24' long but do not have that sort of volume needs at present so I buy 8' pcs.
 
[member=25351]rst[/member] yeah, tell me about it. Had to pick up a full stick (20 feet) of 1/2 inch x 6 inch A36 flat bar from my local steel guy and it was almost $300. Ouch!

That's with a discount for a full stick and cash.  [eek]

Ron
 
rvieceli said:
[member=25351]rst[/member] yeah, tell me about it. Had to pick up a full stick (20 feet) of 1/2 inch x 6 inch A36 flat bar from my local steel guy and it was almost $300. Ouch!

That's with a discount for a full stick and cash.  [eek]

Ron

My $1/# rule of thumb for 5-6' lengths of steel doubled and hasn't eased back down. Rather than just walking in and placing my order, including some random "just in case" material, I now have to ask for prices before buying. Bah humbug, rats, phooey and stuff.

At least they haven't realized that their cut-off's are way underpriced at $0.50/#.

RMW
 
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