Cutting plexiglass

[fivestring]

I want to make some blade guards for jigs.
Can plexiglass be cut with a jig saw?
If so, which blade is best for a smooth cut?
Any tricks to keep it from cracking?

Thanks, Gary.

 

[Hambone]

I have cut Lexan with a jig saw. I think it is pretty simular material. No problem with cracking on that.

 

[mikim]

The coupla times I've tried, the blade heats up and melts the plexi behind the cut and all I ended up with was a mess. I had much better luck scoring and snapping. They sell cheap plexi cutters everywhere to do the scoring. Even with thicker stuff - you just have to make repeat scores - making the score deeper - which is real easy to do after the first one..

 

[DocHeb]

The best blade is a table saw with a carbide tooth blade with lots of teeth. Of course, that will only work for straight cuts. For curves you can use a jig saw with a blade that produces a kerf (not a hollow ground blade) so that the sides of the blade don't rub across the plexiglass and cause heat. The reason for cracking is vibration - the plastic needs to be firmly supported.

I've had good luck cutting curves using a router with a template. Use a small diameter (~1/4") straight edge carbide bit, and go slow.

Once it is cut, use a file or sander to smooth the edges. Professional shops will polish the edges using a muslin wheel charged with rubbing compound. The trick with the muslin wheel is to get the edge hot enough to melt a bit and get smoothed out, but not burn. It takes a few tries to get the hang of it. At home, I've had good success with sandpaper, going through 80 - 100 - 150 - 220 grits, and then using a propane torch to flash the edges. Again, you must balance between heating it enough to polish the edges and burning the edges. Practice on scraps.

 

[gsganzer]

Cut it using a router. Smooth cut with no chipping.

 

[GaryM]

As already mentioned, the plastic melting and sticking to the blade is an issue.

I've never tried the router though! Might have to give that a go.

 

[fivestring]

Is a 1/4 spiral bit the best choice to use?

 

[ljh2]

Gary,
Depends a bit on the thickness that you are trying to cut. If it is thin stuff ( 1/8 in or less ), then I'd probably try to just score it and snap - ofcourse that doesn't work too well for curves, especially compound curves.

I've used the jigsaw on thicker stuff or to do curves. Two things to do to minimize cracks. Be sure to leave the protective film on ( or use masking tape along cut line ). Make sure the tape or film covers the full width of the shoe to keep from scratching the surface. The other thing is to place the material on a sacrificial surface (plywood/osb/???) while cutting. For thin material, you could actually sandwich the plexi between two sacrificial layers to minimize flex around the cut.

I think Lexan is easier to cut cleanly than plexi since it is more crack-resistant. Polycarbonate would be better yet, but is more $$$.

Sanding and torching as mentioned above is nice to clean up your cut edges. The heat helps to 'weld' any micro cracks that might be found along the edge.

 

[gsganzer]

I haven't used a spiral bit. I've used a straight bit or a "bullnose" bit. The bullnose gives you a slightly radiused cut so you don't have square edges that can chip.

 

[sl3uth]

I've used many methods, but I like the band saw the best. It's long blade and single direction reduce heat buildup and cracking, respectively.

Sam

 

[TresCrows]

Lexan and Plexiglass are trade names for two different materials. One is an acrylic and the other is a polycarbonate. The Lexan type materials sold under many names now are what you want for your purpose. The Lexan is what bullet proof windows are made off. It is actually a clear rubber---sorta--my best description. Lexan can be bent in a break and drilled with regular bits and unibits. It saws nicely with a fine tooth table saw, a band saw works good too. Jig saws and scroll saws with fine blades may work on Lexan. Plexi--NOPE--it will crack out, requires special drilling techniques and in general is more brittle. It cannot be bent in a break but it can be heat formed---Lexan does not heat form well. I work with this tuff all the time. Lexan scratches easier than Plexi and scratches can be removed from Plexi with proper materials and procedures, usually not with Lexan.
Oh, you can file the edges with a Vixen file for final shaping or use a belt sander with fine paper. J

 

[jimg]

I think nearly all plastics can be cut w/ conventional woodworking gear. Some have mentioned that bandsawing leads to melting. Im wondering if more kerf might be the answer to that and moving along a bit faster. The router idea could work but then again you need to move right along and use a sharp bit. However, (as was mentioned) for an straight cut use your TS. More teeth on the blade w/o necessrily give a better cut. Its the tooth geometry that makes the cut (well yes it does have to be sharp too). There are blades which have tooth geometry just for hard to cut materials like plastic, melaminea etc. Oh, also for the TS and BS use a 0 clearnce thorat plate. That will make a big differnece in cut too.

 

[fivestring]

Thanks, everyone, for the replies.
I guess I'll be trying several ways until I find what works the best.

I see lexan in my future..... /forums/images/graemlins/wink.gif