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Sawing Plexiglass


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I'm making a new plexiglass cover for my engine control panel. I've got a 9" x 18" piece of 3/8 plexiglass that I must reduce to 9" x 13-1/2". I can use a table saw or a miter saw. 

Seems a blade with few teeth, could cause chips and a blade with lots of teeth could generate too much heat. 
 

Any tips to be had?

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I don’t own a table saw so I use a jig saw

use the correct blade , high friction causes the plastic to melt 

To polish the edges I use  polishing wheel 

flame polishing works but the edge tends to check, crack when used outside 

 

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As mentioned earlier, saw near, but not on, the line.  My preference is to then use the original as a template and a router with a piloted bit to finish off.  Then a light sanding to remove router marks and polish if you want. 

If you need to drill holes, either use a special bit for plastic or slightly dull a regular bit so the cutting angle is about 90 degrees.   

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If you have to saw it, slow feed with a fine toothed blade - treat it like it was metal.

The best way is to use the old piece as a template - stick it to the new piece with double sided tape and cut with a flush trim bit on a router table. I've done that to make new hatch lenses and they come out near perfect with only a little fine sanding to perfect the edge.

If you have swarf "melted" to the edges it's better to use a file than sandpaper to clean it off.

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Our weapon of choice is the bandsaw.  One advantage over the jigsaw is the blade motion is in one direction.  Here my son was trimming the canopy of the airplane we built while I was supporting the other side. 

2018389080_bandsawcanopy.thumb.jpg.27bbb365756a49bd634f5b0f36953a12.jpg

Of course we did the same as everybody else said - cut wide and then use another method to get to your cut line.  We used a belt sander and finished up with hand sanding.

 

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1 hour ago, SloopJonB said:

If you have to saw it, slow feed with a fine toothed blade - treat it like it was metal.

The best way is to use the old piece as a template - stick it to the new piece with double sided tape and cut with a flush trim bit on a router table. I've done that to make new hatch lenses and they come out near perfect with only a little fine sanding to perfect the edge.

If you have swarf "melted" to the edges it's better to use a file than sandpaper to clean it off.

I find the best choice are the fine tooth wood clean cut blades for finishing work.  Metal blades are ok but slow and gum up quickly.

Two things to make it easier:

1.  Set the blade oscillation to 2 not 0, and keep blade speed up and your feed rate wayyyyyyyyy down. 0 oscillation means the blade gets dragged back down the surface and creates melting issues.  Oscillation and pushing the saw too hard leads to chipping.  A little oscillation and a slow feed rate, you can tell when you're going slow enough because you hear the saw blade contact the piece only on the up stroke. 

2.  Lube.  I use a spray bottle of dish soap and water.  Keeps from getting those melted edges and cuts cleaner.

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7 hours ago, slug zitski said:

I don’t own a table saw so I use a jig saw

use the correct blade , high friction causes the plastic to melt 

To polish the edges I use  polishing wheel 

flame polishing works but the edge tends to check, crack when used outside 

 

It’s hard to argue with the results of that video. I can’t saw straight for shit with a jig saw, but I guess there’s where you cut close and sand to the line. 

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Use a saw guide

the tricky part when working with plastic and a saw guide or drilling Templates  is the super slippery surface of the plastic sheet

In addition to clamps use double sided adhesive  tape to stabilize your guide or template to the plastic 

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4 hours ago, Quickstep192 said:

It’s hard to argue with the results of that video. I can’t saw straight for shit with a jig saw, but I guess there’s where you cut close and sand to the line. 

The right blade will help, and the finishing blades are less prone to wander because they have almost no set to the teeth.  They make ones for straight lines and ones for curves, you really want to have both.  Most larger curves can be done with the straight line blade in a pinch though.  

The spray bottle of dish soap and water and the light oscillation to the blade are critical, dry is bad, constant contact is bad, heat is bad.  far fewer boogers on the edge this way.  

For straight line cuts you just clamp a piece of aluminum L or a yardstick onto the work piece.   I have a festool jigsaw with accessory kit which includes soft shoe bases, hard g10 style bases etc.  Also have their guide rails, so it locks onto the track and cuts perfectly straight.  Even bevels of any angle are reasonable with it.   It will cut nice circles in just about anything, I've cut multiple circles of 2' in aluminium fiberglass and steel with it.  That setup is > 1800$ these days though, so unless you're making money with it, 20$ worth of material to make a straight edge is good enough and possibly even free.  

Other thing that is worth every penny and much cheaper are plastic specific drill bits.  

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When i re-did the lenses in my old Lewmar hatches, i rough cut the new lenses with a jig saw and a plexi cutting blade.  To do the final shaping, stuck the old lens onto the new one with double sided tape and used a router with a flush cutting bit. 

Worked very well

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  • 1 month later...
On 12/27/2021 at 12:12 PM, DrewR said:

I have had zero problems cutting both acrylic & polycarbonate (Lexan & Plexiglass) with a sharp table saw blade. No chipping and a blowtorch to smooth the cut.

I've been using plywood blades to cut plastics.  The cut can be clean but if the feed rate is too slow, melting can occur.  Both Amana and Freud make "no melt" table saw blades specifically for cutting plastics and in a variety of sizes.  When we move to replacing fixed ports, I'll be picking up one of those blades.

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On 12/26/2021 at 2:24 PM, gkny said:

cool , but I love the fact that it's labeled  BOSCH   Clean for Plexiglas Bi-Metal Jig Saw Blades and in the picture towards the bottom they state bi-metal is not recommended for plexiglass..

 

bb5f7c94-739a-4c99-a2a3-46c2001a2581._.j

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On 2/21/2022 at 10:40 AM, Grande Mastere Dreade said:

cool , but I love the fact that it's labeled  BOSCH   Clean for Plexiglas Bi-Metal Jig Saw Blades and in the picture towards the bottom they state bi-metal is not recommended for plexiglass..

 

bb5f7c94-739a-4c99-a2a3-46c2001a2581._.j

Then stick to your charts… the bi-metal Bosch jigsaw blades work great.

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Table saw or router work great though the router will make better edges with less stress in them. Polishing the edges with a propane torch is not the best as you will force impurities into the edge which will then create problems later. Oxy-hydrogen is the best gas for polishing edges. 

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I sand to 1200 and then lightly flame the edges - they become as polished as the "good" surfaces.

Just wave a propane torch over the edge and the finish will appear before your eyes.

Easy does it.

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  • 2 weeks later...

Table saw good. Chop saw very very bad.

A table saw works well because, as the blade cuts it pushes the material down into the table. If the plexiglass melts and sticks to the blade, the saw will just cut it again and your cut will continue.

If you try to cut plexiglass with a chop saw, the plastic can adhere to the blade as it rotates up, causing very undesirable effects. (Bang! Holy Crap! Count your fingers!) You can probably guess, how I know this!

Otherwise, most woodworking tools do a pretty good job on the material. I’ve even used electric jointers and hand planes.

Good Luck!

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