1/8" Acrylic on Table Saw?

[massive88]

Im looking to cut out the top panel of my 1-player stick today, and I will want my acrylic to be the exact same dimension.   

Is it a terrible idea to use a table saw to cut down the acrylic to the exact dimension of the plywood panel?

I have 12x12 acrylic sheets that I need to cut down to 11x8

If a table saw is no good, what way do people recommend?  Can I get it fairly good with an exacto-knife using the ply panel as a template?  Or is routing it with a flush trim bit really the only way to travel?

Thanks for any help.

[Chadwick]

Don't use your table saw.  Your material is too thin, your blade will have too few teeth, will have too much hook, and your teeth will have the wrong grind.

You'll trash your acrylic.  Use a router or a utility knife. 

[Encryptor]

I would agree with using a router with a flush trim bit. It works great.

Encryptor

[ChadTower]

I would agree with using a router with a flush trim bit. It works great.

And multiple small passes.  Slow speed.  Watch for melting.

[massive88]

I would agree with using a router with a flush trim bit. It works great.

And multiple small passes.  Slow speed.  Watch for melting.

Multiple passes?  If I have a 12x12 to bring down to 11x8, would a router not cut through to make a 3 1/2" or so strip on my 8" edge?

Would it be better to use the exacto to get it close, say down to 11 1/4" x 8 1/4", then router it flush?

Ive never used the flush trim bit, but I had imagined it would be a one pass operation.

[ChadTower]

Ive never used the flush trim bit, but I had imagined it would be a one pass operation.

Plastic is different than wood.  Cut off too much and it shatters.  Cut it too fast and it melts.

[massive88]

Plastic is different than wood.  Cut off too much and it shatters.  Cut it too fast and it melts.

So would cutting it down to a close size with the exacto make sense?  To then finish with the flush trim. Especially since its as simple as a square?

[ChadTower]

So would cutting it down to a close size with the exacto make sense?  To then finish with the flush trim. Especially since its as simple as a square?

Yep, just make sure you don't try to cut too much with a single pass.  I'd keep it really small like 1/8" at the most.  And don't clamp the sheet, sandwich it between something like ply sheets so that the whole thing is secured.  Plastics vibrate and bounce a lot making a break a lot more likely.

[jeffhlewis]

Here's how I cut mine:

1.) Put acrylic down on a piece of wood
2.) Take a straight edge (clamp it if you can) and lay it down about a quarter inch away from where you want your final cut line to be.
3.) Take a big exacto knife and score the acrylic as deep as you can along the straight edge.  Make sure you add an extra 1/4" or so.
4.) After scoring the acrylic, put another piece of wood on top of the acrylic, creating a "sandwich"
5.) Apply pressure to the wood "sandwich" and bend & snap off the piece of acrylic along the score line.  Be very careful to not crack the acrylic. 
6.) Use the router to cut away the extra 1/4" lip on the acrylic with a flush trim bit.

[nuka1195]

I've never had any issues with cutting plexiglass on a table saw, with a standard 80 tooth thin kerf blade.

i cut to finish size for anything that can be (no curves).

you do need to hold the plexi down, it can lift on the blade and the shards are hot and can burn, but it cuts fine.

[mountain]

Ive never used the flush trim bit, but I had imagined it would be a one pass operation.

Plastic is different than wood.  Cut off too much and it shatters.  Cut it too fast and it melts.

Not true. Acrylic won't shatter or even crack when cut with a router using a two fluted cutter. Also, the slower you go the more chance of melting. Concentrating the friction of the cut by cutting too slow tends to melt the Acrylic. Do a few practice cuts, if you pay attention, you will get a feel for it and proper speed for the cut will be obvious.

I use a table saw to cut large pieces of acrylic down to a more manageable size. You need to have a high tooth count blade for it to work properly though.

[ChadTower]

Not true. Acrylic won't shatter or even crack when cut with a router using a two fluted cutter.

I saw it happen.  Big chunk cracked off near the end of the cut... broke a 2" triangle off the corner.  Most likely because dude was forcing the cut rather than letting the bit do the work.  Could have been a piece that already had invisible cracking in that area, though.

Also, the slower you go the more chance of melting. Concentrating the friction of the cut by cutting too slow tends to melt the Acrylic.

I don't know, man.  Routers don't go slow enough for that.  Saw blades, yeah, but even slow speeds on a router are pretty damn fast.

[mountain]

Not true. Acrylic won't shatter or even crack when cut with a router using a two fluted cutter.

I saw it happen.  Big chunk cracked off near the end of the cut... broke a 2" triangle off the corner.  Most likely because dude was forcing the cut rather than letting the bit do the work.  Could have been a piece that already had invisible cracking in that area, though.

Also, the slower you go the more chance of melting. Concentrating the friction of the cut by cutting too slow tends to melt the Acrylic.

I don't know, man.  Routers don't go slow enough for that.  Saw blades, yeah, but even slow speeds on a router are pretty damn fast.

I was talking about the speed of the pass, not the speed of the cutter.

[ChadTower]

I was talking about the speed of the pass, not the speed of the cutter.

Ah!  Then we agree.  I was talking about RPMs.

[Chadwick]

Speed = RPM of the spindle
Feed = feed rate of the bit through the material, usually measured in inches per minute

too slow of a feed rate = bit dwells and heats up which causes chips to re-melt.

[facesmiths]

it sounds like you dont have what it takes for this properly so to do it garage style you might try (I have used this in the past and it worked fine for me) cut it to the size nearly and then use a sadning disc and a drill to finish with it clamped inbetween two peices of as hard a material as a guide as you can get (thick steel straight edge would work fine just realise the straight edge is not going to be mechanicly perfect anymore so some hard word or thicker peices of plastic would work as well just make sure to use eye protection with extra on the protection so you can stay close to the work piece to make sure you are not taking off to much.

ONE FINAL NOTE TOO. you can NEVER have to much protection on the surface of your plastic so be sure to cover most if not all of it with masking tape and  the wider the tape the better (lesss places for the tape to catch on somthing and lift causing all sorts of problems as well as exposing your surface. I know it usually comes covered but that cheap thin seranwrap stuff just does not stand up right especially if there is even a hint of heat involved

about the routing too they make single flute bits for routing out plastic and soft sticky metals (such as aluminum as it causes the same types of problems. if you need some links to pics of the bits and where to get them let me know. as far as cheap for good quality goes the best I have found is wholesale tool.

[massive88]

I ended up scoring and breaking at the near dimension, then routing out the remaining material to get it flush.  Worked like a charm.

Double fluted router bit cut it like butter, if butter made a zillion little plastic chips.