cutting 3/4 inch plastic

[lum747]

i am going to build a new sled for my bt3000, and i purchased a piece of plastic 3/4 x 12 x8 and i need to cut it into strips for the runners, and my question is need to know what is the best blade to use for cutting the plastic, and is there a secret to cutting the runners, like maby making shallow cuts and not trying to cut in on pass, any suggestions, how smooth the rough edges
thanks, lum

[cabinetman]

I use a 10" x 60T tripple chip carbide tipped blade. I cut with the blade well above the stock.

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[capncarl]

Like cabnetman said, run the blade high. Be careful. If you make multiple passes you will have lots of blade marks. You may never be able to get it as smooth as the factory finish though, I think that they run it through a heat smooth process.
capncarl

[phrog]

Like cabnetman said, run the blade high. Be careful. If you make multiple passes you will have lots of blade marks. You may never be able to get it as smooth as the factory finish though, I think that they run it through a heat smooth process.
capncarl

We smoothed dentures with an acrylic-cutting burr with many teeth to get rid of the deep marks.and a buffing wheel with a compound called Acriluster to get rid of the last shallow marks and bring a high shine (when I practiced dentistry). I didn't believe it could be done until I saw it.

[LCHIEN]

the plastics shops I dealt with flame-polished the edges of acrylic with a blow torch. I imagine that it takes a bit of practice to get the right clear, smooth edge w/o damaging the plastic. But the flame-polished edges were super looking. Takes the sharp edge off as well as softens the profile a bit. Good for exposed edges in furniture and decorative accessories with exposed edges. May lose precise thickness at the edge and deform the dimensions, depending on how hard yo hit it with the flame.

[pelligrini]

I'm not sure if the runners for a sled need to be perfectly polished.

[cabinetman]

Edges can be flamed polished even with a handheld propane/MAPP torch. It does take some practice but that process will invariably leave the sharp edges (on the faces sides) deformed. It creates a slight buildup. Moving too slow or overheating the edge can produce bubbles.

The best way to polish edges is block sand with increasingly smoother grits. When the edge gets to 800x to 1000x, and all the abrasive marks are gone, the edges can then be polished out with rubbing compounds, and polishing compounds.

I use several cloth buffing wheels that can be motor shaft mounted and group several together, so the buffing surface is wide...like 1½" - 2".

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[LCHIEN]

Don't cut too slow or you will melt the edges and it won't result in polishing! It'll stick all over your blade and be a mess.
Use dust collection as good as you can do it, there'll be white static-y dust all over everything. Think snowstorm.

Heres' some professionally done ways to polish acrylic. they don't recommend flame polishing over 3/8" thick.
http://www.eplastics.com/Plastic/Ple...ishing_Charges
There also some You-tube videos and instructable How-tos on flame-polishing acrylic (Google "Flame polish Acrylic"). You could probably also search "polish acrylic edges" for more ideas.

[cabinetman]

I'm not sure if the runners for a sled need to be perfectly polished.

Actually a sanded edge will slide more easily than a polished edge.

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[pelligrini]

If he's doing dome thin rips of 3/4" material any saw marks would be on the top and bottom of the runner. One face will be on the bottom of the sled, and the other shouldn't be touching the bottom of the miter slot. Doesn't really matter too much.

[cabinetman]

If he's doing dome thin rips of 3/4" material any saw marks would be on the top and bottom of the runner. One face will be on the bottom of the sled, and the other shouldn't be touching the bottom of the miter slot. Doesn't really matter too much.

I would just scuff sand the factory face if it slides on metal or wood/plywood. The finish texture holds also for high pressure laminates...like Formica type laminates. The gloss slick finishes don't slide as well as the textured finish (including the Melamine finish).

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[LCHIEN]

If he's doing some thin rips of 3/4" material any saw marks would be on the top and bottom of the runner. One face will be on the bottom of the sled, and the other shouldn't be touching the bottom of the miter slot. Doesn't really matter too much.

exactly right. The 3/4" vertical thickness will end up horizontal in the slot and the cutting marks will be in the top and bottom. The smoothness of the edges of the runner will be based upon the smoothness of the top and bottom of the original material.

[d_meister]

I didn't see mention of what kind of plastic. If it's a polyethylene type, like UHMW or Starboard, any good table saw blade will do. The better the blade and the better the saw is set up, the better will be the finish on the cut sides. Acrylic (Plexiglass) and polycarbonate (Lexan) are a different story at that thickness with a regular woodworking blade. The "sawdust" doesn't clear from the kerf very well and melts in the kerf. The hot "sawdust"melts together and fills the teeth of a regular blade and soon causes more melting and less cutting. The gob of melted plastic can glue the cut pieces back together behind the blade, and I've seen the mass of melted plastic stall a tablesaw.
My blade for acrylic is a specially made Freud Industrial Plexiglass & Plastics 10" 80T with a NEGATIVE 3 degree Hook. It's a Freud Item No. LU94M010.
Cabinetman is right about successive finer grits and then polishing. I use nothing but wet or dry paper. It doesn't clog and prevents melting at the point of contact. Be careful with the polishing wheel, too. Held in one place to long or going over a larger area too aggressively will melt the plastic and send you back to square one.

[pelligrini]

I didn't see mention of what kind of plastic. If it's a polyethylene type, like UHMW or Starboard, any good table saw blade will do.

I was wondering what type too. Most everyone has been assuming lexan or the like. UHMW cuts a lot like wood, except for the static cling of the chips.

I've cut up a couple of the big cutting boards Sam's carries into smaller ones with my OEM blade and rounded the edges on a router table with a small roundover bit.

[lum747]

cutting 3/4 inch plastic

i reserched what the material is i am refering to and it is polyproylene, it is real dense and heavy,