Re: OT - cutting thick polyethylene

Thanks. That is exactly the kind of info I needed. I think I wasted about $100 on 8" and 10" Freud "plastics" blades -- unless I can think of a plexiglass project. Just to see how a more aggressive blade would do, I just tried cutting some scrap 1" LDPE with a Freud 10" 60 tooth thin kerf miter blade on my TS and it did great. So then I used it to "rip" a 48" long 1.5" strip of the 2 1/4" LDPE and it also went well -- no significant melt, smooth enough (like you wrote, a few saw marks which is OK for what i am doing), and I could actually feed the stock at a reasonable speed with reasonable effort -- unlike w/ the plastics blade.
Boy, is LDPE heavy. Over 300 lbs for a 4x8 sheet of the 2 1/4". I had the supplier cut it down into 6+ sections so I could handle it.
Thanks for the detailed info re routing. No need for that yet, though I can see that it may be in the future. What I may be doing soon is using the notorious Craftsman moulding head with a custom set of cutters. (My "dado" cuts are too deep for a router or moulder.) I did a test on my RAS with the moulding head (top-down) and that was a bit too scary. The cut was surprisingly smooth with HSS cutters, and I have found a guy who will do custom cutters in carbide for the moulding head for a decent price. Problem was that on the RAS there was no way to hold the stock down as it first goes through the cutters -- and once it rode up and gouged the stock -- while on the TS I can featherboard it all along the way.
The bottom line with LDPE is that it seems that even aggressive blades can work OK from the standpoint of the finish of the cut. I was starting to suspect that and it helped to get your comments. Again, thanks.

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Igor,
I've been working with 1 to 2.5" HDPE as well as 7/16" Polyproplyene sheet and am using a Freud TK906 (thin kerf 50 tooth carbide combination blade) on my direct drive table saw with no issues. I find the saw motor is the limiting factor in how fast I can feed material ... wood or plastic. I've also cut the same material on my Dewalt CMS with a 12" Series 40, 80-tooth blade and have found I can bog that saw down if I feed too fast. I get very clean cuts ... and adjust my feed rate by listening to the saw slowing down (I try to keep blade RPM as high as possible while still making some progress through the material). When the lights start dimming in the shop, you are feeding too fast (DAMHIKT, TYVM).
2.5 inch MAY require you to take several passes per cut. That's quite a lot of chips to be pulling out in one pass.
Get a nice smooth finish (depending on how well you keep the work against the fence of course) that appears sawn, but is not too rough.
I'm also using the Freud 8" stacked dado set to cut large grooves in the HDPE (up to 2" wide with a 3/4" stack ... multiple passes of course) with great results.
Don't have any experience with the Freud plastics blade ... though it does sound like it's meant for sheet acrylic (and other brittle plastics).
I know you didn't ask about routing, but that's where the bulk of my experience has been lately:
When routing, I try to use an "O" flute, 2-flute straight bit from Onsrud .... more to keep from pulling the work to the router (it's mounted overhead) and to not pack the chips into the cut. I get fairly good results on a hogging pass (I only cut ~76% of bit diameter on each pass ... with a 0.250" bit I'm only taking 0.190" depth of cut). I have noticed I get a better finish if I rough cut approximately 0.10 large and come back for a final cut .... but for the work I was doing it was more an "oh gee ... look at that" rather than any production change. Router speed was 21000, and cut speed was 2.5 inches per second.
Hope this helps,
Rick

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