I need advice for cutting HDPE plastic im a newbie
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  1. #1
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    Default I need advice for cutting HDPE plastic im a newbie

    Ok so its my first post on the forum.... I want to learn how to cut HDPE sheets with a circular saw and use a router as well to cut out basic shapes like squares out of 1/4 inch HDPE sheets of 4' x 8' material max 3/8 inch material...

    So im just confused because I hear about deep feeding when cutting, cooling when cutting, certain rpms to it does not melt so im overwhelmed...

    I just want an answer to these 3 questions

    1. How to cut HDPE sheets with a circular saw like what specific saw blades should I use and why those specific ones? If it helps I have a dewalt 60V cordless brush less circular saw.... Holds a 7 1/4" saw blade and I will just be doing straight cuts with the saw. Cutting 4 x 8 sheets into 4 x 4 then 4 x 2 sheets. Literally like that

    2. Then I want to know about cutting HDPE with routers like what drill bits do I need I keep seeing "O" flute and ball nose which I have no idea what it is... So ill be making basic square cuts in the middle of a sheet of HDPE so what type of bits and strategies/tips do you know..

    3. Do I need to cool off hdpe while cutting? How can I do that?

    Thank you guys in advance!

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    Well what your saying is all hobby based methods with some risk involved, i have not had to use those methods so cannot answer your questions.

    All the plastics i have cut are on a lathe or mill or water jet industrial quality machines giving a precise result, well as far as you can go with plastic.

    A waterjet is great for cutting out complex shapes to a reasonable tolerance and will do things at a speed its not worth trying to muck around at home, just buy time on a machine.ie get someone to do it for you, unless your trained in the use of the machine and can get time on it.

    Ball nose cutter is a milling cutter a quick duck duck go search will pull one of those up so you can have a look at it, it can mount several different ways, they may have a router bit that looks like it but will be a router bit not a milling bit. The milling bit is used in a milling machine.

    All your methods you cannot alter the cutting speed so you get what you get, cooling water and electricity don't mix very well its really dangerous so don't do it.

    So suck and see using the tools you are trying to use, you could also try a post on a hobby type forum if you wish to continue but be careful you don't hurt yourself.

    circular saws will always have a radius so cutting to a sharp corner will be a issue requiring most likely hand sawing to finish it off. Same with a router even if you pocket it out fully it will leave a radius in the corner, hand finishing is time and time is money for commercial ventures.

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    I've cut this stuff for years and never had to use coolant for routing or sawing. You just need to make sure your tools are sharp. Freshly sharpened tools and not "oh i cut 2 bits of wood with this it will be ok".

    Always use freshly sharpened tools and it will make your life a ton easier.

    For routing we use single flute End mills, If you are using a hand router you will most likely drill a pilot hole and work with that. If you are using a CNC machine then you will need to ramp your plunge moves to stop the ribbons wrapping around the tools.

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    OK thank you guys so I guess what I got out both your replies is that use a waterjet cutter (Expensive for me) Or use a milling machine... I just looked on google and seen this forum talking about people cutting HDPE with circular saw but a lot of jargon was used and it takes a lot of research which im fine with but while researching I want to ask a question and see what people say. Just being proactive...

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    If you want to keep it simple - unless you're on high speed high volume production this will get you through

    1 Uber sharp tools.

    2 Make sure all tools have plenty of clearance on cutting angles

    3 Speed down & feed up

    4 Circular Saws - IME Triple chip negative grind are the best.

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    Thousands of pounds of that stuff every year. Your 60v saw will do fine with .250 and .375 if you use a very sharp triple chip blade. Very sharp any blade but triple chip is best. Positive rake too. Use some sort of saw guide and feed as fast as the saw will allow. Listen to the motor. Slow feed=melting mess. I frequently cut stacks of the stuff 4" thick with a semi dull 18" blade. But the feed is aggressive and the blade has 25 HP behind it. No issue. Holzma beam saw.
    Routing or milling for sure use sharp tools and feed needs to make chips. Whispy crap flying around is a no go. Make as big of a chip as you can. HDPE needs to be cut, not rubbed to size.
    If you keep your HDPE tools separate from other tools you can expect 10s of years between sharpening, or more. Close to 20 on some of the tools loaded on the magazine.

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    Buy it cut to size. I hate cleaning up plastic chips. For any quantity it is not to expensive. I use plastics international in Minnesota (been a while since last order from them) good finish, to size, and you can get on with the job!
    Last edited by ponderingjunkman; 01-11-2020 at 07:18 AM. Reason: Clarify

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    Quote Originally Posted by ponderingjunkman View Post
    Buy it cut to size. I hate cleaning up plastic chips. For any quantity it is not to expensive. I use plastics international in Minnesota (been a while since last order from them) good finish, to size, and you can get on with the job!
    We used to do that until we realized you pay $$$$ just for the cutting, I'd rather keep that money in the business and have something for the lower paid employees to do.

    Sent from my Pixel 3 using Tapatalk

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    Normally I'd agree with as9100d

    But you have to check, this is lifted from a quote I received 8:54 am yesterday

    ================================================== =========================================

    Virgin PTFE Rod

    110mm dia x 1000mm long 1pc. £243.36/m

    110mm dia x 55mm long 28pc. £13.38/pc

    ================================================== =========================================

    To get the 28 pcs I need 1.6 M bar = £389.76

    28 pcs x £13.38 ea = £374.64

    A saving of £14.74 (or at 1.3 $ to the £) = $19.16 ……..with no work and nothing to clear up

    Go figure !

    & FWIW, the above quote was by far the cheapest …..by a large margin.

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    Quote Originally Posted by as9100d View Post
    We used to do that until we realized you pay $$$$ just for the cutting, I'd rather keep that money in the business and have something for the lower paid employees to do.

    Sent from my Pixel 3 using Tapatalk
    I use a supplier (Piedmont Plastics) who will (if you buy a full sheet) cut it into as many pieces as you want for free. Other suppliers charge for cutting sheets down, but it's typically still cheaper than me doing to work.

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    Most everything important has been covered already by previous posters, such as sharp (new) cutting tools, high feed rate, triple-chip saw blade for circular saw (you'll find usable blades at Lowes/Home Depot as "non-ferrous and/or plastic laminate" cutting blades). For HDPE you CAN use even alternate bevel toothed blades, but the triple-chip will give better cut quality. Lower tooth count will keep the heat down. Use a saw guide.

    For routing, I just use standard straight 2-flute carbide bits, and if there is a lot to do, hook up a vacuum to suck up chips, and ideally an air blast to keep things cool and get the chips out of the cut immediately to avoid heat buildup. Use a router guide of some sort if you want straight edges and best control.

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    Two quick thoughts: 1) A worm drive circular saw such as the Skil 77 turns more slowly than a typical "sidewinder" circular saw. 2) A smaller-diameter blade will have a lower cutting speed (Surface Feet Per Minute, aka SFPM) than a larger-diameter blade turning at the same RPM.

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    Sometimes you need to make small cuts with a handheld jigsaw. A saw with blade oscillation is absolutely necessary and works amazingly well.

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    Thank you all. For the advice I also called a local plastic company they told me to use 40-60 teeth blades rip blades of course carbide.

    The guy explained less teeth for more airflow and because the blade size....

    As far as the routing yeah I seen a track saw guide and then seen a router track attachment so I can make the straight cuts so thats what ill use with carbide bit tools. Thanks guys.

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    40 - 60 teeth??

    How big is that saw blade cos that's a lotta teeth, and on your 7 1/4 dia would give a pitch between 0.57'' (40T) & 0.38'' (60T …….which for ''roughing out'' cutting I'd call fine.

    You mileage my vary

    Just a thought


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