Cutting polycarbonate sheet 10mm

Twinwall:
What best to use, if possible I dont want to buy as it is a one off job. from a 2 metre sheet I want to cut 3 x2x2 foot squares. Tools at hand: Blunt tenon saw, angle grinder, normal saws, circular saw 48 tooth, Multi tool, stanley knife,jig saw with various blades.
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On 10/10/2017 15:19, ss wrote:

Power hacksaw blade, with a temporary handle made from duct tape.
http://www.ebay.co.uk/itm/like/371457450247?chn=ps&dispItem=1&adgroupidB200108823&rlsatarget=pla-327277252998&abcId 28946&adtype=pla&merchantidr59694&poi=&googleloc45579&device=c&campaignid…6856138&crdt=0
Stiffer and stronger than a normal hacksaw blade. Fine tooth panel saw will work, the problem with a tenon saw is that you will have to maintain a shallow angle to clear the spine.
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On 10/10/17 15:35, newshound wrote:

I don't know if polycarbonate has similar cutting properties to acrylic but I thought I'd mention that, when cutting Perspex, keeping the cut cool by moving the saw slowly gives a huge improvement IMO.
Nick
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On 10/10/2017 20:44, Nick Odell wrote:

Very true. You can sometimes get away with a slow (powered) jigsaw. IME a circular saw is too fast. Not sure about multi tools, may be OK if you keep the pressure down but cut rate will be slow (although of course they are unsurpassed for cutting, say, a small rectangular hole in the middle of a sheet).
I don't have much experience with twinwall. On single polycarbonate and thin acrylic, deep scoring with a stanley knife and snapping can work, but I have had cracks divert from the chosen line. If you have a small protrusion to be removed from the required line, scoring and then snapping with a pincers or pliers can work well.
You want a sharp saw blade, not a blunt one like the OP says he has.
For trimming down to size, a rasp or surform is best. Angle grinder (with sanding disk, not grinding one) may work but you need a very light touch.
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On 10/10/2017 20:57, newshound wrote:

Yes, but not nice for a long straight cut. If you have to do it use a steel guide.

I tried a grinder with a 1mm disk and it overheated the work. It might be OK if you took it very steady though.
Bill
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Bill Wright used his keyboard to write :

Just the surface friction from a fast moving disc, without doing any cutting, will be enough to melt it.
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On 11/10/2017 11:02, Harry Bloomfield wrote:

The stuff forms a hard bead though which is difficult to get off.
Bill
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Indeed. I cut quite a lot of the stuff last year, and it takes time, but my method is Stanley knife first, then pencil in the knife groove (easier to see), then cut slowly with a hand saw. Fine toothed tenon saw is good but, as has been said, watch the spine. Finally, a quick up and down with a surform to remove any bits, and any bead as Bill said. Easy to form that bead just with a hand saw. My sheet wasn't 10mm thick, though.
--
Graeme

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wrote:

And that can still be improved...
In my experience with acrylic of 8mm or so: Using a large table saw with TCT blades, going slow still left a raised/melted burr. A faster second pass taking off a millimeter or less gave a good edge. I think that because very little material is removed, there is less heat involved.
I have also used compressed air as a "coolant" when sanding edges or drilling.
Thomas Prufer
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On Wed, 11 Oct 2017 08:44:02 +0200

Multiple shallow cuts?
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On Tue, 10 Oct 2017 20:44:39 +0100, Nick Odell
experience into a viable and meaningful comprehension...

I was cutting some perspex last night using a fine toothed jigsaw blade on slowest setting and the material just welded itself together at the back of the blade. Fortunately accuracy wasn't essential, but drilling accuracy was, and a set of Poundland wood drills used at high speed worked very well.
--

Graham.
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On Wednesday, 11 October 2017 11:30:49 UTC+1, Graham. wrote:

Drill bits are prone to crack acrylic. I prefer to use a stone in a dremel, it mostly melts the hole. No risk of breakage, just take care to avoid the hole wandering.
NT
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On Wed, 11 Oct 2017 05:03:33 -0700 (PDT) snipped-for-privacy@gmail.com wrote:

Using an ordinary drill in reverse rotation might do the trick, or maybe grind a bit to have negative tip clearance, so the actual "cutting" is friction but the flute still clears the waste material. I'm almost inclined to go do an experiment, but there's so much that actually /needs/ doing that I shouldn't put off any longer.
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On Wed, 11 Oct 2017 15:55:28 +0100, Rob Morley wrote:

It'd need a shallow pit to start without wandering, then a sharp masonary bit will scrape the material rather than cut it. At work, we had some backed off bits of about 80 - 85 deg. for material that would crack with a standard bit.
As an aside, when I wanted a small scraper, I slowly ground a square file (about 8 - 10mm) with 2 acute angles, 2 obtuse angles and a small chisel tip. The angles are all sharp and the obtuse ones are ideal for hard plastics. It's worth using a good file - not worn out - as then another file isn't needed for a lot of jobs.
--
Peter.
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I have occasionally used a circular saw. Nasty dust so best done outdoors. I have also used a jigsaw with a fine tooth blade for cutting PIR foam backed plasterboard.
If you do use a handsaw on thick foam it is worth finding an offcut with a known 90 deg. corner to use as a saw gauge.
--
Tim Lamb

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Oops! I see the OP was about polycarbonate!

--
Tim Lamb

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On 10/10/2017 15:19, ss wrote:

You need some sacrificial boards. Hardboard, ply, whatever. Clamp the boards on both sides of the sheet. Transfer the cutting line to the top board. Cut with a fine toothed blade (a steel cutting blade) in a jigsaw, with the saw set to a slow speed. Slow speed is important. You are cutting through both boards and the sheet. Ideally you should have the work on two Workmates (etc) close together with a narrow space in between them. As an alternative I made a cutting board for this job. It was a stout piece of 1" multiply with a slot cut in it. After cutting hand sand the edge.
Bill
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On Tuesday, 10 October 2017 15:19:08 UTC+1, ss wrote:

Stanley knife.
NT
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On 11/10/2017 02:04, snipped-for-privacy@gmail.com wrote:

Assuming this is a 10mm thick sheet, I think you'll be a long time with your Stanley knife before cutting right through?
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On Wednesday, 11 October 2017 03:03:12 UTC+1, Fredxxx wrote:

He said it's twinwall. Most of the replies have been more suited to solid sheet, and 10mm solid polycarb is not really a diy item.
NT
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