[brownp]

My new potting shed is up and functional. One thing we didn't make adequate provision for when we designed it was ventilation. I can already tell that it is going to get too hot in there. In the summer we will be away for an extended period so I need to get some ventilation sorted. I have got an automatic greenhouse vent opener. The best way that I can come up with is to cut an opening section in the polycarbonate window and bolt the opener to it, creating a vent.
Can anyone advise me on the neatest way to cut a square into the 5mm polycarbonate? I was thinking a really fine saw blade might do it but unsure on how to start it off....any thoughts? thanks
Phil

[8doubles]

A fine blade in a electric jigsaw is favourite, drill a pilot hole on the inside of the line to start the saw.

You need to set the speed as slow as possible or the sheet will try to weld together behind the blade. The weld is not strong but is a nuisance best avoided.

Keep the sheet well supported while cutting , if the saw catches and bangs you will crack it for sure !

[brownp]

Thanks, I'll try that

[Annen]

Ooh, you have given me an idea about my potting shed.  It has only one small opening window and it got very hot in there last year.  The big windows only have little bracket things keeping the perspex in, maybe if I put turn buckles on instead I could lift a whole window out when its sunny.  I will have to examine the possibilities.  Thank you!

[Sparkyrog]

best thing to do is take it out and clamp between 2 pieces of wood . you need to take away the flexibility

[Markw]

If you are using a battery jigsaw try to spray the blade with some water when cutting, like as 8doubles has said this helps it from trying to weld it's self back together again.

[grendel]

its also worth putting tape over the cut line as this will stop the foot of the jigsaw marking the polycarbonate.

[archibtbm]

best thing to do is take it out and clamp between 2 pieces of wood . you need to take away the flexibility

I agree with Sparkyrog on this as I cut some recently, clamping it between wood took the bounce out