cutting plexiglass??

[eh?]

Anyone have any ideas how to get a good smooth hole for fans in the plexiglass

[Rob Cork]

I used my dremel to cut the hole in my top window for my blowhole fan. I cut out most of the material inside the hole with one of the cutoff wheels, and then sanded down to the line I had marked using one of the 'sanding drums' (see pic). I just used a low speed setting on the dremel so it didn't melt the perspex, and went nice and slowly. The dremel eats away at the perspex so easily you can get a nice smooth round hole in no time at all.

[eh?]

so use the low setting so it doesn't melt???

[The Overclocker]

yeh, it melts. if you dont have a speed setting (like me) then dont work, just pic the melted bits off, the cutting will look a bit rough but sandpaper will sort it out

[fuzzba11]

I found going in the opposite direction to the sander's spin at 30k rpm worked well, and in shortish bursts. Careful, if it catches the plastic it will take want to burrow, so keep a strong hold...

[bdf24]

I found that to work great as well by going in the opposite direction of the dremel. Seems to leave less mess behind. Although if it does leave melted chunks behind they do break off very easily. Once you get a fan guard on there you'll never notice it anyway.

[cool_hand_joe13]

:D You can also use a hole saw as I did.Just find out the hole size a cut.

[Kingslayer]

Use a hole saw, it works and makes better circles. BUT. You have to brace the plexi when you use it or the hole saw may shatter it. Get some think styrofoam, I mean like 2 or 3 inches thick, and lay the plexi in it and then cut. Use the smallest drill bit and fastest drill you have to cut the pilot hole for the center bit of the hole saw.