Cutting and drilling Acrylic 1/4" sheet for windows.

[zz4gta]

How can I get a smooth edge on acrylic and drill for screw holes w/o worrying about the sheet cracking? Any special techniques? Thanks.

[arf145]

I've run a fine flat file lengthwise over the edge to round it out.

[Northeaster]

You can use a belt sander to easily shape / even out the edge, etc.

Have you considered using something like 3M VHB tape, as an adhesive, instaed of drilling / using screws / bolts that will leak later. Also use something like Dow Corning 795 or 791 adhesive sealant to keep the water out.

I redid my deadlights using this method "sexy windows" thread on link below.

Very happy with it. They use the 3M tape to hold big windows in skycrapers, etc.
My old frames were through bolted to the cabin, but the acrlyic was just siliconed to the outside of the frame!!! So, now I have the acrylic sealed to the cabin, with no frame, no holes to leak. I tapered the black Dow 795 sealant along the edges, to give it about a 45 degree taper.


Was not able to upload pics here!!

Dscn0808 - Cruisers & Sailing Photo Gallery

new "sexy" windows - Cruisers & Sailing Forums

HOW TO HAVE SEXY WINDOWS!? - Cruisers & Sailing Forums

[Faster]

Wet sanding after cutting with a fine tooth blade on a table saw works, but is a bit labour intensive. There are special drill bits available for drilling plastics, they are worthwhile picking up, also be sure to drill the hole oversize for the fasteners so that you don't stress the hole during expanion/contraction.

We have also had good luck with Dow Corning 795.

[tommays]

We scrape it by hand with a knife to get a final clear finish

[jarcher]

Originally Posted by Northeaster

Have you considered using something like 3M VHB tape, as an adhesive, instaed of drilling / using screws / bolts that will leak later. Also use something like Dow Corning 795 or 791 adhesive sealant to keep the water out.

Dow 795 and Dow 791 are both silicon based sealents, so if you are planning to seal the acrylic against the fiberglass you may want to consider a different adhesive. As has been discussed here, silicon is bad for fiberglass.

[zz4gta]

How fine should the blade be? I only have a skill saw with a blade I used to put my flooring in. It's fine toothed........for wood.

[jarcher]

Lots of information about 3M VHB Tape here:

http://multimedia.3m.com/mws/mediawe...6EVs6E666666--

[jarcher]

Im in the process of the same job, and I am considering (have not decided yet) using 3M 560 or 540. 3M says:

3M™ Scotch-Seal™ Polyurethane Sealant 540 and 3M™ Scotch-Seal™ Polyurethane Adhesive Sealant 560 are one component, moisture curing products which form permanent elastic bonds. They bond to a wide variety of materials including plastics, FRP, SMC, aluminum, steel, coated metal, and wood.

Here is all the data:

http://multimedia.3m.com/mws/mediawe...6EVs6E666666--

The only catch is I only see 540 on sale on their web site, can't find 560. 3M says that 560 has a tensile strength of 580psi and an elongation before break of > 300%. For windows that might be a good strength, although if you want less than the 540 has 250psi and > 800%.

I can't say I know just how strong a dead light bond should be, hopefully someone who knows will chime in

[tommays]

One problem is that the saw will MELT the plastic as you cut SO you need to keep it a bit wet and work slow

Then you can use a sanding block to clean up the edges