How to cut / trim clear perspex?

Skylark

Skylark

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I've just had a new chartplotter fitted within the steering pedestal. The drop-down, clear perspex engine control and instrument panel weather cover now requires trimming on one side only to accomodate the slightly raised backing plate of the new plotter.

The cover is 6mm clear perspex. I need to trim 10mm off the bottom edge of one of the side piece. An approx 7 inch long required cut.

The side piece measures 2 inch by the 7 inch required cut so there's not a lot of material to grip / hold firm. The major dimensions of the cover are approx 18 x 10 inches so it will be ackward to hold.

This is the (upside down) section |_____| I need to cut 10mm off one of the verticle edges, 7 inches long, if this helps you to visualise it.

I'm very mindful that perspect is very brittle and hence there's a risk of cracking.

Any useful suggestions how to take this cut and live happily ever after?

Many thanks
 
I've cut perspex by clamping it between two sheets of ply and then sawing very gently. Then sand the edge carefully.
 
Frequently I have a problem, which I am contemplating, and lo and behold someone on the forum raises that very same problem - thanks.
 
A router would be the best bet but be careful it's the easiest way I know to destroy a piece of work. Make several passes cutting only a small amount away at a time. Clamp a straight edge to the perspex as a guide. I had washboards made and the chap there used a table saw not at all sure what blade he had in it though so thats another way to go..

Also make sure the perspex is warm. I made the mistake of drilling some when temperature was around 5 degrees c. If you get it to room temperature it will be less likely to chip.
 
If it is thin max 2mm, you can scratch it and break on the scratchline.
Or you can use a elektrick jigsaw with a adjustable speed.
Use a new metalsaw with fine teeth, and on low speed, otherwise it
melts together after your saw. Don't puse to hard, you are not in a hurry.
I have done this many times on 5 to 12mm thick perspex.
 
Most secondary school design & technology departments now have a laser cutter suitable for cutting acrylic (perspex). If you can make contact with them I'm sure they would oblige especially if making a donation to school funds. etc
 
Can you not make a new one out of a fresh piece of perspex.

I add a line of 3 in 1 oil along the line to cut and no longer have problems with melting.
 
I use my bandsaw for cutting and my fixed sander for final shaping.A jigsaw is useless because the heat generated melts the plastic into the cut.
 
Acrylic sheet like Perspex should be cut with an UNSET saw. Failing that a fine tooth hacksaw to minimise heat build up, which is the major cause of stress cracking
 
Cut with a saw as described above BUT finish the last few millimetres by planing with a very sharp plane. This prevents small cracks appearing at the edge at a later date due to thermal stresses from sawing.
 
Job Done

Many thanks to all for such helpful advice.

I did the job on Sunday and I'm delighted with the result.

As always, preparation is 90% of the time taken but good preparation pays handsomely.

First, I scored both sides using a stanley knife blade.

Next, cut two pieces of 20mm thick hardwood to sandwich the piece to be removed. Held in place firmly using two G-clamps.

I used a Dremmel with 25mm dia x 0.5mm cutting disc. Butted-up to the edge of the hardwood.

Took my time to avoid any excessive heat build up.

With the piece fairly easily removed, sanded the edge with two grades of paper, finally wet&dry with automotive paint cutting compound. The new edge now has a near-mirrow finish.

I was not looking forward to the job, due to the risk of cracking, but using advise from the forum enabled me to it very easily.

Thanks.
 
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