Acrylic Case Cover Mini Tutorial

[thebes]

Ok, as promised heres a pic of the finished acrylic case cover for my Scott 299.

As previously discussed in this Section my first attempt was a dismal failure, but thanks to some folks here (especially Michael), a handbook, and some patience, this one turned out pretty good.

For those of you who would like to do something similar heres some pointers:

Use at least ¼ inch thick stock and leave the protective plastic on until the final steps.

If its going to be used for a tube amp lift the height of the top of the case at least a couple of inches so heat wont warp the acrylic (it has a 180 to 200 degree melting point)

If you can use the scoring method it will give you cleaner breaks then sawing. To do this go to Home Depot buy a fixed blade utility knife and a plastic scoring blade (its the one with a funny looking hook on it. Cost for both is about $6 or $7.Measure, draw your cut line and place a ruler or any other straight piece of metal or wood next to the cut line. Very lightly score the plastic protective wrap. Draw the edging blade towards you very carefully. Continue slowly to score the plastic until you have a deep groove-at least a dozen times. Place the piece with the cut line directly over a broom handle or a ¾ inch wooden dowel. Place hand pressure on both sides until it snaps apart. This method will work for parts down to about two inches in width.

If youre going to saw the acrylic a table saw is the best way to go. What is very important is to use a blade with a lot of teeth in it. This prevents splitting and cracking. The one I have has 34 teeth and 40 teeth are recommended. Cut at an even pace but not too slowly or you will melt some of the plastic

Next step is to use a scrapper or sanding to even the cut lines and eliminate most of the saw blade parts.

At this point if you are going to put air holes or vents in the top piece, do it before you glue. For holes I designed a template using some graph paper and a simple protractor. Tape to top of plastic and drill. When drilling you need to clamp the piece and go fairly slowly, especially when you are about to break through. Use a bit designed for plastics. Too much pressure and you will chip the backside of the hole. If youve got a router this is probably a much simpler process. If youre using a hand drill practice quite a bit before you do this.

Now we get to glue it together and for this you should make some specialty purchases. What you want is Weld On #3 acrylic glue which is water soluble for easy clean up. You also need a small squeeze bottle with a very fine needle on the end of it.

Using these tools do a practice gluing before the final gluing.

Ok, carefully remove the plastic covering and then pull a drawer out of a dresser or cabinet. Tightly run some masking tape down a right angle seam at the bottom of the drawer and this will give you a perfect edge for aligning the pieces. Do a dry run and check for gaps between the pieces and scrape and sand to get the pieces as even as possible. This type of glue acts by osmosis and when applied slides in between the pieces to create a finished seam.

Only do one edge at a time. Lay the biggest piece in the drawer up against the taped edge. Place a shorter piece on top and double check the alignment. Run the syringe carefully down the seam from the inside of the seam. You will see the seam fill with the glue. Immediately go back over the parts where the color in the gap is lighter. These are parts that are not fully filled. Wait 10 minutes and glue another piece until your done.

Pour leftover glue back into can and wash out squeeze bottle and syringe right away.

Wait at least an hour and then remove any glue that didnt go where you want it with a soft cloth and some mineral spirits (gentle rubbing with a fingernail will help the spirits along).

Finally flaming. Flaming removes all the dullness from the cut edges and restores the plastics transparency. If youve got a plastics shop in the area take it to them. They use a clean burning torch (hydrogen/oxygen). If youre going to use a handheld propane torch you want to let it burn for a minute or two and then turn it down about as low as it will go. Make one, and only one, pass down the edge at 3 to 4inches a second, and then let it cool. If it needs more work, make another pass after its cool. If you make several passes at once the finished product will have bubbles and runs in it. Practice this first on some scrap.

Clean with soap and water, dry and youre done. Oh, dont use ammoniated cleaners it will turn the acrylic yellow over time.

If you dont have a plastics shop in your town one good online source is www.craftics.com

[thebes]

Here's one of the case from the rear.

[Marvel]

Nice work. Something you might add to the tutorial -- When drilling through the acrylic (or other fragile/brittle material) you can sandwich it between two piecs of plywood. Use clamps to keep the pieces tightly together. If you do this right, the acrylic will just be a part of what you are drilling. Who cares if the wood splits out on the bottom.

The only catch is you would use a lot of wood if you were making a bunch of these, and on a large piece, you will need clamps to reach the middle of the work so it is held tightly together.

Marvel

[WMcD]

Oooo, Very Pretty.

Gosh, to think that when these amps were originally made, covers were used to cover them up. Now they're works of industrial art.

Thanks for the show and tell.

Along the lines of preventing chip out when drilling. From time to time I use a spade bit or hole saw on plywood to make big holes. Some just for holes and some just as rounded corners for using a jig saw to take out a rectangle.

The chip out is almost never at the top side, only the bottom.

These bits make a pilot hole which gets through before the circumfrence cutter. The cutting edges at the circumfrence will tear out the bottom surface.

The solution is to just drill enough so the pilot hole is established, then turn over the piece and drill through from the other side.

This technique might be used with other bits too, like a classic twist drill - - though I understand there are special bits for plastic.

Say your target is a 1/2 inch hole. Make a pilot hole with a 1/16th inch bit all the way through. Then enlarge it half way through with a 1/2 inch bit, and then complete it from the other side with the 1/2 inch bit.

Best,

Gil

[michael hurd]

Thanks for the kudos, thebes! Looks nice! I found that when drilling either the 1/2" Acrylite sheet, or thin lexan, turning the bit at a high rate of speed resulted in the cleanest holes. It is almost like melting it's way through. If you turn the bit too slow, it tends to rip through the bottom edge, causing a chip.

I had heard that brad point bits work better, but I have not found this to be true. Cutting the 1/2" thick acrylite with a jigsaw was a total mess, it just melted back together, even after drilling 1/8" holes about every 1/8" around the perimeter of a 7" diameter hole.

[thebes]

I couldn't of done it without you Mike. Thanks again.

I'm using a bit specifically labelled as for plastic and at the highest rotation my drill press allows. Only had a couple of cracks and it was from bearing down to hard right before the bit broke through.