How does one make a clear plastic dial cover? I have a little knowledge of vacuum forming and PETG plastic, but I do not know how to make the mold. I have formed a few covers with a heat gun, but only very simple ones with small bends. Anything that required a 90 degree or so bend in the plastic has evaded me. So, I guess the solution is to start to vacuum or perhaps a different plastic. Plastics that I have used return to flat if they aren't held in place until they cool. Anyone know?

Ed

I have always used a coping saw to cut a mold from plywood. Use both pieces (the cut out, and the piece you cut from). Put the plastic in the middle like a sandwich, heat, then push down to form.

Peter

Haven't tried it that way. I have a jigsaw, but not a coping saw. I cannot save both pieces after I drill a hole for the blade. I suppose I could cut once for the outside and another piece of wood for the inside. How do you get the plastic flange to form? Most require a 90 turn twice. The second of course for the flange.

I have a small heater/vacuum made for the purpose, but it is too small for all but the smallest radio dials. Even then, no mold is available to form around.

Ed

There was a guy on Youtube that demonstrated how to make them and it looked suprisingly simple. If you do a search I am sure you will find it.

Eddie Brimer used to have photos of the process on a web page. Others have described the process as well. The two pieces of the mold need to have the right amount of clearance between them and the temperature you heat the material to is also important.

The real trick to making it work right the first time and every time is in the material you use. Vivak .020 gives the best results for home molding of dial covers. Anything thicker or thinner is more difficult.

I believe you can fill in the cut made to pass the saw blade from the outside to the center with epoxy or Bondo, then sand it smooth since it will be outside the viewing area of the completed window.

Here is the link to the Youtube video:

http://www.youtube.com/watch?v=laOsR8fR ... e=youtu.be

Thanks, that looks pretty good. You will notice that cover is round. I have tried that with round and square dial covers. The square cover does not work well with this method.........at least for me. There has to be a better way to make the square cover.

Ed

I read a post here sometime back, from a member who would go shopping at a hardware store, looking at the bulbous clear plastic covers over carded merchandise. There are square, rectangular, and round ones, domed and flat. He was buying for the plastic cover, to use as a dial cover.

I have made many.
I use Masonite.
I place the Masonite behind or in front of the opening and draw the opening's shape on it.

I use a piece an inch or two larger than the opening.

Then I use a scroll saw and cut in from the outer edge to reach the inner shape line I drew.
Then I cut the inner shape out.

That makes an inner-shape and an outer collar with a slit in it that I cut from the edge to get in there.
I use duct tape to cover the slit in the collar and hold the collar together better.

Then I use a rough file or Surform tool to soften the edges of the inner form and the collar.
The inner form will then fit very loosely inside the collar.

Then I use a piece of 15-20mil Polycarbonate plastic (some guys use PET plastic) or such about an inch or so wider all around than the inner form and lay it over the inner form and put it in the toaster oven.
When hot enough the plastic will start to droop down over the edges of the inner form.

At that point I open the toaster oven and place the outer collar firmly down over the top which helps shape the edges more distinctly.
It cools in a moment or two.

Here's an easy little one I made for my RCA 5X:

Could you post a picture of the masonite piece that you have cut out? A picture says a thousand words. Thanks.

Thanks to everyone for all of the good information. I tried using packing plastic........one time. The piece I used started shriveling immediately and ended up in a little useless ball. After that, I just bought plastic. If one knew the difference between the two kinds, I am sure that using scrap plastic would work.

I am going to try the two piece method mentioned, but I am not sure how to form the flange. Maybe that will become apparent when I try. I think one problem I have had is that I have .020 plastic and it may be too thick.


Ed

Okay, I added images of a couple of the typical Masonite templates I made in my post above.

Hey thanks for taking the time out to post the picture, that was a big help at least to me!

pbpix,
This looks like fun. I may give it a try. But where do you get the PETG plastic sheets from?

I'm actually using 15mil or maybe 20mil polycarbonate which I bought by the sheet about 25x30" I think for $15-20 bucks.
I bought it locally. They also sell PET plastic:
http://www.acmeplastics.com/index.html

I'm sure you can find a plastic supplier near you or Google it to buy on line or try hobby stores.

I use this 3/8" Masonite and it's about the right thickness for almost every dial cover I've ever made.
But when I need it a little thicker I set the Masonite template up on some coins ... like maybe several stacks of 1 or 2, maybe 3 quarters. Then I place the plastic over it and put it in the toaster oven to melt. Then the sides droop down over the Masonite plus the height of the spacer coins below it.

So ... I've been thinking of easier ways to make these templates.
Masonite or plywood requires a scroll saw or such. That's a lot like work.

Perhaps something thinner but stiff that you can cut out with shears or tin-snips.

If you cut it out of some stiff cardboard or better yet a sheet of aluminum that you can cut with tin-snips, you can then simply place it on top of a piece of 3/8" thick wood or any kind of temporary spacer under the template to give you the proper thickness of the dial window.

Any other clever thoughts?

Well, I tried it. It took two tries to get something useful. First time, I went 3 minutes at 300 degrees and bubbles formed in the plastic. The second time I went 2 minutes at 300 degrees and it worked pretty good, but the end result is not as good as the photos above. My cover has a small buckle near the middle where the plastic did not cooperate, but it can only be seen from a side angle. I think with a few tries, I will have it down pat. Thanks for the advice.

Ed

The way Peter does it works quite well. However your results will vary depending on your plastic and, of course, your skill level. You may destroy the first try or so.

I tried it again with a scroll saw and that makes a difference. I made another dial cover today for an RCA and while the flange is wrinkled, the face was beautiful. The flange worked and cannot be seen. Very pleased to have learned this method. Thanks.

Ed

Here is my 1st attempt from some plastic packaging I found layin around. I used a piece of cardboard for the template, cutting the template with an X-Acto knife. Supporting it with a couple 2 by 4 blocks.
Then used a heat gun and a couple sockets to weigh it down a little (we don't have a toaster oven)
I thought it came out OK for a 1st try. Would really like to find some sheets of the right material u guys are
using locally but not lookin good so far.

Detrola 342 Template
http://db.tt/t7jqPx0l

after heating it up
http://db.tt/4L1oEId9

next to the original
http://db.tt/dbIhJy0b