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Discussion Starter · #1 ·
Most of us like to take old bits n pieces and turn them into cool stuff for use on our Vehicles, among other things, this is one of those tricks I learned a while back and have used a few times over the years,
When cutting up old OEM dash clusters and using the bits left over in my specials I found that salvaged domed lenses made the resulting guages look really special, not to mention that in Australia where I did most of my modification work as a young'in flat lenses are illegal (No Really, helf'n safety gone mad) One day the sizes didn't line up, so no legal means to getting the guages I wanted, well not on my budget...My Dad suggested "So you've built a whole car and you're gonna let a detail like flat guage glasses stop you driving it on the road, just work out how to make it... How hard could it be?...After a little investigation and experimentation I now make lenses for any guage, not to mention all the other things that can be made in similar ways.

The process isn't limited to round guages but for simplicity's sake I am going to describe the process using a hole saw to make the former if you want a different shape simply cut the former by other means and go with any shape you can imagine.

1, Get three square pieces of any metal plate around 6mm or 1/4" thick and each big enough to leave 12mm or 1/2" all round the lens, so a three inch square plate for a 2 inch diameter lens
2, stack the three plates up and drill a 6mm or 1/4" hole in each of the corners,
3, If you've got a lathe, set two of the plates up in a four jaw chuck and bore a hole through the face the same diameter as the inside diameter of the bezel ring, If you've not got a lathe, just cut the hole with a hole saw, make sure you bevel the edges nicely, it helps.
4, take the third plate and drill a hole through it to hook it up to a vacuum/pressure source, I usually thread the hole and fit a brass hose barb, plastic hose barbs don't work so well, in something this small your vacuum/pressure source could just be a large plastic syringe even a bicycle pump will be fine,
5, cut a disc out of 1-2mm perspex, acrylic, plexiglass or whatever else you call this kind of plastic sheet I don't use lexan as it is fiddly on temperatures and water content when heat forming. (Thicker is possible but learn on the thin stuff first, it's cheaper, thicker pieces just take a little longer to heat.
6, clamp all the pieces together, add a little gasket between the middle plate and the plate with the vacuum source hole, I usually just cut a gasket out of an old cereal packet, any old card or heavy paper will do. sometimes a gasket between the former plates and the formed plastic is helpful as it protects the plastic if it proves to be a bit brittle.
7, pop the whole thing into a cold fan forced oven. set the oven to 150 degrees Celcius
8, wearing gloves and making sure not to touch the plastis at any time , as the plastic will mark, connect the syringe to the vacuum hole and suck some air out or blow some into the chamber behind the plastic, just enough to start doming the plastic, depending on whether you blow or suck the ar it'll bubble out or in,
9, when you have the dome where you want it hold the pressure constant and plunge it into cold water and hold it there for three to five minutes, less for thinner plastics, more for thicker plastics.

If the plastic bubbles up into a nasty toffe like mess, it's either too hot or potentially there is water contamination in the plastic which can be readily dried out, just place the next one in the oven at 90-100 C for an hour or so before increasing the temperature to the 150 C you need for forming.

And there you have it new domed lens' for any guage costing pennies + a little work.

Next time I do one I'll add some Pics.

I hope this is of value to someone out there,
 

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I think I understand, but pics would be great, please?
 

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Discussion Starter · #3 ·
Will do, next time I blow some acrylic, I'm in the middle of downsizing my workshop and building a huge vacuum plastic forming machine which is sort of the same process, just in a much bigger scale, but I need some bubbles for another project,

Sadly my testosterone points are going to drop a few levels as the bubbles I'm making are for my little girl so will be heart shaped LOL probably pink and glittery by the time they're finished too.

Rick
 

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like this, I want to do some blown windows on my van and I have read up on how to do but would love some pics of bigger stuff please
 
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