Perspex Acrylic Question

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November X-ray

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Does anyone have a good source for large cube acrylic that is reasonably priced? I have made a few turners cubes out of aluminum and wood before but now I want to try plastic. What is the best way to polish acrylic after cutting? Seems like I have read somewhere that a flame from a MAPP Gas Torch will bring clarity back to acrylic.

Thanks!!
 
November X-ray said:
Does anyone have a good source for large cube acrylic that is reasonably priced? I have made a few turners cubes out of aluminum and wood before but now I want to try plastic. What is the best way to polish acrylic after cutting? Seems like I have read somewhere that a flame from a MAPP Gas Torch will bring clarity back to acrylic.

Thanks!!
Click to expand...

MSC but pricey;
http://www1.mscdirect.com/eCommerce...yaanc?refinement=4290221744&searchandizedOk=Y

McMaster Carr looks better already a cube;
http://www.mcmaster.com/#acrylic-bar-stock/=hjmek5
 
Not sure where you are located, but in California we have a chain called "Tap Plastics". They also have a website (http://www.tapplastics.com/). Not sure how prices compare, but they have a good selection.

I have heard you can solvent weld sheets to build up thicker sheet, but I have not tried it myself.

One thing about acrylic is that it is very brittle. Be very careful on when cutting to corners (light cuts, lubricant, sharp cutter). I made some prototype parts out of some 1" acrylic I had lying around, and I managed to snap of several of the outside corners. Lubricant helps because the stuff has really poor heat transfer, so if you are not careful you end up with a ball of molten plastic encasing your end mill.
 
if it were me I'd look at Lexan insted of Acrylic, it machines better, Lasts longer and less brittle
 
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I made a bunch of duck calls about 15yrs ago out of several different colors of acrylic..

it is not easy material to work with it likes to fracture when it gets warm, not hot, just warm, I used flood coolant in a cnc lathe to turn it, and flood coolant to drill it, also had the coolant mixed thick....


I polished them with 1000grit sandpaper then a white scotchbrite pad using wd-40 the whole time..
 
Make sure that you use cutters AND DRILLS with ZERO rake angle,or your acrylic will shatter for sure. Grind a vertical flat spot on the leading edges of any drill bits you use in the acrylic. If you don't,the drill will grab as it exits the plastic,and shatter it to pieces.

I ran into some guys who were making expensive acrylic speaker cabinets. They said they wouldn't cost as much,except for all the sheets of acrylic they broke trying to drill holes. I drew them a picture of how to grind their drills. This also is imperative for drills to be used on sheet metal AND BRASS. Things can get dangerous in a hurry when breaking through either of these materials,even if they are clamped,the brass can suck right up onto the drill.
 
george wilson said:
Make sure that you use cutters AND DRILLS with ZERO rake angle,or your acrylic will shatter for sure. Grind a vertical flat spot on the leading edges of any drill bits you use in the acrylic. If you don't,the drill will grab as it exits the plastic,and shatter it to pieces.

I ran into some guys who were making expensive acrylic speaker cabinets. They said they wouldn't cost as much,except for all the sheets of acrylic they broke trying to drill holes. I drew them a picture of how to grind their drills. This also is imperative for drills to be used on sheet metal AND BRASS. Things can get dangerous in a hurry when breaking through either of these materials,even if they are clamped,the brass can suck right up onto the drill.
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George : I'd love to see a sketch of how to regrind bits, I use a ton of Plastic and Brass
 
You might try Boedeker Plastics. Good supplier. Good technical resource online as well as great inventory. Talk to Marvin (owner) if he's still taking sales calls. They've grown quite a bit the last few years.

http://www.boedeker.com/
 
I don't know how to post sketches. All you do is get the corners of your grinding wheel sharp and square. Hold the drill bit going straight into the grinding wheel,with a cutting edge rotated vertical. Then,touch it to the corner of the wheel,so the corner of the wheel nests right in the web of the drill. Grind about 1/32" of a flat spot on the cutting edge of the drill. Rotate the drill 180º and grind the other edge exactly like the first as possible. Then,the drill will not have the spiral going all the way to the cutting edge,and the drill will not suck through the plastic,brass,or sheet metal just as it is breaking through. The drill is scrapping rather than cutting its way through.

This doesn't seem to affect the efficiency of the drill bit as long as you are using a machine like a drill press or lathe to run it. Probably would slow down the drilling with a hand held electric drill. I just use my bits for everything,ground for plastic or not. They still work fine.

They used to make drills for brass. I have some old ones. They are made just like spiral drills,except without the flutes going in a spiral. They are straight like a straight flute reamer. You want to emulate just the tip end of these drills with your grinding. Just grind enough vertical on them as the maximum amount the drill will advance into the work in ONE revolution. The spiral part will not engage the material if you do that. I have ground off much less than 1/32" on some of my drills,particularly the smaller sizes,where you CAN'T grind off to much,anyway.
 
Quote Professor:
I have polished acrylic lenses using the same general approach as brucer. I used progressively finer wet or dry sandpaper lubricating with water, then I used automotive polishing compound and a rag to buff out the haze. They turned out quite satisfactory.
I tried a buffing wheel but couldn't control the heat that was generated to get a clear surface. I also tried a quick brush-over with a propane torch flame. It made the surface clear but introduced distortions to the lens.

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I haven't tried it yet, but "chemical polishing" is supposed to work as a final step - suspend the piece in a vapour of a suitable solvent, e.g. methylene chloride (in the UK, a lot of paint/varnish strippers contain it) and the surface melts and reflows - I've been intending to try it on a scratched pair of Squinting Glasses, once I do I'll report back!

Dave H. (the other one)
 
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