Turning Perspex rod

Hi .
I need to turn some perspex rod to a smaller diameter. Am I likely to hit any problems? Are there different grades of Perspex/Acrylic on the market and is there anywhere I can purchase short lengths such as 100mm. X 15mm ?

Sharp tool fairly high feed rate so you don't overheat and melt things.

College do 6" lengths

**LINK**

J

Mike,

I recently machined some 2" diameter thin walled pipe fittings for a guy who wanted to view the operation of an experimental component and I can honestly say I have had better jobs to do.

The parts had to be machined with a fine feed to ensure a nice clear component and as Jason suggests - it is quite difficult to avoid overheating. I would also suggest plenty of coolant and be careful with the cutting speed. One hazard is that the parts can look ok but if you have tried to machine them too quickly they will crack. I had one example (my first attempt) that looked great but when I held it up to the light it was full of 'silver ribbons' i.e., cracks.

Phil H

Gray

I did some work with perspex in the past - but mostly milling thick blocks to make gas tight boxes. I seem to remember that the cutting fluid used was parafin? I certainly used chloroform for joining - a very nasty substance but very effective on perspex! We had too some special graded finishing polishes for perspex and, with care (and time and effort!), it was possible to restore a superb original material finish to the work. I found it a very rewarding material to work with but hugely - expensive especially in the larger sizes.

Yes your "ramblings" ( huh! - some ramblings!) are always of interest..

Regards

Norman

Edited By NJH on 25/09/2012 23:09:27

Type "perspex rod" into fleabay -

Perspex assemblies are often flame polished using a gas torch. It's particularly useful on sawn edges.

Rod

Many thanks to Rod for the flame idea. I have been faffing about for ages trying to polish the ends of a perpex rod for my optical centre punch (the one that wuz in MEW) half a second in the blow lamp flame and it's as clear as glass .

A slower setting Perspex adhesive can be made by putting small clean chips of Perspex into chloroform and leaving it for a day or two, shaking occasionally. It has filling properties which help.

i found graham meek's replies fascinating and very informative. thank you, graham!

i have wanted to make some bulls eye perspex lenses for 5"g loco lamps, but have put this off due to lack of info how to turn and polish the lenses from clear perspex bar.

any cheap sources of small dia clear perspex rod please?!

cheers,

julian

I use Micro-Mesh to polish the perspex, this little oiler glass was polished inside and out with it and it comes up crystal clear, better than the photo shows

For reasons that escape me we weren't allowed to use chloroform in schools when wishing to bond acrylic. Tensol 12 works equally well but it is best to leave the workshop door open!! Tensol 12 seems to be available on eBay.

Hi Niloch

I have a suspicion that chloroform may be carcinogenic and, even if it isn't, you don't want to breathe the fumes! See here in the safety section. Better to use the correct perspex adhesive. Note also its gradual conversion to phosgene when stored in the presence of oxygen.

On second thoughts - get someone else to stick your perspex bits together!

Norman

Edited By NJH on 28/09/2012 12:25:07

I do a fair bit of Acrylic fabrication, in particular glueing acrylic sheet. I would be very careful about using Chloroform in a small home workshop... there is a very real danger of anaesthetising yourself!

I normally use Tesnol 12, it works very well as a solvent glue, but it is nasty stuff and you need to have good ventilation, and use gloves to avoid skin contact. If you look at the product data safety sheet **LINK** you will see that the main two ingredients are Dichloromethane (often used as paint stripper) and Methyl Methacrylate which is the monomer of the acrylic.

Please be careful with any of these acrylic solvent glues, they are all fairly harmful.

Chris

One more point I meant to make: The Dichloromethane in the Tensol 12 evaporates very quickly, and seems to diffuse though some plastics. I use a metal container and keep the lid closed all the time except when removing some with a syringe. Some people recommend keeping it in a fridge and using it whilst cold to reduce evaporation. If you are not careful about evaporation then your expensive bottle of Tensol 12 will quickly become too viscous to use easily, and eventually will turn into a solid block.... don't ask me how I know!

Chris

Edited By Chris Courtney on 28/09/2012 12:51:05

Wet and dry used wet followed by Brasso.

regards David

...and if that isn't shiny enough, finish off with toothpaste.

As to solvent welding, a pal of mine stuck some Perspex together for me, and said he'd used ether. if my memory served me right. Or maybe I'm getting my anaesthetics confused.

Andy

What was the chemical in Airfix glue before they changed to the modern sweet-smelling (ester based?) alternative?

Neil

Just a few observations to add the excellent info above. I CNC-route sheets of Perspex for a Chandelier-maker. We rapidly discovered the difference between Cast and Extruded grades. I machine using large dia cove cutters at 18000rpm to sculpt the surface of 15mm and 20mm thick sheets. The cast grade is decidedly easier as it doesn't weld to the cutter, but comes off in large curled snowflakes. The sheet, which has had one entire face removed in the process, stays flat, which is not true for the Extruded. I imagine that the extruded has stresses built-in which become unbalanced once cut.

I also machine one side off of 30mm rods from time to time and these machine beautifully using the same settings.

If these experiences have any relevance here then it might be to suggest that very high speeds in the lathe would be worth trying, along with a range of feeds and DoCs.

Hi Andyf - Ether is comercial cloriform - I used to buy it from the highstreet chemest for use in small areo engines ( Ether/CasterOil/Parafin) combination - It also glued together the perspex canopies on the models - Disolve slithers of perspex in ether to make sticky goo and then use in well vented (outside) area. - Dont know if Ether as still available (may be not due to some Health and Safety reg.!!!

I'm not sure that's quite right; chloroform is CHCl₃ (carbon, hydrogen and chlorine). "Ethers" are a class of straightforward hydrocarbons (just carbon, hydrogen and oxygen). The one which was once used as an anaesthetic is diethyl ether, CH₃CH₂-O-CH₂CH₃ , but I don't know if this is the particular ether my pal used to weld Perspex for me. I doubt if you can buy it at the local chemist now; long gone are the days when you could buy the ingredients for gunpowder at the local Boots.

Andy