Cutting 3mm thick 200mm dia extruded acrylic tube

I'm not a model engineer.

I have a 150mm long, 3mm thick-wall, 200mm dia extruded acrylic tube.

I want to cut out of it 3 pieces 15mm long.

I don't think I have much option than marking it out as best I can and using a hand/hacksaw.

Unless anyone knows of a more ingenious way that I could knock-up.

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Actually, I wonder if I can put the tube on a flat surface end down (of course). I cut out a 15mm high block of wood. Then I get my juniour hacksaw and rest the blade on the wood block. Then cut, every so ofter turning the tube untill I've cut through it all.

That's my best idea.

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On or around Thu, 7 Aug 2008 19:37:51 +0100, "Rich" enlightened us thusly:

bandsaw, I'd think, if you know of one big enough. It depends on what accuracy you want.

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Austin Shackles

I think if I am prepared to spend a little money a tile cutter has been known to work:

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With those dimensions I'd use a grown up hacksaw rather than a junior. Two

15 mm blocks, one each end of the blade to set the height, connected together in a bigger jig which supports the frame and holds the whole lot parallel to your flat surface. Or just make a hacksaw-shaped "frame" in 15 mm timber / ply and screw a hacksaw blade to it.

The other way to cut acrylic sheet is to scribe and snap. With only 3 mm wall you could perhaps score a sharp V-groove almost all of the way through with a suitable tool supported at the right height by the same sort of method. I think I'd try to clamp the tube down to your base plate perhaps with a length of studding. You could cut a 200 mm dia circle in (say) 18 mm plywood to fit the bore, and screw/glue that to the baseboard to stop the tube moving around when you are cutting.

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Make a hand lathe.

Use two rollers (broom stick tube will work) mounted in blocks and locate the tube on those with a keep block at each end.

Use a ground bit of hacksaw in a block as the tool. If you support this between two guides, so much the better.

press the tool against the tube with one hand and rotate the tube with the other.

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Drop around to a machine shop with a box of donuts, or other appropratie local treat in hand, and ask the guy there if you could get a job done quickly.

Offer to pay cash, too. If he takes the cash, so be it, but, in my experience, small jobs that take less than a few minutes, and are offered to be payed for (and do expect to pay, hoping otherwise!) are often gratis. The treats are for a thank you!

Or hook up with someone local that has a lathe.

I'd estimate the job at about 6 minutes, including finding the tooling I'd need.

I like the home brewed lathe idea, but to work well will require rather more work than several alternatives.

Low tech. Wrap a straight edged piece of paper around the tube to get a parallel set of lines. Aquire a hobby razor saw. Cut around the tube, a bit at a time, then finish the rings on a sheet of abrasive paper taped to a flat surface.

If surface finish is not required to be anything special, a wood bandsaw will do the job nicely. Just need to set up a quickie jig to hold the tub e in alignment during the traverse across the saw blade.

Cheers Trev

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Trevor Jones

Yes, using two rollers on which to rest the tube is good.

If I made the spacing between the rollers variable then I could accommodate different diameter tube.

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Okay my design:

I can get acrylic tube in 1m lengths.

I have a wooden baseboard 500mm in length say 200mm wide.

On each end, is a strip of wood with U shaped holes on the top edge evenly spaced. These strips hold the bottom rollers.

Two strips of wood, one on each end, point upwards and are employed to hold another two strips of wood with U shaped holes like the ones described above for the botton rollers.

So, the acrylic tube is held in place by 4 rollers, two above, two below.

So, I first select the roller spacing appropriate to the tube diameter, and drop the bottom rollers into the end "bearings".

I use the same spacings for the top rollers and I manage to lock the top set to the two uprights. Therefore the tube is "held" by the rollers.

One of the rollers has a handle on, so it can be turned. That makes the tube turn.

A cutting tool is mounted in the top and gravity is used so it presses on the tube. Or springs used to maintain pressure. Or one person turns, (wife, girlfriend, offspring, passing member of the public). Another presses a tool against the work.

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Or, it might be simpler to have two cross-shaped end pieces used in a system to lock the tube into a kind of "cage". Then turn the cage + tube. I bet that is simpler.

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I use acrylic tube often at work. have tried a few ways with machine - generally it snags and cracks just as you finish the cut, especially with thinner wall. Resting the tube on rollers tends to mar the tube surface as the ever-present workshop grit gets ground in repeatedly.

The best way I've found is:

- wrap sheet of paper around the tube and mark along the edge.

- rest tube on an open vice or soft mat

- cut around with a hacksaw, turning to keep blade close to tangential to the tube. If the plastic melts, spit or water reduces the friction. If you get cracks, fit a plug - the added bonus is you can then turn down the cut edge on the lathe with the plug fitted.

- file edge fairly square, then with wet&dry paper stuck on a flat surface.

- to get a clear surface on the acrylic, buff extremely lightly with cotton mop wheel and brown polishing compound. A cloth and brass polish works at a pinch.

hth Guy

Reply to
Guy Griffin

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