On Thursday, 31 August 2017 00:55:19 UTC+1, Dave M wrote:
Dave Platt wrote:
In article ,
Dave M wrote:
Anyone have experience in accurately cutting 1/8" thick acrylic
Plexiglas (Perspex) for LED displays?

yes but not for LED displays.

I've thought about using a table saw with a cabinet-grade finishing
blade.
That's possible, but somewhat dangerous due to the small size of the
filters.

https://www.bobvila.com/articles/how.../#.WadJJnWGNo8

"For thicker sheets of plexiglass, cut with a power saw€”be it a
circular saw, saber saw, or table saw. (To cut anything but a straight
line, opt for a jigsaw.) No matter which type of saw you choose for
the task, its critically important to use the right blade. There
are special blades designed expressly for acrylic, but any
metal-cutting blade with carbide tips can do the trick. Before
committing to one blade or another, double-check that its teeth are
evenly spaced, with no rake, and of uniform height and shape."

For the size you're talking about, I'd think that a table-type
sabresaw or jigsaw (with a fence) would be what you'd want.

I would rule out any type of saw for a few reasons
1. Such a small piece is impossible to hold effectively unless you're using a low speed handsaw, which is very ill suited to acrylic
2. Power saw speed plus very slow feed are required, and there's no way you'll get good enough control with such a fiddly unsupported piece
3. Anything else will crack it
4. Your fingers will be at too much risk


For a fancier approach - the MightyOhm geiger counter kit can be
purchased with a two-piece acrylic case, the upper sheet of which has
some custom cut-outs made for the tube and the batteries. Their web
page says that it's "laser cut". Maker shops may have suitable
laser-cutters for their members to use, and there are service
companies which will laser-cut-to-size in your choise of acrylic
types.

I've contacted four Ebay sellers of Plexiglas panels, asking if they can cut
to my dimensions. Although they all advertise that they can cut to custom
sizes, all but one of them say that they can't cut that small due to
"liability insurance restrictions", whatever that might be. The other
quoted an unbelievably high price for a small order of 25 pieces. That's
why I'm looking to do it myself.

It's doable, but the options shrink heavily.

I looked at the Geiger Counter kit and didn't see any reference to any
plexiglas except for a clear panel covering the front of the unit, clearly
not what I'm after. At any rate, I'm not going to buy several $100 Geiger
Counter kits for which I have no use just to get $15 worth of plastic.

Yes, the finishing blade that I mentioned is a zero-rake blade, so that't
not a problem. Just concerned about my fingers when they get close to the
blade spinning at 3200 RPM.
I'm leaning toward building a hot wire cutter into a frame that will keep
the wire taut enough to make a straight cut through the plastic. Maybe
mount it alongside the fence on my tablesaw. That should keep everything
nice & straight.

Thanks,
Dave M

Hot wire would do it, and gravity tends to keep it cutting straight. You can sand the edges afterwards to get dimension precise. An easier option is to use an abrasive stone in a dremel, cutting/melting as close as you can to your scribed line, but never over it, then sand it.


NT