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"Dave M" <dgminala@mediacombb.net>: Aug 30 05:57PM -0500 Anyone have experience in accurately cutting 1/8" thick acrylic Plexiglas (Perspex) for LED displays?   I need to make filters for some panel meters of my own design, but am having trouble finding off-the-shelf bezels and filters of the sizes I need. Before everyone tells me that there are cheap Chinese panel meters available on the web, I already know about them. My meters are for a unique application and the available digital panel meters can't be modified to fill my needs. The display is the really unique part, and I need to make my own filters for the displays. I need 3 different sizes; 1.25" x 2.5". 2.75" x 5" and 4" x 5".   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. Also thought about hot wire cutting. That's quite possible, relatively safe (just have to keep fingers off the hot wire). Might be hard to keep the wire taut enough to make straight cuts, and guiding the plastic through the wire or the wire through the plastic. Also thought about cutting on a drill press or milling machine. Again, a bit dangerous due to the small size of the work. Clamping would be tricky.   Any suggestions as to a good, safe approach to cutting the plastic?   Dave M

dplatt@coop.radagast.org (Dave Platt): Aug 30 04:32PM -0700 In article <sIWdnVPVfP1e3zrEnZ2dnUU7-IfNnZ2d@giganews.com>,   >>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-to-cut-plexiglass/#.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, it's 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.   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.

Randy Day <randy.day@sasktel.netx>: Aug 30 05:36PM -0600 In article <sIWdnVPVfP1e3zrEnZ2dnUU7-IfNnZ2d@giganews.com>, dgminala@mediacombb.net says... > Anyone have experience in accurately cutting 1/8" thick acrylic Plexiglas > (Perspex) for LED displays?   [snip]   Is there a makerspace near you with a laser cutter, or a laser cutting company?   Water jet cutting?

"Dave M" <dgminala@mediacombb.net>: Aug 30 06:55PM -0500 Dave Platt wrote: > 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.   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

"Dave M" <dgminala@mediacombb.net>: Aug 30 07:30PM -0500 Randy Day wrote:   > Is there a makerspace near you with a laser cutter, > or a laser cutting company?   > Water jet cutting?   Don't know about a makerspace. Never heard of them. Have to see what Google churns up.   Dave M

krw@notreal.com: Aug 30 08:46PM -0400 On Wed, 30 Aug 2017 17:57:06 -0500, "Dave M" <dgminala@mediacombb.net> wrote:     >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.   That should be no problem on a table saw. Make sure to use a zero clearance insert. Cut into the short-side sized strips with a fence than chop those up with a miter gauge with a stop. Perfectly safe.   >Also thought about cutting on a drill press or milling machine. Again, a >bit dangerous due to the small size of the work. Clamping would be tricky.   >Any suggestions as to a good, safe approach to cutting the plastic?   Your first thought should work just fine as long as you take reasonable care.

tabbypurr@gmail.com: Aug 30 05:53PM -0700 On Thursday, 31 August 2017 00:55:19 UTC+1, Dave M wrote: > > Dave M <dgminala@mediacombb.net> wrote: > >> Anyone have experience in accurately cutting 1/8" thick acrylic > >> Plexiglas (Perspex) for LED displays?   yes but not for LED displays.   > > 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     > "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.   > 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

John Larkin <jjlarkin@highland_snip_technology.com>: Aug 30 05:56PM -0700 On Wed, 30 Aug 2017 17:57:06 -0500, "Dave M" <dgminala@mediacombb.net> wrote:   >Anyone have experience in accurately cutting 1/8" thick acrylic Plexiglas >(Perspex) for LED displays?   Polycarb is a bit easier to cut. Acrylic melts and gums up blades easier.     --   John Larkin Highland Technology, Inc picosecond timing precision measurement   jlarkin att highlandtechnology dott com http://www.highlandtechnology.com

Martin Riddle <martin_ridd@verizon.net>: Aug 30 09:26PM -0400 On Wed, 30 Aug 2017 17:57:06 -0500, "Dave M" <dgminala@mediacombb.net> wrote:   >bit dangerous due to the small size of the work. Clamping would be tricky.   >Any suggestions as to a good, safe approach to cutting the plastic?   >Dave M   I have scored and snapped Plexiglas. You would need to mount it firmly so that the corners don't break. A small fixture (plywood) to sandwich the piece should work fine.   Cheers

Bob Engelhardt <BobEngelhardt@comcast.net>: Aug 30 09:28PM -0400 I've had a lot of trouble cutting acrylic on a table saw, or drilling. The problem has been chipping on the back side. I haven't tried backing it with a piece of wood - that should help.   What does work very well for giving a nice edge is a router. Not very convenient for cutting into pieces, but nice for cutting shapes to a template, or for finishing edges that have been cut with too much chipping.

mhooker32@gmail.com: Aug 30 06:47PM -0700 On Wednesday, August 30, 2017 at 6:57:16 PM UTC-4, Dave M wrote: > bit dangerous due to the small size of the work. Clamping would be tricky.   > Any suggestions as to a good, safe approach to cutting the plastic?   > Dave M   at my job, we cut plexiglass( USA) on a sheet metal shear. makes a nice cut that requires little sanding to make smooth. 1/8 is thin. any tin shop would have shear that could cut that, even a manual one would work.

Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net>: Aug 30 06:50PM -0400 On 08/30/2017 06:57 PM, Dave M wrote: > bit dangerous due to the small size of the work. Clamping would be tricky.   > Any suggestions as to a good, safe approach to cutting the plastic?   > Dave M   Stack them in a vise and mill.   Cheers   Phil Hobbs   -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics   160 North State Road #203 Briarcliff Manor NY 10510   hobbs at electrooptical dot net http://electrooptical.net

Joe Chisolm <jchisolm6@earthlink.net>: Aug 30 10:38PM -0500 On Wed, 30 Aug 2017 17:57:06 -0500, Dave M wrote:   > bit dangerous due to the small size of the work. Clamping would be tricky.   > Any suggestions as to a good, safe approach to cutting the plastic?   > Dave M   Variable speed dremel with a cutoff wheel will work.       -- Chisolm Republic of Texas

oldschool@tubes.com: Aug 31 12:32AM -0400 On Wed, 30 Aug 2017 17:57:06 -0500, "Dave M" <dgminala@mediacombb.net> wrote:   >bit dangerous due to the small size of the work. Clamping would be tricky.   >Any suggestions as to a good, safe approach to cutting the plastic?   >Dave M   When a hardware store cuts plexiglass for a storm door or window, they put the sheet in a glass cutting frame. That is nothing more than a rack with a straight edge and a lever to apply pressure against the part you want cut. Then they use a special cutter made for plexiglass, which is really just a sharp blade. They score it with that cutter from top to bottom. Then they use that lever to apply pressure and SNAP, they make a nice clean cut.   I was in a place where I had to cut some myself. I did not have that special cutter or a rack. I marked it with a sharpie. Then I took a straight piece of aluminum, laid it on my mark, and scored it with a utility knife with a new blade. Once it was scored, I placed the scored line along the edge of a board and applied pressure with my hand. That worked fine.   One thing I learned, never try to drill plexiglass. You will end up with small cracks around the hole. I once wanted to put some hinges onto plexiglass and learned the hard way about the cracks. Then I used a soldering iron and melted holes. It was kind of messy, sicne the melted plastic builds up around the hole and needs to be quickly removed while it's still hot and soft, but that did work in the end. (The soldering iron tip was pretty much trash though, I ssaved it for future plexiglass holes, but would never try to solder with it).

N_Cook <diverse@tcp.co.uk>: Aug 31 07:40AM +0100 On 30/08/2017 23:57, Dave M wrote: > bit dangerous due to the small size of the work. Clamping would be tricky.   > Any suggestions as to a good, safe approach to cutting the plastic?   > Dave M   I would use , don't know what they're called, miniture tenon saw from a craft shop for marketry I believe, blade only about 1 x 2 inches, but large handle, and teeth about the same as a hack-saw size and spacing

Tom Gardner <spamjunk@blueyonder.co.uk>: Aug 31 08:37AM +0100 On 30/08/17 23:57, Dave M wrote: > Also thought about cutting on a drill press or milling machine. Again, a > bit dangerous due to the small size of the work. Clamping would be tricky.   > Any suggestions as to a good, safe approach to cutting the plastic?   Have a look at laser cutting. Bonus: you can cut complex shapes as easily as simple shapes. Caution: not all materials can be cut like that.   Look for a local Hackspace or Makerspace, if you want to learn how to use laser cutters yourself.   Alternatively there are many commercial companies available. Usually you just send them the CAD file and they return the items by post, but obviously you could pick them up from a local company.

"Artemus" <bogus@invalid.org>: Aug 30 07:53PM -0700 "Dave M" <dgminala@mediacombb.net> wrote in message news:sIWdnVPVfP1e3zrEnZ2dnUU7-IfNnZ2d@giganews.com...   > Any suggestions as to a good, safe approach to cutting the plastic?   > Dave M >Make and use a small parts sled to hold the pieces and keep your fingers out of harms way. Do a search for "woodworking small parts sled" for an assortment of photos and plans. Use the tablesaw to just score the plastic. Don't cut all the way through. Snap on the score lines and file off any rough edges. A propane torch will polish the edges to a glass like finish. Practice on a scrap first as it's easy to burn the edge. Art

unk <me@privacy.net>: Aug 31 10:41AM On Wed, 30 Aug 2017 17:57:06 -0500, Dave M wrote:   > Anyone have experience in accurately cutting 1/8" thick acrylic > Plexiglas (Perspex) for LED displays?   Does it have to be perspex? 1/8" polycarbonate (Lexan) cuts with tinsnips, no cracks, nice enough edge if you are covering it with any frame; otherwise pass them a few times over a big file held in the vise.

"pfjw@aol.com" <pfjw@aol.com>: Aug 31 04:11AM -0700 Stuff that thin can be scored with a matt knife and broken on the score. With care, even on a curved score. For curved shapes, make a template in thick cardboard and cut along that. If you need to do this more than once, soak the curved edge in a very thin cyanoacrylate glue, then file it to the final shape. That will resist scoring by the blade.   Today, I have a Dremel Scroll-saw with a fine plastic-blade. Makes life easy. I tend to cut a bit proud of the final shape and use a very fine sanding disc to finish. It gives a nice edge and no flash.   Peter Wieck Melrose Park, PA

Jasen Betts <jasen@xnet.co.nz>: Aug 31 11:13AM > 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.   use a drop saw instead.   -- This email has not been checked by half-arsed antivirus software

Jasen Betts <jasen@xnet.co.nz>: Aug 31 11:27AM > "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.     https://www.ponoko.com/laser-cutting/acrylic   send these guys 1:1 scale SVG with your outlines, they'll cut them into a sheet.   they seem to have a "first order free" deal going at the moment.   -- This email has not been checked by half-arsed antivirus software

rickman <gnuarm@gmail.com>: Aug 31 01:17AM -0400 Ralph Mowery wrote on 8/29/2017 5:55 PM:   > Yes, the polarity is very important if the capacitor has one. I have > not installed any of thse backwards to see what happens as of yet. I > have seen the old aluminum and tantalum one blow over the years.   I think you just answered your question. If the caps have polarity markings they are polarized. If they don't have polarity markings, how do you know you have any installed correctly?     > I am not used to seeing capacitors ( other than large AC and speaker > crossover) much over 1 uF.   MLCCs (which are ceramic) can be found above 1 uF. I often use them at 10 uF and I know they are available at higher values. The product of capacitance and voltage determines the size, so in a given size the voltage will drop as the capacitance approaches the max value. There are also different material ceramic caps with widely different tolerances and voltage/temperature responses. X5R is a good general purpose type of ceramic cap.     > shop work,but good enough for hobby,and if it breaks, the replacement is > not that much.   > I am learning a lot about the capacitors with the help here.   While the idea of a cap is pretty simple, the realities can get pretty complex.   --   Rick C   Viewed the eclipse at Wintercrest Farms, on the centerline of totality since 1998

rickman <gnuarm@gmail.com>: Aug 30 01:44PM -0400 Michael A. Terrell wrote on 8/29/2017 7:12 PM:   > Think again. You have a negative and a positive peak, not just a single > peak. You have to add them together. That is why the original DC cap was > 600V, not 300V.   You are very good at math, but not so good at electronics. You don't need to consider the peak to peak voltage because the cap doesn't see them both at the same time. It sees one peak, then it sees the other peak. The fact that they are opposite polarity doesn't mean you need to add them to consider the capacitor voltage rating.   --   Rick C   Viewed the eclipse at Wintercrest Farms, on the centerline of totality since 1998

tabbypurr@gmail.com: Aug 30 05:41PM -0700 On Wednesday, 30 August 2017 00:12:17 UTC+1, Michael Terrell wrote:   > Think again. You have a negative and a positive peak, not just a > single peak. You have to add them together. That is why the original DC > cap was 600V, not 300V.   Sorry but that ain't so.     NT

rickman <gnuarm@gmail.com>: Aug 30 01:46PM -0400 Trevor Wilson wrote on 8/30/2017 1:36 AM: >> he's willing to go (unless he throws in a Super "Shammy" if you order now!!).   > **Dunno what I was thinking. I should have offered to pay him to take the > stuff.   Maybe we can offer to pay him to not post here?   --   Rick C   Viewed the eclipse at Wintercrest Farms, on the centerline of totality since 1998

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