clear acrylic for a turret board?

[chrislathan]

my brother just gave me 12 pieces of clear acrylic, measuring 12x12x.125".

perfect condition, with the protective backing in place.

question is, would it be at all advisable to try to build a turret board out of this material? i am sure i can find other uses if not, but it cuts and drills really well

[pompeiisneaks]

From a quick search it seems that acrylic should be non conductive, but some acrylics have additives or sheeting/surfaces that are.  I found this page that seems to show it quite non conductive: http://macao.communications.museum/eng/exhibition/secondfloor/MoreInfo/2_3_4_ConductorsInsulators.html  A ton better than wood, but plastic seems a bit better. 

I'm not sure if there is a 'perfect' answer, you'd likely do best to actually ask the manufacturer if you can get a datasheet.  It may specify conductivity.

~Phil

[John]

Be sure it doesn't crack too easily, and doesn't melt with the soldering iron.

[chrislathan]

Found this:

[chrislathan]

Guess I need to order some turrets and see how it likes swaging and heat

[Backwoods Joe]

Swaging might be a problem if it isn't really high quality acrylic. I'd hate for you to put a bunch turrets on a board & then it split or crack during the swaging process.

[chrislathan]

this is really nice stuff. i was thinking about maybe 3 or 4 turrets in a scrap piece, see how close i can get them with no damage, etc.

[pullshocks]

I have always assumed melting would be a problem but your post prompted me to test one of the big sized turrets soldering a couple resistors to it..  I had my iron set to 525 F and the plexiglass seemed to tolerate the heat just fine.  No softening and no odor.

As far as setting the turrets, I would suggest hitting all the holes with a countersink.

[chrislathan]

Agreed. A little chamfer goes a long way..

After finding a 3/32 bit that didn't have any wobble in the drill press, I plate around with Sluckey's Lil Maggie layout..

Dust collection could be an issue , but it drills nice

[eleventeen]

In my experience, plexi has a tendency to crack under the kind of pressure exerted by swaging the turrets. Go ahead and try a few, but it would suck to install 25 of them and on the 26th....

[chrislathan]

Yuck. Good point.

[Ugly Distortion]

There are special drill bits for acrylic, they have a conical point so the cutting part doesn't bite or catch right away and chip or shatter it. You can  find them at plastic or crafts vendors that deal w/ acrylic. With smaller bits it's not so important. Seems you are already done with drilling anyway.

I've always found acrylic incredibly static prone and dust attracting. That seems to pass once you are done messing with and it's cleaned up, but maybe something to keep in mind, might cause noise. There are plastic cleaners that help de-static it.

[chrislathan]

I only drilled about 75% of the holes, as this piece had a fairly jagged cut edge and wouldn't be one I'd use anyway. If the test run is successful, I'll actually cut the boards on the router table. Much cleaner edge. Yeah, static is a PITA.

[sluckey]

Since this is just a test piece, take your hot soldering iron and hold the tip to the board for about 15 seconds. If it melts, I would not use it.

Also, I would not use it just because of the static. That static is an electrical charge that may breed all kind of gremlins.

[xm52]

I have several concerns about using a plastic. The reason why FR4 is used is that it is flameproof. Components such as plate resistors can blow and you want the board to act as a firewall. The resistor of a cathode biased amp can run hot. In older amps, it is not uncommon to see scorch marks on fire/heat resistant boards. This is why regulatory agencies require that a flameproof material be used.




Testing heat resistance with a soldering iron is one thing. Some plastics will soften like a wet noodle when put in an oven. This is how they form them into shapes. The plastic is heated till soft, then applied onto a form. If the temperature is high enough inside the chassis, the board can deform.




http://thegundcompany.com/files/index.cfm?pdfpath=FR4%20FULL%20DATA_NEMA%20IEC%20Grade.pdf

[chrislathan]

Thanks so much! Back to known materials

[Ugly Distortion]

Since this is just a test piece, take your hot soldering iron and hold the tip to the board for about 15 seconds. If it melts, I would not use it.

15 seconds! Never tried but I'd guess acrylic would melt the minute the iron touches it. I wouldn't use it either but on the positive side if smoke comes out the amp you'd have the few seconds option of hoping it's the board melting and not a transformer

[chrislathan]

 

[eleventeen]

I think (as a matter of just speculation about the idea) if there was a means of annealing the plexi you could have success. To do this, I think you'd have to do the turret swaging with the material heated, hot enough so I doubt you could touch it. I agree, chamfering or countersinking the holes would otherwise help you. Ultimately...the issue is that you're dealing with a material that acts very unfriendly at its elastic limit (might not be the correct term) and the result would be a snap crackle pop. Plexi does not give up whatever stress is imposed when you work it or form it very well.


And yeah....the static and the non-flameproof is another wave off.

[PRR]

It is electrically terrific.

I think the acrylic will soften on any tough-to-solder turret.

OTOH, it will harden when cool. So as long as it does not fall out/through while soldering, it may be tolerable.

This may imply that you could install turrets without drilling the brittle plastic. Rig a jig and push them through with a big hot iron.

And classy, to those very few people who admire the insides of amps.

Power resistors will need LOTS of air-clearance.

World Tours on bad roads will encourage cracking at the supports.

The fire thing is an issue. Amps shouldn't burn. But any old tech has seen charring. As a worst-case, many plastics will SMOKE horribly, which can cause panic in a crowd.