Routing Plexiglass

Discussion in 'Luthier's Corner' started by count_funkula, Jan 6, 2005.

  1. I'm wanting to transfer some of my wood templates to plexiglass. Is it safe to use a router on plexiglass?

    I think it's actually Lexan but I always call it plexiglass.
  2. You can and that's fine to do with a router, but the lexan gumms up bits pretty quick, so I usually do it in many many passes (like an 1/8" or so at a time), using the end of the bit for most of the work, so it'll more or less clear itself off...still have to stop and continually clean out, as the debris packs in the corners....sometimes the stuff will chip too, so don't be surprised.

    How thick of Lexan you using?
  3. It's 1/4" thick. I'm using it for my control cavity templates. That way I can have a better idea of how the cover will fit over the cavity.
  4. I've made quite a few templates and router bases out of lexan, all of them using a router and cutting on a single pass. you have to keep the router moving, as the heat will gum it up, as Mon said. But it's quite fine to cut it on a single pass. Watch out for those splinters as they are sharp! keep some kind of cover over your shoes because that stuff will get in there and it hurts like heck. Also be prepared to clean up a BIG mess.
  5. Count, Lexan (polycarbonate) is a fairly low temp thermoplastic. The temps that the router can generate at it's highest speeds can easily melt it. I recommend nothing more than about 10,000 rpm with a 2 flute bit. It's best to use a bit with a spiral to evacuate the cut because straight bits just deposit the tailings on the other side of the cut. That phenomenon brings me to another tip. Use a "mill cut" when cutting polycarb. This is where the router (bit spinning clockwise as viewed from the operator position) follows the pattern in a counterclockwise path. This allows the bit to scoop out the material and deposit it on the drop side of the mother sheet. That's where all of that melted gunk will go instead of on your pattern side. The opposite style of cut is called a "climb cut" and is exactly that - the bit literally "climbs" into the work. But that means that the bits first cut is into the drop material - depositing the residue on the work piece. Remember also that should your work have a hole in it - like a donut - you've got to change that direction to a mill cut to make the hole. This is because the piece you want to keep is on the outside of the drop piece.

    Another tip for anyone using plex or poly with paper backing that has gotten old and won't peel off easily is to use xylene to remove the glue layer. Just wipe the offending paper with a cloth with the xylene and then start peeling. This is about the only thing we've found that will help with this truly frustrating process.

    Hope this helps
  6. wyliee


    Jul 6, 2003
    South Hill, WA
    Hambone, thanks for the good info.

    I just stumbled across this thread. I was about to post a question regarding the use of plexiglass for a slap ramp or slap 'shield.' I have a Bee bass that has a wonderful redwood top. I'd like add a ramp between the end of the fretboard and neck PU, but don't want to obscure any of the beautiful wood.

    So, along the lines of this thread, are there different grades or types of plexiglass? What would be the most optically pure and are there any gotcha's in polishing the edges?
  7. Let's be perfectly clear that we are talking about acrylic sheet when you say "plexiglas". There are two types of acrylic that you'll commonly run into. The type that is best suited to your use is the cast acrylic sheet. The other is a calendered sheet and it is softer and tends to gum up tools quicker. Once you get past that, the differences between clear acrylic sheets comes mostly from coatings. There are some that have anti-scratch coatings and other with UV filtration coatings. Every clear cast acrylic sheet I've ever seen from 1/32" thick up to 3" thick quite optically clear. In the thicknesses you'll be using, you won't the distortion that can sometimes be seen in thicker sheets. Always do your work with the paper backing sheet on the material until you've finished shaping your piece. This stuff can scratch and you won't know when you have until it's too late.

    Polishing isn't usually done with abrasives. It's done with flame. After you've smoothed the edges with a fine abrasive - 400-600 grit, you polish them. Using a torch - a small pencil torch is great for thinner sheets - you will gently apply the flame to the edges until they smooth out and become clear. Then a little polishing with a buffer will bring them up to the same gloss as the surface. You should practice this on scrap first. It's an acquired skill but it polishes acrylic like no other method.

    Hope this helps.
  8. Rockin Mike

    Rockin Mike

    May 27, 2011
    What would you use to shape an acrylic neck?
    Is it possible to do with hand tools i.e. a file or sanding block?
  9. Rockin Mike

    Rockin Mike

    May 27, 2011
    How thin can an acrylic body be before problems crop up?
    Thinking about keeping the weight down either through thinness, or chambering, or swiss cheesing.
  10. Bruce Johnson

    Bruce Johnson Supporting Member Commercial User

    Feb 4, 2011
    Fillmore, CA
    Professional Luthier
    The key thing about working with acrylic is that it needs to be cut slowly with sharp tools. Shape it with large, sharp Bastard files, by hand. Work the surface smoother with finer files, and then use scrapers to remove the file marks. Then it can be buffed up to a gloss. Sandpaper generally doesn't work well on acrylic. It just clogs and smears.

    Beware that building an all acrylic instrument is a whole lot of work. Every little scratch and flaw shows, so every square inch needs to be smoothed to perfection. It can be done, but it is a lot of hours.