Thursday, June 8, 2017

The Displeasures of Machining Fiberglass

For part of the <secret project> mentioned in the previous video on wood turning, I needed an insulating material for an electrical connection.  I had found this mystery piece of plastic on the side of the street and figured I'd try using it.  When I first picked it up I actually thought it was aluminum because of the weight and stiffness, but after scraping it on the ground, I started thinking it was chalk or something. I tried parting it off in the lathe, and it appeared to machine pretty decently and left a nice finish, clearly some type of resin or something.
Then I tried turning the outer diameter.... Aww SH*T! It's fiberglass!

Yeah... that wasn't what I was expecting.  The results were a flurry of dust and these hairlike strands delaminating off the piece as I cut into the matrix.  It actually looked like somebody had been dealing cocaine on my machine.  On top of that, I wasn't wearing my OSHA approved respirator either, so I tried my best to stand several feet back while machining.  Nonetheless, I decided to keep going because I might learn something.  I had to drill some holes through the end, so I figured I'd clamp the thing in my boring bar holder so it would go into the vise easier.
Indicating the drill chuck on center with an Intrepid Interapid indicator I found at a garage sale for a good price.  I think this level of precision was a bit excessive for the project, I was able to align it on center within .001"!  This did prove, however, that while the fiberglass is not pleasant to machine, it actually could hold a good tolerance and shape.  So next time I'm stranded on a remote desert island with a lathe and nothing but fiberglass rod.... actually I'd probably rather starve to death.
Drilling some teeny tiny holes.  This drill wandered quite a bit, so the holes weren't as straight as I'd like.  I suppose the material had something to do with that since the glass fibers are oriented lengthwise along the part, so it was like drilling into the end grain of a piece of wood.  Speaking of which, it completely slipped my mind that wood is a viable insulating material, so next time I will consider using that.
Then turning it down some more.  UUUUHHHHH!!!! Dust everywhere!  Not only was that unpleasant to breathe, but after all of this, my hands felt like I had been touching a cactus.  I got a bunch of tiny glass needles embedded in my skin.  Apparently, a cure for this is to cover your hands with glue and peel it off.... I think I'll just wait until they fall out naturally....  Lesson learned: don't machine fiberglass.  I actually had a bit of experience with deburring carbon fiber at one of my old jobs... same type of problem with the splinters in the hand.  To top it all off, I don't think these parts even turned out good enough to use in the final product!  Next time I'll either go with wood or buy some actual plastic.  For now, I will add fiberglass below plywood on my list of things I'd like to machine.


  1. This could have all been avoided if you could wear gloves while machining lololololol

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