On The Road to Powder Coat

Another one of those Bob Hope/Bing Crosby Road movies?  The two of them singing "We're off on the road to Powder Coat"... ?  I used to love those movies when I was a kid.  Of course it's not one of those. 

My last post about my shop shenanigans ended with me saying that since some of the parts I'd been working on were going to be visible in use, I thought I'd powder coat them.  The next day, I dutifully got everything spread out to work on, read everything I had in my instruction manual, and everything I could find online.  (There's an excellent summary of how to powder coat parts online from the Houston Home Machine Shop Club (pdf), if you're interested).  The first thing I did was prep the parts mechanically; made sure the edges were all broken (not sharp) if possible, then wet sanded with 220, followed by 400 grit.  Then I started working at trying to get ready to spray and hang parts. 

This is something that needs to be done with the least amount of handling possible.  The biggest way powder coating gets good coverage is that the paint is charged with static electricity by the gun.  While you can get some paint adhesion without it, coating works best if the gun is grounded to the work; the paint literally jumps on to the piece.  If the colors stand out well, you can see the powder cloud moving toward the work.  Still, while the powder is clinging to the metal, it's just a powder that can be knocked off the part if you bang it around or (especially) touch it.  The easiest way to make sure you don't mess them up is to spray and bake on the same metal rack with the parts grounded to the rack by bare wire.  This is where I discovered my first problem.  My bake-out oven is a plain old toaster oven, and it has a limited selection of positions for the rack.  The oven maker envisioned food on top of the rack; I'm hanging metal pieces below it!  (If I put parts on top of the rack, they'll have bare stripes).

This is one of my motor mounts hanging from a clip looped over the oven rack.  There isn't much room in there and some of my bigger parts didn't fit.  

So now I had a problem.  How do I raise that rack, which is recessed into the sides of the toaster oven?  Thankfully, as I like to say, I know someone with a machine shop.

I first thought of simply making some standoffs and mounting the rack on them, but that rack is too wide.  You can see the grooves it slides in: about an eighth inch deep on both sides.  I thought about cutting the rack narrower, and that might have been an acceptable idea, but I eventually thought I'd just get a piece of perforated sheet metal with lots of holes in it and mount that.  My local Borg store had this stuff in stock - and it's almost exactly what I was thinking of.  All I had to do was cut it to size, and my jig saw cut it like a hot knife through butter. 

I made some 5" tall standoffs from some 1/2" diameter round aluminum bar I had, threaded them 8-32 down the axis, and then found that they were too tall to clear the burner on the bottom.  So I swapped the back two 5" standoffs for some 3" ones I had made for the CNC project.  Voila.  Here's one of my big parts in a fit test.  Tons of room - that motor mount above fits on this one over the big hole - the mount is actually a bit shorter than this end cap.

So, yeah, this had to be done to just get the parts into the oven.  I haven't painted the first part.  The parts are mostly clean, masked and ready to paint, but they've also been touched, or could have been touched, so prudence says I clean them again before painting.  I'll paint outside and maybe run the oven out there, too.  Not quite sure about that part.  Some sources say the fumes are toxic or irritating, and that's enough to say "do it in the backyard" since I don't have a fume hood that vents to the outside.