I’ve been reading the various posts about EMT conduit. I wasn’t happy with the finish on the conduit I got from Home Depot. Since I currently don’t know where else to source a better conduit, I decided to sand the galvanized smooth. Worst case scenario is I have to spend another $20 on new conduit.
Conduit is manufactured from flat stock that is formed and welded with the ID being the major tolerance. After it’s formed, it gets galvanized. Either through dipping or spraying and electrolysis. Don’t really care how that’s done, the point being that it’s sloppy and irregular by default. So I figured as long as I was somewhat symmetrical in my sanding style, I wasn’t going to knock it too far out of true. I found this new sandpaper at my local Ace Hardware called 3M Sandblaster. Instead of a paper backing it uses a rubbery kind of plastic. It works GREAT! Doesn’t fall apart or clog. Just use it until it’s abrasiveness is no longer productive.
So I got a bucket of water, wrapped the pre-perforated half sheet (100 grit) around the conduit and started sanding like I was using a pool queue. Got quite a few funny looks from passersby. Sanding and rotating to keep things even. Found that generally that the zinc was heavier nearer the seam weld. I sanded until it was mostly smooth. At tat point, the weld was plainly visible and the steel under the zinc was starting to show through.
I measured the stock Wheatland EMT from Home Depot and compared it to the EMT that I sanded and I had removed about .005″. Seating a piece in one of my assembled rollers after loosening/tightening the bearing bolts and it went from grumbling over the raw conduit to moving like butter. I’m fairly confident that I didn’t weaken it or take it out of round anymore than it started out. If anything it’s probably closer to true. I’ll be finding out soon. Gonna finish last two pieces with the 100 grit. Gonna apply the 200 grit for grins.
Is there a mostly printed lathe project floating around? It doesn’t have to be too robust, just be able to remove a few thousandths while truing conduit up. I’d just mount up a hand router with a grinding wheel that could dial in while spinning and traversing the length.
Any thoughts on chrome plating trued conduit? I don’t really know the pros and cons.
One last thing: A huge thank you to Ted for hand delivering my hardware bundle on the very same day that I ordered it!!! I know you said you were going to be in the area anyways, but I still think that’s above and beyond and I thank you.