First, let me say that this project was inspired by Fyreaway's e-Vaporator, an evaporator that uses the heating element from a domestic water heater (Edit: Do not use this method. Better options emerged later. Keep reading the thread. -- CE) to boil sap in a custom-designed stainless steel pan. He grabbed the best name for this class of evaporators and his is the best design I've seen. It's more versatile and has a higher capacity than my build. It can be used to make finished syrup and it can reheat syrup for bottling. Due to the shape of his pan, it takes very little liquid to cover the heating element. That's not the case with my repurposed kitchen sink. I'm just hoping my design will boil sap more cheaply than propane.
I started with an old, used, deep, stainless steel, kitchen sink that I picked up beside a road a long time ago, thinking I would eventually add it to my deer camp. It had a sign on it that said "FREE", which happens to be my favorite price. It didn't look as if it had ever contained nuclear waste or anything that came out of a bio-warfare lab, so I plan to just scrub it with whatever it takes to make it look clean and then boil water in it a few times before putting it into service for evaporating sap.
I could have paid somebody to drill the 1-1/4" hole for the heating element in it, but I wanted to do as much as possible on this build and of course, to save money. Stainless steel is hard and difficult to work with. Most cutting tools available from a hardware store are ill suited for working with it. But I knew of two ways to make clean round holes in stainless steel without resorting to expensive special tools, a step bit or a hole saw. If you don't have a drill press available, you will probably want to use a step bit. It's hard to control a hole saw with a handheld drill. Step bits aren't cheap, but I did find one that looks suitable at bargainfittings.com, a popular source for home brewing fittings and tools.
Cheapest 1-1/4" Step Bit I've Found
I have a small drill press, and my plan was to run it very slowly and cool whatever tool I used with oil during the cut, but I had to remove the pedestal and the table from it and mount it at the edge of my workbench in order to get the sink close enough to get the hole as close to the bottom of the sink as I could get it while still drilling through a flat surface. I also had to mount some plywood spacers to the workbench to offset the sink for the bulge for the drain hole. Here's a pic of the drill press setup.
A new bimetal hole saw is cheaper than a step bit if you already have the arbor for it. I set my drill press to operate at the lowest speed setting, which is 760 RPM. Rather than pushing the spindle down, I used one hand to hold the sink against the workbench and I used my knee to push the sink up against the drill. That left one hand free to deal with cooling the saw. I decided to offset the hole from the center line a bit to make the drain well easier to get a hand into for cleaning after the element is installed. I drilled a 1/8" pilot hole, then used two more larger bits before using a 1/4" bit that matched the pilot bit of the arbor. I got a good clean round hole that only required a little deburring with a round file. I don't think the hole saw is still sharp enough to cut another hole in stainless steel, despite the fact that I cooled it almost continuously with WD40 while drilling the hole, but it did the job. This is the hole before deburring.
This is the fit of the heating element before deburring. I actually had to screw the element in, but after deburring, it was just a tight fit.
This is the inside with the heating element in place.
I can only add four images to a post so I'll continue in the next post.