As a few of you know, I'm new here and about to embark on my first Bok Mini based on a mid priced SS stockpot. Like many of you I've spent many hours reading the main site and the forums, which led to my decision. There's nice summarized info on things like soldering, assembly, coiling, cleaning and distilling. Just about everything.
Missing seemed to be a good summary on cutting or making holes in spun SS stockpots, lids and bowls. After much research and a goodly number of PM's to many of the well known and respected distillers here, I was able to accumulate a bunch of very good info which I thought would be worth sharing in this one post. Here goes:
1. Stainless steel is difficult to work with and requires better drills and tools. Working with it requires special techniques - SS can easily work harden and mess up your project.
2. SS stockpots/lids/bowls tend to be made of lower grades of stainless that are spun or stamped - which means the SS is already work hardened to some degree. They are also thin - another factor requiring special techniques.
3. The two type of holes usually needed include a large hole (say 3 or 4 inches) for the column flange or SS drain, made in the lid or bowl serving as the cover. The other hole(s) include small (say 1 to 1-1/2 inches) to be made in the lower side of the stockpot for inserting heating elements.
Now let's consider some of the techniques I found:
1. Plasma Cutting and/or SS Welding: expensive equipment and process that most of us are not equipped to do.
2. Hole Saws: ordinary hole saws will not work on SS. At the least this requires what are called bi-metal hole saws. This is practical and affordable. More expensive are the carbide or tungsten carbide tipped hole saws. All require the same technique - very slow speed and use of ordinary or cutting oil, lots of pressure. Allowing ANY tool to spin fast on SS will work harden it and your hole drilling is over.
The key - you must keep cutting, slow and with pressure to avoid any work hardening slippage or spinning. But not so much pressure that the saw stalls or catches. SS pots/lids are often less than 1/16" thick and need to be supported from the back, so you can use adequate pressure without bending them.
Before you actually cut the large hole, it is acceptable to lightly centerpunch the center, then drill a small starter hole, then drilling to enlarge it to the same size as the center guide on the hole saw (to avoid the center guide breaking through without warning). Now you can drill the large hole. Use oil or a bit of oil soaked sponge which you can stuff into the hole saw - avoids need for a third hand.
3. Hole Punch: these are VERY expensive ($50 for a small hole, hundreds for a large hole), but do a great job. You could pay a plumber to punch your holes, and a few rental centers will rent them. Unbelievably, IKEA sells one of their "Fixa" tool sets for $9.95 (available in the kitchen/sink department). This amazing kit includes a nice tubing cutter - great for copper - and a 1.4 inch hole punch - designed for cutting holes in their SS sinks.
4. Drills: "High Speed Steel" bits can be used (though NOT at high speed). Carbide or Tungsten Carbide tipped are better, but more expensive. "Coated" drills don't improve the drilling, cost more.
The technique is the same. Very slow speed, lots of pressure, cutting oil - keep cutting! Begin by prick punching so the drill won't wander and you can apply plenty of cutting pressure from the get go. Start with 1/8" - then 1/4" - then 3/8". As drill size increases, the already slow speed gets slower and the pressure gets higher. Keep cutting or else.
Be careful - take your time. Thin SS overheats easily - if the metal turns blue it is overheating and you are work hardening it. Don't.
5. Step Drills: same considerations as drilling (above). These are expensive, and it would be a shame to ruin one for a few holes in your still.
Bourbonbob: Hi Soc. I used a 4" angle grinder with a worn down disk, you have to be careful but it is possible. Alterately you could use a drill and half round file, drill a pilot hole and then use a large bit, you should be able to use the drill like a router to gouge the hole out, then use the file to get a neat finsh. I have used both methods and with a bit of patience you will be successful.
Tracker: Lid is pretty thin so I used a hand operated nibbler to cut large hole.
As-Ol-Joe: I drew the outline of the holes I wanted to make. Then used a small drill bit, 1/8", and drilled holes just to the inside of my outlilne. After all the holes were drilled, I took a dremel tool with a grinding wheel on it and cut between the holes and clean it up the best you can with the grinder. Then use a file and sand paper to dress it up. It took me about 3 hours to cut the hole in the lid.
GingerBreadMan: I found Stainless steel to be hard to cut. The only holes I made was small holes using a drill bit. I started with a small bit and drilled, went to a slightly bigger one, drilled and repeated until I had the hole the size I wanted. To cut the Stainless steel bowl I used a dremel tool. That worked pretty well - went through about 20 cut off disks to cut a SS mixing bowl in half.
1. Cutting large hole in lid or bowl: the easiest, simplest, cheapest way would be to buy 1/8" high speed steel drills, pack of 10 maybe 25 cents each. They will be ruined after your still is done, but so what. Mark the diameter of the hole needed, prick punch for a series of holes around the circumference, and drill the holes (as above). Support the lid as needed. Connect them by using a Dremel using cutoff discs. File or not as desired or needed, or use a Dremel grinding head.
2, Making small holes (for heating elements): The IKEA punch is close to perfect as it makes a 1.4 (1-2/5) inch hole. This will accomodate the standard water heater element whose thread is 1-1/4" (I plan to use a copper or SS female threaded coupler on the inside), SS washer and sealant outside). Alternative: appropriate bi-metal hole saw used as above. In either case you need to prick punch and drill the series of holes (starting with 1/8") for the center guide (hole saw) or for the tightening bolt (IKEA punch).
3. Cutting Oil: Some recommend WD-40 (reputed to run) or ordinary oil. One experienced source recommended "Rapid Tap" cutting fluid, as it "tends to resist running, is affordable in the very small quantities needed, has excellent cooling capability - your drills will last much longer".
4. Drills: Best bought from an industrial supply rather than from WalMart or even Home Depot. Their high speed steel are better quality and cost not much more.
In summary, let me quote one expert "Drilling SS is a pretty brutal process; when you get going, have immediate, continuous, strong, even, correct angle, speed and steady pressure on the drill and pour on the cutting fluid, which is as much of a coolant as anything".
Thanks to all for your kind responses... let's all offer our methods and experiences here.
Last edited by Socrates
on Tue Sep 09, 2008 11:07 am, edited 3 times in total.