Often times when locating hardware, or planning a project you need to put a few choice holes in a fiberglass deck. Fine. Easy. Sometimes it’s tapping into aluminum. Ok. Actually kind of fun! Carbon has it’s own issues, but can make for an interesting project with a nice finish. Stainless steel, however, has been something that I avoided drilling as much as possible for years and years. It’s extraordinarily hard, work hardens in the blink of an eye, and generally is the dark god that demands the sacrifice of $30 drill bits. In fact, the original title for this article was going to be some version of The Simpsons “So You’ve Decided to Ruin Your Life” pamphlet.
But it doesn’t have to be so difficult, and it didn’t seem fair to give stainless such a bad rap. Over time I’ve been given a few tricks from others, and come up with a few myself. It’s still not enjoyable, and when quoting the project I usually inform the customer that there will probably be some new drill bits on the bill, but with patience and the right tools it can be just another step in a project.
I’ve always used cutting fluid, but recently a friend got me started on this wonderful stuff.
It’s called Tap Magic, and it’s designed just for this kind of nonsense; ie cutting or drilling into hard metals like stainless. The extra thick is-suprise-an extra thick version, which is great for drilling as it tends to stick to the surface and tool. It absolutely blows away cutting fluid in my opinion, and I anticipate the bottle being a real time saver for future projects. Caution: your sense of smell will immediately confirm all the toxic warnings on the bottle, be very careful handling!
The absolutely essential part of the process is good drill bits. I really like cobalt bits with a titanium coating. Not cheap, but neither is time, and it’s way more expensive to extract that broken high speed steel bit than to just use the right one in the first place. For pretty much all special tools and small parts, I go to www.mcmaster.com
For horizontal surfaces (and a few angles or vertical ones) I like to keep a ribbon of butyl rubber around. You can read about why this is a great material to use on your boat here: http://www.pbase.com/mainecruising/sealing_the_deck but below you’ll see how it has some uses on this project as well.
The first step here is to locate the hole with a center punch. With aluminum I have no problem making a nice large dent to start the hole, as it makes it easier to keep the bit centered (this can be tough, especially when aloft) With stainless however, moving the material by impact seems to make it much tougher to drill, as it’s possible to work harden the material, even with a small impact. So I like to keep the “ding” quite small, and take extra care with the drill.
Above you can see the tiny dimple made with a punch. Also, some black stuff? That is the butyl rubber, and it’s there to make a small reservoir of the cutting fluid. Having the butyl rubber around the hole means you can have a greater quantity of fluid, which keeps the tool cooler and makes sure you don’t run dry. Neat.
Above you can see the reservoir, and the chips that have been removed. What you can’t see is heat or smoke, which is a sure sign that your drilling is about to go a lot slower!
Above you can see the shavings, which are nice and continuous, and not a series of chips. In addition to the fluid, it takes a bit of technique to get this result. Low speed on the drill, with decent pressure and a steady hand means you get the nice long shavings characteristic of a cool quick cut. I started with a pilot hole of 1/8″ before moving through a few sizes to 5/16″. When the smallest hole was made, a bit of butyl rubber was used to plug the bottom in order to make the reservoir water tight again.
On the above project, the first hole towards the middle of the plate was done quite easily, with no breakage or mess. The outboard most hole however, was still quite tough as it was on/next to a weld, which completely changed the hardness of the material and made it quite hungry for drill bits!
If you ever do break a bit, the butyl rubber can be used again, as in a decently dry hole it does a great job of pulling out broken tools.
Hopefully this helps the next time you’re faced with a piece of stainless that absolutely positively must be perforated!