How to Use a Step Bit to Drill Stainless Steel
Drilling stainless steel with a hand drill is a hefty job, especially so with the robust stainless found in a keg. After drilling my first couple holes I dreaded having to drill more, until I figured out some tricks which made it 10 times easier.
The two most important parts of drilling stainless are speed and pressure:
You should, almost always, drill at a very low speed. Patience is extremely important to this process. Run your drill at low speed and high torque. If you run your bit too fast, you'll heat the surface you are trying to drill to the point of melting, which makes it nearly impossible to proceed and will wear down your bit. You may have a tendancy to gun the drill if the bit starts to slow, but resist this urge! Stop what you are doing, and restart going at a slow speed. When you encounter snags or lips, it helps to start the drill running before you apply downward pressure, but never apply too much speed. As noted below, a good drill is very helpful for this process and cutting oil will make this much more forgiving.
You'll need to apply a lot of pressure to the drill to start the initial hole, and I mean a lot. Really put some weight on the drill, but be careful to apply the weight straight down so you don't bend or break the bit. Once you've drilled your pilot hole and you are on to the step bits, you don't need as much pressure.
This simple rule will allow you to know that you've got the correct speed and pressure: while drilling, you should always see a small ribbon or other discharge of stainless coming from the spot where you are drilling. In other words, your bit should always be making progress at enlarging the hole. If it is not, you are likely hardening the hole and wearing out your bit, so slow down and apply more pressure.
The following tools will make your life much easier (in order of importance):
- Step Bit: You don't need anything fancy if you only plan to drill a few holes. If done carefully, one of the inexpensive Neiko Bits should last you a dozen holes!
- A good drill: I recommend a variable speed lithium ion battery powered drill for this job, with a backup battery available so you can charge and swap out as you run each one down (as you are likely to do with this heavy-duty work). My Ridgid drill has a lifetime warranty on all parts, which gives me comfort after the stress this process puts on it
- Cutting Oil: I can't say enough good things about cutting oil. I drilled my first 5-6 holes using vegetable oil and WD-40, and I refrigerated my bit periodically to keep it cool. Then I discovered the magic of cutting oil which revolutionized this process for me. You only need a few drops (that bottle will last you years), and it makes drilling these holes significantly faster and easier. It also makes the job gentler on your step bit, which will allow it to last longer
- Smaller diameter drill bit: While step bits work well at larger diameters, they are not great at starting the holes. We recommend using a 1/8" cobalt bit for this job
- Center Punch: This will prevent the drill bit from wondering, which is key to a good start. You can also use a heavy duty nail or screw, but a center punch is much easier
Here are the steps for easy stainless drilling:
- Mark the location you plan to drill with a sharpie. Triple check that you are in the right spot as it's hard to undo a hole! Typically you want to be 3/4" above the skirt of a keg (to avoid the lip) and away from any vent holes to avoid heat
- Lay the vessel on it's side, either on a carpet (to avoid scratching and damage) or supported lengthwise by 2 4x4s
- Use a center punch to create a divot where you intent to drill. This will prevent the bit from wondering
- Drill a pilot hole with a smaller diameter bit. Be sure to drill extremely slow and apply a ton of pressure, while keeping your bit lubricated using the cutting oil
- Once you've punched through with the small bit, switch to your step bit
- Lubricate your step bit and the rim of the hole with the cutting oil before starting
- Apply medium pressure to the drill, and begin drilling at a slow pace. If you aren't throwing off a ribbon of stainless discharge, apply more pressure. If you are frequently being stopped by heavy burrs, apply less pressure
- Work in this way, slowly and steadily, from step to step. Be sure to lubricate the bit and the hole every step, and take a break if either starts to get hot
- When you've nearly reached the desired hole size, shop vac off the discharged stainless from around the hole and inside your vessel, then stand the vessel up
- Test the hole to make sure it is the appropriate size. Once it's very close, deburr the hole using your step bit for major burrs (it helps to go from the inside of the vessel out for this, and be sure not to apply much pressure or you'll enlargen the hole beyond your desired size) and use sandpaper to round it out and finish it off. At that point it should be smooth to the touch with no burrs (this is critical to a good seal)
Make sure you take care of yourself in this process, as it's hard and potentially painful work. Wear protective eyewear and shoes to protect yourself from flying shards of hot steel, and be careful with your wrists. All that pressure can cause pain or soreness if you're not careful, a recoil by the drill can even make it dangerous. Also, a burred hole will be very sharp and will cut you, so don't run your finger over a potentially sharp cut. Be careful!
That's everything! Easier said than done, maybe, but excersizing patience, care and a healthy amount of cutting oil will make this job easier than you could have imagined.