Once you do this once, you will be able to tune almost any metal pipe! If you have consistent metal, do the math right, and cut carefully, it works every time. I usually cut a couple of millimeters long to be safe and shave off the remainder with the saw blade, checking the pitch frequently. After the math is done, it only takes a couple minutes per pipe.
Read through the steps, look at the example, and try it!
A note about materials
A few times I've bought pipe that had a large bead/weld or seam of sorts along the entire inside length of the pipe. This seam tended to make the metal inconsistent. Each length that I cut behaved differently. The thinner/lighter the pipe, the faster this process will go. You can fine tune and make cuts in a fraction of the time. You sacrifice resonance/volume/presence when you go lighter... But excluding Lang So-Called II, most people are using lighter copper or conduit these days. Last time I used the light conduit I cut nearly an octave in about an hour.
-Tape measure or Meter stick (metric makes your math much easier, worth searching for the metric tape measure
-Poly-foam/caulk saver from Home Depot or Lowe's to put under node of a pipe when checking pitch. Home Depot 3/8" or 1/2" works. Incidentally, this works great to suspend the pipes on a trap table for the performance.
-Pencil and scrap paper for your math
-Sharpie for marking your material
-A bunch of pipe of almost any sort
-Metal cut-off saw/angle grinder/ or rotary pipe cutter (rotary is only if you’re using small copper pipe, or electric metallic tube conduit: the standard electrical conduit like from home depot)
-If you're using the manual rotary cutter: A bench grinder or some serious metal files (or confidence in your math that it will work the first time) If you're using an angle grinder or metal cutoff, you can easily press the abrasive wheel/blade onto the end of the pipe and shave off small increments)
-A tuner app that will show frequency in hertz (instuner works great)
-A mallet to check pitches
-A bucket of water to cool the fresh cut hot ends
-Any safety gear you deem necessary
1. You need to first find a constant (K) for your material. The constant is a number that tells us how your particular material vibrates at a given length. You need to cut a pipe to a reasonable length (the raw material from the store may be too long/low and could leave more room for error), and check the Hertz with your tuner. Once you have your constant, this pipe may become one of your instruments (if it's not already too short).
CUT YOURSELF A 1-2' PIPE AND CHECK IT'S FREQUENCY WITH THE TUNER APP. THEN USE THE FREQUENCY TO FIND YOUR (K).
To get your constant (K), here is the formula-
K= (length of pipe) x (square root of frequency in Hertz)
Again, I prefer to use millimeters or centimeters if possible because inches/decimals make the math slightly more complicated.
2. You'll need to know what the frequency of your first desired pitch. The website below has a chart of frequencies at whatever standard. (a=440 or perhaps a=442 if you're needing to match mallet instruments)
3. This is the big scary math equation! Once you have your target frequency from the chart (X), divide the constant (K) by the square root of X. Here is that formula.
L is the length you'll need for your first pitch.
4. Measure twice, cut once. Never cut it too short. Unfortunately you can't add material if you go to far.
5. Continue plugging in all of your target frequencies for X (I cut and check one pipe at a time just in case). A metal cut-off saw works best, but you can definitely use the rotary pipe cutters as well.. Be sure to account for any blade widths when cutting to an exact length.
If you use a cut-off saw, allow the metal to cool before checking pitch and be sure to get any debris out of the pipe. If your material is consistent and your math doesn't suck, this method is really accurate.
Here's an example of the math!
With my tuner app, I've just determined that a pipe 48.8 cm long vibrates at a frequency of 512 Hertz. Multiplying the length (48.8 cm) times the square root of the frequency (22.63) equals 1104.344. This is a constant for your particular material. To calculate the length of a pipe that should resonate at C, (261.63 Hertz), divide the constant by the square root of 261.63 (which is 16.174) and you should get 68.25 cm as the calculated length of the desired pipe!