Here is an Instructable on how I made a pair of Hollow Bolt Earbuds. I call them earbolts.

There is a fair amount of skill necessary with a power drill, Dremel motor tool, soldering iron, and hand tools to perform this build described. I am only describing my method of making this, which is easiest for me. If you feel you need a drill press to drill a hole instead of by hand, then by all means do what you think is easy and safe for you. Some of the practices I do in this Instructable may be tricky, risky, and dangerous when proper safety practices are not adhered to. USE COMMON SENSE! Wear eye protection and hearing protection when using a Dremel, drill or other power tools. With that out of the way, HAPPY BUILDING:)

Step 1: Materials List

A pair of broken earbuds, or old earbuds, of the small in-ear type that have a silicone seal.
From them, we get a 1/4" earphone jack, wire, and 2 speaker elements.

Electrical tape

4 Grade m5 bolts, with a head diameter of a little more than your speaker outer diameter. Around 1" long.

Friction tape (optional)

Solder

Super glue

1 pack Sugru (Moldable silicone). Sugru.com (good stuff to have anyway)

2 steel nails, slightly bigger than the hole you drill for the sound hole. I used 8 Penny nails, and 3'16" bit.

For tools, here is what helps to have on hand:

Dremel, and cutoff wheels

Hand drill, or drill press

Soldering iron

Vise

Scissors

Wire stripper (optional)

Various common hand tools

Volt Ohm Milliammeter (VOM)

An assortment of common drill bit sizes, including a 5/8", 5/16", (the drill bits I used)

Small eyeglass repair screwdriver, regular tip

Hammer (ball peen is best, but any will do)

Step 2: Extracting the Speaker Elements

The speaker size is the determining factor of how big these earbuds will be. Technically speaking, you want Neodymium 5-7 mm driver speakers, just like the ones in Skull Candy earbuds and the good quality type. The Apple earbuds are too big, with a speaker that will not fit inside the head of a bolt. You need the small, in ear type that have a silicone seal that you shove way into your ear canal, allowing the speaker to sympathetically vibrate your eardrums. That airtight seal is the secret to sealing in the grinding bass, and being in a blissful world of sound. A down side of this type of earbud is that it can cause hearing damage if played too loud.
I got mine from an old pair, but you can find small old earbuds at thrift stores, and on ebay.com, craigslist.com, and retail.

Step 1. Pull earbuds carefully apart, along a seam in the plastic body shell. You can use a small screwdriver here, but be slow and careful. Here I didn't have to, they were coming apart already! Once you see wires, you are at the back of the speaker element. Be careful! Don't pry the speaker out, as you can very easily sever the two extremely small wires coming from the solder pads to the coil on the diaphragm. They are protected by a small dribble of rubber cement compound. But it won't protect from a small screwdriver tip! If you take a small regular eyeglass repair type screwdriver, and scrape around the edge of the speaker element, where it joins to the body of plastic, you can usually make it spin, or get a small catch in the metal rim of the speaker you can VERY CAREFULLY ease it out far enough to grab. Once again, be careful of those two small wires. Don't scrape on their side of the speaker, to be safe.

Step 2. Once you get the speaker element out, test it's internal resistance with a VOM to make sure that those two small wires are good. Seeing about 10-50 ohms is good, and will vary by manufacturer. Seeing infinity resistance means that the wires are blown. Scrap it and start over. Assuming you have good elements...

Step 3.The pictures show pretty well the steps of taking the earbuds apart. Just be careful, and don't manhandle the speaker diaphragm with your fingers. Save any useful parts, but what we need for this project are the speaker elements, Speaker element protectors, and the wire. If the speakers have their speaker protector on, then leave them! It will protect you from touching the diaphragm. I removed them for this Instructable only.

Step 3: Get Bolts of Right Size

Here is the parts list:

4 x steel m5 hardness (standard) 1" long bolts. Thread does not matter. If you are hardcore, and really want to show off your skill at hand machining through metal, use 4 stainless steel bolts instead of mild steel.

The size of your bolts depends on your speaker outer diameter. Have your earbud elements ready to measure against the top of your bolt head. You want the bolt's head to be about 6-7mm bigger than your speaker. See picture below. This will allow enough metal all around the speaker hole for the wall. Once you select the bolts, then...

Step 1. Put bolt into vise, center punch exact middle in top of bolt head.

Step 2. Get a drill bit that is the same size, or slightly bigger than your speaker elements outer diameter, (I used a 6 mm speaker element, and a 5/8" bit.) High speed cobalt or titanium coated bit for stainless.

Step 3. With hand drill, drill the speaker hole in the top of the bolt head, using the punch mark for starting. If you see the hole you are drilling getting slightly off, angle the hand drill in the direction the hole needs to go. The drill bit tip will "walk" the hole center back into true. Be careful! This is easy to make out of center by hand, and easy to break drill bits. Take your time, drilling with a steady vertical pressure. Walk the hole back into centered if it gets off. Drill about 3 mm deep for now, and finish drilling to required depth after doing the next step.

Step 4. With Dremel and cutoff wheel, cut bolt to length. About 1/2 " has worked for me. Sugru Moldable Silicone is used to make a custom ear seal, so leave enough thread to put Sugru onto. You can get Sugru at Sugru.com.

Find a drill bit that is about half the diameter of the threaded part of the bolt. This will drill a hole in the middle down the length of the bolt, for the sound passage. In the picture it shows too big of a bit, on the threaded side. Substitute a half-diameter drill bit instead. The bolt needs more wall thickness to be strong down the length of threads, thus, a smaller diameter drill bit is needed.

Step 5. Center punch the threaded side (tip) of the bolt, in the center. I drilled one of the earbuds from the tip first, and another from the head first, and the tip-to-head method proved more accurate. Drill with a drill bit that is half of the diameter of the bolt. Drill like the head side, walking the bit into true center. Drill a little in, and pull the bit out to look down the hole, and clean it out. If you see it getting off center, correct for it by angling the hand drill. Spray WD 40 frequently on the bit to lubricate it. It cuts way better when it's cool, sharp, and lubricated. Throughout the drilling process, stop frequently to spritz some on the bit, and in the hole.

Step 6. Finish drilling the bolt head to fit the speaker, and check fit of element frequently. It should be snug in it's hole. The depth of the hole should be the height of the speaker, so it sits mostly flush.
It's okay if the back of the speaker sticks out of the bolt head a bit, there is room because of the other cap you will make later.

Step 7. Repeat on another bolt, and try to duplicate everything, including errors, if present, so they match.

Step 4: Make the Other Earbud Half

Here we are making the other half of the speaker enclosure. It is a bolt head, cut off and hollowed out.

Step 1. Use the same center punching and the drill bit walking trick to get the bolt head hollowed out evenly. You are wanting to make a hollow cap. Drill about 4 mm deep hole, not too big. After its almost all drilled out, go around the edge, wobbling the bit, making it all even lipped and centered.

Step 2. After drilling, smooth off and round sharp edges with Dremel and cutoff wheel.

Step 5: Make Sound Hole Screen With a Nail

In this step we make an ear screen in the earbud. It protects the inside diaphragm from getting dirt and lint in it from down the sound tube. It is a sharpened Galvanized 8 penny nail with 4 grooves cut in it. That tip of the nail, with those grooves in it, is then cut off, and hammered into the ear side of the sound tube.

Step 1. Find a steel nail that is slightly bigger in diameter than the sound hole through the middle of the bolt.

Step 2. With cutoff wheel, cut 4 grooves into the nail, lengthwise, at equal intervals, around the sharp point. Groves should be 2-3 mm deep.

Step 3. Cutoff 5-7 mm of the sharp, grooved nail tip. This little tip is what we need.

Step 4. Put bolt, threaded tip end up, into vise. Tap sharp end of little nail tip into the sound hole in bolt with a hammer. If you cut enough of the nail, then it should be a snug fit. If the 4 grooves were cut deep enough, there will be 4 small looking holes which act as a screen in the end of the earbud now.

Step 5. Take a sharp finishing nail, and ream those 4 small holes as clean and open as you can get. Those carry the sound through, and need to do a minimum of blocking the sound hole.

Step 6. Clean up with Dremel grinding.

Step 6: Putting It All Together! YAY!

Step 1. With a soldering iron, solder the wires to the back of the speaker. The wires that were connected to each earpiece should be reconnected to the speakers (I like to redo wire connections, to assure quality.) Match red with red, if a color is present on the speaker. Each side (Left and Right) of the headphone wire should be carefully stripped, and soldered with short leads to the speakers. The other side of the wire re-solder to the 1/4" earphone jack. See picture. When you strip the wire, you will see a shield, (outer conductor). This is ground. This goes to the outermost conductor on the jack. The red goes on the middle conductor, and the blue goes to the center conductor. The red and blue color on the wires is a plastic enamel, and is of no concern. It is an insulator, but when heated to tin the wires with a soldering iron, it melts off and doesn't affect soldering.

Step 2. Cut 2 small circles out of a piece of standard electrical tape with scissors or a wire cutters. They should be just big enough to cover the back electrical connections on the speaker, where the wires connect. Push circles onto speaker firmly, so connections are covered well. Cut 6 more circles of the same size out of friction tape this time, and layer over the electrical tape on the back of the speaker, 3 per side. If you don't have friction tape, use electrical tape. This acts as a spacer, and keeps the speaker in place.

Step 3. Gorilla Super Glue, or regular super glue, is used to adhere the two halves of the earbud bolts together. Put speakers into the sound tube bolt, with the diaphragm facing the right way, and put the cap bolt head on to cover the speaker. Align the wire passage holes, and center completely. Put the glue on as a small drop, like in the picture. It wicks down into the groove. That's all you need. Make sure to not use too much glue, because if it gets into the speaker cavity, it will destroy the speaker element. Clamp gently for 6 hours to dry completely.

Step 4. Mold creatively a Sugru jack cover, and make sure that the sugru sticks to the metal well, and around the wires.

Step 5. Mold the custom ear seals out of two equal small balls of Sugru. Alternatively, you can use the silicone earseals that the original earbuds came with, if you have them, which may be more comfortable than the sugru ones. Mold by hand around tip of bolt, making sure not to plug the 4 sound holes at the end of the bolt. Put earbud tip with Sugru on it in a piece of saran wrap, or sandwich bag, and pull the plastic tight around tip of bolt and Sugru. The saran wrap is there so the Sugru doesn't stick to your ear canal. Gently push in your ear, straight, and slowly, so it doesn't excessively mash the sugru. Wiggle around with very small movements in your ear, so it is comfortable. Pull it out slowly so it doesn't change from your ear mold. Remove plastic slowly to not pull away Sugru. CAUTION!!! BE CAREFUL. USE COMMON SENSE. DON'T STICK ANYTHING TOO DEEP IN YOUR EAR. BE GENTLE. TEST EDGES FOR SHARPNESS BEFORE PUSHING IN YOUR EAR.

Step 6. Repeat on other earbud for the other ear seal.

Step 7. You're DONE!!!:)