Your Hard Drive Needs A Diamond Blade

If you find yourself in need of a precision chop saw don’t overlook the value of adding a diamond blade to a spinning HDD platter. [Tony’s] four-part writeup of this build springs out of some very special design considerations for a ham radio that operates in the 47 GHz band. That frequency pretty much rules out using normal components in the circuit and in his case it even makes connecting the components together difficult. He’s using this chop saw to cut small pieces of a ceramic substrate with gold traces on them that will be used to route the signals on the circuit.

We’ve seen hard drives used in a couple of different clocks, and even as a set of speakers. This one makes for a nice addition as a way to reuse those defunct devices that litter your junk box.

[Thanks Thomas]

17 thoughts on “Your Hard Drive Needs A Diamond Blade

  1. That’s seriously impressive. Works great. Looks like something he could even produce commercially and sell to hobbyists. I don’t understand why he wanted to create a 47GhZ ham radio though… anyone know?

  2. @John
    That’s what he’s doing. Many(if not most) HAMs build their own rigs, and it’s cool to see someone continuing that through near-unobtainable frequencies.

    You never really give a lot of thought to the requirements of HF until you have to deal with it, though I can see why it needs such precision and custom tooling. Nice build.

  3. @jay;Anymore fewer and fewer hams construct rigs. Homebrew is the only option for those hams who want to experiment from away from the crowd.

    Respectfully ask why a ham would want to do this, is like asking why anyone would want to do any of the projects posted on hackaday :)

    UHF circuitry can be tricky enough until one gains some experience working with it, I’m sure the same is true of this portion of the microwave bands. But this article shows why few experienced with UHF homebrew may never homebrew at 47 GHz. Not as dedicated as others to the craft, to each our own thing.

  4. Nice build Tony!

    Next time you want to make the inner platter perfectly round, one answer is to cut it to a slightly oversize diameter on your lathe (perhaps +.010 if you can manage the accuracy,) then mount it back on your hard drive spindle. Mount a rotary grinder (Dremel) on the chuck so the axis of the grinder is parallel to the axis of the hard disk drive motor, and the grinding wheel is centered on the platter. Rigidly fix the height of the chop-saw vertical travel so the platter can meet the middle of the grinding wheel. Using the hard drive motor to spin the platter at full speed, bring it down to the final diameter by moving the chuck very, very slowly into the rotating platter. Sparks should be no brighter than barely visible during this operation, or you could distort the platter with heat or cause some problem.

    I would consider using a dribble of water or a mister as a coolant during this operation, but if you’re going slow enough it shouldn’t be necessary. Keep in mind that as the aluminium platter gets hotter, it expands. A hot platter will give a falsely large diameter reading.

    The trick is to use the mounting position on the axle as the axle for truing the wheel. By definition, it won’t be out of round, as long as you finish the cut extremely carefully.

    You could also consider shrink fitting the blade to the trued platter. Leave the platter over the size of the blade’s inside diameter by .003 or so. Make sure the platter is just slightly too big to fit in the blade’s hole. Place the platter in the freezer for an hour, laying flat. Lay the frozen platter on a cool and very flat work surface. Lay the room-temperature saw blade on the platter — it should fit easily. As the platter heats, it will expand to fill the blade’s inner diameter, leaving a very snug fit.

  5. @jwt

    you could die from driving … you could die from eating … you could die from taking a shower … you could die doing 90% of the stuff you do every single day
    but will you? …. well … yah most likely …. eventually … i dont think a spinning hard drive miter saw will raze or lower that chance any

  6. @Jeff: From what I understand, one of the challenges of really high frequencies is that the short wavelengths turn PCB traces and even component legs into tiny antennae. They transmit some signal, wasting power, and also receive signal from other transmitting parts, causing interference. Massive headache.

  7. @Imroy

    Its worse then that. Every component naturally has a capacitance and inductance associated with it. That includes the traces, the component legs, the ground plane, the leads on components, etc. As the frequency increases, the more these values affect the circuit since their reactance is larger. At these frequencies a right angle trace or a thick trace over a ground plane might act as a larger capacitor then any he would place on the board itself.

  8. This is a very impressive build- quick a hard hack. He gets bonus points for using stuff normally used when making processor chips!

    This is some serious geek, hacker, and machinist cred. I can definitely use something like this in cutting precision watch parts, or precious metals for minimum loss. Very very cool stuff.

  9. nice, i’d like to figure out how to make this water resistant so i could spray water on the blade so i could carve in to glass. i’m a glassblower and this would be cool to have in the shop for small intricate cuts

  10. For those asking why – there are no commercially available sources of narrowband radio equipment above the 1.2 GHz band. Hams are active on the microwave bands at 3, 5, 10, 24, 47, 76 , 122, 134, and 241 GHz, with 10 GHz being the most popular. Everyone has to assemble their own equipment on these bands. It is a challenge and an acomplishment to operate on these bands.

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