Attn: Mic Modders & Builders-- I need to find some very tiny screws!

A while back, I picked up a pair of AKG C451Ls, which come stock with a Lemo connector, rather than XLR or Tuchel. I ran across someone (perhaps on the TapeOp board) who mentioned getting around the cost of buying Lemo cable connectors (at $66 each!) by grinding the threads off of some Neutrik XLR plugs and sticking them in the mic bodies where the original Lemo connectors went (they were not machined as part of the body like the normal variants). So I ground the threads off of some Neutrik XLR connectors and they fit where the old Lemo connectors would fit.

Now I just need a way to secure the connectors in the end of the mics. The mics originally came with 3 mounting screws per mic, which went through the body and into the connector wall within the body. Unfortunately, I only received 3 screws across both mics, two of which have been lost due to their extremely small size, which is my current and final problem to overcome-- the size of these screws. Please see the attached photo for a sense of scale.

I've looked on fastener dealers' websites and local hardware stores, but can't find anything even remotely this small. My father suggested a local hobby store, but once he saw the screw he was pretty sure they wouldn't have anything like this. I have a feeling that if I find a online store that carries small fasteners, that I won't have a way to measure the thread pitch, etc. appropriately due to the small size.

I work at an AKG dealer and could theoretically go through the many phone calls required to get someone from Vienna on the phone, but everything I've read indicates that AKG keeps piss-poor records of things like this. If you guys think it's worthwhile, I'll do it, but I'm kinda hoping someone has some previous experience replacing these screws and can tell me a useful spec or two (and maybe where to buy them). Oh yeah, and maybe someone has an idea about tapping the hole in the XLR connector? I doubt these screws come in a self-tapping variety...

Here's another photo which shows the mic body, Lemo connector, and XLR connector, along with the screw.

There is a small jewelers tap and die set on Amazon (Search jewelers tap)

And for screws try http://www.mcmaster.com

As for figuring sizing, unfortunately I can;t help you there, my tap and die set is currently lost (it is really small... the whole thing is smaller than 2 matchbooks) but if you have any repair diagramms for the AKG mic's (or newer mice) you should look for the screws and they may have a designation next to them (like m1 or m2 or something) those are metric screw sizes.  But the small screws may be done with wire gauge numbering... maybe someone else can chime in on that.

Thanks Bruce, I think between the sizes in the jewelers' tap kit and what McMaster-Carr offers, I should be able to find what I need. It's funny, as McMaster-Carr was the answer to my last question here, too. Time to talk to one of my guys over there...

As far as the repair diagram goes, I've never seen one for the 451Ls, and since the Es and Cs have the connector integrated into the machined body, these screws wouldn't appear on their repair diagrams.

I would guess M1.4 or M1.6. But do you have a micrometer? That would stop the guesswork. You can find digital ones pretty cheaply these days.

You've probably realised that the Neutrik barrel is made from some soft alloy. Unfortunately it doesn't hold a small thread very well, and you may struggle to tap it to anything less than M2 or M2.5 size.  I would be tempted to get some short M2 screws and an M2 tap, and widen out the holes in the mic slightly if needed.

Cheers!

Stewart

Good point about the softness of the connector. I'm gonna bring the body down to work tomorrow-- the tech has some small measurement tools there, although I'm not sure if he has the right thing for this.

I'd like to avoid enlarging the holes on the body as they are tapered to flush-mount an oval head machine screw, and I don't believe I have any way to create that bevel on a larger hole.

Well then, just go gently when tapping it and don't force anything. I'm sure you'll be fine.

One more thing. With the Neutrik plugs, the insert slides in from the rear.  Have you figured a way to stop the insert sliding up into the mic when you plug in the cable?

Cheers!

Stewart

zebra50 said:

Have you figured a way to stop the insert sliding up into the mic when you plug in the cable?

Click to expand...

Yes, I brought one of the mics to my local hardware store and picked out a couple of nuts which posses an external diameter just smaller than the inside diameter of the mic at the nuts' widest points, and are the same thickness as the gap between the circuit board and the custom-trimmed remaining part of the connector's strain relief.

I originally thought that doing this would allow me to tape the mics together and start using them while I found the appropriate screws, but the ground connection is still intermittent when subject to even minute vibrations (i.e., after it was cutting out bad on snare bottom (which is what I bought the mic for), I tried it on acoustic guitar in a less-cable-weighted position and it was still cutting in and out a bit).

OK, the tech at work didn't have anything to measure small holes ("I don't do that kind of thing," he says), but they did have a metric ruler. I put the screw on it and it appears to be 1 mm in diameter and 2 mm long. It's not an oval head, as I thought earlier, but flat head slotted drive. So that pretty much gives me my spec, but I'm having trouble actually finding exactly that by putting those terms into a Google search and McMaster-Carr doesn't go that small. Anybody have any ideas on sources for 1M x 2mm slotted flat-head machine screws?

Miniature metric screws are available here:

http://www.jimorrisco.com/miniature-screws-and-fasteners/unm-screws.html

Also possibly eyeglass screws, or a dead analog watch might have a size that works

Thanks Youngwhisk. I just purchased some tiny screws from J.I. Morris. Hopefully they're compatible with the holes in the mic bodies.

I also bought a tap & die set off Amazon. It was like $8 or $9 bucks. I couldn't find a tap & die set this small with any good reviews, so I went for the cheap one (which seems identical to some higher priced ones). With the Neutrik connector being so soft, I figured I should at least be able to get this one use out of them before the 1mm tap craps out.

I'll post some pictures of the final result when I'm done (which I hope isn't any longer than a week, 'cause I'm dying to use these on all sorts of sources).

I got real lucky with tiny screws. When groove tubes sold off all their remaining supplies before going to fender, I was down there picking up all kinds of things, got a small parts box full of microphone screws.

You might dis-assemble an old 35mm SLR camera.  They have countless bits of very small hardware.

I wish I had a box full of mic screws and an old film SLR camera. I'd use the screws in the mic and get the camera working again...


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Minor update (for any who are curious)-- the screws arrived a few days ago, but they're actually two small! I'm gonna have to examine J.I. Morris's measurement criteria and order the proper size on Monday night.