Longer mounting screws or alternate ways of mounting large stacks

[nikhil]

I am building a TinyDuino stack that is currently 5 boards tall. I want to screw this onto a PCB onto which I have soldered other components. The screws that come with the tinyduino are too small to accommodate this - I need something at least 2.5 cm long. Down the line I will very likely want to add another board on (when I figure BTLE out - look at my other threads!).

Where can I buy longer screws? Measuring with a calliper, the screws that ship with the TinyDuino are 1.2mm in dia. But M1, M1.2 are really hard to find - I did quite a bit of searching online. Any suggestions on where I should look or alternate ways of mounting these?

[amdrake]

I also am interested in longer screws.  After measuring the diameter of the provided screws, 0.046", I believe they are the standard 00-90 thread size.  I could not find any online that were longer than 1/2".  A couple of places had threaded rod in that thread size, but their prices were too high for a hobbyist, in my opinion.  I was hoping that the next size up would fit, i.e., 0-80, but they are 0.06" in diameter, and the hole I measured was only 0.058"; "close but no cigar".  If anyone finds a source for longer 00-90 screws, please share.

In the meantime, I'm going to try making my own threaded rod.  Micro Mark and some hobby stores sell 3/64" brass rod, as another poster mentioned, which is 0.047".  I ordered some from Micro Mark, along with a 00-90 die to cut the threads.  This is not cost effective, since the die is over $20, but I'm doing it anyway.  I'll just add the die to my collection of other sizes.  I've never cut a thread this fine before.  Wish me luck.

--Tony

[TinyCircuits]

I've done some searching online, as you guys say these size screws are pretty rare, but I did find an option for longer mounting options.  I ordered some 00-90 threaded rod and 00-90 nuts from JI Morris (http://www.jimorrisco.com/), which works well.  The threaded rod is 12 inches long, so you can cut it down for your project.  The only problem is that it's really pricey ($18 for one 12 inch rod), but so far it's the best I've found. 

Thanks,

Ken
TinyCircuits

[heliboy]

Try mcmastercarr.com

[TinyCircuits]

Unfortunately McMaster Carr doesn't sell screws or nuts that go down this small.

[EKMallon]

Well, at $18/ foot,  I might try to buy a die

http://www.microfasteners.com/die0090-00-90-dies-carbon-steel.html

and some generic brass rod from the local hobby shop, and see if I can thread my own.   

I've never tried that before though, anyone else?

[amdrake]

I said I was going to try threading my own rod in my post on Jan. 20, above.  Since then, I received the die and the brass rod, and gave it a go.  While I have threaded many things over the years, I failed at this one.  I could not get the thread to catch in the die and feed the rod forward.  I think it was because the metal was too soft, and the tiny beginning threads torn off rather than helping to feed the die further down the rod.  I haven't given up yet.  I intend to try again.  I think it would go better with an appropriate gauge steel rod instead of brass.  I'll have to look for a source for that.

--Tony

[EKMallon]

Well... I can confirm the frustration that amdrake expressed about trying to turn down those brass rods. Gad!

So I went back to searching for another solution.  And I think I might have found one. RC aircraft push rods:

http://www.radicalrc.com/category/.032-Pushrods-469

As far as I can tell, many of them are threaded all the way down the shaft, so we can cut them to the length we need. I have no idea what the threads are, but the sets usually come with "clevis" ends, that ought to do well enough as hold down nuts. Might even be easier for my fat fingers to deal with.

I have some on order now, and will let you know if they work.

[EKMallon]

Just an update on the RC aircraft pushrods for 5+ board stacks:

I have been using HBZ7128 Pushrod and Clevis Set for the Cub aircraft, as extra long mounting pins.
 
They are about $1/pair on ebay, but unfortunately they are only threaded to 3/4 of an inch on one end of the rod.  I have been bending the rods into an angular "U" shape, and threading them up through a plastic platform, so that the two threaded ends are at the non-stack connector side of the boards. The rods "just" make it through the tiny board holes, so they are probably 1.45mm in diameter, and I have no idea what the thread dimensions are. The plastic clevis ends that come with them are easily cut down with an exacto knife into 3mm high hold down screws for those threaded ends. The metal in the rods is reasonably easy to bend and cut.  I am still using the spacers from the tiny board mounting kits. So its a workable solution, but probably not as elegant as just ordering those 00-90 brass rods
(which I also ordered from http://www.specialshapes.com/threadedrod.html for $14.95, they sell the 00-90 nuts 12/$3.60, shipping was $10)

[tinybuilder]

Here are two possibilities from fastenersclearinghouse
FMP   MA   Machine Screw   Brass   Plain   #00-90 x 1   slotted fillister   400
FMP   MA   Machine Screw   Brass   Plain   #00-90 x 1   slotted round   140

And some inexpensive threaded brass rods from scalehardware
http://www.scalehardware.com/threaded-rod-c-26/1-2-mm-x-63-5-mm-threaded-rod-2-pcs-p-200
http://www.scalehardware.com/threaded-rod-c-26/1-0-mm-x-63-5-mm-threaded-rod-2-pcs-p-199

Hex Nuts
http://www.scalehardware.com/product_tech_info/miniature-hex-nuts-c-2/1-2-mm-hex-nut-brass-qty-25-p-229
http://www.scalehardware.com/product_tech_info/miniature-hex-nuts-c-2/1-0-mm-hex-nut-brass-qty-25-p-32

[rdrink]

Dumb question here: what is the size (and better still the part number) of the screws in the original mounting kit?

[braza]

http://www.smallparts.com.au/store/partscombined/machinescrews/Machinescrews/A/23/#SIZES

[jcarter]

Dumb question here: what is the size (and better still the part number) of the screws in the original mounting kit?

According to the website:

    Four M1.2 Machine Screws, No Slot Oval Head, 15.0mm length
    Four M1.2 Hex Nuts, ACF 2.2mm
    Twelve Plastic Spacers, 3.0mm Height, 2.3mm ID, 3.2mm OD