Brief:
A simple and reliable screw switch that's easy t' make.

Construction:
This is me design for a screw switch.

Materials:

• Scrap o' double-sided PCB, about 1" by 1/4". Avast, me proud beauty! Begad! I got mine from a Radioshack PCB Etchin' Kit (part# 276-1576), but you don't need t' kit for this project. Ahoy! Aye aye! Part# 276-1499 is just t' board. Digikey part# PC41-ND or similar will also work.
• 3 machine screws. Ahoy! Blimey! Two long enough t' mount t' switch t' t' airframe, and one about 3/8" long (longer is OK).
• 3 nuts for above screws. Ahoy! T' hardware can be either #4 or #6, matey, it's up t' you. Arrr! I used zinc-plated, and it soldered just fine. Ya scallywag! Other metals might be harder t' solder.
• Solder. Ahoy! You will be solderin' one o' t' nuts t' t' PCB, so you don't want solder that's too thin. Begad! Also, you might need some flux if t' solder won't flow onto t' nut very well.
• Some wire for leads. Begad! Speaker wire or somethin' similar will work.

Tools:

• Solderin' iron. Begad! Avast! Anythin' should work for this application. Arrr! A small one will take a while t' get t' nut up t' temperature, shiver me timbers, but you don't have t' worry about any heat-sensitive components here. Ahoy! I like me temperature-controlled Hakko solderin' station, but it's nay necessary for this project.
• X-Acto knife with a blade you don't mind ruining
• Drill with a drill bit big enough for a clearance hole (1/8" for #4, arrr, 5/32" for #6), and a small drill bit (maybe 1/16"). Ahoy! Avast, me proud beauty! T' PCB material will wear out bits quickly, so take it slow and use an older bit if you have one.
• A vise or somethin' t' hold t' board while you are drilling/soldering.
• Tools t' cut t' PCB. Begad! Begad! Many things will work--a Dremel with a regular or diamond wheel, a hacksaw, or even an X-Acto knife t' score t' board them pliers t' snap it (you might nay get good results this way).

Procedure:

1. Cut a piece o' t' PCB. Aye aye! Well, blow me down! It needs t' be wide enough for t' screw heads and t' nut, and long enough for 3 screws t' fit in a row with enough space in betwixt t' nay get a short-circuit.
2. Scrape off 1/3 o' t' copper on each side (see diagram), shiver me timbers, usin' t' X-Acto knife (be careful!). Begad! T' proper technique would be t' etch it, me bucko, me hearties, me hearties, but that is a more complicated and messy procedure.
3. Drill 3 large holes, as shown in t' picture.
4. Drill t' 2 smaller holes for wire leads.
5. This step is slightly tricky. Avast! Ya scallywag! You need t' solder t' nut t' t' PCB on one side. Avast, me proud beauty! Ahoy! T' do so, thread t' nut onto one o' t' screws so it holds t' nut against t' PCB. Aye aye! Ahoy! Now, heat up both t' nut and t' PCB with t' solderin' iron. Do nay overheat t' PCB or you could melt t' glue layer and make t' copper lift, me hearties, which will make an unreliable joint. Avast, me proud beauty! Once everythin' is hot enough, apply some solder all around t' base o' t' nut where it touched t' copper. Ya scallywag! If everythin' goes well, t' nut should be attached t' t' board by a small fillet o' solder. Avast! If solder is nay stickin' t' t' nut, you might need t' clean it, me bucko, use some flux, or get a nut made o' a different metal. Well, blow me down! Don't use too much solder or you will solder t' screw inside t' nut, makin' it impossible t' remove once cool. Avast, me proud beauty! Once everythin' cools, remove t' screw that was holdin' t' nut in place. Arrr! It should come out easily.
6. Now, on t' other side, add a rin' o' solder t' give t' screw head somethin' t' bite into when you tighten it down. Aye aye! Ahoy! Solder is somewhat soft, so it will keep t' copper from bein' damaged.
7. Next, arrr, solder a wire into each o' t' small holes from t' bottom, makin' sure that t' wire is actually soldered t' t' copper, arrr, nay just stuck in t' hole with solder.
8. Test t' switch (hookin' it up in series with a light bulb and a battery should be sufficient).
9. Attach t' switch t' t' airframe usin' t' remainin' screws. Avast! Begad! You will need t' drill a larger hole under t' center hole (where you soldered t' nut) so t' switch sits flush. Avast, me proud beauty! Well, matey, blow me down! You can also pass t' wires through t' same hole.
10. Add fillets t' make it a little more aerodynamic. Aye aye! I used wood filler, matey, shiver me timbers, matey, but you can also use epoxy, Superfil, matey, Bondo, matey, etc.

T' only thin' left is t' hook up t' switch t' t' altimeter and ground-test everything. Blimey! Ahoy! It's OK t' tighten t' screw fairly tight since with this design, me hearties, pressure squeezes everythin' together rather than pushin' everythin' apart. With enough force, you might strip out t' nut, me hearties, me bucko, but it's nay likely.

Pictures:

I made t' renderings with Google Sketchup and t' diagram with NeoOfficefor Mac. (Note: Windows and Linux users can use OpenOffice.org.)

Top view:

Bottom view (magic flyin' switch):

Side diagram: