Common thread size for instrument panel screws?

[danny_galaga]

Just had the thought that is like to match the screws on my instrument panel. Since done of my instruments didn't come with them off thought I might add well make them all the same. I forgot to check what the size is and want to hear straight to the bike shop from work. Would they all be the same thread? Talking ASI, radio, altimeter, tacho. 

[kgwilson]

Depends on the source. US will be imperial, European will be metric, Chinese will be whatever the customer specifies.

[IBob]

Just removed old Becker (German) Xponder. Screws for that are 3mm.

[Marty_d]

All the ones I recently put in were M4.

 

 

Edited February 1, 2022 by Marty_d

[Blueadventures]

11 hours ago, danny_galaga said:

Just had the thought that is like to match the screws on my instrument panel. Since done of my instruments didn't come with them off thought I might add well make them all the same. I forgot to check what the size is and want to hear straight to the bike shop from work. Would they all be the same thread? Talking ASI, radio, altimeter, tacho. 

Check in Aircraft Spuce under instrument screws they list some sizes.  Years ago I bought some.  Their size (thread and length) list may help.

[facthunter]

US will be AN won't it? That's a gauge thread in the smaller sizes The brit instruments are BA. (British Association) if you had a warbird or such. Nev

[danny_galaga]

Mix of US and european instruments. 

[Blueadventures]

Hi Danny

 

Maybe work out what you need (thread, length, head type)and give the radio repair shop at Archerfield a call; I'm sure they have an assortment container of used instrument screws that you may be able to sort through and select some and then work out a cost.  Maybe some beers or cash.  Easy enough to then light spray in matt black if needed.

 

Your build must be getting close, any images of the build and dash etc.

 

Cheers Mike

Edited February 2, 2022 by Blueadventures

[Marty_d]

I bought black steel Allen drive dome head bolts, then sprayed the heads with a coat of clear paint to prevent rust.  They turned out really well, nice gloss finish but unobtrusive against the carbon fibre pattern dash. 

[djpacro]

Instrument screws are brass for a reason https://www.aircraftspruce.com/catalog/hapages/brassinstrscrew2.php 

 

[facthunter]

Non magnetic has relevance on an instrument panel. You still have Tacho  drive and throttle cables and Spring Back binders to muck up your compass. Brass screw slots are easy to destroy with a crook screwdriver. The ones that have been really badly reshaped on the grinder. Nev

[danny_galaga]

Might combine those two ideas. Same type of screws as Marty went for, but SS. and then I'll paint em 🙂

[facthunter]

SS with an SS nut can weld together (gall) and be impossible to remove later. Nev

[kgwilson]

Depending on the grade of SS it will also rust and is magnetic. Plated (not Nickel plated) or plain brass is the best.

[onetrack]

You'll be struggling to find any paint that will stick to stainless steel.

[facthunter]

Zinc is the safest to plate. Cadmium used to be the go but is poisonous. Zinc-nickel has replaced it in the aero game. Electroless nickel plates even and sticks better and is a dull finish.. Zinc gives GALVANIC protection and is softer  so better on threaded parts.. Nev

[danny_galaga]

8 hours ago, kgwilson said:

Depending on the grade of SS it will also rust and is magnetic. Plated (not Nickel plated) or plain brass is the best.

Very little magnetism though. The instrument panel is held on by about twenty SS screws so I don't think magnetism will be a problem. I admit painting them might be problematic though. 

[SilverHammer]

As a retired ex metallurgist I simply can't resist adding my ten cents worth...

The two most common types of stainless steel are ferritic, which is magnetic, and austenitic, which is not (there are 5 main types, based on crystal structure).

Austenitic stainless has a higher nickel content and is more corrosion resistant.

One example is 18/8 or AISI grade 304, others are grades 302, 303, 316, 32, 347, & 348. Happily, Bunnings Aerospace division has fasteners in 316, as do boating suppliers. Check with a magnet, I doubt many Chinese fasteners are true to label.

Now, the avoidance of magnetic fasteners is to prevent affecting the calibration of the compass, the primary navigation instrument until the late 70's. With local flying, the use of GPS and moving maps, accuracy isn't as vital, and seeing many ultralights with rudimentary compasses and no correction card, probably only of academic interest.

With Danny's 20 screws, if a manufacturer uses them, they are probably OK, and if not, the compass could have been adjusted to compensate for them. The main issue is not to inadvertently disturb any calibration that has been done.

Painting stainless isn't difficult. Degrease with acetone, sand lightly, prime first. Rattle can enamels are fine indoors.

[danny_galaga]

On a related note, a couple of bolts for my door latch were too short so I went to my local bolt shop to get something a little longer. They are 8.8 and rather small (maybe 4mm shaft) . I asked if they had some longer ones. They had trouble finding something so asked me what it was off. I told them an ultralight and they ummed and ahhed a bit. They eventually found some Allen head bolts. Maybe 9.8 or summink, and told me theyre not keen to sell if it's an aircraft. But they did anyway. I was going to tell them since it's in the experimental category of aircraft I could make it from rolls of old newspaper and no one would be liable but me. But instead, I've decided from now on I'll just say it's a kit CAR instead 🙂

Edited February 4, 2022 by danny_galaga

[Blueadventures]

1 hour ago, danny_galaga said:

On a related note, a couple of bolts for my door latch were too short so I went to my local bolt shop to get something a little longer. They are 8.8 and rather small (maybe 4mm shaft) . I asked if they had some longer ones. They had trouble finding something so asked me what it was off. I told them an ultralight and they ummed and ahhed a bit. They eventually found some Allen head bolts. Maybe 9.8 or summink, and told me theyre not keen to sell if it's an aircraft. But they did anyway. I was going to tell them since it's in the experimental category of aircraft I could make it from rolls of old newspaper and no one would be liable but me. But instead, I've decided from now on I'll just say it's a kit CAR instead 🙂

Cap screws are 12.9 usually.

[onetrack]

For a range of small fasteners suitable for non-critical applications, I found the company below have a good range of small automotive fasteners, and they're quite satisfactory to deal with as a company.

 

https://www.jnsfasteners.com.au/

[danny_galaga]

This has all come about BTW because the ASI and radio I got recently don't come with mounting screws! On closer inspection the radio says to use M3, and from what you guys are saying, the UMA ASI will have something non-metric. I have a feeling I will have to make do with whatever I can find, but so long as they are all phillips heads (which all the other instruments I have are) I guess that'll be fine 🙂