Reckon what size these screws need to be?

DKirkpatrick

DKirkpatrick

Pre-takeoff checklist
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DKirkpatrick
Relaxing the old panel in a 172-D with a new aluminum one. Want to put in new brass screws… what size for mounting all the indicators? I know length is important too…
Coaching would be much appreciated.
-dan
 
It’s likely you will have to Trial Fit each instrument.

My guess is many of the units are not original.

With some gyros using too long a screw will cause damage.
 
Instrument mounting screws are typically 6-32 threads, with varying lengths.
 
reckon I don't know*


*I just wanted to use 'reckon' in a sentence
 
That’s right… newer and/or overhauled instruments. Also installing nulites rings. Which may change lengths I suppose.
 
Instrument screws are almost always 6-32. Occasionally, for something like a Sandel or something with a constriction mount, you might find a larger screw.

Length is trial & error. But if an instrument has a limitation on screw length it's typically stamped or engraved on the housing of that instrument.

Pro tip: replace the nuts while you're at it. MS33737-xxC. The "xx" determines the length and the "C" denotes cadmium plating. Head over to Aircraft Spruce and have a look in the catalog for which "xx" corresponds to which instrument bezel thickness. They're a cheap investment in preserving your sanity.
 
Der Fliegermeister said:
Instrument screws are almost always 6-32. Occasionally, for something like a Sandel or something with a constriction mount, you might find a larger screw.

Length is trial & error. But if an instrument has a limitation on screw length it's typically stamped or engraved on the housing of that instrument.

Pro tip: replace the nuts while you're at it. MS33737-xxC. The "xx" determines the length and the "C" denotes cadmium plating. Head over to Aircraft Spruce and have a look in the catalog for which "xx" corresponds to which instrument bezel thickness. They're a cheap investment in preserving your sanity.
Click to expand...

Also, take flat wire lace string and tie the butterfly nut to the instrument. Sucks to get to the last one and it pushes out!
 
JAWS said:
Also, take flat wire lace string and tie the butterfly nut to the instrument. Sucks to get to the last one and it pushes out!
Click to expand...
Yes, but I have a very particular way of doing this so that the tension of the lacing cord doesn't force the nut legs closed. Otherwise the screw just fights it and it'll bend the legs and never thread.

If you buy the right size this is unnecessary. If you know someone else might work on the ship again before you do (like for a transient customer or an airplane that's being sold/bought) I would lace them up. Can't trust the next guy not to hammer a screw in there and pop it out so it falls into the controls or into a wire bundle...seen it!
 
Der Fliegermeister said:
Yes, but I have a very particular way of doing this so that the tension of the lacing cord doesn't force the nut legs closed. Otherwise the screw just fights it and it'll bend the legs and never thread.

If you buy the right size this is unnecessary. If you know someone else might work on the ship again before you do (like for a transient customer or an airplane that's being sold/bought) I would lace them up. Can't trust the next guy not to hammer a screw in there and pop it out so it falls into the controls or into a wire bundle...seen it!
Click to expand...

I've used these in my recent instrument panel rebuild (where you can, for instance, A/S, Alt (just cut off the lower side not needed) and VSI):
https://www.aircraftspruce.com/catalog/inpages/instrumentmtkit.php Yeah, a little expensive (what isn't in aviation?), but a time (time is $) saver, and mounts the gauge nice and snug.

My IA was impressed; he ordered stock for the shop. Those grasshopper nuts just seem to fly off, get lost, wrong size of the tangs...put a dot of RTV on the mounting face to hold in place..or piece of double face tape and it just works.

All of my instruments used 6-32 screws; I bought a bag of 1" brass from spruce. Most decent commercial crimp tools have a screw cutter so if you buy long ones, you can always cut them down (especially brass, since it's softer than steel or stainless). Just measure the length from the joint in the cutter to under the head...

Just a thought.
 
Those look like they would be worth the bucks in time savings… not to mention my ham size hands don’t fit well in tight places
 
DKirkpatrick said:
Those look like they would be worth the bucks in time savings… not to mention my ham size hands don’t fit well in tight places
Click to expand...

They do make it easier to pull gauges in and out if need be. There is an art form to filling a panel (if it's not removable...the only good feature of the floating panels in 172/182s...) by starting at the most inaccessible (airspeed) and building from there. Yeah, your arms look like you had a discussion with a cat's claws, but you can do it if you plan ahead.

Luckily, by removing the vac system from my 172 when I went to the G5s, it's lock the yoke full back, take off the cap nuts holding the panel on the isolation studs, release the closure plate under the yoke bushing to free up the coil cord, pull the panel forward, disconnect the ganged power feed for the TC and clock, release the connectors for the ELT and Nav2 head, the two connectors for the G5s, and the pitot and static lines from the airframe to the first T connector. 10 minutes maximum to get the pilot panel out. Then you can work on it on the bench! THAT makes it easier, too.

I don't have any financial interest in either Spruce OR Skyhawk Panels...but if you're looking to upgrade your panel...I'd seriously consider talking with Lyle about producing a new panel to YOUR specs...owner produced part, no airframe mods needed (assuming you have the floating panel or it's removable, not riveted in place like in a cherokee or derivative)...can't say enough good things about the quality in the end.
 
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