Servo frames and mounting screws

[tewatson]

Having grown tired of phillips head sheet metal screws supplied with most servo frames, decided to look into an alternative solution. These Servorahmen bearing frames are made of a very tough plastic that actually drills and taps very cleanly, so decided on 3mm socketed machine screws with coiled stainless steel thread inserts. This provides great serviceability, and eliminates the risk of a screwdriver slipping out of the slot and stabbing something (like your wing skin.)

The retrofit process is very easy...got used to working with these tiny thread inserts repairing Solex carburetors about 35 years ago.

Tom

[Mark9]

Markie likey...but how easy would it be to frames already installed Tom? I have many installed that I slotted the heads on those cheap Phillips screws provided. Then your working with a blind hole.

[tewatson]

Technically, it could be done, depending on the frame style. You would need to use a positive mechanical stop on the pilot drill to make sure it doesn't damage the wing skin. The challenge could be tapping the hole...bottoming taps are available, but there must be enough depth to start with a conventional tap. You might also need to shorten the install tool tang engagement prongs (see pic of insert and tool.)

IMO, this would less feasible with installed frames for horizontal lug servos like the 6130.

[Mark9]

Those were exactly my thoughts too Tom. I have many HV6100's using that similar type frame and a few 6130's in frames. It uses a wedge clamp, but the same basic concept. My Ventus I just finished has 8 HV6100's in those frames. To chase the threads on my X3 wing I just ground down a standard tap to make it into a bottoming tap, it was much cheaper. I wonder what the tap size is. It would be quite fiddly installing the Helicoils, but I loath Phillips head screws. Don't like flat blade screws either, but they are better than Philips. Would make a good retro fit project if I can't fly due to bad weather.

[tewatson]

A simpler solution for installed frames would be the socket head servo screws from Micro Fasteners. They come in two different diameters and various lengths:

https://www.microfasteners.com/stw0205-2-x-5-16-servo-mounting-socket-head-washer-head-sheet-metal-screws.html

[Mark9]

That's a good idea Tom. I have some of their #2 X 5/16". I need to see how that might work, but in some of my applications the standard Phillips head just barely fits under the servo covers. The aileron servos in the Ventus are one. The new thin airfoils sure limit the servo thickness height clearance.

[tewatson]

They also have similarly sized button head hex drive screws - perhaps a shallower head profile:

https://www.microfasteners.com/stp02...al-screws.html

[Mark9]

Those might work Tom! The next time I make up an order I'll get a bag. Thanks!