Screw size for Pitot Tube to Pitot mount mast

[BlueCH750]

Thinking tap for 6-32? Any thoughts anybody who has done this recently?

Thanks

 

[swatson999]

Yep. The installation manual for the pitot tube has several links to builders' sites with details on this. Biggest caution is *don't drill into the pitot and AOA tubes inside the pitot tube itself*.

 

[GKC Aviation]

Yes, 6/32 is the go.
I drilled the mast first, then inserted the pitot tube in and marked it.
Then drill the pitot tube in a drill press.
It's a bit fiddly to get the hole angles correct, but as mentioned above, there is lots of good info around.

 

[airguy]

And after you've removed and reinstalled the pitot from the mast a few times, you will ultimately strip out one or more of those 6-32 screws - and you'll end up enlarging them to #8 screws. 2 out of 4 on my airplane (10 years and just over 2000 flight hours) now carry #8 screws.

But yes, 6-32 for the initial holes, and that leaves you enough material to enlarge later when they strip out.

 

[swatson999]

A good reason to mount it in a location such that you don't *need* to remove it unless it's failed (or, in my case many years ago, subject to a recall/replacement). That was the only time I've ever removed it, in 1000+ hours.

 

[jakej]

There are obviously differing methods, including mine -
note : the aluminium ‘casting’ of the pitot base, that fits into the mount, has 4 x ‘pads’ that are much thicker than the rest of the oval area - that’s the area that you drill & tap threads through, in a later step.
All below can be done before the tube mount is fitted for the last time.
Eyeball & mark a point (I use a fine point permanent marker) that is at 90deg to the outside of the curved surface, & does not interfere with the tubes when drilling, mark a line vertical down the pitot body (& onto the mount when the pitot is fitted to the mount) need also to allow for a horizontal point after the mount & tube are together for drilling Initially use a 3/32” drill for drilling through the assembled mount & pitot tube. Separate both & drill/ tap as necessary.
Drill the mount to allow for short 6-32 screw.
Drill & tap the TUBE, using a bit sized for 6-32 screw, carefully & use something like Boeshield during the process - you’ll need to do this progressively, by inserting/extracting the tap, cleaning out the swerve & using the boeshield again because of the soft alloy which can be easily stripped out. HTH.
It’s much easier to do this process with the mount & tube off the plane - that’s why I nearly 100% always mount the pitot tube on an inspection panel YMMV

 

[swatson999]

nearly 100% always mount the pitot tube on an inspection panel YMMV

This is decidedly *not* true.