Wing main spar updrilling

[at7000ft]

Thank you Paul, good info. You have a good Easter too.

Rick H

[psalter]

Rick,

NAS6603 and NAS7403 are both close tolerance bolts with the same dimensions and drill/ream requirements. You need a tight fit of the bolt to the hole for the maximum strength. A very slight interference fit is best for strength.

The AN470AD6/AN426AD6 also known as MS20470AD6/MS20426AD6 respectively have hole tolerance limits of .187" to .202".

So a regular drill 3/16 (.1875) drill bit, #11 (.191") drill bit, or the .189 reamer is fine. The reamer always gives a better hole quality, but that isn't as important with solid rivets as they swell to fill strange shaped holes. A slightly loose hole is recommended for solid rivets. Just keep the holes under the .2" max dimension, the #11 (.191") bit is a standard recommended drill bit for solid rivets, #10 (0.194") is slightly larger.

Rivets like the AN bolts have tolerances of +-.003 inches. Which is the reason we went to close tolerance bolts instead of AN bolts. If using an AN bolt, you might need up to 9 different sizes of reamers to get a tight fit. With close tolerance bolts you would only need a maximum of 3 reamers, and usually the .189 is all you need.

Happy Easter,
Paul

[at7000ft]

The 'newer' version of the main wing spar is put together with four fastener types:
NAS6603-xx Hex Bolt
NAS7403-xx Flush Bolt
AN470AD6-xx Rivet
AN426AD6-xx Flush Rivet

The bolts measure between .1880 and .1890" diameter, and the rivets between .1870 and .1890 diameter.

Version 3.4 or the wing manual says: "Later kits use NAS6603 bolts that are tight tolerance bolts with only 0.001” tolerance. For these bolts, we recommend drilling with a #16 (0.177”) then use a 0.1890” reamer."

And "Drill all holes marked for the 3/16” rivets to #10 and cleco as needed."

Any problem updrilling with #16 and reaming with 0.1890 for all NAS bolts and #10 updrill for all AN470 and AN426 rivets?

Thanks