Our planes use a very large number of small clips that hold a floating captured nut. These clips exist around most of the access panel openings, inside and outside the plane. What are they called, how can I identify them, and where can they be found?
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Technical Editor:
These are called ‘Clip-nuts’ or ‘clipnuts’. They were made under at least three brand names, with subtle differences within each brand. The Monadnack or Monadnock /brand is the one most commonly used by Beech; these will typically match the original fasteners on our planes. You can find a useful, though incomplete, cross-reference chart in the Genuine Aircraft Hardware Manual (available from GAH). The nuts differ in shape and style, type of metal plating, type of nut (fixed or floating), edge distance to the threaded hole, and compatible panel thickness. They are emphatically NOT the same as the similar fixed-nut U-clips found at automotive supply stores. If you use automotive clip-nuts, which often actually cost more than the proper hardware, you are almost guaranteed to have clip corrosion at best, and panel corrosion at worst.
Below is a chart of clip-nuts. I have identified the nuts that are most commonly needed, and which are available from Aircraft Spruce. These puppies have been rocketing up in price in recent years. I suspect it is because there are no remaining large stocks of New Old Stock (NOS) hardware showing up in the aviation parts environment. As restocking is forced to shift to new-manufacture (NE) hardware, the price of the hardware triples. Since it also makes any remaining NOS hardware more valuable, residual pricing goes up as well. These are key reasons why there can be a very large pricing disparity between brands and sizes.
IMPORTANT NOTE #1! You can also purchase Tinnerman plates (flat plates) or Tinnerman clips (U-shaped); the flat plates can be had either is the unattached style, or the rivet-on style. These Tinnermans are designed for the thread pitch and diameter of Type B (blunt) sheet-metal screws (SMS). To some degree they will work with pointed SMS, and even machine screws; but take care. They will not have the correct alignment, and full holding strength, with anything but Type B SMS. This type of Tinnerman ‘nut’ can be extremely handy. It can be used on the back of interior trim panels, where a reinforced ‘nut’ is needed for things like placards. This is particularly true when a proper aluminum panel is used as the backer-board for upholstery side trim. The Tinnerman rivet-on anchor nut can be used, which provides permanent, non-wearing attachment points for the trim SMS.
IMPORTANT NOTE #2! I have learned that these stocks have often been misidentified in the parts system. In other words, you may order what is technically a shorter version, but actually receive a longer version, of a given clip-nut. This usually does no harm, as all the lengths have good applicability. You can alter your part number ordering to accommodate a given company’s stock numbering.
CLIP-NUTS (Description; edge distance from the panel edge to the centerline of the screw hole; range of allowable panel thickness, without excessive cocking of the nut; manufacturer’s equivalent part numbers.
Short 6-32 Clipnuts: 281” edge, .030-.062” panel thickness; 294667; A4972-5-62; 130290-4
NOTE: Seldom needed, but invaluable for things like non-structural interior panels and plates. Enables you to retain the proper size 6-32 trim fasteners, rather than 8-32, when you need the reliability and strength of machine screw threads rather than sheetmetal screw threads. Available from Spruce as 4972-5-62 in the LHA brand, and as Monadnock 04-00151.
Long 6-32 Clipnuts: .500” edge, .020-.160”; SL213-06-1
NOTE: These would be useful in locations having a longer edge distance, but I have not found any in bulk pricing.
Extra-short 8-32 Clipnuts: .250” edge, .020-.120”; 294672; A4972-4A-82; 130290-3; 13080000-1; SL210-08-2
NOTE: This is the most common thread size used on our planes. Seldom needed, but helpful to have ten or so on hand, in this very short length.
Short 8-32 Clipnuts: .281”, .020-.120”; A4972-5A-82; 13080000-2
NOTE: This is the most common thread size used on our planes. Seldom needed, but helpful to have ten or so on hand.
Medium 8-32 Clipnuts: .375”, .020-.120”; 294672; A4972-6-82; 130008; SL211-08-1; 130290-3
NOTE: This is the most common thread size used on our planes, coupled with one of the two most common clip-nut lengths used on our planes. Buy fifty or so, if you can. Available from Spruce as 4972-6-82 in the LHA brand, and as Monadnock 04-00152. You can also buy these from Beech as P/N 130290-3, for $0.78 each (cheaper than Spruce).
Long 8-32 Clipnuts: .500”, .020-.120”; 294671; A4972-8-82; 130007; SL213-08-1; 130290-1
NOTE: This is the most common thread size used on our planes, coupled with being the longer of the two most common clip-nut lengths used on our planes. Buy fifty or so, if you can. Available from Spruce as 4972-8-82 in the LHA brand, and as Monadnock 04-00152. You can also buy these from Beech as P/N 130290-1, for $0.90 each.
Extra-long 8-32 Clipnuts: .625”, .020-.120”;; A4972-10-82; 13080000-5; SL215-08-1
Extra-short 10-32 Clipnuts: .250” edge, .020-.120”; A4972-4-73; 13100000-1; SL210-3-2
Short 10-32 Clipnuts: .281”, .020-.120”; A4972-5-3; 13100000-2
Medium 10-32 Clipnuts: .375”, .020-.090”; A4972-6-02; 130069; SL211-3-1
Long 10-32 Clipnuts: .500”, .020-.120”; 294617; A4972-8-02; 13100000-4; SL213-3-1; 130290-2
NOTE: This is the second most common thread size used on our planes (10-32), coupled with being the most common clip-nut length used on our planes in this thread size. Buy fifty or so, if you can. Available from Spruce as 4972-1032 in the LHA brand, and as Monadnock 04-00153. You can also buy these from one of the Hawker-Beech affiliates (such as Elliott) as P/N 130290-2, for $0.33 each. That’s a good bargain these days.
Extra-long 10-32 Clipnuts: .625”, .020-.120”; 294618; A4972-10-02; 130062; SL215-3-1
Super-long 10-32 Clipnuts: .705”, .140-.250”; A4972-11-02; 130068
Long ¼-28 Clipnuts: .500, .050-1.25”; 13400000-1
When it says ‘AIRPLANE’, it always seems more complicated than it should have to be….