1.1 Metal Surface Preparation - Murphy Aircraft

1 Standard Methods and Practises26/06/98 Page 1 Please read the following information carefully and refer to it often throughout the building process. Itcontains information on corrosion protection, drilling, deburring, gusset building etc. Also included is asection on bolt and rivet selection to assist you in areas of the manual where bolt or rivet sizes have notbeen Metal Surface PreparationSome of our kits include the following chemicals to be used for Surface Preparation and treatment:C-2200 MET-L-SOL Surface CleanerEP-420 Epoxy Chromate Metal PrimerEP-430 Epoxy Primer CatalystAs a protective measure against corrosion, mating Metal surfaces should be fully deburred, cleaned with C-2200,then coated liberally with epoxy chromate primer.

2 This provides a seal between the surfaces to prevent corrosionand moisture buildup. It is a good practice to coat the end of the rivet on the inside Surface after an optional measure, the rivets can be dipped in chromate prior to installation. This provides protection insidethe hole and seals out moisture. If the airframe is not to be painted be careful to avoid excess chromate on epoxy primer is to be pre-mixed in accordance with the manufacturers directions as displayed on thecontainers. It is advisable to mix only the amount you need in a small container each time you work, however,larger amounts can be mixed and reused in a sealable Drilling HolesIt is good practice to use a #40 drill when doing any assembly- if possible never drill to final hole sizeuntil assembly is complete.

3 This allows for any movement between parts or adjustment you may want tomake that may cause misalignment of the holes during use a sharp drill bit as:-A sharp bit will not wander as easily as a dull can drill faster with a sharp don t have to push as hard, risking bending flanges be careful to drill squarely to the work make sure when drilling through multiple parts or layers that they are clampedtogether tightly so as not to move around whole debur holes on both sides of each part before final Standard Methods and Practises26/06/98 Page BoltsThroughout the building process there will be instances where bolts are used to fasten parts or materialstogether. In some instances It may be for the builder to determine the correct length of the bolt to Rule of Thumb for determining bolt length is that the bolt must be long enough to pass through theparts or material being fastened together so that:1.

4 The threaded part of the bolt is never in shear (no threads are allowed inside hole).2. No more than three and no less than one thread must be showing when the nut isattached and tightened to the correct torque At least on flat washer must be used under the nut and no more than three are precise determinations of Grip Length are found in a number of books including the Standard AircraftWorker s following information is provided for reference when using AN grade hardware. Most of the time torque valuesare done to feel. But this table does provide a good outline. Occasionally bolts, other than a standard bolt will becalled out for use in the manual. Please ensure that these bolts are used where called out. The EngineeringDepartment selected these as they provide the strength for the connection where a standard bolt can not Standard Torque Table (Inch Pounds) *Fine Thread SeriesBolt SizeStandard NutsShear Nuts(MS20365, AN310, AN315)(MS20364, AN320, AN316, AN23-31)10-3220-2512-15 1/4-2850-7030-405/16-24100-14060-853/8-2 4160-19095-1107/16-20450-500270-3001/2-2 0480-690290-4109/16-18800-1000480-6005 Standard Methods and Practises26/06/98 Page 3 Coarse Thread SeriesBolt SizeStandard NutsShear Nuts(MS20365, AN310, AN315)(MS20364, AN320, AN316, AN23-31)

5 8-3212-157-910-2420-2512-151/4-2040-5025 -305/16-1880-9048-553/8-16160-18595-1107 /16-14235-255140-1551/2-13400-480240-290 9/16-12500-700300-4205/8-11700-900420-54 0* The above calculations were obtained from the Standard Aircraft Handbook. Figure bolts may be obtained in the following materials. The coding symbols shown follow the basic dash number andidentify the material required in the callout. Figure shows how the material of the bolt may be distinguishedby bolt head markings.( - ) = Steel, cadmium platedC=Corrosion resisting steelDD=Aluminum alloyExample: AN4 - H10 AAN - Army Navy Standard 4 - Diameter in 1/16 inch increments or 1/4 inch diameter( - ) - Steel, cadmium plated H - Bolt with drilled head and shank required.

6 Leave off if plain head required10 - Refer to table 1 for bolt length and bolt thread corresponding to 10 A - The adding of the letter A indicates that the cotter pin hole is not Standard Methods and Practises26/06/98 Page 4 Note: To determine grip length, deduct the figure indicated below from the lengths shown in table - 13-32AN8 - 25-32AN14 - 1-1/4AN4 - 15/32AN9 - 29-32AN16 - 1-3/8AN5 - 17/32AN10 - 61/64AN18 - 1-1/2AN6 - 41/64AN12 - 1-3/32AN20 - 1-11/16AN7 - 21 AN3-AN20 Hex Head Bolt LengthTABLE 1 BoltsDashAN3AN4AN5AN6AN7AN8AN9AN10 Number10-321/4-285/16-243/8-247/16-201/2 -209/16/185/8-18315/3215/32417/3217/3219 /32521/3221/3223/3245/6423/32625/3225/32 27/3253/6427/3227/3231/32729/3229/3231/3 261/6431/3231/321-1/321-1/64101-1/321-1/ 321-3/321-5/641-3/321-3/321-5/321-9/6411 1-5/321-5/321-7/321-13/641-7/321-7/321-9 /321-17/64121-9/321-9/321-11/321-21/641- 11/321-11/321-13/321-25/64131-13/321-13/ 321-15/321-29/641-15/321-15/321-17/321-3 3/64141-17/321-17/321-19/321-37/641-19/3 21-19/321-21/321-41/64151-21/321-21/321- 23/321-45/641-23/321-23/321-25/321-49/64 161-25/321-25/321-27/321-53/641-27/321-2 7/321-29/321-57/64171-29/321-29/321-31/3 21-61/641-31/321-31/322-1/322-1/64202-1/ 322-1/322/3-322-5/642-3322-3/322-5/322-9 Standard Methods and Practises26/06/98

7 Page 5 Table 2 ScrewsRecommended Hole Sizes for Self-tapping Sheet Metal ScrewsMetalClearance Drill for Sheet Metal ScrewsThicknessMaterial.#2#4#6#7#8#10#12 # Standard Methods and Practises26/06/98 Page 6 Table 3 Clearance Drill Sizes for AN Bolts, Screws and Cotter PinsAN BOLTSAN SCREWSCOTTER PINSBoltDrillSizeDrillSizeDrillSize#10#1 1#4#321/16#481/41/4#6#283/32#365/165/16# 8#191/8#283/83/8#10#115/32#167/167/161/4 1/43/16#41/21/25/165/161/4#19/169/165/85 /811/1611/163/43/47/87 NutsAN310 CASTELLATED NUT Figure AN310 Castle Nut is designed to be used in conjunction with a cotter pin for safetying. The nut maybe used in tension and on assemblies that turn on the bolt or vice versa. This nut is used primarily with theAN3 to AN20 series Standard Methods and Practises26/06/98 Page 7AN310D4 An AN310 aluminum nut (D) for use on a 1/4 in (4) bolt.

8 Thread from table - 1 PLAIN NUT Figure AN315 Plain Nut may be safetied through the use of a shakeproof or lock washer - may be used inconjunction with the AN3 to AN16 series bolt. The nut may be had in right (R) or left (L) hand thread(see example callout).AN316 CHECK NUT Figure nut is used as a check nut to eliminate travel of other nuts or parts on the threads of a bolt or nut must not be used in tension or shear. The AN316 nut may be had in either right (R) or left (L)hand thread (see callout).UNF-3 THREAD SIZE6-408-3610-321/4-285/16-243/8-247/16 -201/2-209/16-185/8-183/4-167/8-141-141- 1/8-121-1 Standard Methods and Practises26/06/98 Page 8AN365 SELF-LOCKING FIBRENUT Figure Fibrenut is used extensively throughout the Aircraft .

9 Because of the locking ability of the fibre in thenut cotterpins or lock washers are not needed. Do not use the same fibrenut over and over as the nylonwears with each tightening and does not give the same locking strength. If you come to a step that callsfor repeated nut use on the same bolt use a plain nut until the final Washers Figure AN960 plain washer is furnished in the following materials: Steel (Cadmium plated), Aluminum alloy(D), Brass (B), and corrosion resistant Steel (C). The code letter (none for steel) follows the inside diameter is indicated by the last dash number which is expressed in screw sizes as #6, #8 and#10, or; AN960-6, AN960-8, AN960-10. Washers requiring an or 3/8, 7/16 or 1/2 inch are calledout as AN960-616, AN960-716, and washer is made in a regular and light (L) series in all metals indicated except brass.

10 If the washer is ofthe light (L) series, the L will follow the dash the letter P before the dash number to obtain aluminum washers that have been AN-970 washer provides a greater bearing area than the plain type, and is used to prevent localcrushing of the Standard Methods and Practises26/06/98 Page Plastic CoatingThe plastic film on the aluminum should be left on for as long as possible during the assembly of youraircraft. This helps to prevent the aluminum from being LayoutsUse a fine tip felt pen for accuracy (some felt pens will not write on aluminum). It will show up well anddoes not wipe off layouts are no longer needed, clean off felt pen marks with solvent ( works well) before finalassembly as some inks may be corrosive if left DeburringHoles can be deburred with a deburring tool or a drill bit of a larger size than the hole being deburred -BY HAND ONLY!