Sockets. Dimensions; Mechanical & Performance Requirements. Socket Head Cap Screws Body & Grip Lengths - Socket Cap Screws...

Transcription

1 imensions; Mechanical & Performance Requirements Socket Head Cap Screws Body & Grip Lengths - Socket Cap Screws Low Head Socket Cap Screws... 7 Button Head Socket Cap Screws... 8 Flat Head Socket Cap Screws Socket Set Screws - Flat point Socket Set Screws - Oval point Socket Set Screws - Half-og point Socket Set Screws - Cone point Socket Set Screws - Cup point Socket Shoulder Screws Socket Pipe Plugs ry Seal Flush Seating Hex Keys and Bits External Threads Class 3A

2 Alloy & Stainless Socket Cap Screws Sockets C T H G F J A K SOCKET HEA CAP SCREWS ASME B A H C J F T G K Screw iam. Body Head Head Height Top Chamfer or Radius Hex Socket Fillet Transition Key Engagement Wall Thickness Bottom Chamfer or Radius Max Min Max Min Max Min Max Nom Max Min Min Min Max / / / / / / / / / / / / / / / / / / / / / / / / / / / / Tolerance on Length Screw Up to 1 in., Incl. Screw Length Over 1 in. to 2-1/2 in., Incl. Over 2-1/2 to 6 in., Incl. Over 6 in. 0 thru 3/8, Incl /16 thru 3/4, Incl /8 thru 1-1/2, Incl

3 Socket Cap Screws Alloy Steel MECHANICAL PROPERTIES OF ALLOY STEEL SOCKET CAP SCREWS Blue evil Tensile Strength (lbs., min.) Yield Strength (lbs., min.) Body Section Tightening Torque (In.-Lbs.) Single Shear UNRC UNRF UNRC UNRF Strength (lbs., min.) UNRC UNRF ,090 1, ,070 1, ,430 1,490 1,290 1,345 1, ,640 1,825 1,470 1,645 1, ,520 2,650 2,270 2,385 2, ,150 3,600 2,835 3,240 3, /4 5,725 6,550 5,150 5,900 5, /16 9,430 10,440 8,490 9,395 8, /8 13,950 15,805 12,555 14,225 11, /16 19,135 21,365 17,220 19,230 16, /2 25,540 28,780 22,990 25,905 21, /8 38,400 43,500 34,550 39,150 31,300 3, , /4 56,750 63,400 51,100 57,050 45,050 6, , /8 78,500 86,500 70,700 77,850 61, , , ,700 92, ,450 80,100 12, , /4 164, , , , ,100 25, , /2 238, , , , ,200 43, ,000.0 escription Heat Treatment Hardness An externally threaded fastener with unified threads, a cylindrical head with a flat chamfered top surface, knurled cylindrical sides and hexagonal recess, made from alloy steel. Ideal for precision assembly work with close tolerances and applications needing a well tooled appearance. Supplies greater tensile strength than equivalent sizes of Grade-5 or Grade-8 hex head cap screws while requiring less surface area or counterbore since the fastener is internally wrenched. Cap screws shall be made from an alloy steel which conforms to the following chemical composition requirements (per product analysis)-- Carbon: 0.31% minimum; Phosphorus: 0.040% maximum; Sulfur: 0.045% maximum. Also, one or more of the following elements shall be present in sufficient quantity to meet the strength requirements listed below: chromium, nickel, molybdenum or vanadium. Cap screws shall be heat treated by oil quenching from above the transformation temperature and then tempered at a temperature not lower than 650 F. 0 through 1/2" diameters: Rockwell C39 minimum; 5/8" diameter & larger: Rockwell C37 minimum Cap screws of a length 3 or greater, where equals the nominal diameter of the screw, are subject to tensile strength, yield strength, elongation and reduction of area testing. Tensile Strength Yield Strength Elongation Reduction of Area Plating 0 through 1/2" diameters: 180,000 psi. minimum; 5/8" diameter & larger: 170,000 psi. minimum 0 through 1/2" diameters: 162,000 psi. minimum; 5/8" diameter & larger: 153,000 psi. minimum 10% minimum (applies to machined specimens of length at least 4 where equals the nominal diameter of the screw) 33% minimum (applies to machined specimens) See Appendix-A for information on the plating of alloy steel socket cap screws. 174

4 Stainless Steel Socket Cap Screws Sockets MECHANICAL PROPERTIES OF STAINLESS STEEL SOCKET CAP SCREWS Blue evil Tensile Strength (lbs., min.) Yield Strength (lbs., min.) Body Section Tightening Torque (In.-Lbs.) Single Shear UNRC UNRF UNRC UNRF Strength (lbs., min.) UNRC UNRF , ,400 1, /4 2,550 2,910 1,273 1,455 2, /16 4,200 4,645 2,100 2,320 3, /8 6,100 7,025 3,100 3,510 4, /2 11,350-5,675-8, escription Heat Treatment Hardness An externally threaded fastener with unified threads, a cylindrical head with a flat chamfered top surface, knurled cylindrical sides and hexagonal recess. It is made from austenitic stainless steel. Although stainless socket cap screws have significantly less tensile and yield strength than alloy sockets, they have superior resistance to corrosion. They retain their mechanical and performance capabilities at higher than ambient temperatures. Cap screws shall be made from one of the following stainless alloys: 302, 303, 304, 305, 384, XM1 or XM7. The austenitic alloys develop their strength through work hardening during the fastener manufacturing process, as seen from the hardness properties below. The only heat treatment normally available on austenitic stainless alloys is annealing, which is done at approximately 1900 F to a dead soft condition and is not normally thermally reversible. Rockwell B80 minimum Cap screws of a length 3 or greater, where equals the nominal diameter of the screw, are subject to tensile strength, yield strength, elongation and reduction of area testing. Tensile Strength Yield Strength Elongation Reduction of Area 80,000 psi. minimum 30,000 psi. minimum 10% minimum (applies to machined specimens of length at least 4 where equals the nominal diameter of the screw) 30% minimum (applies to machined specimens) 175

5 Socket Cap Screws Length Specifications ASME BOY AN GRIP LENGTHS OF SOCKET HEA CAP SCREWS B Nom Basic Thread Length L T Length L LG LB LG LB LG LB LG LB LG LB LG LB LG LB LG LB LG LB Nom. 1/4 5/16 3/8 7/16 1/2 5/8 3/4 7/8 1 Basic Thread Length L T Length L LG LB LG LB LG LB LG LB LG LB LG LB LG LB LG LB LG LB

6 Length Specifications Socket Cap Screws Sockets L LG LT LB Notes Regarding the Thread Length of Socket Head Cap Screws The basic thread lengths (L T ) listed directly below the nominal sizes in the table on page 176 represents the nominal length up to which all screws of that diameter shall be fully threaded. To determine the threaded portion of the screws with a nominal length greater than L T, subtract the minimum design grip length (L G ) from the nominal length (L). For screws over 1 in. in diameter and of nominal lengths longer than L T, the maximum grip gaging length (L G ) and the minimum body length (L B ) of the screws shall be determined as follows: L G = L - L T L B = L - L TT Where: L L T L TT = length = Minimum thread length tabulated below = Maximum total thread length tabulated below Min Thread Length (L T ) Max Total Thread Length (L TT ) / /

7 Low Head Cap Screws Alloy Steel H H T T J A F F LOW HEA SOCKET CAP SCREWS -ALLOY STEEL Blue evil A H J T F Tensile Strength Basic Pounds Min. Head Head Height Hex Key Fillet Screw Socket Engagement Max Min Max Min Min Max Min UNRC UNRF ,310 2, ,890 3, / ,250 6, / ,650 9, / ,800 14, / ,400 26, Tightening Torque Inch Pounds Tolerance on Length Screw Length Screw Up to 1 in., Incl. Over 1 in. to 2-1/2 in., Incl. 0 thru 3/ / escription Heat Treatment Hardness Tensile Strength Yield Strength Elongation Reduction of Area Similar to a standard alloy socket cap screw except the head height is 50% of the standard's and the socket size is smaller. The low-head style is supplied only in plain steel. Used in applications where the limited clearance would not accomodate the head height of a standard socket cap screw. Also used in counterbored holes of material too thin for a regular socket cap screw. However, because of their design, they cannot withstand the same preloads as a standard socket head. Cap screws shall be made from an alloy steel which conforms to the following chemical composition requirements (per product analysis)-- Carbon: 0.31% minimum; Phosphorus: 0.040% maximum; Sulfur: 0.045% maximum. Also, one or more of the following elements shall be present in sufficient quantity to meet the performance requirements listed below: chromium, nickel, molybdenum or vanadium. Cap screws shall be heat treated by oil quenching from above the transformation temperature and then tempered at a temperature not lower than 650 F. Rockwell C38 minimum 170,000 psi. minimum 150,000 psi. minimum 10% minimum (applies to machined specimens of length at least 4 where equals the nominal diameter of the screw) 33% minimum (applies to machined specimens)

8 Alloy Steel Button Head Socket Cap Screws Sockets T S J A H F L SOCKET BUTTON HEA CAP SCREWS -ALLOY STEEL ASME B , Blue evil A H S J T F L Head Head Height Head Side Height Hex Socket Key Engagement Fillet Transition Max Standard Length Tensile Test Load Single Shear Strength of Body Max Min Max Min Ref Nom Min Max Min Nom Lb. Lbs., Min. Seating Torques in./lbs. Coarse Thread Fine Thread / / ,260 1, / ,940 2, / ,440 2, / / ,430 4, / / ,300 7, / / ,800 10, / / ,800 18, / / ,500 29,400 1,700. 1,900. Tolerance on Length Screw Length Screw Up to 1 in., Inclusive Over 1 in. to 2-1/2 in., Inclusive 0 thru 3/8, Inclusive /2 and 5/8, Inclusive escription Heat Treatment Has a similar thread design as a socket cap screw. The dome-shaped head is wider and has a lower profile than a socket cap screw. Used when a wider bearing surface or a smoother, more finished appearance is desired. Button head cap screws do not afford the strength of socket head cap screws and are designed for light fastening applications. They are not recommended for critical, highstrength applications. Screws shall be made from an alloy steel which conforms to the following chemical composition requirements (per product analysis) - Carbon: 0.28 to 0.50%; Phosphorus: 0.045% maximum; Sulfur: 0.035% maximum. Also, one or more of the following elements shall be present in sufficient quantity to meet the performance requirements listed below: chromium, nickel, molybdenum or vanadium. Screws shall be heat treated by oil quenching from above the transformation temperature and then tempered at a temperature not lower than 650 F. Hardness Rockwell C38-44 Tensile Strength Yield Strength Elongation Reduction of Area Finish 180,000 psi. minimum (material only) 160,000 psi. minimum (material only) 8% minimum (applies to machined specimens of length at least 4 where equals the nominal diameter of the screw) 35% minimum (applies to machined specimens) Screws are supplied with a thermal black finish. 179

9 Flat Head Socket Cap Screws Alloy Steel T F Edge of head may be rounded or flat A A Theoretical Sharp Absolute Minimum J 82 +/- 2 P Protrusion Gage H G SOCKET FLAT HEA CAP SCREWS -ALLOY STEEL ASME B , Blue evil A H G P J T F Body Max Min Head Theoretical Sharp Max Abs. Min Head Height Protrusion Gage Protrusion Hex Socket Key Engagement Fillet Transition iam. Tensile Strength, Lbs. Min Ref Max Min Max Min Nom Min Max UNRC UNRF Single Shear Strength of Body lbs., Min Recommended Seating Torques, in./lbs / / ,185-1, / ,350-1, / ,085-2, / ,610 2,610 2, / / ,750 4,750 4, / / ,800 7,800 7, / / ,600 11,600 10, / / ,900 15,900 14, / / ,200 21,200 18, ,000. 5/ / ,800 33,800 29,450 1, / / ,000 50,000 42,400 3,000 - Coarse Thread Fine Thread Tolerance on Length Screw Up to 1 in., Incl. Screw Length Over 1 in. to 2-1/2 in., Incl. Over 2-1/2 in. to 3 in., Incl. 0 thru 3/8, Inclusive /16 thru 3/4, Inclusive escription Heat Treatment Similar in design to a socket button head cap screw but with an 82 countersunk flat head. Used when a flush mounting, high strength screw is required. Commonly used in tools and dies where moving parts pass over the fastened area. Screws shall be made from an alloy steel which conforms to the following chemical composition requirements (per product analysis)-- Carbon: 0.28 to 0.50%; Phosphorus: 0.040% maximum; Sulfur: 0.045% maximum. Also, one or more of the following elements shall be present in sufficient quantity to meet the performance requirements listed below: chromium, nickel, molybdenum or vanadium. Screws shall be heat treated by oil quenching from above the transformation temperature and then tempered at a temperature not lower than 650 F. Hardness Rockwell C38-44 Tensile Strength Yield Strength Elongation Reduction of Area Finish 180,000 psi. minimum (material only) 160,000 psi. minimum (material only) 8% minimum (applies to machined specimens of length at least 4 where equals the nominal diameter of the screw) 35% minimum (applies to machined specimens) Screws are supplied with a thermal black finish.

10 Body & Grip Lengths Flat Head Socket Cap Screws Sockets LGH LBH L LT LTT For screws of nominal lengths longer than those for which LGH and LBH values tabulated in this table and for screws over 1 inch in diameter, the maximum grip gaging length LGH and the minimum body length LBH of the screws shall be determined as follows: LGH = L - LT LBH = L - LTT where L = nominal length, LT = minimum thread length, and LTT = maximum total thread length. BOY AN GRIP LENGTHS OF FLAT HEA SOCKET CAP SCREWS ASME B /4 LT MIN LTT MAX Length LGH LBH LGH LBH LGH LBH LGH LBH LGH LBH LGH LBH /16 3/8 7/16 1/2 5/8 3/4 LT MIN LTT MAX Length LGH LBH LGH LBH LGH LBH LGH LBH LGH LBH LGH LBH

11 Socket Set Screws Alloy Steel SLIGHT FLAT OR ROUNING PERMISSIBLE T SLIGHT FILLET PERMISSIBLE Q C 118 +/- 5 P CUP POINT HALF OG POINT SLIGHT CHAMFER OR RAIUS PERMISSIBLE SOCKET SET SCREWS -ALLOY STEEL ASME B , Blue evil Shortest Length To Which Column T Applies J Tightening Torque (Inch-Lbs.) Cup & Flat Point Cone & Oval Point Half og Point Hex Key / / / / / / / / / / / / / / / / / / / / / escription Heat Treatment Cup point: A headless screw threaded the entire length. It has a hexagonal drive at one end and a cup-shaped indentation at the other end. Half-og point: A set screw with a protruding tip with a flat surface at the end opposite that of the hexagonal drive. Oval point: A set screw with an oval-shaped point at the end opposite that of the hexagonal drive. Flat point: A set screw with a flat surface at the end opposite that of the hexagonal drive. Cone point: A set screw with a sharp conical-shaped point at the opposite end from the hexagonal drive. Cup point: The cup point is the most used style set screw. esigned for fast, permanent and semi-permanent location of parts on shafts with hardness differential of Rockwell C points and where cutting in of cup edge on the shaft is acceptable. Half-og point: Intended for permanent setting. The point should fit closely to the diameter of the drilled hole or against the flat. Often used instead of a dowel pin. Oval point: Preferred style for frequent reset on soft or hard shafts with minimum deforming. Also chosen for permanent setting on shafts spotted, splined or grooved, and for applications where point meets shaft on an angle. Sometimes substituted for the cup point style. Flat point: esigned for frequent resetting or relocating on hard steel shafts and where minimal damage to shafts is necessary. Ground flats on the shaft improves the contacts. Cone point: For permanent setting on soft or hardened shafts. The deep penetration it offers gives this style set screw the highest torsional & axial holding power. For shafts of Rockwell hardness C15 or over, spot point half its depth. Can also be used as a pivot or hanger. When two set screws are used in a set screw collar, their holding power is determined by their location with respect to each other. Screws shall be made from an alloy steel which conforms to the following chemical composition requirements (per product analysis)-- Carbon: 0.28 to 0.50%; Phosphorus: 0.040% maximum; Sulfur: 0.045% maximum. Also, one or more of the following elements shall be present in sufficient quantity to meet the strength requirements listed below: chromium, nickel, molybdenum or vanadium. Screws shall be heat treated by oil quenching from above the transformation temperature and then tempered at a temperature sufficient to meet the hardness requirements listed below. Hardness Rockwell C45-53 Torsional Strength Finish Socket set screws of a sufficient length to be tested (as listed in the above table) shall withstand application of the test torque specified in said table without evidence of the socket reaming or the screw bursting. Screws are supplied with a thermal black finish.

12 Alloy Steel Socket Set Screws Sockets SLIGHT FLAT PERMISSIBLE J SLIGHT FLAT OR ROUNING PERMISSIBLE R C Y OVAL POINT FLAT POINT CONE POINT Socket Set Screws - Alloy Steel ASME B J T C R Y P Q Hexagon Socket Key Engagement Cup & Flat Point Oval Point Radius Cone Pt. Ang for these lengths and over; 118 ± 2 for shorter lengths Half og Point Length Nom Min Max Min Basic Max Min Max Min / / / / / / / / Screw Length Tolerance on Length Up to 0.63 in., Incl. Over 0.63 to 2.00 in., Incl. Over 2.00 to 6.00 in., Incl. ±0.01 ±0.02 ±

13 Socket Shoulder Screws Alloy Steel J A T H L ±.005 SEE ETAIL Y SEE ETAIL Z E K 1 C G Length of a socket shoulder screw is measured from the underhead bearing surface to the plane of the shoulder at the threaded end. SOCKET HEA SHOULER SCREWS -ALLOY STEEL ASME B A H C J T M R K F Shoulder Head Head Height Chamfer or Radius Hex Socket Key Engagement Fillet Transition Head Fillet Radius Shoulder Neck Shoulder Neck Width Max Min Max Min Max Min Min Nom Min Max Min Min Max 1/ / / / / / / / / / / / escription Heat Treatment A hex socket head screw with an enlarged, unthreaded, cylindrical shoulder under the head, the diameter of which serves as the basis for the derivation of the nominal size. For rotation or sliding applications, such as pulley shafts, in punch and die work, or for use as a bearing pin. Shoulder screws are also referred to as "stripper bolts". Shoulder screws shall be made fabricated from an alloy steel having one or more of the following elements: chromium, nickel, molybdenum or vanadium, in sufficient quantity to assure the hardness specified below. Shoulder screws shall be heat-treated by oil quenching from above the transformation temperature and then tempered at a temperature not lower than 650 F. Hardness Rockwell C32-43 Tensile Strength 140,000 psi. minimum (material only) Yield Strength 120,000 psi. minimum (material only) Elongation 15% minimum (applies to all machined specimens of length at least 4 where equals the nominal diameter of the screw) Reduction of Area 45% minimum (applies to all machined specimens) Plating Shoulder screws are usually supplied with a plain finish. 184

14 Alloy Steel Socket Shoulder Screws Sockets F I M R THIS IA NOT TO EXCEE MAJOR IA OF THREA N ENLARGE ETAIL Y ENLARGE ETAIL Z SOCKET HEA SHOULER SCREWS -ALLOY STEEL (CONTINUE) ASME B , Blue evil 1 Thread Threads Per Inch G I N E Thread Neck Thread Neck Width Thread Neck Fillet Thread Length Thread Section Tensile Strength (Lbs) Single Shear Strength (Lbs) Shoulder Thread Neck Max Min Max Min Basic Min Min Min Seating Torque (Inch Lbs) 1/ ,540 4,515 1, /16 1/ ,610 7,100 2, /8 5/ ,600 10,280 3, /2 3/ ,240 18,350 5, /8 1/ ,570 28,785 11,140 1,150 3/4 5/ ,770 41,515 17,800 2,000 Screw s Tolerance on Thread Length Up to 3/8 in., Inclusive Over 3/8 in

15 Pipe Plugs ry Seal J T L G SOCKET PIPE PLUGS -RY SEAL ANSI B Outside Threads Per Inch J T G L Hex Socket Key Engagement Wall Thickness Overall Length Min Min Max Min Tightening Torque (Inch - Lbs) Tap rill * 1/ / /64 1/ / /64 1/ / /64 3/ / /16 1/ / /16 3/ / / /2 5/ /8 1-1/ /2 3/ MM 1-1/ / MM / /16 *Taper reaming after drilling is recommended for tapping ease and to give fully formed, uniform threads. escription A dry seal plug is one having a tapered (0.750" diametral per 12") thread extending its entire length and designed to have its threads mesh tightly with those of a taper-threaded hole. Both ends of the plug shall be flat and chamfered approximately 45. The chamfer shall extend slightly below the root of the thread, and the edge between flat and chamfer shall be slightly rounded. Heat Treatment The thread trunction is closely controlled at root and crest to assure metal to metal contact, preventing spiral leakage and forming a positive seal without the use of sealing compounds. ry seal plugs can be used in American Standard Taper ryseal Pipe Thread (NPT) tapped holes, but for fullest protection against leakage, should be used in dryseal tapped holes which are taper reamed before tapping. High grade alloy steel Pipe plugs shall be heat-treated by quenching in oil from above the hardening temperature and tempered to achieve the hardness requirement listed below. Hardness Rockwell C36-43 Finish Plugs are supplied with a standard black finish. 186

16 Flush Seating Pipe Plugs Sockets J T L G SOCKET PIPE PLUGS -FLUSH TYPE ANSI B Outside Threads Per Inch J T G L Hex Socket Key Engagement Wall Thickness Overall Length Min Min Max Min Tightening Torque (Inch - Lbs) Tap rill * 1/ / /64 1/ / /64 1/ / /64 3/ / /16 1/ / /16 3/ / / /2 5/ /8 1-1/ /2 3/ MM *Taper reaming after drilling is recommended for tapping ease and to give fully formed, uniform threads. escription A flush type plug is one having a tapered (0.875" diametral per 12") thread extending its entire length and designed to provide a flush condition with a standard tapped hole (0.750" diametral per 12"). Both ends of the plug shall be flat and chamfered approximately 45. The chamfer shall extend slightly below the root of the thread, and the edge between flat and chamfer shall be slightly rounded. Six equally spaced identification grooves are located equidistant between corners of the hex socket and edge of the chamfer (Note: on the 1/16-27 plug, 3 identification grooves are permitted because of limited space). Heat Treatment A high pressure seal is achieved through the difference in taper, with dimensions precalculated to provide a higher sealing load near the large end of the plug and the threads near the top of the tapped hole. The flush type plug is preferred where high pressures are encountered and where protrusion is undesirable. High grade alloy steel Pipe plugs shall be heat-treated by quenching in oil from above the hardening temperature and tempered to achieve the hardness requirement listed below. Hardness Rockwell C36-43 Finish Plugs are supplied with a standard black finish. 187

17 Hex Keys & Bits Alloy Steel Y L A W W R + B 90 +/- 2 C Bit Hex Key K HEX KEYS &BITS, LONG AN SHORT ARM ASME B W Y B C R K Key or Hex Width Across Hex Width Across Length of Short Length of Long Arm Radius Bit and Socket the Flats the Corners Arm of Bend Short Series Long Series Chamfer Max Min Max Min Max Min Max Min Max Min Min Max / / / / / / / / / / / / / / / / / / Tolerance on Length of Key Bits ±

18 Alloy Steel Hex Keys & Bits Sockets HEX KEYS AN BITS Blue evil Torsional Shear Average (Inch-Pounds) Torque Rating (Inch-Pounds) / / / / / / / / / / /16 1, , /8 2, , /16 4, , /2 6, , /16 8, , /8 12, , /4 19, , /8 29, , , , escription Heat Treatment Surface Hardness Torsional Shear Strength Torque Rating A hex key is a six-sided shaped bar bent at a 90 angle at one end. A hex bit is an unbent piece of such a bar. esigned to be inserted into a like-sized, hollow recess of a socket screw to manually tighten or loosen the fastener. Alloy steel containing at least two of the following elements: chromium, nickel, molybdenum or vanadium, in sufficient quantity to assure that the minimum surface hardness meets the standards listed below. Hex keys are hardened by quenching from the austenitizing temperature and tempered. s through 3/8": Rockwell C 48 minimum s over 3/8": Rockwell C 45 minimum The average torsional shear strength as listed above is the average maximum torque which standard keys and bits will transmit when tested to destruction. When tested this way, failure will occur by a clean, square shear fracture. Keys cut into bits for use in torque wrenches will transmit the above torques. These values are 90% of average torque required to develop a permanent visible twist in bits which have one inch of hexagon exposed between the torque wrench and the socket. These are also the torque values which keys transmit when the short arm is inserted in a socket and the long arm is deflected or bent through an angle of by the application of force near the end of the long arm. 189

19 Thread imensions Class 3A EXTERNAL THREAS -CLASS 3A ANSI B1.1 Screw Major Pitch Minor Basic Max Min Basic Max Min Max / / / / / / / / / / / / / / *Class 3A threads over 1" diameter screws are Class 2A threads. * 1 1/ * 1 1/