What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
Length conversion The length of the American screw must be converted to be the metric mm size. Conversion formula: (Length Code / 32) x 25.40 = metric length mm B-3,B-4,B-5 : The marking method is the same as the metric system.
National Standard 1 GB/T3103.3-2000 Fastener Tolerance Flat Washers 2 GB/T5286-2001 General Scheme of Flat Washers for Bolts, Screws and Nuts 3 GB/T9074.1-2002 Bolts or Screws and Flat Washers Assemblies 4 GB/ T9074.18-2002 Self-tapping screws and flat washers assembly 5 GB/T 95-2002 Flat washers C grade 6 GB/T96.1-2002 Large washers A grade 7 GB/T96.2-2002 Large washers C grade 8 GB/ T97.1-2002 Flat washer Class A 9 GB/T97.2-2002 Flat washer chamfered Class A 10 GB/T97.4-2002 Flat washer for screw and washer assemblies 11 GB/T97.5-2002 Flat Washers for self-tapping screws and washer assemblies 12 GB/T848-2002 Small washers Class A 13 GB/T5287-2002 Extra large washers Class C 14 GB/T4678.13-2003 Die-casting mold parts Part 13: Push plate washers 15 GB /T4605-2003 Rolling bearing thrust needle roller and cage assemblies and thrust washers 16 GB/T97.3-2000 Flat washers for pins 17 GB/T18230.5-2000 Flat washers for bolted structures quenched and tempered 18 GB/T9074 .5-2004 Cross recessed small pan head screw and flat washer assembly 19 GB/T9074.20-2004 Cross recessed hexagon head self-tapping screw and flat washer assembly 20 GB/T3762-1983 Sharp angle seal for tube fittings Washers 21 GB/T1231-2006 High-strength large hexagon head bolts, large hexagon nuts, and washers for steel structures Specifications 22 GB/T1230-2006 High-strength washers for steel structures 23 GB/T2861.10-2008 Die guides - Part 10 : Washers 24 GB/T5649-2008 Lock nuts and washers for pipe joints 25 GB/T94.3-2008 Technical conditions for elastic washers Saddle, wave elastic washers 26 GB/T3099.1-2008 Terms of fasteners threaded fasteners , pins and washers 27 GB/T10447-2008 Elements and tolerances of semicircular thrust washers for sliding bearings 28 GB/T94.1-2008 Technical conditions for elastic washers Spring washers 29 GB/T10446-2008 Dimensions and tolerances for full circle thrust washers for sliding bearings 30 GB/T93-1987 standard spring washer 31 GB/T94.2-1987 elastic washer technical conditions toothed, serrated lock washer 32 GB/T98-1988 stop washer technical conditions 33 GB/T849-1988 spherical washer 34 GB/ T850-1988 Cone Washer 35 GB/T851-1988 Split Washer 36 GB/ T852-1988 Square bevel washer for I-beam 37 GB/T853-1988 Square bevel washer for channel steel 38 GB/T854-1988 Single ear stop washer 39 GB/T7244-1987 Heavy spring washer 40 GB/T855-1988 Double lug Stop washers 41 GB/T7245-1987 Saddle spring washers 42 GB/T7246-1987 Wave spring washers 43 GB/T856-1988 Outer tongue stop washers 44 GB/T858-1988 Stop washers for round nuts 45 GB/T859- 1987 Light spring washer 46 GB/T860-1987 Saddle elastic washer 47 GB/T861.1-1987 Internal tooth lock washer 48 GB/T861.2-1987 Internal serrated lock washer 49 GB/T862.1-1987 External tooth Lock Washers 50 GB/T862.2-1987 External Serrated Lock Washers 51 GB/T955-1987 Wave Elastic Washers 52 GB/T27938-2011 Sliding Bearing Thrust Washers Failure Damage Terms, Appearance Features and Reasons 53 GB/T956.1 -1987 Conical Lock Washer 54 GB/T956.2-1987 Conical Serrated Lock Washer 55 GB/T28697-2012 Rolling Bearing Self-aligning Thrust Ball Bearing and Self-aligning Seat Washer Dimensions 56 GB/T9074.2-1988 Cross Groove Pan head screw and external serrated lock washer assembly 57 GB/T9074.3-1988 Cross recessed pan head screw and spring washer assembly 58 GB/T9074.4-1988 Cross recessed pan head screw, spring washer and flat washer assembly 59 GB/T9074.7-1988 Cross recessed small pan head screw and spring washer assembly 60 GB/T9074.8-1988 Cross recessed small pan head screw and spring washer and flat washer assembly 61 GB/T9074.9-1988 Cross recessed Countersunk head screw and conical lock washer assembly 62 GB/T9074.10-1988 Cross recessed half countersunk head screw and conical lock washer assembly 63 GB/T9074.11-1988 Cross recessed pocket hexagon head bolt and flat washer Assembly 64 GB/T9074.12-1988 Cross-recessed hexagon head bolt and spring washer assembly 65 GB/T9074.13-1988 Cross-recessed hexagon head bolt, spring washer and flat washer assembly 66 GB/T9074.15 -1988 Hexagon head bolt and spring washer assembly 67 GB/T9074.16-1988 Hexagon head bolt and serrated lock washer assembly 68 GB/T9074.17-1988 Hexagon head bolt, spring washer and flat washer assembly 69 GB/ T9074.26-1988 Spring washers for assemblies Ring 70 GB/T9074.27-1988 External Serrated Lock Washers for Assemblies 71 GB/T9074.28-1988 Conical Lock Washers for Assemblies 72 GB/T1030-1988 Inner Spherical Washers
High-strength fastener materials mainly include ML35, 35K, ML40Cr, ML35CrMo steel, etc., of which 75ML35CrMo steel is imported. The main problems of the material are box segregation, decarburization, cracks and so on. The material needs to be spheroidized and annealed before cold forming, and the annealing is carried out in an oil furnace. There is no protective atmosphere in the furnace, and there is a decarburization phenomenon. 1.2 The high-strength fasteners, mainly grade 12.9, are quenched and tempered on the chain casting furnace production line. The temperature and atmosphere in the furnace are controlled by computer, and Rx gas is used as a protective atmosphere. Heating and anti-oxidation and decarburization can be effectively controlled, and the quality of the fasteners is intact during the heating process. The high-strength fasteners mainly of grade 8.8 are quenched and tempered on the vibrating hearth furnace. Affected by the structure of the vibrating hearth furnace, the sealing performance of the furnace is poor, the Rx atmosphere is not easy to control, the temperature difference of the furnace is large, and the parts are heated in the furnace. The collision and the length of time are inconsistent, and the quality of the fasteners during the heating process is poor, and there are phenomena such as decarburization, bumps, and uneven heating.
flat washer is a part that is placed between the connected part and the bolt to protect the surface of the connected part from being scratched by the nut and to disperse the pressure of the nut on the connected part. At present, a flat washer in the prior art generally includes a washer body; the washer body has a bolt hole in the middle for a bolt to pass through. Although the flat washer of the above structure has a simple structure, it still has a disadvantage. When the flat washer is cushioned between the connected part and the bolt, the bolt head is usually exposed outside the connection part, so the bolt head is easy to It is damaged under the impact of external force, thus affecting its fixing effect.
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