How much do you know about tape measures?

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Repost: Tape measure* B8 O& ^& j: h3 X- f' g. D( v3 A6 N An essential measuring tool for home and work use 8 J/ P. o; L- L- H4 `( ^ k! g But after using it for such a long time, have you noticed that the hook on the tape measure moves back and forth? 3 Y) m4 }% c+ b! x- Q# T' u3 ~1 Q What are the numbers on the tape measure casing for? http://www.cmiw.cn/data/attachment/forum/201812/03/121620momcrtqwilu7rx77.jpg China is a major producer of tape measures, with production taking place in Yuyao, Zhejiang, and Shangqiu, Henan.) }) p& D. _' b/ E2 O The quality of products made in Yuyao is better, though of course they are more expensive ( w; h+ Y. \3 o6 P' g Production also takes place in other places. A5 v d5 ^8 K8 \ A well-known brand is Ningbo Great Wall Precision – |. r4 L5 N P- C8 A I believe everyone has heard of or used this brand before; g/ i8 x& `$ L8 Q \# m" E ' N. ^( r: L4 I# Q Since we’re talking about tape measures, let’s take a closer look at their structure. 2 k( ]5 q3 e8 w C Structure of a tape measure 0 `) }% q& P. O http://www.cmiw.cn/data/attachment/forum/201812/03/121619jc2hkyaukyqt6haa.jpg ; S: Q% m7 k" y& l5 \ A tape measure consists of eight main components: a casing, a measuring strip, a braking mechanism, a hook, a carrying strap, a spring, an anti-drop protective cover, and labels. Their functions are as follows: 1. Casing: Made of ABS plastic, with a shiny surface； Shock-resistant, wear-resistant, and not prone to deformation. 2. Strips: 50# grade A strip steel with a thickness of 10 silk (0.10 mm) ； 3. Braking: It features three-dimensional braking in the up, side, and bottom directions, providing a stronger manual control feel. & }. g. f1 h) I( }9 {/ h 4、Rivet hook: features a rivet-based hook structure that resists deformation, ensuring more accurate measurements. 5. Straps: rubber and nylon, two options ； High-quality premium ； Durable and sturdy, with a good feel. / q) d8 h' b5 T" m& `/ Y( O 6. Spring coils: Generally made of 50# carbon steel or 65# manganese steel, which offer high toughness and precision. 7. Drop protection cover: Made of high-quality plastic to prevent damage from drops and collisions, enhancing durability. 8. Labeling: Production can be carried out with labeling as per the customer’s requirements. . A, t" C _8 }/ s & V0 v' Z0 B- P" d2 O Principle of operation of a tape measure: The tape measure can be rolled up after it has been extended because there is a spring inside it. When the tape is extended to measure a length, what happens is that both the scale and the spring get longer; once the measurement is complete, the spring inside the tape measure contracts automatically, and the scale also contracts due to the force exerted by the spring, which is why the tape measure rolls up. 6 O) % H' K/ N+ s ) }! I4 The manufacturing process of tape measures 6 u+ ]: l% K% |3 r& Q After manufacturing, a series of inspection and testing procedures are carried out ( g$ j& h. V' Z. Q 0 C9 V' T" `' x& O: I9 A+ y The hardness of the tape measure – no further explanation is needed here. 1 \' q2 F6 M* v9 D7 N6 W It is measured directly using a Vickers hardness tester; |( j B* k3 { The paint on the tape measure must be removed before testing. http://www.cmiw.cn/data/attachment/forum/201812/03/121619pxk4j696kddkxdk0.jpg ( E' M( B+ Q8 H. q http://www.cmiw.cn/data/attachment/forum/201812/03/121619ynnzt2x8n23tan6l.jpg The thickness of the tape measure is measured using a dial indicator or micrometer & F- ^" b% z+ f7 J4 v Again, the paint on the tape measure needs to be removed before testing. & X0 q( }+ s0 I6 http://www.cmiw.cn/data/attachment/forum/201812/03/121618sr1znhco3rw7z77f.jpg http://www.cmiw.cn/data/attachment/forum/201812/03/121618y7u534ghz3jgip3p.jpg ( n3 m4 k* _0 A( Q$ O u7 ! x* p$ f# j0 B* Q0 p3 l) Y0 f * A4 n' D# J$ w4 D" l; K$ C Paint adhesion test – a fixed amount of special emery is used to impact the tape measure* ~1 i( N& j' V1 C: \/ j% N7 n. n/ t To check if the paint on the tape measure peels off. t# N6 ~" N* u4 }2 v) k http://www.cmiw.cn/data/attachment/forum/201812/03/121618hbfppn0bkk04r9np.jpg ( V2 t% C2 ]7 S& K http://www.cmiw.cn/data/attachment/forum/201812/03/121617khwwo10qyoa1a2ua.jpg : O ^8 t& B# h0 L. m7 P0 h http://www.cmiw.cn/data/attachment/forum/201812/03/121617nh1ewb4whfbbrzif.jpg % G8 F1 I/ H) u2 b. J http://www.cmiw.cn/data/attachment/forum/201812/03/121616v5k9kiaikgw9sxe4.jpg Tape measure accuracy test – it involves comparing the accuracy with that of a standard ruler. Grade I has higher accuracy than Grade II, with lower allowable errors compared to the standard ruler. Under standard testing conditions, the accuracy of steel tape measures for different grades is calculated using the following formulas: Grade I: △=±(0.1＋0.1L) mm - T+ k8 g! F. U2 f Grade II: △=±(0.3＋0.2L) mm ; H3 v0 _% o1 f I' e) F& A4 Q# { Here, L refers to the length in meters. " u( b; e V" }, b% C% X7 Z) f There are many other standard parameters related to tape measures as well 7 ?5 J; v. F% S% r6 L0 E7 @& No further analysis is provided here, as these all have established standards. + Q- {# p6 B5 s: G Light industry standard QB/T 2443-2011& f0 v0 {: K7 t5 k x1 Metrological standard JJG 4-2015