EML 2023 Threads and Fasteners Lecture 1 Nomenclature

EML 2023 – Threads and Fasteners Lecture 1 - Nomenclature

Thread Terminology EML 2023 Computer Aided Design 2

Thread Callouts - Metric (mm) EML 2023 Computer Aided Design 3

Thread Callouts – ANSI Unified 1 – loosest fit 2 – normal fit 3 – most exact fit B represents internal thread (in) UNC – UNF – UNEF – UN – Unified National Course Unified National Fine Unified National Extra Fine Unified National EML 2023 Computer Aided Design 4

Thread Callouts – ANSI Unified (in) Assumes course threads with a nominal fit (2). EML 2023 Computer Aided Design 5

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Goal: • connect the top part to the bottom part using a #10 -24 cap screw which has a head taper of 82˚ • must determine length of screw EML 2023 Computer Aided Design 11

Steps: • buy the screw • drill a countersunk hole without threads (clearance hole) into the top part • drill a threaded hole in the bottom part EML 2023 Computer Aided Design 12

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2 things to know 1. if you tap a hole – the thread length should be at least twice the diameter of the fastener 2. if you use a bolt to connect some bodies – the bolt should extend beyond the nut by at least two thread pitches g n o l w Ho ? e b w cre s e h t should EML 2023 Computer Aided Design 14

• the major diameter of the #10 screw is . 190” • the length of the screw must be at least as long as. 30” + 2. 19” =. 68 • will purchase a #10 -24 screw that is. 75” long EML 2023 Computer Aided Design 15

. ” 0 9 1. ? e s i b w e l e o cr h s e e c h n t a f r o a r e l e c t e e h m t a f i o d r r e o j t The ma uld the diame ho s t a h W EML 2023 Computer Aided Design 16

17 Engineer’s Handbook http: //www. engineershandbook. com/

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Was able to download a Solid. Works part file of this cap screw. EML 2023 Computer Aided Design 20

A clearance hole has been created for a #10 flat head screw with an 82˚ head taper. EML 2023 Computer Aided Design 21

• A tapped hole for a #10 -24 screw. • The screw we selected is. 75” long. Therefore thread depth of the hole must be at least. 75”-. 3” =. 45” deep. • I selected a thread depth of 0. 45” and a pilot hole depth of. 66”. EML 2023 Computer Aided Design 22

If you only tap the blue body to the recommended depth of 2 major , i. e. . 38”, you will have the following. EML 2023 Computer Aided Design 23

2 nd Example Problem 3/8” – 24 cap screw blocks are 1. 5”. 50” EML 2023 Computer Aided Design 24

2 things to remember 1. if you tap a hole – the thread length should be at least twice the diameter of the fastener 2. if you use a bolt to connect some bodies – the bolt should extend beyond the nut by at least two thread pitches EML 2023 Computer Aided Design 25

Determining Bolt Length EML 2023 Computer Aided Design 26

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Bolt length calculation Bolt must be 1. 988” long plus the distance of 2 extra pitches. . 50” 1. 988” . 08” 21/64” The bolt has 24 threads per inch. Two extra pitches will require an extra 1/12” of an inch. Total minimum length is 1. 988+0. 083 = 2. 071”. Find the next longest available bolt. EML 2023 Computer Aided Design 29

2 things to remember 1. if you tap a hole – the thread length should be at least twice the diameter of the hole 2. if you use a bolt to connect some bodies – the bolt should extend beyond the nut by at least two thread pitches EML 2023 Computer Aided Design 30