Threads and Fasteners

Thread Terminology

Thread Callouts - Metric (mm) (mm) (mm)

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

Thread Callouts – ANSI Unified Assumes course threads with a nominal fit (2). (in)

Goal: connect the top part to the bottom part using a .75” long #10-24 cap screw which has a head taper of 82˚

Steps: buy the screw drill a countersunk hole without threads into the top part drill a threaded hole in the bottom part

2 things to know if you tap a hole the thread length should be at least twice the diameter of the hole if you use a bolt to connect some bodies the bolt should extend beyond the nut by at least two thread pitches

Was able to download a SolidWorks part file of this cap screw.

Use ‘hole wizard’ to place a tapered hole, through all, for a #10 flat head screw with an 82˚ head taper.

Note that the major diameter of a #10 screw is 0 Note that the major diameter of a #10 screw is 0.19” so we have clearance.

Use ‘hole wizard’ to place a tapped hole for a #10-24 screw. I selected a hole depth of 0.51” and a threaded depth of 0.38” (typically there should be at least 2  dia. of thread, i.e. at least 0.38” of thread).

This is the ‘default’ drawing after inserting dimensions from part file.

This is the ‘default’ drawing after inserting dimensions from part file. delete this one hide this one Add the hole callout.

Design Library Tools -> Add in -> SolidWorks Toolbox SolidWorks Toolbox Browser

Assembly with washers Select a 3/8-24 bolt to connect the parts.

Assembly with washers and nut

Determining Bolt Length

Bolt length calculation Bolt must be 1.92” long plus the distance of 2 extra pitches. The bolt has 24 threads per inch. Two extra pitches will require an extra 1/12” of an inch. Total minimum length is 1.92+0.083 = 2.003” . Find the next longest available bolt.

Smart Fasteners

2 things to remember if you tap a hole the thread length should be at least twice the diameter of the hole if you use a bolt to connect some bodies the bolt should extend beyond the nut by at least two thread pitches