2.4 ISO thread forms

• identify the parts of ISO thread forms used in drawing
• describe types of ISO thread forms used in drawing
• illustrate types of ISO thread forms used in drawing
• appreciate the importance of ISO thread forms in power mechanics

“What are the characteristics of ISO thread forms?”

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1. Pitch, crest and root
   40 min · 1 practice tasks · quiz
   Name the ridge, the groove and the axial distance between one thread and the next, and find a pitch by counting gaps.
2. Major diameter, minor diameter and flank
   40 min · 1 practice tasks · quiz
   Place the crest and the root on the major and minor diameters of a bolt, and swap those names on a nut.
3. The metric thread
   40 min · 1 practice tasks · quiz
   Sketch the 60 degree truncated metric profile and read an M designation as diameter and pitch.
4. The unified thread
   40 min · 1 practice tasks · quiz
   Read a threads-per-inch designation, convert the pitch to millimetres, and keep the 60 degree form off a metric nut.
5. The square thread
   40 min · 1 practice tasks · quiz
   Sketch a square profile of depth and width half the pitch, used to move a load rather than to clamp a bracket.
6. The Acme thread
   40 min · 1 practice tasks · quiz
   Sketch a 29 degree thread of basic depth half the pitch, with a flat crest 0.3707 times the pitch.
7. The buttress thread
   40 min · 1 practice tasks · quiz
   Sketch a 7 degree pressure flank and a 45 degree clearance flank, with basic depth three-quarters of the pitch.
8. Choose the form
   40 min · 1 practice tasks · quiz
   Match metric, unified, square, Acme and buttress to the angle and the job, without mixing a near size.
9. Threads on an orthographic view
   40 min · 1 practice tasks · quiz
   Show an external thread with a thick crest and a thin root, and reverse those weights on a sectioned nut.
10. Match the pitch before you run the nut
    40 min · 1 practice tasks · quiz
    Check a measured pitch against the designation, and start a nut square so the crest is not stripped.