Acme Thread Specifications

not very important. This includes many types of vise and jack screws. Thread fit tolerances come in three different classes: 2G, 3G and 4G. The PDF gives a chart of basic form dimensions and relationships of Acme threads including threads per inch, pitch, depth of thread, total depth, thread thickness, crest of nut, root of nut, minimum depth, minimum width of flat, maximum fillet radius root of centralizing tapped hole, minimum classes and maximum classes.Centralizing Acmes have a main purpose in use for feed screws because they have a limited clearance at the major diameter of the screw and the nut. The advantage of the limited clearance is that a bearing at the major diameter can maintain alignment of the thread axis so this prevents flank wedging and part sagging. Centralizing Acmes have five different classes: 2C through 6C. The Acmes with classes 5C and 6C have limited backlash. A chart is available defining the differences between General Purpose and Centralizing Acme threads, especially in relation to limiting dimensions and tolerances.Charts are also available in the PDF for standard Stub Acme threads. Stub Acmes are derived from General Purpose Acmes but Stub Acmes are specialized for situations where a coarse pitch of shallow depth is needed. Charts are also available for M1 and M2 Stub Acme thread forms. In some cases, standard Stub Acmes cannot give an acceptable thread for all applications. The M1 Modified Form assumes that the pitch and minor diameters are smaller than similar values typically used for the standard form and the M2 Modified Form assumes that the pitch and minor diameters are larger than the values typically used for the standard form. Some products available for use with Acme threads are available here: http://www.threadcheck.com/acme-thread-specifications/related.htm. More reference links: http://www.atilandisthreading.com/ThreadCutting/Library/TC_AcmeThreadforms.pdf http://www.threadcheck.com/acme-thread-specifications/related.htm