Standard vs. Stub thread
Standard vs. Stub thread
(OP)
What is the advantage of using a stub Acme thread vs. a standard Acme thread? And what about a 60 degree stub thread? Right now I am driving/actuating a piston using a standard Acme and need to know if there would be a gain in mechanical advantage or a friction reduction using a different thread type. Thanks. DM





RE: Standard vs. Stub thread
As such, the Stub Acme thread is about 57% the height of a Regular Acme profile. One major disadvantage is that a true Stub Acme thread is a Class 2G fit; Regular Acme threads can be 1G, 2G, 3G, 4G or 5G(s).
In surface, sub surface oilfield equipment applications, the Stub Acme profile is commonly found because of the limited space found in downhole applications. Most tubes are "thin walled", hence the advantage using Stub Acme(s).
Hope this answers your question.
Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada
RE: Standard vs. Stub thread
I too use Stub Acme in place of Standard ACME due to space contraints and I often wondered if, from a stress and shear standpoint, if the two thread forms are equivalent. Any thoughts?
RE: Standard vs. Stub thread
RE: Standard vs. Stub thread
To answer your question "zakk", consider a 4.000-6 Acme-2G thread in comparison to 4.000-6 Stub Acme-2G. The shear area of the pin (screw) are less than that of the box (nut), therefore the pin ALWAYS fails before the box threads. In terms of pin shear area per unit length of thread the Acme is 8.512% greater than the Stub Acme. This is due to threading geometry for basic major, pitch and minor diameters: 4.000, 3.917, 3.833 for the Acme and 4.000, 3.950, 3.900 for Stub Acme.
I would concurr with your thoughts, the Acme and Stub Acme threads are virtually identical, stress performance wise.
Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada