VDI 2230 February 2003 includes a change to the thread engagement calculation, adding the factor 0,8&[ignore]middot[/ignore];P. This was due to new research from Konstruktion 47 (1995) 285-291. I obtained this article and can explain why this factor was added.
Physical testing was performed on several materials - wrought steel, wrought stainless steel, cast iron, cast aluminium, and a wrought titanium alloy. The stripping force from these tests was compared with the standard thread engagement calculation (no 0,8&[ignore]middot[/ignore];P factor), and it was found that the actual stripping force was up to 20% less than the calculated value. The reasons for the difference include thread tolerances not used in the standard equation, and incomplete loading of the last nut thread. To make the actual and calculated values agree, the 0,8&[ignore]middot[/ignore];P factor was added.
Overall, this was a very informative article with good figures that help to explain the issue. The article is written in German, which will limit its use for people who cannot read German or can't get a translation. More information is available from the publisher Springer-VDI Verlag at:
Scroll down to Leser-Service (this is "Reader Service" in English).
Cory
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
Physical testing was performed on several materials - wrought steel, wrought stainless steel, cast iron, cast aluminium, and a wrought titanium alloy. The stripping force from these tests was compared with the standard thread engagement calculation (no 0,8&[ignore]middot[/ignore];P factor), and it was found that the actual stripping force was up to 20% less than the calculated value. The reasons for the difference include thread tolerances not used in the standard equation, and incomplete loading of the last nut thread. To make the actual and calculated values agree, the 0,8&[ignore]middot[/ignore];P factor was added.
Overall, this was a very informative article with good figures that help to explain the issue. The article is written in German, which will limit its use for people who cannot read German or can't get a translation. More information is available from the publisher Springer-VDI Verlag at:
Scroll down to Leser-Service (this is "Reader Service" in English).
Cory
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
