Design and Engineering Forum Forum Moderators: randykimball, Administrator
 Thread Pitch & Major Diameters Post Reply Forum
 Posted by: knuyenly ® 03/27/2006, 17:13:52 Author Profile eMail author Edit Hello, Can sonmeone please help me out how to get the Pitch & Major diameters of a M37 x 0.75 external thread? Thank you very much

 Post Reply | Recommend | Alert Administrator View All | Next |

 Replies to this message

 Re: Thread Pitch & Major Diameters Re: Thread Pitch & Major Diameters -- knuyenly Post Reply Top of thread Forum
 Posted by: randykimball ® 03/27/2006, 23:41:22 Author Profile eMail author Edit Sure, I'd be happy to.. and I'll explain how I do it.Let's take a known thread from the Machinery's Handbook and extrapolate it out.Doing internal first.An M4.5x.75mm internal thread has: Major diameter of 4.5mm Minor diameter of 3.838 to 3.688 Effective diameter of 4.108 to 4.013If we take 37mm and subtract the 4.5 we get 32.5mm.the major dia. + 32.5mm becomes 37mm the minor dia. + 32.5mm becomes 36.338 to 36.188 effective dia. + same becomes 36.608 to 36.513 Now let's do your external.An M4.5x.75mm external thread has: Major diameter of 4.5 to 4.410 Minor diameter of 3.580 to 3.470 Effective diameter of 4.013 to 3.953Same process....the major dia. + 32.5mm becomes 37.000 to 36.91 the minor dia. + 32.5mm becomes 36.080 to 35.97 effective dia. + same becomes 36.513 to 36.453metric Effective Diameter = our Pitch DiameterNo matter the diameter, the thread pitch still effects it the same way. However, the thread form and roundness of the part become more critical with diameter increases.Also, I would tend to run some on the loose side with a larger diameter (smaller end of the external and larger end of the internal tolerances).I need to state, although I'm quoting from the book, I have a bit of a problem with the internal and external major diameters being allowed to both tolerance into the same 4.5mm. I recommend that you DO NOT allow the external thread major diameter ever actually reach 4.5mm (or 37mm).Be sure to check my work.... wink../←randy→/ The worst suggestion of your lifetime may be the catalyst to the grandest idea of the century, never let suggestions go unsaid nor fail to listen to them. Modified by randykimball at Tue, Mar 28, 2006, 00:08:51

 Post Reply | Recommend | Alert Administrator Where am I? Original Top of thread | |
 Re: Thread Pitch & Major Diameters Re: Re: Thread Pitch & Major Diameters -- randykimball Post Reply Top of thread Forum
 Posted by: knuyenly ® 03/28/2006, 12:06:31 Author Profile eMail author Edit Thank you very much! That was clearly help.