Threads and tolerances, calculating diameters and pitch diameter offset

[@billshiff2060]

I know the effort of your deep dive. I did it using the ASME standard and made a spread sheet to calculate every parameter of any thread size and pitch. I have been working on it for years. From that work I now know that no machinist I've seen actually knows what a correct thread is and neither did I until I did that.

[@brucewilliams6292]

Thank you for taking the time to go through this. Always being short of time having a video like this really helps! Thank you.

[@JohnSL]

Thanks. It took me a long time to pull this information from the Machinery's Handbook and then derive the equation for Fusion 360's pitch diameter offset. But now I understand thread milling much better than I did before.

[@bernhard_derProtoTyp]

Thank you so much for making this video! I‘m not sure how often I have to re-watch it until I get it but at least now I have a chance to do so. With only the diagram and tables I‘d be lost and would stick to my creep-up-on-it-until-it-feels-right approach. 😊

[@JohnSL]

I've added chapters to the video. In particular, I have a chapter called Final Screw/External Dimensions and another one called Final Nut/Internal Dimensions. These have the final set of equations you'll. Plus, I'm working on a blog post and will try to have it up in the next day or so that summarizes it.

[@ViceChief]

@@JohnSL I echo mr. prototyp! Thank you

[@RogerGuisinger]

I have found that the easiest way to find your numbers for an odd size diameter-pitch combination is to find the closest standard size in the Machinery's Handbook tables with the same pitch and add or subtract the difference in the diameters. It is not exact but very close.

[@BA-ul7rl]

I'm making a telescoping screws so imagine a telescoping pole but there are threads around for extension. It's been so hard to figure out how to design custom threads, thank you so much!!!!!!!

[@malburrgg4246]

Thank you for taking the time to simplify this. While its still not simple, at least theres a place that explains it thoroughly. My head was spinning trying to read the ANSI B1.1

[@kevincrawford6864]

Excellent presentation, thank you for taking the time to explain this in a way that makes sense.

[@georgedreisch2662]

Excellent presentation and explanation! Thanks for sharing.

[@PeterWMeek]

Very clear explanation of calculating dimensions of an unlisted combination of diameter and pitch. I'm planning a video on the differences between theoretical sharp crests and roots and reality, and how to shorten crests to avoid interference with roots which can never be really a sharp V. You have given me some clear ideas on where to begin and how to present it. Thank you.

[@copperkerf3846]

Good video John! I recently had to cut 63 x 4 mm internal threads for three adapter locking nuts on an industrial meat extrusion machine. Despite it taking longer, I usually prefer thread milling. I also like the bonus of being able to walk a thread in using wear compensation. Thanks for taking the time to show your process.

[@cogentdynamics]

Excellent information, thank you. Measuring pitch diameters using thread wires and then manipulate the O.D. setting the thread height (conversational thread parameters) limits the minor diameter. Since the cutting tool and the tool entry can be done in different ways… yes, I get lost. Your tolerance details helps me. Doing the algebra isn’t the biggest strength for me. I do see the light (maybe(.

[@greglaroche1753]

I need to watch this at least another time. Thanks for the video.

[@oscarjosefsson9300]

Thank you very much! I was very confused how there could be just one nominal set of dimensions shared between screw and nut. But I think I understand it not since the es and EI moves the tolerances away from the nominal dimensions. That really seems counter intuitive too but yeah. That's just how it is I guess.

[@vittoriocannata3561]

Thank you so much for making this video!

[@localele1]

Nice work John. I like and use analysis views as a way to check fits and tolerances. Another interesting view is to make your model a bit transparent and then zoom in until your view becomes from inside the threaded nut and looking out to the threaded shaft.Hard to describe but play with the zoom until your perspective is from inside the part. This really helped me to see the fit of some tapered components that were offset.

[@MF175mp]

I have thought about making a chart for myself with actual cut depths for each pitch for lathe use. Otherwise could just use the calculator every time but the nose radius on the tool causes some extra steps

[@bigmeatyxclaws876]

Amazing video!

[@jbrownson]

great work

[@JohnnieBravo1]

This is awesome. Thank you for a clear explanation! I now have to migrate to Fusion 360 from MicroStation, which has always been my mechanical design software (but the versions I have do not have ports for doing 3D printing, or machine control files).

[@JohnSL]

Thank you!

[@Alexandru_Iacobescu]

I would love to see a final draft of with actual values and tolerances for all discused.

[@vrsecky100]

Great research to do this. I'm not sure how you arrived at Td2 though. In the example at (12:30 minutes) you said d is 27mm then you looked up table 11, couldn't find P=5 (which looking at the numbers would be around 0.24) and then you chose 0.075 mm from a substantially different major diameter?

[@mohammedfathy1450]

best video ever

[@bigmeatyxclaws876]

At 14:08 I think you swapped what you swapped the TD1 and TD2. I believe you should be adding TD1/4 and subtracting TD2/4.

[@JohnSL]

I believe what I have is correct. Here's the way to think about it. Given the ideal height of the threads, you're increasing the height by TD2/4 and then decreasing the height by TD1/4.

[@tdg911]

I ithought the pitch diameter offset is the difference between the major and minor diameter?

[@JohnSL]

That's close to being correct. Adding tolerancing into the mix means you have to change this slightly.

[@FilmFactry]

My head hurts:-)

[@JohnSL]

Imagine how my my head hurt figuring this out 😉

[@Suvicharshorts-mq7ql]

Sir did you make it for custom threads? you made it super, I liked it

[@JohnSL]

Yes, a more recent episode uses these equations to make a custom thread for a threaded watch back: kzbin.info/www/bejne/qYnYh4Olp7uDqpY

[@mattmaring4080]

I tried using your formula for a 24 x 3 mm external thread and got a pdo of 4.503 mm which seems awfully deep even if I divide that be 2.

[@billshiff2060]

For that 24 x 3 , I get a BASIC pdo (thread depth) of 1.6238. Obviously a 3mm pitch can't have a depth greater than 3 so clearly there is a mistake there. The formula based on the standard proportion is Pitch x 0.54126588 = Basic height of single side thread. You would double that to get a diameter. So 3mm x 0.54126588 = 1.62379764 Single side and X 2 = 3.24759528mm BASIC on the diameter. That includes no tolerance adjustment so the final number will vary slightly within the value of the tolerances you select. That said, you should never rely on "cut depth" to actually cut your thread to size, it is guaranteed to be off since you will not know the minute details of your tool. You use that number as an approximation target then when you get close you measure what you actually have then finish it to size.

[@sathishkumarvava]

12mm thread hole drii how much

[@Dcassimatis]

Did you forget to show calculation for nut,.. what's its diameter and pitch,... are they the same?