# How to calculate Thread Pitch Diameter for non standard TPI like 5/8" 17.75 NF3

#### kedarg6500

##### Quite Involved in Discussions
how to calculate pitch dia for non standard TPI like 5/8" 17.75 NF3

#### Stijloor

Staff member
Super Moderator
A Quick Bump!

Can someone help?

Thank you very much!

#### JLyt207

##### Involved In Discussions
You can calculate the Pitch diameter using (D-.64952p).
D = major diameter
p = 1/ thds per inch

That should be the max pitch dia for external thds or the min for internal thds. I don't know how to calculate the tolerance for a class 3 thd. We used a program to calculate it for us. I am surprised I remembered that this formula existed.

#### Wayne

##### Gage Crib Worldwide
how to calculate pitch dia for non standard TPI like 5/8" 17.75 NF3
First note that NF = National Fine. That designation was changed back in 1959 to Unified National Fine. See this discussion here: NF vs. UNF

Second note that the F = the Fine series of threads which is a specific set of threads defined in ANSI/ASME B1.1. Here is the list of UNF sizes.

Third note that since 17.75-TPI (threads-per inch) does not fit any of the UNF defined threads; it is correctly designated UNS (Unified National Special).

Fourth note that in 1959 the thread class changed from 3 to 3A or 3B depending on if the thread is internal or external. For the UNS Class 3A/3B class-of-fit the basic pitch diameter (MMC) is identical for both the internal and the external screw thread. (That statement is not true for the 1A/1B or 2A/2B class-of-fit which have a defined allowance between the male and female screw threads.) The tolerance moves toward the LMC in all cases for screw threads.

Fifth note that there is a piece of software available for you to use for calculating screw thread sizes: ThreadTech. <--This link takes you to a Free 30-Day trial of ThreadTech Screw Thread Engineering software.

Finally; the calculated values for this screw thread pitch diameters are:
3A External Thread Pitch Diameter: 0.5884"/0.5850" (14.945/14.859mm)
3B Internal Thread Pitch Diameter: 0.5884"/0.5928" (14.945/15.057mm)

I hope this information helps.

Formula that will calculate the NoGo Major Diameter of an M20 x 1.5 6H Thread gage Inspection, Prints (Drawings), Testing, Sampling and Related Topics 3
L Calibration of ring thread gauge with master gauge: How to calculate Uncertainty? General Measurement Device and Calibration Topics 1
Commercial excel templates that calculate overhead, hourly rates, fee proposal Excel .xls Spreadsheet Templates and Tools 0
How to calculate benefits? Moving some developed non controlled software/automation systems Service Industry Specific Topics 2
Calculate number of people in processes, considering cycle time/takt time = quantity of people Lean in Manufacturing and Service Industries 9
How to calculate the maximum allowable hysteresis of a pressure gauge General Measurement Device and Calibration Topics 1
How to Calculate the producer Risk AQL - Acceptable Quality Level 25
Methods to Calculate Available Production Rate ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 0
Why calculate LCL in P-chart? Statistical Analysis Tools, Techniques and SPC 4
How to calculate CPK with n = 1 Manufacturing and Related Processes 2
Add-On software for VMC to calculate setting time, Idle Time, OEE etc.. Manufacturing and Related Processes 2
L How to calculate the Probability of Deficiency of the AQL of an Inspection AQL - Acceptable Quality Level 16
V How to Calculate Unbiasing Constant C4 Statistical Analysis Tools, Techniques and SPC 1
J How to Calculate OEE Indicator for a Workshop (15 Machines) Lean in Manufacturing and Service Industries 6
R How to calculate UCL (Upper COntrol Limit) and LCL (Lower Control Limit) Statistical Analysis Tools, Techniques and SPC 5
I want to calculate reliability at 750 hours Reliability Analysis - Predictions, Testing and Standards 8
R How To Calculate & Print CDF and Lower Bound CDF value for some t(time) with Minitab? Using Minitab Software 1
How to calculate the Premium Freight charges Service Industry Specific Topics 4
A How to calculate Mean and standard deviation without sample size in Minitab Using Minitab Software 5
When do I need to calculate Process OEE? Manufacturing and Related Processes 12
C Definition and Way to Calculate some Metrics Lean in Manufacturing and Service Industries 6
M How calculate P value for Linearity and Bias using Excel Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 8
M How to calculate Cg and Cgk for a 2-Dimensional Area Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 4
T Calculation Question - Calculate the runner weight for a part Manufacturing and Related Processes 2
M Spreadsheet on How to Calculate SMT Capacity wanted Manufacturing and Related Processes 2
F How to Calculate the unbiased Standard Deviation in Excel using Minitab Formula Capability, Accuracy and Stability - Processes, Machines, etc. 6
Spreadsheet that will Calculate Audit Duration times based on IAF MD5 and MD11 Excel .xls Spreadsheet Templates and Tools 6
Calculate PPMs by going back to Date of Production or Date Noticed Quality Tools, Improvement and Analysis 7
M How to calculate MTTF (Mean Time to Failure) Reliability Analysis - Predictions, Testing and Standards 1
H How to calculate the Lot Reject Rate Inspection, Prints (Drawings), Testing, Sampling and Related Topics 4
L How calculate the number of samples Statistical Analysis Tools, Techniques and SPC 2
A Simple 125 piece part Capabilty Excel .xls sheet to calculate Cpk Capability, Accuracy and Stability - Processes, Machines, etc. 3
R How to calculate MMC when is placed after datum Inspection, Prints (Drawings), Testing, Sampling and Related Topics 4
S Which one is better to calculate, Cpk or Ppk? Statistical Analysis Tools, Techniques and SPC 11
C How to calculate P value on Probability Plot Statistical Analysis Tools, Techniques and SPC 1
S Supplier Disruption Score and how to calculate it Quality Tools, Improvement and Analysis 4
IAQG OASIS - New tool to calculate Audit Time AS9100, IAQG, NADCAP and Aerospace related Standards and Requirements 1
M How to calculate dimensions of trapezoid ? Quality Tools, Improvement and Analysis 3
How to calculate Surveillance Audit Days in Corporate Audit Scheme IATF 16949 - Automotive Quality Systems Standard 4
S How to calculate Supplier PPM at Receiving Inspection Document Control Systems, Procedures, Forms and Templates 2
How to Calculate Sample Size at 95% Confidence Interval on Surface Roughness Inspection, Prints (Drawings), Testing, Sampling and Related Topics 1
R How to calculate the value add time? Lean in Manufacturing and Service Industries 2
Should I calculate both Cp and Cpk for a Unilateral Tolerance? Statistical Analysis Tools, Techniques and SPC 8
H Continuous Monitoring Instrument Data Validation and how to calculate Outliers Quality Tools, Improvement and Analysis 1
How to calculate the Air Flow Rate in clause 201.12.4.4.105 of IEC 60601-2-16:2012 IEC 60601 - Medical Electrical Equipment Safety Standards Series 1
A How to calculate Cpk & Ppk if the tolerance changes during the period? Capability, Accuracy and Stability - Processes, Machines, etc. 5
S PPAP - How to calculate tolerance on basic dimension APQP and PPAP 5
B Attrition Rate and the formula to calculate Attrition Rate Quality Manager and Management Related Issues 1
How to calculate the Current Quality Level (CQL) of a Process Statistical Analysis Tools, Techniques and SPC 5
CDSCO-India: Draft Guideline to Calculate Compensation for Victims of Clinical Trials Other Medical Device Regulations World-Wide 0