A guide to the proper tooling and gauges required for efficiently thread rolled pre-plate parts.
It is important when manufacturing component parts to take into account the correct plating requirements. Having knowledge of the specific plating specifications as well as making allowances to the thread rolls and gages are critical in producing a functional thread. Below are some important things to consider that will ultimately allow you to run pre-plate parts efficiently.
Plating Thickness
It is important to determine how much plating thickness will be applied to the thread. Plating specifications and type of thread (including angle of thread form) will determine how much plating build-up there will be. Pre-plate thread gages should be utilized to ensure that parts will assemble and fit correctly. The pre-plate ratios for the pitch diameter build-up generated on various types of threads are as follows:
- 60° Unified thread = 4:1 ← most common
- 29° Acme thread = 8:1
- 7°/ 45° Buttress thread = 4.3:1
- 10° Square thread = 23:1
Determining pre-plating dimensions for external threaded parts:
There are specific rules for determining pre-plate pitch diameters, pre-plate major diameters, and pre-plate minor diameters of parts. The calculated pre-plate specifications will be used to design the thread rolls to produce the proper pre-plate geometry, and are used for manufacturing thread rolls and gages.
Get specifications for plating thickness Min plating thickness and Max plating thickness:
(Key: PP = pre-plate)
Major diameter Max PP = Max major diameter – (2 x Min plating thickness)
Major diameter Min PP = Min major diameter – (2 x Max plating thickness)
For a 60° Unified thread:
Pitch Diameter Max PP = Max pitch diameter – (4 x Min plating thickness)
Pitch Diameter Min PP = Min pitch diameter – (4 x Max plating thickness)
If available:
Minor diameter Max PP = Max minor diameter – (2 x Min plating thickness)
Minor diameter Min PP = Min minor diameter – (2 x Max plating thickness)
Example Calculation Featuring 5/8-20 UN2A Thread
Major Diameter .6237 / .6156
Pitch Diameter .5912 / .5869
Minor Diameter Max (Reference) .5642
Plating thickness = .0002/.0004
Major diameter Max PP = Max major diameter – (2 x Min plating thickness)
.6237 – (2 x .0002) = .6233
Major diameter Min PP = Min major diameter – (2 x Max plating thickness)
.6156 – (2 x .0004) = .6148
Pitch Diameter Max PP = Max pitch diameter – (4 x Min plating thickness)
.5912 – (4 x .0002) = .5904
Pitch Diameter Min PP = Min pitch diameter – (4 x Max plating thickness)
.5869 – (4 x .0004) = .5853
If available
Minor diameter Max PP = Max minor diameter – (2 x Min plating thickness)
.5642 – (2 x .0002) = .5638
Minor diameter Min PP = Min minor diameter – (2 x Max plating thickness) – Not available
Using this process to design and produce thread rolls with pre-plating allowances will prevent gaging issues, and allow you to run pre-plate parts more efficiently. Threads will form, track and gauge properly before and after plating is applied.
Send your thread and plating thickness specifications to CJWinter for review. Our team has the capabilities to design and manufacture a thread roll to produce the proper pre-plate geometry form on your part. There is no additional charge for this service, and delivery is the same as a standard thread roll.
Access our Guide to Thread Rolling Solutions
Lib Pietrantoni
Lib has been with the Brinkman International Group, Inc. for the last 30 years. Currently the Director of Global Sales, Lib has held numerous positions in Engineering, Operations, Sales and Product Management with CJWinter and its manufacturing divisions. Lib is a member and has served on governing boards for the Society of Automotive Engineers, The American Society of Mechanical Engineers, and Precision Machine Products Association.
