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Metallographic Testing

Metallographic testing refers to the process of studying the physical structures and characteristics of metal components, and, in our case, thread rolled parts. STR performs metallographic testing as a secondary service for our customers, meaning that we do not offer it as a standalone option for parts manufactured elsewhere, but rather, we perform it for every applicable order that we manufacture in our facility.

Why Use Metallographic Testing?

There are various benefits associated with metallographic testing. These advantages include gaining a better understanding of the metal structures involved in each project, on both a micro- and macro-scale. This information informs the way that our team approaches each project’s manufacturing process, specifically impacting our thread rolling methods. Ultimately, metallographic testing ensures that every manufacturing project we work on meets the precise requirements specified by our customers.


Root Grain


Root Grain 2
  • Cut threads in half
  • Mount threads in black phenolic powder → a hockey “Puck”
  • Grind/polish the puck
  • Etch the puck with acid to bring out the grain structure
  • Inspect the puck using high-powered microscope (100X – 500X)

Crest Seam

Every rolled thread has a crest seam, and each crest seam has a maximum tolerance to meet to adhere to proper industry standards. The crest seam is directly related to the liquid penetrant inspection procedures involved in the thread rolling process. During the liquid penetrant inspection process, a testing fluid is injected into the surface-breaking crack, or crest seam, and eventually removed using a specialized powder. As you can see, this crest seam is not cause for rejection, but a typical part of the thread rolling process.

Crest seam pass 200x
Crest seam pass 500x
Crest seam fail 200x

Our  Metallographic Testing Specifications

  • AS7452 
  • AS7456
  • AS7458 
  • AS7460
  • AS7464
  •  AS7466 
  • AS7468
  • AS7471
  • AS7472
  • AS7474
  • AS7477
  • AS7478
  • AS7479
  • AS7467
  • AS7470
  • AS81935
  • BAPS 188‐001
  • BPS 4445
  • BPS‐B‐180
  • BPS‐F‐69
  • C50TF13 
  • DPS 4.507
  • FES 0006 
  • FES 0007 
  • GT 16A, GAT 16A
  • HP 18‐2
  • LMA-PA411 
  • MDP 18‐2 
  • MP‐134 
  • NAS 498 
  • NAS 4002
  • NAS 4003 
  • NAS 4004
  • NAS 4008 
  • NASM 7838, 
  • NASM 8831
  • NASM 8906 
  • PS 19205 
  • QAI 6039 
  • STP 0478
  • STP 0510 
  • STP51‐400
  • STP 0478
  • STP 0510
  • TS.07.05‐001
  • 2ZZP0005
Metallographic Testing Specs

Quality In Everything We Do, Using Metallographic Testing and More!

STR’s dedication to thorough metallographic testing is the result of a larger, overarching commitment to quality that our company holds. STR has an extensive history of working with aerospace and defense customers, having worked with the leading companies in each industry. We understand that the markets we serve depend on our products to reliably hold their equipment together, which is why we never cut corners when it comes to quality.

In addition to metallographic testing, STR also boasts the following quality assurance certifications, systems, and tools:

  • ISO9001 & AS9100 Certified for over 18 years
  • Oasis Thread Vision Inspection System
  • 600+ thread ring gauges
  • 200+ thread plug gauges
  • Thread Tri-roll inspection tools
  • In-house calibration to ISO 10012, ISO 17025 and ANSI/NCSL Z540.1