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Helical Coil Thread Plug Gages (STI)

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Helical Coil Thread Plug Gages (STI)

  • STI Thread plug gages are used to gage threaded holes prior to the insertion of screw thread inserts
  • Widely used in the automotive industry
  • Class X Tolerance
  • Class 2B or 3B
  • GO and/or NO GO plug members
  • ASME/ANSI B1. 2 compliant
  • Precision hand lapped to provide superior accuracy , optimum finish and maximum wearability
  • Final inspection of gages is completed in an environmentally controlled ISO 17025 laboratory
  • Available in steel
  • Free NIST certificate of accuracy

Standard Pitch Diameter Chart - Inch

Standard Pitch Diameter Chart - Metric




Size Member Item # Price Sale Price
2-56 GO / NOGOHCPS-01$55.00$49.00
DOUBLE ENDHCPSDE-01$120.00$110.00
3-48 GO / NOGOHCPS-02$53.00$48.00
DOUBLE ENDHCPSDE-02$116.00$106.00
3-56 GO / NOGOHCPS-03$53.00$48.00
DOUBLE ENDHCPSDE-03$116.00$106.00
4-40 GO / NOGOHCPS-04$49.00$45.00
DOUBLE ENDHCPSDE-04$110.00$100.00
4-48 GO / NOGOHCPS-05$49.00$45.00
DOUBLE ENDHCPSDE-05$110.00$100.00
5-40 GO / NOGOHCPS-06$49.00$45.00
DOUBLE ENDHCPSDE-06$110.00$100.00
6-32 GO / NOGOHCPS-07$49.00$45.00
DOUBLE ENDHCPSDE-07$110.00$100.00
6-40 GO / NOGOHCPS-08$49.00$45.00
DOUBLE ENDHCPSDE-08$110.00$100.00
8-32 GO / NOGOHCPS-09$47.00$43.00
DOUBLE ENDHCPSDE-09$106.00$97.00
8-36 GO / NOGOHCPS-10$47.00$43.00
DOUBLE ENDHCPSDE-10$106.00$97.00
10-24 GO / NOGOHCPS-11$47.00$43.00
DOUBLE ENDHCPSDE-11$106.00$97.00
10-32 GO / NOGOHCPS-12$47.00$43.00
DOUBLE ENDHCPSDE-12$106.00$97.00
12-24 GO / NOGOHCPS-13$47.00$43.00
DOUBLE ENDHCPSDE-13$105.00$96.00
1/4-20 GO / NOGOHCPS-14$45.00$41.00
DOUBLE ENDHCPSDE-14$100.00$92.00
1/4-28 GO / NOGOHCPS-15$45.00$41.00
DOUBLE ENDHCPSDE-15$100.00$92.00
5/16-18 GO / NOGOHCPS-16$45.00$41.00
DOUBLE ENDHCPSDE-16$100.00$92.00
5/16-24 GO / NOGOHCPS-17$45.00$41.00
DOUBLE ENDHCPSDE-17$100.00$92.00
3/8-16 GO / NOGOHCPS-18$47.00$43.00
DOUBLE ENDHCPSDE-18$105.00$96.00
3/8-24 GO / NOGOHCPS-19$47.00$43.00
DOUBLE ENDHCPSDE-19$105.00$96.00
7/16-14 GO / NOGOHCPS-20$49.00$45.00
DOUBLE ENDHCPSDE-20$109.00$99.00
7/16-20 GO / NOGOHCPS-21$49.00$45.00
DOUBLE ENDHCPSDE-21$109.00$99.00
1/2-13 GO / NOGOHCPS-22$53.00$48.00
DOUBLE ENDHCPSDE-22$115.00$105.00
1/2-20 GO / NOGOHCPS-23$53.00$48.00
DOUBLE ENDHCPSDE-23$115.00$105.00
9/16-12 GO / NOGOHCPS-24$60.00$54.00
DOUBLE ENDHCPSDE-24$130.00$118.00
9/16-18 GO / NOGOHCPS-25$60.00$54.00
DOUBLE ENDHCPSDE-25$130.00$118.00
5/8-11 GO / NOGOHCPS-26$60.00$54.00
DOUBLE ENDHCPSDE-26$130.00$118.00
5/8-18 GO / NOGOHCPS-27$60.00$54.00
DOUBLE ENDHCPSDE-27$130.00$118.00
3/4-10 GO / NOGOHCPS-28$64.00$58.00
DOUBLE ENDHCPSDE-28$138.00$126.00
3/4-16 GO / NOGOHCPS-29$64.00$58.00
DOUBLE ENDHCPSDE-29$138.00$126.00


Helical coil (STI) work plug gage is used to gage threaded holes prior to the insertion of the screw thread insert (STI) and are typically taperlock design. Screw thread inserts are used to repair a damaged thread or provide a stronger threaded assembly and are widely used in the automotive industry.

Available with GO and/or NOGO plug members and manufactured to Class X tolerance in 2B or 3B. All gages are inspected in an environmentally controlled lab and manufactured in full conformance to ASME/ANSI B1. 2. WESTport helical work plug gages are manufactured to the highest end of the ANSI specifications to ensure the longest gage life possible.

WESTport Gage provides a Certificate of Accuracy, traceable to NIST (National Institute of Standards and Technology), free of charge with every helical coil (STI) thread plug gage.

WESTport Manufactured Products. 24th Anniversary Servicing Industry Worldwide (1989-2013)