Kit Types
- USS (coarse) thread kits: 2-56 through 1-1/2-6, plus 3-size kits (6-32/8-32/10-24 and 1/4-20/5/16-18/3/8-16), master kits, Big Boy kits and total kits with free running or locking inserts.
- SAE (fine) thread kits: 3-56 through 1-1/2-12, including 1-14, plus 3-size kits, master kits and Big Boy kits.
- Left hand kits: 1/4-20, 5/16-18, 3/8-16, 7/16-14 and 1/2-13 left hand USS coarse thread.
- Metric kits: M2 x 0.4 through M24 x 3 in coarse and fine pitches, plus 3-size kits, master kits, Big Boy kits and total kits.
- Metric left hand kits: M6 x 1, M8 x 1.25 and M10 x 1.5.
- Pipe thread kits: 1/8-27 through 1-11-1/2 NPT.
- Spark plug kits: M10 x 1, M12 x 1.25, M14 x 1.25 and M18 x 1.5.
What's in a Kit
- High speed steel STI tap: same pitch as the original thread but oversize, to cut the hole for the insert.
- Installation tool: winds the insert into the tapped hole and doubles as the tang break-off tool.
- Helical inserts: a supply of inserts 1-1/2 times the thread diameter in length.
- Drill not included: the drill size is printed on the package. We stock drill bits in our Drills & Cutting Tools category.
Specifications
- Insert material: 18-8 stainless steel diamond-shaped wire, meets or exceeds AMS-7245
- Insert length: 1-1/2 times the nominal diameter (1.5D)
- Surface finish: 22 microinch or better for a smooth running, wear resistant thread
- Fit: controlled interference fit in the STI tapped hole; returns the hole to its original thread size
- Brand: Chrislynn
How to Install a Helical Insert
- Drill out the damaged threads with the drill size shown on the kit, deep enough for the insert and the bolt.
- Tap the hole with the STI tap from the kit.
- Insert: wind the insert in with the installation tool until the top coil sits 1/4 to 1/2 turn below the surface.
- Remove the tang: snap off the driving tang with the end of the installation tool. The hole is now back to its original size.
Drill... Tap... Insert... Remove Tang... Done.
Related Categories
Helical Thread Repair Inserts | EZ-Lok Thread Repair Inserts | Key-Serts Thread Repair | Drills & Cutting Tools | Taps & Dies | Thread Repair Files | Thread Lockers | Threaded Inserts
FAQ
What is included in a helical thread repair kit?
Each single-size kit includes an oversize STI tap, an installation tool (which is also the tang break-off tool) and a supply of 18-8 stainless steel helical inserts. A drill bit is not included; the drill size is printed on the package.
Is the repaired thread as strong as the original?
Usually stronger. The insert spreads the load over a larger area of the parent material, and the stainless steel thread is tougher than soft metals like aluminum, magnesium and cast iron.
What is an STI tap?
STI stands for screw thread insert. An STI tap has the same pitch as the original thread but a larger diameter, so the hole fits the outside of the helical insert. Once the insert is installed, the hole accepts the original size bolt.
Can I buy replacement inserts without a new kit?
Yes. Refill packs for every kit size are in Helical Thread Repair Inserts.
What is the difference between the master, Big Boy and total kits?
They hold several sizes in one case. 3-size kits cover the three most common sizes, master and Big Boy kits cover a wider range of sizes, and total kits cover the full range, each with the tap, tool and inserts for every size. Total kits come with free running or locking inserts.
Can I remove a helical insert?
Yes. If needed, an installed insert can be removed with an extracting tool, and a new insert can be installed in the same tapped hole.
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