Thread Repair Kits, UNC 1/2 - 1,5D

• for repairing damaged or worn UNC 1/2 x 13 internal threads
• for components where the original internal thread no longer provides reliable holding force
• for thread reinforcement in materials with lower shear strength
• for creating a durable internal thread with a free-running Type S wire thread insert
• for maintenance workshops, assembly work, service departments, machine building and metalworking
• Process: manual or assisted drive depending on your tool holder and machine configuration
• Use: thread cutting, thread recutting and thread cleaning depending on the condition of the thread

Note Before starting the repair, check the thread designation, component condition, wall thickness and available installation depth. Stable alignment is essential so the insert seats correctly in the STI thread.

• complete kit configuration for UNC 1/2 x 13 internal thread repair
• STI drill and STI tap are matched to the wire thread insert repair process
• 10 included wire thread inserts allow several repairs in the same thread size
• Type S is free running and suitable for standard screw connections without locking effect
• stainless steel wire thread inserts support a strong and corrosion-resistant internal thread
• useful for service jobs on inch-based UNC assemblies where component replacement should be avoided

• The repair is only reliable when drilling, STI tapping and insert depth are carried out cleanly; follow the kit sequence carefully from preparation to final inspection.

1. Inspect the damaged internal thread and confirm that the component structure is suitable for a wire thread insert repair.
2. Securely align the component and make sure the tool axis follows the existing thread axis.
3. Drill out the damaged thread area using the included STI twist drill.
4. Cut the STI receiving thread with the matching STI tap and a suitable cutting lubricant.
5. Clean the receiving thread thoroughly and remove all chips from the repair area.
6. Place the wire thread insert into the manual inserting tool and guide it straight to the receiving thread.
7. Install the insert in a controlled movement until the intended installation position is reached.
8. Remove the driving tang with the tang break tool.
9. Check the repaired thread with a matching screw or suitable inspection method.

• 1x STI Short Machine Tap ISO 529 Form D HSS-G for UNC 1/2 x 13 VÖLKEL 03111
• 1x Tang Break Tool No. 15 VÖLKEL 07015
• 1x Manual Inserting Tool with locking ring No. 15 VÖLKEL 08015
• 10x V-COIL wire thread inserts, free running Type S, UNC 1/2 x 13, 1.5 D VÖLKEL 08311
• 1x STI Twist Drill 13.0 mm VÖLKEL 00130

• Product class: thread repair
• Product type: V-COIL thread repair kit
• Thread system: UNC
• Nominal size: UNC 1/2 x 13
• Insert length: 1.5D
• Insert type: Type S, free running
• Insert standard reference: DIN 8140
• Insert tolerance: ISO 2 (6H)
• Insert material: stainless steel
• Tap: STI short machine tap ISO 529 Form D HSS-G
• Drill: STI twist drill 13.0 mm
• Inserting tool: manual inserting tool with locking ring No. 15
• Tang break tool: No. 15

What is this thread repair kit used for?
It is used to repair damaged, worn or stripped UNC 1/2 x 13 internal threads. The wire thread insert restores a functional internal thread inside the prepared STI receiving thread.

Why is the UNC 1/2 x 13 designation important?
The thread designation is the key selection criterion. It must match the component, the screw and the repair requirement so that the drill, STI tap and insert work together correctly.

Why can’t a standard UNC tap be used for the insert?
A standard tap produces a normal screw thread. The insert requires a special STI receiving thread, which is created with the STI tap included in this kit.

Where can I find technical information on V-COIL thread repair?
The repair principle with STI thread and wire thread insert is explained here: Technical information V-COIL Thread Repair as PDF.

What does free-running Type S mean?
Type S inserts are designed for normal screw running without a self-locking function. They restore the internal thread while keeping the standard fastening behavior.

Where can I find information on wire thread inserts according to DIN 8140?
Further technical details are available here: Technical information Wire Thread Inserts DIN 8140 as PDF.

What should be checked before breaking off the tang?
Check that the insert is installed at the correct depth and that it follows the thread cleanly. The tang should only be removed once the insert position is correct.

Where can I find the V-COIL system catalogue?
The catalogue for V-COIL thread repair systems and accessories is available here: VC 23 catalogue as PDF.