Thread Repair Kits, UNC 9/16 - 1,5D

• for repairing damaged or worn UNC 9/16 x 12 internal threads
• for components where the original internal thread no longer provides reliable engagement
• for thread reinforcement in materials with lower shear strength
• for producing a durable internal thread with a free-running Type S wire thread insert
• for maintenance, machine building, technical workshops, assembly work and small repair series
• 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 repair, compare the thread designation with the component and screw. With UNC 9/16 x 12, stable alignment is important so the STI receiving thread follows the original thread axis accurately.

• compact repair set with STI tap, inserting tool and matching wire thread inserts
• 10 included inserts support several repairs in the same UNC size
• manual inserting tool with locking ring helps control the installation depth
• Type S is free running and suitable for standard screw connections without locking effect
• stainless steel inserts support a strong and corrosion-resistant internal thread
• helps retain existing components instead of replacing them after internal thread damage

• The repair depends on clean preparation, correct STI tapping, controlled insert depth and suitable process tools; for system selection, refer to the VÖLKEL thread repair range.

1. Inspect the damaged internal thread and confirm that the component structure is suitable for a wire thread insert repair.
2. Secure the component and keep the tool guidance aligned with the existing thread axis.
3. Prepare the damaged thread area for the STI receiving thread according to the repair process.
4. Cut the STI receiving thread using the included STI tap.
5. Clean the new receiving thread carefully and remove chips from the repair area.
6. Place the wire thread insert in the inserting tool and guide it straight into the receiving thread.
7. Install the insert in a controlled movement until the intended position is reached.
8. Remove the tang according to the system procedure using a suitable tool.
9. Check the repaired thread with a matching screw or appropriate inspection method.

• 1x STI Short Machine Tap ISO 529 Form D HSS-G for UNC 9/16 x 12 VÖLKEL 03112
• 1x Manual Inserting Tool with locking ring No. 16 VÖLKEL 08016
• 10x V-COIL wire thread inserts, free running Type S, UNC 9/16 x 12, 1.5 D VÖLKEL 08312

• Product class: thread repair
• Product type: V-COIL thread repair kit
• Thread system: UNC
• Nominal size: UNC 9/16 x 12
• 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
• Inserting tool: manual inserting tool with locking ring No. 16
• Repair principle: STI receiving thread with wire thread insert

What is this thread repair kit used for?
It is used to repair damaged or worn UNC 9/16 x 12 internal threads. The wire thread insert restores the thread function inside the prepared STI receiving thread.

Why is the UNC 9/16 x 12 designation important?
The designation must match the component, screw and repair case. Only then do the STI tap, inserting tool and wire thread insert fit the intended repair process.

What does STI mean in this repair process?
STI means Screw Thread Insert. The STI tap cuts the receiving thread for the wire thread insert, not the final screw thread. Further details are available in the technical information V-COIL Thread Repair as PDF.

What is important when using the manual inserting tool?
The insert should be guided straight into the receiving thread without tilting. The locking ring helps control the installation depth during manual insertion.

What does free-running Type S mean?
Type S creates a normal free-running internal thread. It does not add a locking function and is suitable for standard screw connections.

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

Why does the kit include several inserts?
The 10 inserts are practical for repeated repair work in the same UNC size or for service teams that need several identical repairs.

Where can I find the V-COIL system catalogue?
The V-COIL repair systems and accessories are shown in the VC 23 catalogue as PDF.