Thread Repair Kits, BSW 1/4 - 1,5D

• for repairing damaged or worn BSW 1/4 x 20 internal threads
• for components where the original internal thread no longer provides reliable holding force
• for thread reinforcement in materials with lower shear strength, such as aluminium and magnesium alloys
• 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 BSW 1/4 x 20 internal thread repair
• STI drill and STI tap are matched to the wire thread insert repair process
• 20 included wire thread inserts allow several repairs in the same thread size
• Type S is free running and restores a normal internal thread without a locking effect.
• stainless steel wire thread inserts support a strong and corrosion-resistant internal thread
• useful for service jobs where component replacement should be avoided
• the plastic case protects the individual parts and simplifies workshop organisation

• 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 6.7 mm STI twist drill.
4. Cut the STI receiving thread with the STI short machine 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 inserting tool and guide it straight to the receiving thread.
7. Install the insert in a controlled movement in the thread direction until the intended installation position is reached; never turn it against the running direction.
8. Remove the driving tang with the tang break tool.
9. Check the repaired thread with a matching screw or suitable inspection method.

Taps, dies and cutting tools

• 1 piece STI Short Machine Tap ISO 529 Form D HSS-G - BSW 1/4 x 20 (03203)

Drills and preparation

• 1 piece STI-Twist Drill, 6.7 mm (00067)

Thread inserts and repair components

• 1 piece V-COIL Inserting Tool No. 9 (08009)
• 1 piece Tang Break Tool No. 9 (07009)
• 20 pieces V-COIL Wire thread insert Free running type S BSW 1/4 x 20 - 1.5 D (100 pcs.) (08343)

Storage and identification

• 1 piece plastic case (99VC951)

• Product class: thread repair
• Product type: V-COIL thread repair kit
• Thread system: British Standard Whitworth thread (BSW)
• Nominal size: BSW 1/4 x 20
• 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 - BSW 1/4 x 20
• Drill: STI twist drill 6.7 mm
• Inserting tool: V-COIL Inserting Tool No. 9
• Tang break tool: Tang Break Tool No. 9
• Storage: plastic case

What is this thread repair kit used for?
It is used to repair damaged, worn or stripped BSW internal threads BSW 1/4 x 20. The wire thread insert restores a functional internal thread inside the prepared STI receiving thread.

Why is the thread designation so important?
It 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 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.

Which insert type does the kit contain?
Type S is free running and restores a normal internal thread without a locking effect.

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 catalog as PDF.