Oversize Big-Sert Thread Repair
Technical guide to repairing severely damaged threads with Big-Sert oversize inserts.
What is Big-Sert?
Big-Sert is an oversize version of the Time-Sert thread repair system. It features a larger outer diameter than standard Time-Sert inserts, making it ideal for situations where the threaded hole has been excessively damaged or previously repaired unsuccessfully.
Like Time-Sert, Big-Sert uses solid steel construction and a roll-forming locking mechanism to create a permanent repair stronger than the original thread. The larger diameter provides maximum strength when parent material has been compromised.
When to Use Big-Sert
Oversized Damage
When the threaded hole has been drilled oversize, damaged beyond standard repair dimensions, or a previous repair has failed leaving an oversized hole.
Spark Plug Thread Repair
Specialized Big-Sert spark plug kits repair stripped spark plug threads in aluminum cylinder heads. Available for 14mm and 18mm spark plug threads.
Failed Previous Repair
When a standard thread repair has failed or pulled out, Big-Sert provides a second chance by using the additional parent material available at a larger diameter.
Maximum Strength Required
Applications demanding the highest possible thread strength benefit from Big-Sert's larger diameter and increased thread engagement area.
Installation Process
Step 1: Assess the Damage
Measure the existing hole to determine if Big-Sert is required. If the hole is already larger than standard Time-Sert drill size, Big-Sert may be your only option.
Step 2: Select Proper Kit
Choose the Big-Sert kit that matches your required internal thread size. The kit includes the oversize drill, counterbore, tap, and installation tool.
Step 3: Drill to Size
Drill the hole to the Big-Sert specification. This will be larger than a standard Time-Sert drill size. Ensure the drill is perpendicular to the surface and drill to the full depth.
Step 4: Counterbore
Create the recessed lip using the Big-Sert counterbore tool. The counterbore depth is critical for proper insert seating.
Step 5: Tap Threads
Tap the hole using the Big-Sert tap. Use cutting fluid and ensure clean, complete threads to full depth.
Step 6: Install Insert
Install the Big-Sert insert using the driver tool. The roll-forming action locks the insert permanently in place.
Big-Sert vs Standard Time-Sert
| Feature | Standard Time-Sert | Big-Sert |
|---|---|---|
| Outer Diameter | Standard oversize | Larger oversize |
| Use Case | Normal thread damage | Oversized holes, severe damage |
| Thread Strength | Stronger than original | Maximum strength |
| Material Removal | Minimal | More parent material removed |
| Installation | Same process | Same process, larger tools |
Common Applications
Spark Plug Repair
The most common Big-Sert application. Aluminum cylinder heads frequently suffer spark plug thread damage, and Big-Sert provides a permanent repair without removing the head.
Oil Pan Drain Plugs
Repeated overtightening damages aluminum oil pan threads. Big-Sert repairs the thread without replacing the pan.
Failed Helicoil Repair
When a Helicoil insert pulls out, the hole is now oversized. Big-Sert provides a permanent solution.
Stripped Head Bolts
Severe cylinder head bolt hole damage in aluminum blocks can be repaired with Big-Sert when standard repair is insufficient.
Need Big-Sert Kits?
Browse our complete range of Big-Sert kits or contact our technical team for application advice.