OVERVIEW
• Kit for installing EGT Probe 1/8" NPT Male Thread Compression Fittings
• 1/8"-27 Carbon Steel NPT Tap
• Size"R" HSS Drill Bit
The drill and tap kit for installing EGT Probe 1/8" NPT Male Thread Compression Fittings comes with an 1/8" Carbon Steel NPT Tap anda Size "R" HSS Drill Bit. See the document attached below for additional EGT Probe mounting instructions.
TECHNICAL SPECIFICATIONS
Tap Specifications: | 1/8"-27 Carbon Steel NPT Tap |
Drill Bit Specifications: | Size"R" HSS Drill Bit (0.339") |
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About - TAP-KIT-18-NPT: Drill & Tap Kit — 1/8"-27 NPT Thread
The TAP-KIT-18-NPT includes the two tools required to create a 1/8"-27 NPT threaded port in an exhaust manifold, exhaust pipe, intake duct, or similar component for installing a TSC compression fitting—without welding.
The kit includes:
- Size “R” HSS drill bit (0.339")
- 1/8"-27 carbon steel NPT tap
Used together, these tools produce a tapered pipe thread ready to accept any TSC 1/8" NPT male compression fitting.
Drill & Tap vs Weld Bung
There are two common ways to create a 1/8"-27 NPT port:
| Method | Best For |
|---|---|
| Drill & Tap (this kit) | Thick-wall pipe, cast manifolds, solid material |
| Weld Bung | Thin-wall tubing, headers, sheet metal |
Key Considerations
- Drill & tap requires sufficient wall thickness (generally around 1/4" or greater)
- Thin-wall tubing does not support adequate thread engagement
- Weld bungs add material and are preferred for thin sections
Attempting to tap thin-wall tubing often results in stripped threads or leaks.
Why Drill Size Matters
NPT (National Pipe Taper) threads seal by interference as the taper tightens during installation.
The correct tap drill size for 1/8"-27 NPT is:
- Size “R” = 0.339"
This size is critical.
Using incorrect drill sizes can result in:
- Oversized hole → weak threads, leaks
- Undersized hole → excessive tap load, breakage
The included Size R drill ensures proper thread geometry.
Material Considerations
The included carbon steel tap is suitable for:
- Mild steel
- Cast iron
- Cast aluminum
- Ductile iron
For stainless steel:
- A cobalt or coated tap is recommended
- Stainless can work-harden and damage standard taps
Installation Procedure
Step 1 — Mark and Center-Punch
Mark the location and center-punch to prevent drill walking.
Step 2 — Drill
Drill perpendicular to the surface using the Size R bit.
- Use appropriate cutting fluid
- Typically drill through full wall thickness
- Remove all chips and burrs
Step 3 — Tap Threads
Apply cutting fluid and begin tapping.
- Advance slowly
- Back off regularly to clear chips
- Maintain alignment
Broken taps are difficult to remove—avoid excessive force.
Continue tapping until:
- Fitting threads in ~3–4 turns by hand before tightening
Step 4 — Clean and Test Fit
Remove all chips from the bore and interior.
Thread in the compression fitting:
- Hand-tight start
- Final tightening with wrench
Sealing the Port
Use a stainless steel bung port plug (sold separately) when the port is not in use.
PTFE tape is not recommended for exhaust applications due to high temperatures.
Kit Specifications
| Parameter | Specification |
|---|---|
| SKU | TAP-KIT-18-NPT |
| Tap | 1/8"-27 NPT, carbon steel |
| Drill Bit | Size “R” HSS, 0.339" |
| Thread Type | NPT (tapered) |
| Compatible Fittings | All 1/8"-27 NPT compression fittings |
| Suitable Materials | Steel, iron, aluminum |
| Not Recommended | Stainless (use upgraded tap), thin-wall tubing |
What You’ll Also Need
- Compression fitting (included with TSC probes)
- Cutting fluid
- Tap handle or wrench
- Drill or drill press
- Center punch
Applications
- EGT probe installation in exhaust systems
- Intake air temperature probe installation
- Adding sensor ports to manifolds or ducts
Summary
The TAP-KIT-18-NPT provides a simple, effective way to create a threaded port for sensor installation without welding.
- Includes correct drill and tap
- Designed for 1/8"-27 NPT fittings
- Ideal for thick-wall materials
- Enables clean, precise sensor installation