Integrated locking function
The locking area is a local coil inside the insert.
SCREW-LOCKING WIRE INSERT
Screw-Locking Wire Inserts
The locking action works on the screw.
Contact between the locking coil and screw thread creates frictional resistance. Consider the screw, lubrication and installation hole as one system.
DESIGNED FOR CONNECTION
Understand the locking coil first.
Screw-locking wire inserts use a locally non-circular coil. As the screw passes through, elastic deformation creates contact pressure. This acts on the screw and does not additionally lock the insert to the parent material. Prevailing torque is distinct from final joint tightening torque.
Consider mating conditions
Screw material, finish and lubrication affect performance.
Define inspection criteria
Specify separate acceptance requirements for screw installation and removal resistance.
01 / STRUCTURE
Start with the right structure.
The insert structure determines how screw-locking wire inserts connect and install.
Locking type
A local locking coil works with the mating screw.
Custom type
Confirm locking torque and acceptance conditions against the drawing.
Related product:Explore the related product →
02 / MATERIAL
Match the material to the conditions.
These material options are discussion points; not every model is available in every combination.
304H / 316 / 316L
Stainless steel options. Select with regard to the environment, mating screw and corrosion requirements.
1Cr18Ni9Ti
A stainless steel option; confirm the grade and applicable material standard.
Nitronic 60
An option to discuss where resistance to galling is required.
Inconel X-750
A nickel-alloy option to discuss for high-temperature conditions.
Titanium alloy / phosphor bronze
Discuss weight, media and electrochemical compatibility.
Custom materials
Provide operating temperature, loads and material specifications.
03 / SURFACE
The finish is part of the connection.
Consider friction, corrosion resistance and identification in the operating environment. Confirm available combinations with an engineer.
Dry-film lubricant
An option for controlling friction and assembly consistency.
Silver plating
Consider high-temperature operation and mating-thread compatibility.
Passivation
A surface-treatment option for stainless steel; not equivalent to nickel plating.
Xylan coating
Confirm friction, corrosion and temperature requirements for the selected coating system.
Color identification
Helps identify models or batches; not a substitute for material documentation.
Cadmium plating / custom treatment
Confirm separately for the environment, applicable standards and supply requirements.
INSTALLATION
From preparation to final inspection.
Prepare the hole before installing the insert. These seven steps show a through-hole installation, including tang break-off, recovery and inspection.
Compare tangless installation →Tanged Wire InsertsInstall → Recover tang → Inspect
Cutting tools, gauges and installation mandrels are shown separately
The gray section represents the parent material and hole
Tanged installations require separate tang recovery
STEP 01Drill the through-hole
Select the drilling diameter for the thread and parent material, then drill through the workpiece. Check rear clearance and remove chips and burrs at both ends.
Steps 01–07 use a through-hole example.- STEP 02
Prepare the entry
Chamfer and deburr the entry as specified, then inspect the through-hole exit to keep both installation and tang-recovery paths clear.
Chamfer requirements depend on the selected insert system and drawing. - STEP 03
Tap the installation thread
Use a matching STI tap to produce the installation thread. Cutting or forming must be compatible with the parent material and insert system.
A conventional screw tap of the same nominal size is not a substitute. - STEP 04
Clean and gauge
Clean the hole and use a matching STI gauge to check the installation thread. If coating or treatment follows, reassess its dimensional effects.
This checks the installation hole before the insert is fitted. - STEP 05
Install using the tang
Use the matching tool to drive the tang and install to the specified depth. Avoid cross-threading, excessive compression and premature tang breakage.
Set the depth according to the drawing, entry geometry and tool depth stop. - STEP 06
Break off, recover and inspect
Ensure sufficient downward travel for the break-off tool. Break the tang as instructed, recover it through the hole exit and verify recovery.
Through-holes provide space for tool travel and tang removal; confirm rear access is available. 
STEP 07Complete the inspection
Inspect depth, insert condition and both ends of the through-hole. Confirm no tang or chips remain and record tang recovery. Complete fit or locking checks as specified.
Follow the locking insert's acceptance procedure; do not force a standard GO gauge through a locking coil.
Check tang break-off clearance first. Through-holes help provide tool travel and a recovery path. Insufficient bottom clearance in a blind hole may prevent break-off or trap the tang. Assess hole depth, tooling and recovery separately.
Tool shapes are process illustrations. Images are not to scale and do not replace tool drawings or process documents. Hole preparation, chamfer, installation depth and acceptance requirements must follow approved drawings and tool instructions.
The rendering shows a locking wire insert and screw. Red is a visual identification feature; locking performance cannot be inferred from color or a rendering.
CONFIGURATION
Bring your requirements to our engineers.
Choose a preferred configuration and add thread size and operating conditions. This is an engineering enquiry, not a confirmed supply configuration.
Confirm these details for a clearer discussion.
Locking requirements
Define acceptance tests for installation and removal torque.
Screw fit
Check hardness, surface condition and lubricant compatibility.
Assembly cycles
Specify maintenance intervals and expected assembly/disassembly cycles.
Identification
Color is only an identification aid. Use the model designation and documentation.
DRILL & STI TAP DIMENSIONS
Drill & STI tap dimensions.
Browse metric and unified tables by material, tap type and insert length. Download for offline use.
Reference edition. Compatibility with ZCOIL products has not been verified. Check approved drawings, parent material and actual tooling before machining; this is not a supply specification.
Metric drilling mm
Unit: mm · Number, letter and fractional drill designations use inch sizing unless explicitly marked mm.
Download CSV (opens in Excel) ↓| Series | Thread | Drill / Al | Drill / Steel | Plug F 1D | Plug F 1.5D | Plug F 2D | Plug F 2.5D | Plug F 3D | Bottom F 1D | Bottom F 1.5D | Bottom F 2D | Bottom F 2.5D | Bottom F 3D |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Coarse | M2X0.4 | #44 (0.0860) | #44 (0.0860) | 5.40 | 6.40 | 7.40 | 8.40 | 9.40 | 3.60 | 4.60 | 5.60 | 6.60 | 7.60 |
| Coarse | M2.2X0.45 | 2.30 | 2.35 | 6.00 | 7.10 | 8.20 | 9.30 | 10.40 | 4.00 | 5.10 | 6.20 | 7.30 | 8.40 |
| Coarse | M2.5X0.45 | 2.70 | 2.70 | 6.45 | 7.70 | 8.95 | 10.20 | 11.45 | 4.30 | 5.55 | 6.80 | 8.05 | 9.30 |
| Coarse | M3X0.5 | 3.15 | 3.20 | 7.50 | 9.00 | 10.50 | 12.00 | 13.50 | 5.00 | 6.50 | 8.00 | 9.50 | 11.00 |
| Coarse | M3.5X0.6 | 3.70 | 3.70 | 8.85 | 10.60 | 12.35 | 14.10 | 15.85 | 5.90 | 7.65 | 9.40 | 11.15 | 12.90 |
| Coarse | M4X0.7 | 4.20 | 4.25 | 10.20 | 12.20 | 14.20 | 16.20 | 18.20 | 6.80 | 8.80 | 10.80 | 12.80 | 14.80 |
| Coarse | M5X0.8 | 5.20 | 5.30 | 12.30 | 14.80 | 17.30 | 19.80 | 22.30 | 8.20 | 10.70 | 13.20 | 15.70 | 18.20 |
| Coarse | M6X1 | 6.25 | 6.30 | 15.00 | 18.00 | 21.00 | 24.00 | 27.00 | 10.00 | 13.00 | 16.00 | 19.00 | 22.00 |
| Coarse | M7X1 | 7.25 | 7.30 | 16.50 | 20.00 | 23.50 | 27.00 | 30.50 | 11.00 | 14.50 | 18.00 | 21.50 | 25.00 |
| Coarse | M8X1.25 | 8.30 | 8.40 | 19.50 | 23.50 | 27.50 | 31.50 | 35.50 | 13.00 | 17.00 | 21.00 | 25.00 | 29.00 |
| Coarse | M10X1.5 | 10.50 | 10.50 | 19.00 | 24.00 | 29.00 | 34.00 | 39.00 | 16.00 | 21.00 | 26.00 | 31.00 | 36.00 |
| Coarse | M12X1.75 | 12.50 | 12.50 | 22.50 | 28.50 | 34.50 | 40.50 | 46.50 | 19.00 | 25.00 | 31.00 | 37.00 | 43.00 |
| Coarse | M14X2 | 14.50 | 14.50 | 26.00 | 33.00 | 40.00 | 47.00 | 54.00 | 22.00 | 29.00 | 36.00 | 43.00 | 50.00 |
| Coarse | M16X2 | 16.50 | 16.50 | 28.00 | 36.00 | 44.00 | 52.00 | 60.00 | 24.00 | 32.00 | 40.00 | 48.00 | 56.00 |
| Coarse | M18X2.5 | 47/64 | 47/64 | 33.00 | 42.00 | 51.00 | 60.00 | 69.00 | 28.00 | 37.00 | 46.00 | 55.00 | 64.00 |
| Coarse | M20X2.5 | 13/16 | 13/16 | 35.00 | 45.00 | 55.00 | 65.00 | 75.00 | 30.00 | 40.00 | 50.00 | 60.00 | 70.00 |
| Coarse | M22X2.5 | 57/64 | 57/64 | 37.00 | 48.00 | 59.00 | 70.00 | 81.00 | 32.00 | 43.00 | 54.00 | 65.00 | 76.00 |
| Coarse | M24X3 | 25.00 | 25.00 | 42.00 | 54.00 | 66.00 | 78.00 | 90.00 | 36.00 | 48.00 | 60.00 | 72.00 | 84.00 |
| Coarse | M27X3 | 28.00 | 28.00 | 45.00 | 58.50 | 72.00 | 85.50 | 99.00 | 39.00 | 52.50 | 66.00 | 79.50 | 93.00 |
| Coarse | M30X3.5 | 31.00 | 31.00 | 51.00 | 66.00 | 81.00 | 96.00 | 111.00 | 44.00 | 59.00 | 74.00 | 89.00 | 104.00 |
| Coarse | M33X3.5 | 34.00 | 34.00 | 54.00 | 70.50 | 87.00 | 103.50 | 120.00 | 47.00 | 63.50 | 80.00 | 96.50 | 113.00 |
| Coarse | M36X4 | 37.00 | 37.00 | 60.00 | 78.00 | 96.00 | 114.00 | 132.00 | 52.00 | 70.00 | 88.00 | 106.00 | 124.00 |
| Coarse | M39X4 | 40.00 | 40.00 | 63.00 | 82.50 | 102.00 | 121.50 | 141.00 | 55.00 | 74.50 | 94.00 | CHECK | 133.00 |
| Fine | M8X1 | 8.25 | 8.30 | 18.00 | 22.00 | 26.00 | 30.00 | 34.00 | 12.00 | 16.00 | 20.00 | 24.00 | 28.00 |
| Fine | M10X1 | 10.25 | 10.25 | 16.00 | 21.00 | 26.00 | 31.00 | 36.00 | 14.00 | 19.00 | 24.00 | 29.00 | 34.00 |
| Fine | M10X1.25 [2] | 10.25 | 10.25 | 17.50 | 22.50 | 27.50 | 32.50 | 37.50 | 15.00 | 20.00 | 25.00 | 30.00 | 35.00 |
| Fine | M12X1.25 [2] | 12.25 | 12.25 | 19.50 | 25.50 | 31.50 | 37.50 | 43.50 | 17.00 | 23.00 | 29.00 | 35.00 | 41.00 |
| Fine | M12X1.5 [2] | 12.25 | 12.50 | 21.00 | 27.00 | 33.00 | 39.00 | 45.00 | 18.00 | 24.00 | 30.00 | 36.00 | 42.00 |
| Fine | M14X1.5 [2] | 14.25 | 14.50 | 23.00 | 30.00 | 37.00 | 44.00 | 51.00 | 20.00 | 27.00 | 34.00 | 41.00 | 48.00 |
| Fine | M16X1.5 [2] | 16.25 | 16.50 | 25.00 | 33.00 | 41.00 | 49.00 | 57.00 | 22.00 | 30.00 | 38.00 | 46.00 | 54.00 |
| Fine | M18X1.5 [2] | 18.25 | 18.50 | 27.00 | 36.00 | 45.00 | 54.00 | 63.00 | 24.00 | 33.00 | 42.00 | 51.00 | 60.00 |
| Fine | M20X1.5 [2] | 20.25 | 20.50 | 29.00 | 39.00 | 49.00 | 59.00 | 69.00 | 26.00 | 36.00 | 46.00 | 56.00 | 66.00 |
| Fine | M22X1.5 [2] | 22.25 | 22.50 | 31.00 | 42.00 | 53.00 | 64.00 | 75.00 | 28.00 | 39.00 | 50.00 | 61.00 | 72.00 |
| Fine | M18X2 | 18.50 | 18.50 | 30.00 | 39.00 | 48.00 | 57.00 | 66.00 | 26.00 | 35.00 | 44.00 | 53.00 | 62.00 |
| Fine | M20X2 | 20.50 | 20.50 | 32.00 | 42.00 | 52.00 | 62.00 | 72.00 | 28.00 | 38.00 | 48.00 | 58.00 | 68.00 |
| Fine | M22X2 | 22.50 | 22.50 | 34.00 | 45.00 | 56.00 | 67.00 | 78.00 | 30.00 | 41.00 | 52.00 | 63.00 | 74.00 |
| Fine | M24X2 | 24.50 | 24.50 | 36.00 | 48.00 | 60.00 | 72.00 | 84.00 | 32.00 | 44.00 | 56.00 | 68.00 | 80.00 |
| Fine | M27X2 | 27.50 | 27.50 | 39.00 | 52.50 | 66.00 | 79.50 | 93.00 | 35.00 | 48.50 | 62.00 | 75.50 | 89.00 |
| Fine | M30X2 | 30.50 | 30.50 | 42.00 | 57.00 | 72.00 | 87.00 | 102.00 | 38.00 | 53.00 | 68.00 | 83.00 | 98.00 |
| Fine | M33X2 | 33.50 | 33.50 | 45.00 | 61.50 | 78.00 | 94.50 | 111.00 | 41.00 | 57.50 | 74.00 | 90.50 | 107.00 |
| Fine | M39X2 | 39.50 | 39.50 | 51.00 | 70.50 | 90.00 | 109.00 | 129.00 | 47.00 | 66.50 | 86.00 | 105.50 | 125.00 |
| Fine | M36X3 | 37.00 | 37.00 | 54.00 | 72.00 | 90.00 | 108.00 | 126.00 | 48.00 | 66.00 | 84.00 | 102.00 | 120.00 |
| Fine | M39X3 | 40.00 | 40.00 | 57.00 | 76.50 | 96.00 | 115.50 | 135.00 | 51.00 | 70.50 | 90.00 | 109.50 | 129.00 |
Metric STI tapping mm
Unit: mm · Number, letter and fractional drill designations use inch sizing unless explicitly marked mm.
Download CSV (opens in Excel) ↓| Series | Thread | Minor min | Minor max | M min | M max | Pitch dia min | Pitch dia max 4H | Pitch dia max 5H | H 1D | H 1.5D | H 2D | H 2.5D | H 3D | Tap major max |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Coarse | M2X0.4 | 2.087 | 2.199 | 2.30 | 2.70 | 2.260 | 2.295 | 2.310 | 2.4 | 3.4 | 4.4 | 5.4 | 6.4 | 2.581 |
| Coarse | M2.2X0.45 | 2.297 | 2.422 | 2.60 | 3.00 | 2.492 | 2.532 | 2.547 | 2.7 | 3.8 | 4.9 | 6.0 | 7.1 | 2.845 |
| Coarse | M2.5X0.45 | 2.597 | 2.722 | 2.90 | 3.40 | 2.792 | 2.832 | 2.847 | 3.0 | 4.2 | 5.5 | 6.7 | 8.0 | 3.147 |
| Coarse | M3X0.5 | 3.108 | 3.248 | 3.40 | 4.00 | 3.325 | 3.367 | 3.384 | 3.5 | 5.0 | 6.5 | 8.0 | 9.5 | 3.716 |
| Coarse | M3.5X0.6 | 3.630 | 3.790 | 4.10 | 4.70 | 3.890 | 3.940 | 3.959 | 4.1 | 5.9 | 7.6 | 9.4 | 11.1 | 4.354 |
| Coarse | M4X0.7 | 4.152 | 4.332 | 4.70 | 5.30 | 4.455 | 4.509 | 4.529 | 4.7 | 6.7 | 8.7 | 10.7 | 12.7 | 5.006 |
| Coarse | M5X0.8 | 5.174 | 5.374 | 5.80 | 6.40 | 5.520 | 5.577 | 5.597 | 5.8 | 8.3 | 10.8 | 13.3 | 15.8 | 6.142 |
| Coarse | M6X1 | 6.217 | 6.407 | 7.10 | 7.70 | 6.650 | 6.719 | 6.742 | 7.0 | 10.0 | 13.0 | 16.0 | 19.0 | 7.422 |
| Coarse | M7X1 | 7.217 | 7.407 | 8.10 | 8.70 | 7.650 | 7.719 | 7.742 | 8.0 | 11.5 | 15.0 | 18.5 | 22.0 | 8.423 |
| Coarse | M8X1.25 | 8.271 | 8.483 | 9.50 | 10.10 | 8.812 | 8.886 | 8.911 | 9.3 | 13.3 | 17.3 | 21.3 | 25.3 | 9.787 |
| Coarse | M10X1.5 | 10.324 | 10.560 | 11.80 | 12.40 | 10.974 | 11.061 | 11.089 | 11.5 | 16.5 | 21.5 | 26.5 | 31.5 | 12.131 |
| Coarse | M12X1.75 [1] | 12.379 | 12.644 | 14.20 | 14.80 | 13.137 | 13.236 | 13.271 | 13.8 | 19.8 | 25.8 | 31.8 | 37.8 | 14.478 |
| Coarse | M14X2 | 14.433 | 14.733 | 16.50 | 17.10 | 15.299 | 15.406 | 15.444 | 16.0 | 23.0 | 30.0 | 37.0 | 44.0 | 16.822 |
| Coarse | M16X2 | 16.433 | 16.733 | 18.50 | 19.10 | 17.299 | 17.406 | 17.444 | 18.0 | 26.0 | 34.0 | 42.0 | 50.0 | 18.821 |
| Coarse | M18X2.5 | 18.541 | 18.896 | 21.20 | 21.80 | 19.624 | 19.738 | 19.778 | 20.5 | 29.5 | 38.5 | 47.5 | 56.5 | 21.514 |
| Coarse | M20X2.5 | 20.541 | 20.896 | 23.20 | 23.80 | 21.624 | 21.738 | 21.778 | 22.5 | 32.5 | 42.5 | 52.5 | 62.5 | 23.513 |
| Coarse | M22X2.5 | 22.541 | 22.896 | 25.20 | 25.80 | 23.624 | 23.738 | 23.778 | 24.5 | 35.5 | 46.5 | 57.5 | 68.5 | 25.512 |
| Coarse | M24X3 | 24.649 | 25.049 | 27.90 | 28.50 | 25.948 | 26.093 | 26.135 | 27.0 | 39.0 | 51.0 | 63.0 | 75.0 | 28.237 |
| Coarse | M27X3 | 27.649 | 28.049 | 30.90 | 31.50 | 28.948 | 29.093 | 29.135 | 30.0 | 43.5 | 57.0 | 70.5 | 84.0 | 31.238 |
| Fine | M8X1 | 8.217 | 8.407 | 9.10 | 9.70 | 8.650 | 8.719 | 8.742 | 9.0 | 13.0 | 17.0 | 21.0 | 25.0 | 9.423 |
| Fine | M10X1 | 10.217 | 10.407 | 11.10 | 11.70 | 10.650 | 10.719 | 10.742 | 11.0 | 16.0 | 21.0 | 26.0 | 31.0 | 11.422 |
| Fine | M10X1.25 [1] | 10.271 | 10.483 | 11.50 | 12.10 | 10.812 | 10.886 | 10.911 | 11.3 | 16.3 | 21.3 | 26.3 | 31.3 | 11.788 |
| Fine | M12X1.25 [1] | 12.271 | 12.483 | 13.50 | 14.10 | 12.812 | 12.898 | 12.926 | 13.3 | 19.3 | 25.3 | 31.3 | 37.3 | 13.787 |
| Fine | M12X1.5 [1] | 12.324 | 12.560 | 13.80 | 14.40 | 12.974 | 13.067 | 13.099 | 13.5 | 19.5 | 25.5 | 31.5 | 37.5 | 14.133 |
| Fine | M14X1.5 [1] | 14.324 | 14.560 | 15.80 | 16.40 | 14.974 | 15.067 | 15.099 | 15.5 | 22.5 | 29.5 | 36.5 | 43.5 | 16.131 |
| Fine | M16X1.5 [1] | 16.324 | 16.560 | 17.80 | 18.40 | 16.974 | 17.067 | 17.099 | 17.5 | 25.5 | 33.5 | 41.5 | 49.5 | 18.131 |
| Fine | M18X1.5 [1] | 18.324 | 18.560 | 19.80 | 20.40 | 18.974 | 19.067 | 19.099 | 19.5 | 28.5 | 37.5 | 46.5 | 55.5 | 20.132 |
| Fine | M20X1.5 [1] | 20.324 | 20.560 | 21.80 | 22.40 | 20.974 | 21.067 | 21.099 | 21.5 | 31.5 | 41.50 | 51.5 | 61.5 | 22.131 |
| Fine | M22X1.5 [1] | 22.324 | 22.560 | 23.80 | 24.40 | 22.974 | 23.067 | 23.099 | 23.5 | 34.5 | 45.50 | 56.5 | 67.5 | 24.130 |
| Fine | M18X2 | 18.433 | 18.733 | 20.50 | 21.10 | 19.299 | 19.406 | 19.444 | 20.0 | 29.0 | 38.0 | 47.0 | 56.0 | 20.823 |
| Fine | M20X2 | 20.433 | 20.733 | 22.50 | 23.10 | 21.299 | 21.406 | 21.444 | 22.0 | 32.0 | 42.0 | 52.0 | 62.0 | 22.822 |
| Fine | M22X2 | 22.433 | 22.733 | 24.50 | 25.10 | 23.299 | 23.406 | 23.444 | 24.0 | 35.0 | 46.0 | 57.0 | 68.0 | 24.823 |
| Fine | M24X2 | 24.433 | 24.733 | 26.50 | 27.10 | 25.299 | 25.414 | 25.454 | 26.0 | 38.0 | 50.0 | 62.0 | 74.0 | 26.820 |
| Fine | M27X2 | 27.433 | 27.733 | 29.50 | 30.10 | 28.299 | 28.414 | 28.455 | 29.0 | 42.5 | 56.0 | 69.5 | 83.0 | 29.822 |
| Fine | M30X2 | 30.433 | 30.733 | 32.50 | 33.10 | 31.299 | 31.414 | 31.454 | 32.0 | 47.0 | 62.0 | 77.0 | 92.0 | 32.822 |
| Fine | M33X2 | 33.433 | 33.733 | 35.50 | 36.10 | 34.299 | 34.414 | 34.454 | 35.0 | 51.5 | 68.0 | 84.5 | 101.0 | 35.822 |
| Fine | M39X2 | 39.433 | 39.733 | 41.50 | 42.10 | 40.299 | 40.414 | 40.454 | 41.0 | 60.5 | 80.0 | 99.5 | 119.0 | 41.821 |
| Fine | M36X3 | 36.649 | 37.049 | 39.90 | 40.50 | 37.948 | 38.093 | 38.135 | 39.0 | 57.0 | 75.0 | 93.0 | 111.0 | 40.236 |
| Fine | M39X3 | 39.649 | 40.049 | 42.90 | 43.50 | 40.948 | 41.093 | 41.135 | 42.0 | 61.5 | 81.0 | 100.5 | 120.0 | 43.236 |
Unified drilling in
Unit: in · Number, letter and fractional drill designations use inch sizing unless explicitly marked mm.
Download CSV (opens in Excel) ↓| Series | Thread | Drill / Al | Drill / Steel | Plug F 1D | Plug F 1.5D | Plug F 2D | Plug F 2.5D | Plug F 3D | Bottom F 1D | Bottom F 1.5D | Bottom F 2D | Bottom F 2.5D | Bottom F 3D |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Coarse | 1-64 | #47 ( .0785) | #46 (.0810) | 0.203 | 0.240 | 0.276 | 0.313 | 0.349 | 0.136 | 0.172 | 0.209 | 0.245 | 0.282 |
| Coarse | 2-56 | 3/32 (.0938) | #41 (.0960) | 0.236 | 0.279 | 0.322 | 0.365 | 0.408 | 0.157 | 0.200 | 0.243 | 0.286 | 0.329 |
| Coarse | 3-48 | #36 (.1065) | 7/64 (.1094) | 0.273 | 0.323 | 0.372 | 0.422 | 0.471 | 0.182 | 0.232 | 0.281 | 0.331 | 0.380 |
| Coarse | 4-40 | #31 (.1200) | #31 (.1200) | 0.318 | 0.374 | 0.430 | 0.486 | 0.542 | 0.212 | 0.268 | 0.324 | 0.380 | 0.436 |
| Coarse | 5-40 | 3.4mm (.1339) | #29 (.1360) | 0.338 | 0.400 | 0.462 | 0.525 | 0.588 | 0.225 | 0.288 | 0.350 | 0.412 | 0.475 |
| Coarse | 6-32 | #26 (.1470) | #25 (.1495) | 0.394 | 0.464 | 0.532 | 0.602 | 0.670 | 0.263 | 0.332 | 0.401 | 0.470 | 0.539 |
| Coarse | 8-32 | #17 (.1730) | #16 (.1770) | 0.434 | 0.516 | 0.598 | 0.680 | 0.762 | 0.289 | 0.371 | 0.453 | 0.535 | 0.617 |
| Coarse | 10-24 | 13/64 (.2031) | #5 (.2055) | 0.535 | 0.630 | 0.725 | 0.820 | 0.915 | 0.357 | 0.452 | 0.547 | 0.642 | 0.737 |
| Coarse | 12-24 | #1 (.2280) | #1 (.2280) | 0.574 | 0.682 | 0.790 | 0.898 | 1.006 | 0.383 | 0.491 | 0.599 | 0.707 | 0.815 |
| Coarse | 1/4-20 | H (.2660) | H (.2660) | 0.675 | 0.800 | 0.925 | 1.050 | 1.175 | 0.450 | 0.575 | 0.700 | 0.825 | 0.950 |
| Coarse | 5/16-18 | Q (.3320) | Q (.3320) | 0.801 | 0.957 | 1.113 | 1.269 | 1.425 | 0.534 | 0.690 | 0.846 | 1.002 | 1.158 |
| Coarse | 3/8-16 | X (.3970) | X (.3970) | 0.750 | 0.938 | 1.125 | 1.312 | 1.500 | 0.625 | 0.812 | 1.000 | 1.188 | 1.375 |
| Coarse | 7/16-14 | 29/64 (.4531) | 29/64 (.4531) | 0.867 | 1.086 | 1.305 | 1.524 | 1.743 | 0.724 | 0.943 | 1.162 | 1.381 | 1.600 |
| Coarse | 1/2-13 [1] | 33/64 (.5156) | 17/32 (.5312) | 0.962 | 1.212 | 1.462 | 1.712 | 1.962 | 0.808 | 1.058 | 1.308 | 1.558 | 1.808 |
| Coarse | 9/16-12 [1] | 37/64 (.5781) | 19/32 (.5938) | 1.062 | 1.343 | 1.624 | 1.905 | 2.186 | 0.895 | 1.176 | 1.457 | 1.738 | 2.019 |
| Coarse | 5/8-11 | 21/32 (.6562) | 21/32 (.6562) | 1.170 | 1.483 | 1.795 | 2.108 | 2.420 | 0.989 | 1.301 | 1.614 | 1.926 | 2.239 |
| Coarse | 3/4-10 | 25/32 (.7812) | 25/32 (.7812) | 1.350 | 1.725 | 2.100 | 2.475 | 2.850 | 1.150 | 1.525 | 1.900 | 2.275 | 2.650 |
| Coarse | 7/8-9 | 29/32 (.9062) | 29/32 (.9062) | 1.542 | 1.979 | 2.417 | 2.854 | 3.292 | 1.319 | 1.757 | 2.194 | 2.632 | 3.069 |
| Coarse | 1-8 | 1-1/32 (1.0312) | 1-1/32 (1.0312) | 1.750 | 2.250 | 2.750 | 3.250 | 3.750 | 1.500 | 2.000 | 2.500 | 3.000 | 3.500 |
| Coarse | 1-1/8-7 | 1-11/64 (1.1719) | 1-11/64 (1.1719) | 1.982 | 2.545 | 3.107 | 3.670 | 4.232 | 1.696 | 2.259 | 2.821 | 3.384 | 3.946 |
| Coarse | 1-1/4-7 | 1-19/64 (1.2969) | 1-19/64 (1.2969) | 2.107 | 2.732 | 3.357 | 3.982 | 4.607 | 1.821 | 2.446 | 3.071 | 3.696 | 4.321 |
| Coarse | 1-3/8-6 | 1-27/64 (1.4219) | 1-27/64 (1.4219) | 2.375 | 3.062 | 3.750 | 4.437 | 5.125 | 2.042 | 2.729 | 3.417 | 4.104 | 4.792 |
| Coarse | 1-1/2-6 | 1-35/64 (1.5469) | 1-35/64 (1.5469) | 2.500 | 3.250 | 4.000 | 4.750 | 5.500 | 2.167 | 2.917 | 3.667 | 4.417 | 5.167 |
| Fine | 0-80 | #52 (.0635) | #52 (.0635) | 0.165 | 0.195 | 0.225 | --- | --- | 0.110 | 0.140 | 0.170 | --- | --- |
| Fine | 3-56 | #37 (.1040) | #36 (.1065) | 0.256 | 0.305 | 0.355 | 0.404 | 0.454 | 0.170 | 0.220 | 0.269 | 0.319 | 0.368 |
| Fine | 4-48 | 3mm (.1181) | #31 (.1200) | 0.293 | 0.349 | 0.405 | 0.461 | 0.517 | 0.195 | 0.251 | 0.307 | 0.363 | 0.419 |
| Fine | 6-40 | #26 (.1470) | #25 (.1495) | 0.357 | 0.426 | 0.495 | 0.564 | 0.633 | 0.238 | 0.307 | 0.376 | 0.445 | 0.514 |
| Fine | 8-36 | #17 (.1730) | #16 (.1770) | 0.413 | 0.495 | 0.577 | 0.659 | 0.741 | 0.275 | 0.357 | 0.439 | 0.521 | 0.603 |
| Fine | 10-32 | #7 (.2010) | 13/64 (.2031) | 0.472 | 0.568 | 0.662 | 0.758 | 0.852 | 0.315 | 0.410 | 0.505 | 0.600 | 0.695 |
| Fine | 1/4-28 | G (.2610) | 6.7mm (.2638) | 0.589 | 0.714 | 0.839 | 0.964 | 1.089 | 0.393 | 0.518 | 0.643 | 0.768 | 0.893 |
| Fine | 5/16-24 | 21/64 (.3281) | 21/64 (.3281) | 0.718 | 0.874 | 1.030 | 1.186 | 1.342 | 0.479 | 0.635 | 0.791 | 0.947 | 1.103 |
| Fine | 3/8-24 | 25/64 (.3906) | 25/64 (.3906) | 0.625 | 0.812 | 1.000 | 1.187 | 1.375 | 0.542 | 0.729 | 0.917 | 1.104 | 1.292 |
| Fine | 7/16-20 | 29/64 (.4531) | 29/64 (.4531) | 0.738 | 0.957 | 1.176 | 1.395 | 1.614 | 0.638 | 0.857 | 1.076 | 1.295 | 1.514 |
| Fine | 1/2-20 | 33/64 (.5156) | 33/64 (.5156) | 0.800 | 1.050 | 1.300 | 1.550 | 1.800 | 0.700 | 0.950 | 1.200 | 1.450 | 1.700 |
| Fine | 9/16-18 | 37/64 (.5781) | 37/64 (.5781) | 0.895 | 1.176 | 1.457 | 1.738 | 2.019 | 0.784 | 1.065 | 1.346 | 1.627 | 1.908 |
| Fine | 5/8-18 | 41/64 (.6406) | 41/64 (.6406) | 0.958 | 1.271 | 1.583 | 1.896 | 2.208 | 0.847 | 1.160 | 1.472 | 1.785 | 2.097 |
| Fine | 3/4-16 | 49/64 (.7656) | 49/64 (.7656) | 1.125 | 1.500 | 1.875 | 2.250 | 2.625 | 1.000 | 1.375 | 1.750 | 2.125 | 2.500 |
| Fine | 7/8-14 | 57/64 (.8906) | 57/64 (.8906) | 1.304 | 1.741 | 2.179 | 2.616 | 3.054 | 1.161 | 1.598 | 2.036 | 2.473 | 2.911 |
| Fine | 1-12 | 1-1/64 (1.0156) | 1-1/32 (1.0312) | 1.500 | 2.000 | 2.500 | 3.000 | 3.500 | 1.333 | 1.833 | 2.333 | 2.833 | 3.333 |
| Fine | 1-1/8-12 [1] | 1-9/64 (1.1406) | 1-5/32 (1.1562) | 1.625 | 2.187 | 2.750 | 3.312 | 3.875 | 1.458 | 2.021 | 2.583 | 3.146 | 3.708 |
| Fine | 1-1/4-12 [1] | 1-17/64 (1.2656) | 1-9/32 (1.2812) | 1.750 | 2.375 | 3.000 | 3.625 | 4.250 | 1.583 | 2.208 | 2.833 | 3.458 | 4.083 |
| Fine | 1-3/8-12 [1] | 1-25/64 (1.3906) | 1-13/32 (1.4062) | 1.875 | 2.562 | 3.250 | 3.937 | 4.625 | 1.708 | 2.396 | 3.083 | 3.771 | 4.458 |
| Fine | 1-1/2-12 [1] | 1-33/64 (1.5156) | 1-17/32 (1.5312) | 2.000 | 2.750 | 3.500 | 4.250 | 5.000 | 1.833 | 2.583 | 3.333 | 4.083 | 4.833 |
Unified STI tapping in
Unit: in · Number, letter and fractional drill designations use inch sizing unless explicitly marked mm.
Download CSV (opens in Excel) ↓| Series | Thread | Minor min | Minor max 3B | Minor max 2B | M min | M max | Pitch dia min | Pitch dia max 3B | Pitch dia max 2B | H 1D | H 1.5D | H 2D | H 2.5D | H 3D | Tap major max | Pitch P |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Coarse | 1-64 | 0.0764 | 0.0823 | 0.0823 | 0.09 | 0.11 | 0.0832 | 0.0843 | 0.0850 | 0.09 | 0.13 | 0.16 | 0.20 | 0.24 | 0.0958 | 0.01563 |
| Coarse | 2-56 | 0.0899 | 0.0961 | 0.0961 | 0.11 | 0.13 | 0.0976 | 0.0989 | 0.0996 | 0.10 | 0.15 | 0.19 | 0.23 | 0.28 | 0.1117 | 0.01786 |
| Coarse | 3-48 | 0.1036 | 0.1104 | 0.1104 | 0.12 | 0.14 | 0.1126 | 0.1140 | 0.1148 | 0.12 | 0.17 | 0.22 | 0.27 | 0.32 | 0.1289 | 0.02083 |
| Coarse | 4-40 | 0.1175 | 0.1252 | 0.1252 | 0.14 | 0.17 | 0.1283 | 0.1299 | 0.1308 | 0.14 | 0.19 | 0.25 | 0.31 | 0.36 | 0.1473 | 0.02500 |
| Coarse | 5-40 | 0.1305 | 0.1373 | 0.1373 | 0.15 | 0.18 | 0.1413 | 0.1430 | 0.1438 | 0.15 | 0.21 | 0.28 | 0.34 | 0.40 | 0.1603 | 0.02500 |
| Coarse | 6-32 | 0.1448 | 0.1527 | 0.1527 | 0.17 | 0.20 | 0.1583 | 0.1601 | 0.1611 | 0.17 | 0.24 | 0.31 | 0.38 | 0.45 | 0.1817 | 0.03125 |
| Coarse | 8-32 | 0.1708 | 0.1781 | 0.1781 | 0.20 | 0.23 | 0.1843 | 0.1862 | 0.1872 | 0.20 | 0.28 | 0.36 | 0.44 | 0.52 | 0.2077 | 0.03125 |
| Coarse | 10-24 | 0.1990 | 0.2080 | 0.2087 | 0.24 | 0.27 | 0.2170 | 0.2192 | 0.2203 | 0.23 | 0.33 | 0.42 | 0.52 | 0.61 | 0.2475 | 0.04167 |
| Coarse | 12-24 | 0.2250 | 0.2340 | 0.2347 | 0.26 | 0.29 | 0.2430 | 0.2453 | 0.2464 | 0.26 | 0.37 | 0.47 | 0.58 | 0.69 | 0.2735 | 0.04167 |
| Coarse | 1/4-20 | 0.2608 | 0.2704 | 0.2723 | 0.31 | 0.34 | 0.2825 | 0.2851 | 0.2864 | 0.30 | 0.43 | 0.55 | 0.68 | 0.80 | 0.3187 | 0.05000 |
| Coarse | 5/16-18 | 0.3245 | 0.3342 | 0.3372 | 0.38 | 0.41 | 0.3486 | 0.3515 | 0.3529 | 0.37 | 0.53 | 0.68 | 0.84 | 0.99 | 0.3884 | 0.05556 |
| Coarse | 3/8-16 | 0.3885 | 0.3987 | 0.4026 | 0.45 | 0.48 | 0.4156 | 0.4189 | 0.4203 | 0.44 | 0.63 | 0.81 | 1.00 | 1.19 | 0.4602 | 0.06250 |
| Coarse | 7/16-14 | 0.4530 | 0.4639 | 0.4688 | 0.52 | 0.55 | 0.4839 | 0.4875 | 0.4890 | 0.51 | 0.73 | 0.95 | 1.17 | 1.38 | 0.5343 | 0.07143 |
| Coarse | 1/2-13 [1] | 0.5166 | 0.5273 | 0.5335 | 0.59 | 0.62 | 0.5499 | 0.5537 | 0.5554 | 0.58 | 0.83 | 1.08 | 1.33 | 1.58 | 0.6042 | 0.07692 |
| Coarse | 9/16-12 [1] | 0.5806 | 0.5918 | 0.5986 | 0.66 | 0.69 | 0.6167 | 0.6208 | 0.6225 | 0.65 | 0.93 | 1.21 | 1.49 | 1.77 | 0.6751 | 0.08333 |
| Coarse | 5/8-11 | 0.6447 | 0.6564 | 0.6641 | 0.73 | 0.76 | 0.6841 | 0.6885 | 0.6903 | 0.72 | 1.03 | 1.34 | 1.65 | 1.97 | 0.7477 | 0.09091 |
| Coarse | 3/4-10 | 0.7716 | 0.7838 | 0.7926 | 0.86 | 0.89 | 0.8149 | 0.8196 | 0.8216 | 0.85 | 1.23 | 1.60 | 1.98 | 2.35 | 0.8850 | 0.10000 |
| Coarse | 7/8-9 | 0.8990 | 0.9119 | 0.9218 | 1.00 | 1.03 | 0.9471 | 0.9522 | 0.9543 | 0.99 | 1.42 | 1.86 | 2.30 | 2.74 | 1.0247 | 0.11111 |
| Coarse | 1-8 | 1.0271 | 1.0421 | 1.0521 | 1.14 | 1.17 | 1.0812 | 1.0898 | 1.0898 | 1.13 | 1.63 | 2.13 | 2.63 | 3.13 | 1.1681 | 0.12500 |
| Coarse | 1-1/8-7 | 1.1559 | 1.1730 | 1.1834 | 1.29 | 1.32 | 1.2178 | 1.2239 | 1.2262 | 1.27 | 1.83 | 2.39 | 2.96 | 3.52 | 1.3171 | 0.14286 |
| Coarse | 1-1/4-7 | 1.2809 | 1.2980 | 1.3084 | 1.41 | 1.44 | 1.3428 | 1.3490 | 1.3514 | 1.39 | 2.02 | 2.64 | 3.27 | 3.89 | 1.4421 | 0.14286 |
| Coarse | 1-3/8-6 | 1.4110 | 1.4310 | 1.4416 | 1.56 | 1.59 | 1.4832 | 1.4900 | 1.4926 | 1.54 | 2.23 | 2.92 | 3.60 | 4.29 | 1.5982 | 0.16667 |
| Coarse | 1-1/2-6 | 1.5360 | 1.5560 | 1.5665 | 1.69 | 1.72 | 1.6082 | 1.6151 | 1.6177 | 1.67 | 2.42 | 3.17 | 3.92 | 4.67 | 1.7232 | 0.16667 |
| Fine | 0-80 | 0.0628 | 0.0665 | 0.0665 | 0.07 | 0.11 | 0.0681 | 0.0691 | 0.0697 | 0.07 | 0.10 | 0.13 | --- | --- | 0.0775 | 0.01250 |
| Fine | 3-56 | 0.1029 | 0.1086 | 0.1086 | 0.12 | 0.14 | 0.1106 | 0.1119 | 0.1126 | 0.12 | 0.17 | 0.22 | 0.27 | 0.31 | 0.1247 | 0.01786 |
| Fine | 4-48 | 0.1166 | 0.1229 | 0.1229 | 0.14 | 0.17 | 0.1256 | 0.1271 | 0.1279 | 0.13 | 0.19 | 0.24 | 0.30 | 0.36 | 0.1419 | 0.02083 |
| Fine | 6-40 | 0.1435 | 0.1503 | 0.1503 | 0.17 | 0.20 | 0.1543 | 0.1560 | 0.1569 | 0.16 | 0.23 | 0.30 | 0.37 | 0.44 | 0.1733 | 0.02500 |
| Fine | 8-36 | 0.1701 | 0.1771 | 0.1771 | 0.20 | 0.23 | 0.1821 | 0.1840 | 0.1849 | 0.19 | 0.27 | 0.36 | 0.44 | 0.52 | 0.2032 | 0.02778 |
| Fine | 10-32 | 0.1968 | 0.2041 | 0.2041 | 0.23 | 0.26 | 0.2103 | 0.2123 | 0.2133 | 0.22 | 0.32 | 0.41 | 0.51 | 0.60 | 0.2337 | 0.03125 |
| Fine | 1/4-28 | 0.2577 | 0.2646 | 0.2661 | 0.29 | 0.32 | 0.2732 | 0.2754 | 0.2765 | 0.29 | 0.41 | 0.54 | 0.66 | 0.79 | 0.2995 | 0.03571 |
| Fine | 5/16-24 | 0.3215 | 0.3288 | 0.3312 | 0.36 | 0.39 | 0.3395 | 0.3421 | 0.3433 | 0.35 | 0.51 | 0.67 | 0.82 | 0.98 | 0.3700 | 0.04167 |
| Fine | 3/8-24 | 0.3840 | 0.3910 | 0.3937 | 0.42 | 0.45 | 0.4020 | 0.4047 | 0.4059 | 0.42 | 0.60 | 0.79 | 0.98 | 1.17 | 0.4325 | 0.04167 |
| Fine | 7/16-20 | 0.4483 | 0.4561 | 0.4598 | 0.50 | 0.53 | 0.4700 | 0.4731 | 0.4744 | 0.49 | 0.71 | 0.93 | 1.14 | 1.36 | 0.5062 | 0.05000 |
| Fine | 1/2-20 | 0.5108 | 0.5186 | 0.5223 | 0.56 | 0.59 | 0.5325 | 0.5357 | 0.5371 | 0.55 | 0.80 | 1.05 | 1.30 | 1.55 | 0.5687 | 0.05000 |
| Fine | 9/16-18 | 0.5745 | 0.5826 | 0.5872 | 0.63 | 0.66 | 0.5986 | 0.6020 | 0.6035 | 0.62 | 0.90 | 1.18 | 1.46 | 1.74 | 0.6384 | 0.05556 |
| Fine | 5/8-18 | 0.6370 | 0.6451 | 0.6497 | 0.69 | 0.72 | 0.6611 | 0.6646 | 0.6661 | 0.68 | 0.99 | 1.31 | 1.62 | 1.93 | 0.7009 | 0.05556 |
| Fine | 3/4-16 | 0.7635 | 0.7720 | 0.7776 | 0.82 | 0.85 | 0.7906 | 0.7945 | 0.7961 | 0.81 | 1.19 | 1.56 | 1.94 | 2.31 | 0.8352 | 0.06250 |
| Fine | 7/8-14 | 0.8905 | 0.8994 | 0.9063 | 0.96 | 0.99 | 0.9214 | 0.9257 | 0.9274 | 0.95 | 1.38 | 1.82 | 2.26 | 2.70 | 0.9718 | 0.07143 |
| Fine | 1-12 | 1.0181 | 1.0281 | 1.0361 | 1.10 | 1.13 | 1.0542 | 1.0589 | 1.0608 | 1.08 | 1.58 | 2.08 | 2.58 | 3.08 | 1.1126 | 0.08333 |
| Fine | 1-1/8-12 [1] | 1.1431 | 1.1531 | 1.1611 | 1.22 | 1.25 | 1.1792 | 1.1841 | 1.1860 | 1.21 | 1.77 | 2.33 | 2.90 | 3.46 | 1.2376 | 0.08333 |
| Fine | 1-1/4-12 [1] | 1.2681 | 1.2781 | 1.2861 | 1.35 | 1.38 | 1.3042 | 1.3092 | 1.3112 | 1.33 | 1.96 | 2.58 | 3.21 | 3.83 | 1.3626 | 0.08333 |
| Fine | 1-3/8-12 [1] | 1.3931 | 1.4031 | 1.4111 | 1.47 | 1.50 | 1.4292 | 1.4343 | 1.4364 | 1.46 | 2.15 | 2.83 | 3.52 | 4.21 | 1.4876 | 0.08333 |
| Fine | 1-1/2-12 [1] | 1.5181 | 1.5281 | 1.5361 | 1.60 | 1.63 | 1.5542 | 1.5595 | 1.5615 | 1.58 | 2.33 | 3.08 | 3.83 | 4.58 | 1.6126 | 0.08333 |
Reading notes, applicability and data exception
- Reference hole-preparation data for tangless and tanged wire inserts. Use matching STI taps. Confirm compatibility with ZCOIL drawings, tooling and parent material; this is not a ZCOIL qualification or supply specification.
- D is nominal thread diameter; 1D to 3D identify installed insert length. F is minimum drilling depth; H is minimum tapping depth. Plug and Bottoming are tap types, not through-hole / blind-hole categories.
- Metric dimensions: mm. Unified dimensions: in. Drill designations retain source units: # drills, letter drills and fractions use inch sizing. The M2 drill #44 (0.0860) is also in inches. Explicit mm drill labels remain metric.
- Countersink M: 120 degrees +/-5 degrees. Keep 3B / 2B and 4H / 5H limits separate. Suggested drill diameter is not the after-tapping minor diameter.
- Source notes: for Plug taps at 5/16 in / M8 and smaller, F allows for a male center equal to half the nominal tap diameter. Bottoming taps have the thread-end male center removed. Verify actual tool geometry.
- [1] / [2] after a thread are source footnote markers, not pitch digits. Unified [1] and metric tapping [1] flag standard drills differing slightly from referenced minor-diameter requirements. Metric drilling [2] is retained as supplied.
- For through holes, verify material thickness, tool exit and effective thread. Tanged inserts also require tang break-off and recovery. Check blind-hole clearance separately; F and H are not plate thickness.
- CHECK: source M39X4 / Bottom F 2.5D reads 1135.00 and is withheld pending verification. --- means not listed. Do not interpolate missing dimensions.
- Compiled from the user-supplied Drill-Tap.pdf, Rev. 03/26. Third-party reference data; ZCOIL product compatibility is not verified. Document ZC-DT-20261001-R1.
ZC-DT-20261001-R1 · Not applicable to key-locking inserts.
KNOWLEDGE & RESOURCES
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Frequently asked questions
Is the red color itself the locking feature?
No. Red may be an identification mark. Locking comes from internal geometry and contact forces.
Is greater screw-in resistance always better?
No. Unusual resistance may result from the installation hole, mating screw or lubrication. Check against the specified torque range.