Reduce process steps
No installation tang needs to be broken off or recovered.
TANGLESS WIRE INSERT
Tangless Wire Inserts
One less step from the start.
An end notch drives the insert into a prepared installation thread, with no tang to break off. Suitable for processes that include tang control in quality planning.
DESIGNED FOR CONNECTION
The drive feature stays in the insert.
Tangless inserts are made from helically coiled wire. The tool transfers installation torque through an end notch, eliminating tang break-off and recovery. Hole preparation, installation depth and tool compatibility still matter. Tangless does not mean cleaning-free: machining chips must still be removed.
Focus on cleanliness
Helps reduce the risk of a loose installation tang remaining in the assembly.
Reinforce the thread
The insert provides an internal thread for the screw.
01 / STRUCTURE
Start with the right structure.
The insert structure determines how tangless wire inserts connect and install.
Standard type
For general thread reinforcement and repair.
Locking type
A local locking coil provides screw-retention resistance.
Custom type
Confirm size, length and special requirements for the connection.
For custom structures, provide drawings and operating conditions for engineering review.
02 / MATERIAL
Match the material to the conditions.
From stainless steels to specialty alloys, choose materials for the environment, temperature and mating components.
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. Tangless inserts use a drive notch and require no tang break-off or recovery.
Compare tanged installation →Tangless Wire InsertsInstall → Withdraw tool → 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 pilot hole
Set drilling diameter and depth for the thread size, parent material and blind-hole allowance. Maintain alignment and remove chips.
Confirm the pilot-hole dimensions before machining.- STEP 02
Prepare the entry
Chamfer or deburr the entry as specified to provide a smooth start for the insert. Do not transfer chamfer angles or diameters between different systems.
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 05Install using the drive notch
Engage the notch with a matching tangless tool, install smoothly to the specified depth, then withdraw the tool as instructed.
Set the depth according to the drawing, entry geometry and tool depth stop.
STEP 06Complete the inspection
Check position, insert condition and hole cleanliness. Tangless installation has no tang break-off or recovery step, but final inspection is still required.
Follow the locking insert's acceptance procedure; do not force a standard GO gauge through a locking coil.
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.
This page explains general tangless wire-insert principles. Specific sizes and processes must follow approved ZCOIL drawings.
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.
Thread size
Confirm metric or inch thread, diameter and pitch.
Effective length
Determine from engagement length and blind-hole clearance.
Material and finish
Discuss media, temperature and mating screw.
Installation tools
Confirm the tool tip matches the tangless drive notch.
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
Can a tangless insert use a tanged installation tool?
Not on size alone. The driving mechanisms differ, so the tool's intended application must be checked.
Can it be installed in a standard tapped hole?
Wire inserts require a matching installation thread. A standard tapped hole for the screw is not an STI insert installation hole.