Lock Bolts
Threaded Insert
Wire Screw Thread Inserts (Helically wound)
Key Locking Thread inserts
Installation Tools
Tool Parts
  HeliCoil Inserts, Kato Inserts, ReCoil Inserts  
      Free Running (UNC)  
      Free Running (UNF)  
      Screw-Locking (UNC)  
      Screw-Locking (UNF)  
       Metric Inserts  
       Tangless Inserts  
       Thread Repair Kits  






HeliCoil, Recoil, Kato - General Design Practices

HeliCoil Installation
Drilling And Countersinking  
Extraction Tools 
Hand Inserting Tools  
Power Tools 
Tang Break-Off Tool 
Thread Gages

How To Install A HeliCoil Screw Thread Insert

Drill - Drill out the damaged threads using the drill size specified in the catalog. Drill to sufficient depth to accommodate the insert length and bolt or screw being used.
Tap - Use the Heil-Coil Tap specified in the catalog. Check the size on your shank to make sure you have the right one. Tap the hole to sufficient depth to accommodate the insert length and bolt or screw being used.
Install - Use the specified installation tool. Just wind the insert into the hole until the top coil is 1/4-1/2 turn into the tapped thread.

Note: Remove tang with the appropriate tool specified.



Drilling And Countersinking a Helicoil

The suggested drill sizes for aluminum Iisted in the catalog are within the minor diameter Iimits for HELI-COIL tapped holes. Alternate drill sizes are suggested in many instances for magnesium, steel and plastics to provide for maximum tap wear life. In the case of magnesium, the larger size is recommended to allow for material close-in. The MINOR DIAMETER AFTER TAPPING should be within the limits shown.

Minimum drilling depth allows one pitch chip clearance between the point of the plug tap and the bottom of the drilled hole. Minimum drilling depths for bottoming taps which have a shorter chamfer and no male centers are given separately.


To prevent the feather edge at the start of the hole, a 120o +-5o countersink to diameter is recommended BEFORE TAPPING. The minimum depth of the full tapped thread takes into consideration 0.5 pitch for depth of countersink.

Drawing Callout - Example
Here is a typical drawing callout for HELI-COIL Screw-Lock Insert M8xl.25 1.5 diameters long, for Tolerances Class 5H. This can be abbreviated by using a production process sheet to provide the operational steps thus limiting the drawing to dimensional data only.

  • 8.3mm Drill maintaining 8.271/8.483 Hole Diameter to 23.5 minus 0 plus your standard drilling depth tolerance.
  • Countersink 120o ± 5o @ to 9.50/10.10 Diameter
  • Tap with HELI-COIL STI Tap No. 2087-8 (Tolerance Class 5H) to 13.3 Min. Full Thread Depth
  • Gage with HELI-COIL Gage No. 1324-8 according to your sampling plan. P.D. 8.812/8.911.
  • InstalI HELI-COIL Screw-Lock Insert 4184-8CN12.0 with HELI-COIL Inserting Tool No. 7751-8.
  • Break off driving tang with HELI-COIL Tang Break-Off Tool No. 4238-8.



Extraction Tools

TooIs to remove HELI-COIL Inserts are Iisted below. This is done by applying the tool to the insert, striking the head of the tool a light blow and turning it counterclockwise, maintaining steady downward pressure.

NOMINAL                          EXTRACTING
DIAMETER                        TOOL

2.2mm, #2                         1227-02
2.5 - 4.5mm, #3 - #8           1227-06
5 - 10mm, #10 - 3/8"           1227-6
11 - 24mm, 7/16" - 1"          1227-16
27 - 39mm, 1-1/8" - 1-1/2"   1227-24



HeliCoil Hand Inserting Tools

Hand tools are designed with threaded mandrel and patented driving contour to install HELI-COIL Inserts correctly and efficiently. Complete instructions are furnished with each tool. 

HELI-COIL Strip Feed used with the Strip Feed Hand Tool speeds up assembly, eliminates handling each insert individually, eliminates waste and facilitates counting. Strip Feed Hand Tools are available in sizes up thru M7xl. To designate, add suffix -15 to Hand Inserting Tool part number. Example: 7751-4-15.

The various designs of HELI-COIL hand inserting tools are shown in the catalog corresponding to the active insert. Generally, finer pitch inserts are proportionately larger in the free state than the coarse pitch inserts and thus have to be "pre-wound" to a smaller diameter for installation. Large coarse pitch inserts (and 2-56 and 3-48 inserts) need only a threaded mandrel tool for installation.



HeliCoil Power Tools

HELI-COIL Power Tools are available in UNC & UNF sizes #2 - 1/2" and up to 12mm, for rapid installation of inserts. Power Tools consist of a front end assembly, an adapter and a reversible air motor. All three components are ordered separately. A Front End Assembly consists of a prewinder, mandrel, and spacers.

Exhaust overhose, Part Number 8511-40, is available and may be attached to the rear end of the air motor to discharge air and mist.



HeliCoil Tang Break-Off Tools

The driving tangs of HELI-COIL Inserts should be removed to eliminate their interference with the end of the assembled bolt. Their removal provides greater latitude in the depth location of the bolt.

Tang Break-Off Tools are available for use with inserts up through 12mm / 1/2" nominal diameter. Their operation is automatic, having a spring loaded, easily triggered punch that strikes a sharp, uniform blow against the tang of the installed insert. It can be operated with one hand.

For sizes >12mm / >1/2" use long nosed pliers. Bend tang up and down to snap off at notch.



Tapping A HeliCoil

 Types of taps:

  • Plug Style 
  • Bottoming Style
  • Spiral Pointed - Plug
  • High Spiral Flute - Bottoming
  • Roughing Tap

HELI-COIL Taps in various types and styles to produce holes for Tolerance Classes 4H5H and 5H for use in the general range of aluminums, magnesiums, mild steels. These taps are designed and manufactured of high speed steel to the most rigid specifications.

Conventional shop practice and production procedures, speeds, feeds and lubricants should be used in combination with proper fixturing and good tapping machines or tapping heads.

The tapped hole must be held within the stated pitch diameter limits for the required Tolerance Class of fit for the installed HELI-COIL Insert.

When anodizing, Iridite or other finishes are used, all tapped hole dimensions must be met after finishes are applied.



Heli-Coil® Thread Gages

Working Gages - Working gages provide a guaranteed minimum wear allowance on the pitch diameter of the GO members of .0002".

Reference Gages - Reference gages have pitch diameters on or close to minimum. They are essentially laboratory or master gages and should be used in case of conflict between 2 working gages, which can arise due to one of them having more use and wear.

Complete Gages - The Complete Gage consists of the GO thread plug gage, the HI thread plug gage and the appropriately marked gage handle.




TANGLESS® is a registered trademark of Advanex Inc.
POP Rivet® is a registered trademark of Emhart Teknologies, LLC.
Recoil® is a registered trademark of Alcoa.