Helicoil Twinsert Inserts, Taps and Kits

Helicoil Twinsert assemblies as the name implies consist of two Heli-Coil Inserts: an Helicoil Outer Insert,

always Free-Running and an Inner Helicoil Insert which can be either Free-Running or Screw-Lock.

WHEN TO USE

Helicoil Twinserts are used to correct STI* or standard tapped holes that are stripped, off-center,

damaged or beyond the correction range of Oversize Inserts or standard Heli-Coil Inserts.

SIZES AVAILABLE

Helicoil Twinsert Kits and components come in inch sizes UNC and UNF, and Metric sizes as shown

in the following tables. When Twinserts are installed, the original internal thread size is reestablished

allowing installation of the original size bolt. 

KIT CONTENTS

Each kit contains the quantity of Helicoil Twinserts indicated in Tables E & G, a special Helicoil Twinsert bottoming

tap, an Outer Insert installation tool and a tang break-off tool for the Outer Insert.

Tang break-off tools are included in kits through 7/16″ UNC and UNF and M10 Metric sizes.

Use long nose pliers to break off the tang on nominal thread sizes above 7/16″ and M10.

HOW TO INSTALL

1. Drill hole to the minor diameter as specified. Drill hole to the original depth.
2. Tap the hole to the original depth using the special bottoming tap furnished in the kit.
3. Install outer Helicoil insert with the Helicoil tool furnished in the kit 1/4 to 1/2 pitch below the top

surface.

4. Break off the driving tang with the Helicoil tang break-off tool furnished in the kit. (Sizes above

7/16″ or M10 use long nose pliers, bend tang up and down to snap off at notch.)

5. Install Helicoil Inner Insert to the position where the end of the last coil is flush with the end of

the Helicoil Outer Insert as shown below. Use the same installation tool as used for the standard

Heli-Coil Insert of the same thread size.

6. Break off the driving tang with the tang break-off tool used for the standard Heli-Coil

Insert of the same thread size. (Sizes above 1/2″ or M12 use long nose pliers, bend tang