How To Use Fix A Thread Inserts

HeliCoil Thread Insert

Features and Benefits

A HeliCoil is a coiled-wire blazon of thread repair insert used to create internal screw threads to accommodate standard-sized fasteners.

Some of the advantages of using a Helicoil include...

HeliCoil Thread Repair Kit

Thread Size Range
A large range of available thread diameters let for employ in a variety of thread repair applications.
According to published data, inserts are available as minor as a #ii spiral size, and as large as one ane/ii" diameter. Corresponding metric sizes are also available.

Thread Type Selection
Inserts are available in various thread type and pitch configurations including UNC, UNF, Metric Coarse Pitch and Fine Pitch, UNEF, UNS, and Pipage Thread.
Each insert is offered in several different length options.

Material Options
Several fabric choices are available including Stainless Steel, Phosphor Bronze, Inconel Ten, Nitronic 60, and Titanium. A option of finish coatings is also offered.

How It Works:

HeliCoil Details

As its proper noun suggests, a HeliCoil is a helically coiled stainless steel wire that has a diamond-shaped cantankerous-section.

The wire cantankerous-department allows the external portion of the wire to spiral into the receiving threads in the housing during installation.

On the inner portion of the wire, the spacing between the coils of the insert form new conventional lx° threads.

The coils of the insert are compressed during installation equally the insert is threaded into the housing.

Like a coiled leap, the compressed windings of the installed insert attempt to expand against the walls of the threaded housing. The resulting tension between the insert and the walls of the housing helps to retain the insert and keep it from unthreading.
The insert is provided with a drive tang that is used during installation to thread the insert into the receiving threads in the housing. A special installation tool engages the tang of the insert to bulldoze it into the housing. Once installed, the tang is no longer needed, and is removed.
A small notch is formed into the insert that slightly reduces the whorl cross sectional surface area at that location. When the time comes to remove the tang, the notch volition crusade it to break-off at that point.

Installation Instructions:

HeliCoil Installation Process

Installation Procedure:

Drill out the old threads using the drill size that is recommended on the thread repair kit packaging. The shank of the tap also lists the recommended drill size.
Tap the hole using the Spiral Thread Insert (STI) tap.
Install the insert using the installation tool.

For coarse-pitch threads, use the following procedure:
1. Slide the insert onto the installation tool.
2. Rotate the insert until the tang contacts the commuter notch of the installation tool.
3. Spiral the insert into the STI threaded pigsty to the proper depth using a tap handle to rotate the installation tool.
4. After the insert is seated to the proper depth, unthread the installation tool.
For fine-pitch threads, employ the following process:
1. Utilise the pre-scroll body supplied in the thread repair kit. The pre-coiler helps to shrink the threads of the insert prior to installation in the housing.
2. Slide the insert into the pre-coil body.
3. Rotate the installation tool to thread it through the insert until the notch in the tool contacts the tang of the insert.
4. Go along rotating the installation tool to wind the insert into the threaded end of the pre-coil trunk.
5. Using one mitt, hold the pre-whorl torso squarely against the surface of the workpiece over the tapped hole. Rotate the installation tool to drive the insert through the pre-coil body and into the tapped hole in the housing.
  As the insert is installed, be sure to permit the pre-coil body to float as needed to permit the windings of the HeliCoil to align with the threads in the housing.
6. After the insert is seated to the proper depth, unthread the installation tool.

Repair Tip:

One of the reasons that HeliCoils fail in service is that they are improperly installed initially.

A good dominion-of-pollex is to install the HeliCoil then that the acme of the insert is 1/4 to ane/2 plow beneath the elevation surface of the workpiece. Ane easy style to determine the installed depth is detailed beneath...

Earlier starting time the HeliCoil installation procedure, look closely at the STI threads cut in the hole. Notice the location where the STI thread first starts to enter the hole.
Make a small-scale temporary reference mark on the surface of the housing that is rotated 3/4 plough from the location where the STI thread first enters the hole. This mark is used decide the installed depth of the insert.
Install the insert using the process previously described, and screw the HeliCoil into the housing until the (non-tang) stop of the insert is rotationally aligned with the temporary reference mark.

Post-obit this procedure, the top of the insert is installed 1/4 turn below the top surface of the housing.
If a deeper seating of the insert is desired, rotate the installation tool upwardly to one/4 additional turn.

Remove the tang of the insert.

HeliCoil Tang Notch

Use a punch or a piece of circular bar stock that fits snugly into the inside diameter of the installed insert.
The end of the punch or bar should have a square terminate (without a chamfer).
Allow the bar or punch to rest against the tang of the insert, and hold information technology squarely in the hole.
Strike the end of the tool with a sharp tap with a hammer. The tang should break-off at the notch in the insert that is designed for that purpose.

On larger diameter inserts, it is sometimes easier to use a pair of needle-nose pliers to twist-off the tang.
Recover the tang from the housing prior to re-assembling the machine.

Questions and Answers: Why does the installation of a HeliCoil require the use of an STI tap? What is an STI tap? Can a standard tap be used instead?

One time installed, the internal threads of the HeliCoil insert are designed for utilise with standard sizes of fasteners. To piece of work correctly, the spacing of the coils of the HeliCoil wire is installed with the same pitch (spacing between threads) as the fastener for which it is intended.

Because the external thread bore and pitch is determined past the dimensions of the installed fastener, the resulting external thread does not correspond with a standard tap size.

A "Spiral Thread Insert Tap" (besides known as an STI Tap) is designed specifically to be used in the installation of some types of thread inserts, including HeliCoils. An STI tap is different than a standard fastener thread tap; they tin not be used interchangeably.

To illustrate the divergence betwixt a standard tap and an STI tap...

A standard tap used to create threads for a 1/2" NF fastener has a major diameter of .500" with a pitch of xx threads per inch.

The corresponding STI tap for that particular insert has the same thread pitch of 20 threads per inch, but has a larger major diameter. (In this example, the STI tap major diameter measures .568".)

Rather than just relying on the HeliCoil bound tension to retain the insert, is there any style to positively lock the insert into the housing threads?

The following methods are recommended to help secure an insert into the housing...

Apply a calorie-free blanket of Loctite Thread-Locker compound to the external portion of the coils of the insert prior to threading it into the housing. If this method is used, exist sure not to apply likewise much Loctite and be sure to wipe the internal threads of the HeliCoil insert clean after it is installed so that the fastener does non bond to the insert.

Using a punch and hammer, peen the threads of the housing slightly at the (non-tang) end of the installed insert. The intent with this method is to slightly deform, or compress the housing thread to make it more difficult for the insert to accidently back-out of the housing.

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