what kind of thread should be used to make repairs?

Internal Thread Repair

The selection of an advisable thread repair method selected for a given application is determined by several factors including...

• Design of the workpiece beingness repaired
• Workpiece cloth of manufacture
• Type of thread damage being corrected
• Pull-out strength required of the repaired thread
• Concrete admission to the workpiece to achieve the repair

The following flowchart provides some full general guidelines to consider when determining an appropriate repair method.

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What causes thread damage to occur?

Thread harm can occur equally the result of ane or more of these factors...

• Use of incorrect bolt torque specifications.
• Cross-threading or improper installation of fastener.
• Utilise of incorrect fastener size or thread pitch.
• Thread galling caused by engagement with fasteners with a similar fabric hardness. Some materials, such every bit stainless steels are especially susceptible to this type of harm.
• Rusting (oxidation) or dissimilar metal corrosion of the engaged fastener in the threaded hole.
• Failure of a threaded connection due to excessive pull-out force.
• Thread fretting caused by vibration during automobile operation.
• Wear of the thread material itself as a result of repeated utilise.
• Thread damage as a effect of breaking a fastener or tap in the hole.

Oversize Thread Repair Method Sometimes the well-nigh straight-forward repair method is to merely drill out the stripped thread and either tap or threadmill the hole for the side by side larger size.

This method is sometimes is used to repair threads in power-generation valves and turbine casings that get corroded subsequently years of service.

What are the advantages and disadvantages of using the Oversize Thread Repair Method?

Advantages:

• Depending on the circumstances, this tin be the fastest and easiest thread repair method to reach.

Disadvantages:

• The perception of using a mix of thread sizes in a commodities pigsty design is normally undesirable. A mix of thread sizes requires a non-standard selection of fasteners, different torque specifications, and is cosmetically obvious.

  For these reasons, the selection is often made to over-size all of the threads in a pattern, even if only a unmarried threaded hole really requires a repair. The time required to modify all of the threaded holes tin be significant.

• Depending on the pattern of the part, a modification to the corresponding holes of the mating part is sometimes also required to accommodate the oversized fasteners.
• The oversized tapped hole may weaken the function as material is removed in a slender cross-department, depending on the design of the role.

Render to Flowchart

Epoxy Thread Repair Method

For non-critical, low-cal-duty applications, the mating fastener itself can be used as a tool to form the new threads using epoxy thread repair chemical compound.

Caution:

Epoxy thread repair products are not intended for use in "critical" applications or in highly-stressed parts.

Critical applications are those that could consequence in damage to either equipment or life in the event of a part failure. Examples of critical applications include brake systems, steering linkages, internal car parts, etc.

Epoxy Thread Repair Procedure:

Following is a general process step outline.

If considering this method, be sure to obtain and follow the specific recommendations provided by the manufacturer of the epoxy thread repair chemical compound to make up one's mind its suitability for the intended use.

1. Clean the surface to be repaired to remove all grease, dirt, and contamination.
2. Roughen the damaged female threads to help create a surface to which the epoxy will bond. Tools typically used in hole surface preparation include drills, carbide burrs, grinding stones, and rotary files.



3. Utilize a coating of release agent to the fastener male threads to help prevent the epoxy compound from bonding to those threads during the curing process.
4. Following the instructions included with the thread repair kit, dispense both parts of the epoxy compound and mix thoroughly.
5. Again, post-obit the instructions included with the thread repair kit, employ epoxy fabric to both female person and male person parts making certain that that the threads of both parts are completely filled.
6. Insert the coated male fastener into the female thread using a twisting motion. Center the fastener in the hole, and remove excess material.
   Do not apply torque to the fastener at this point.
7. Following the instructions in the kit, permit the epoxy compound to cure before removing the fastener.
8. Once the compound is cured, and the fastener is removed, the repaired threads are ready for use.

What are the advantages and disadvantages of using an epoxy thread repair compound? Advantages:

• Epoxy chemical compound is used to repair many common sizes, types, and grades of threads. One repair kit is used for all thread sizes.
• Can be used in-place in awkward, hard-to-access locations, if necessary, in a variety of applications.
• Epoxy chemical compound is used to repair threads in most metals.
• Considering the epoxy polymer compound does not corrode like other metals, it may actually provide a longer-lasting surface than the original base textile in some applications. Refer to the manufacturer'south specific recommendations.

Disadvantages:

• Intended only for use in light-duty, non-critical applications.
• Limited fastener torque values and thread pull-out force, as compared to the force of the base of operations metal. Refer to instructions included with the epoxy thread repair kit for fastener torque recommendations.
• The epoxy may be affected past ambient weather condition of the awarding including elevated temperatures, exposure to gasses or liquids that are not compatible with the compound. Refer to the manufacturer's specific recommendations.

Return to Flowchart

Welding Thread Repair Method

Welding is a viable stripped thread repair method if the process can be performed without business organisation of distorting the part.

Thread Repair Procedure:

1. Clean the expanse thoroughly using solvent to help minimize the possibility of contaminating the weld.



Any grease or contaminants trapped in the original hole tin cause hard spots to develop in the weld material.

To minimize the possibility of creating weld hard spots, information technology is a proficient idea to drill-out the damaged threads prior to welding the hole.

Also, drilling the hole slightly larger than the major diameter of the original threads volition reduce the difficulty of tapping through the material estrus-affected zone that tin occur during welding.

2. Weld-up the existing pigsty. A flux-less, gas-shielded welding process is recommended to minimize the possibility of slag inclusions in the build-up textile.

   Afterward the welding process is complete, remove the excess weld cloth by either milling or grinding so that it is flush with the surrounding surface.

3. Drill the new hole so that its axis is perpendicular with the originating surface. To properly locate the position of the new threaded hole, the following techniques are often used...
   
   
   • Apply the mating part to locate the position of the new pigsty. Simply align the 2 parts together and use a transfer punch to mark the new hole location.
   • Threaded holes are typically arranged in a pattern. The locations of the existing holes in the design can be used as a reference in positioning the newly created threaded hole.


4. Cut new threads in the pigsty by thread milling or using a tap.

What are the advantages and disadvantages of using welding as a thread repair procedure? Advantages:

• If performed properly, the weld procedure tin outcome in a repair that is cosmetically and structurally no dissimilar than the original material.
• If an improperly-positioned threaded hole needs to be relocated in a part, welding is frequently the first selection repair method.

Disadvantages:

• Oestrus distortion during welding is a concern for close-tolerance parts, and for parts with a slender cross-section pattern.
• The tendency of some materials to form hard spots during welding limits the number of materials that are well-suited for this weld-repair procedure.

Return to Flowchart

Thread Repair Inserts

What are threaded inserts, and why are they used?

Every bit the name suggests, a thread insert is a part that is installed - or inserted - into a workpiece. When properly installed, inserts provide high-quality, wear resistant, permanent internal threads.

In many situations, thread inserts are ideal to repair stripped threads. Thread inserts are also commonly used in new function designs because of the many benefits that they offer.

Thread inserts are supplied in a diversity of configurations. Withal, at that place are basically two general categories of inserts...

• Helical Coiled-Wire Thread Insert
• Solid Body Thread Insert

Helical Coiled-Wire Thread Insert

This type of thread insert is made of a wire with a sixty caste, diamond-shaped cross-department.

The wire is coiled, and acts as a clock spring that becomes compressed when it is installed into receiving threads in the workpiece.

This commodity covers Helicoil Thread Insert features and benefits, installation instructions, and process animation video.

Solid-Body Thread Inserts

A solid thread insert is a metal cylindrical sleeve with threads on the inside and outside of the office. Various types of solid thread inserts are available. These inserts are differentiated by the mode that each type is installed and retained.

Keyed-Mode Threaded Insert

This blazon of insert is supplied with integral locking tabs (called kees) that drive into the housing material during installation.

This article covers Keensert Thread Insert features and benefits, installation and removal instructions, and process animation video.

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Synchronized-Thread Insert

This type of insert has a compact trunk design that is made possible by synchronizing the pitch of the internal and external threads of the insert.

This commodity covers Fourth dimension-Sert Thread Insert features and benefits, installation and removal instructions, and process animation video.

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Locking-Compound Insert

This type of insert utilize pre-applied thread-locking chemical compound on its external threads that begins to gear up-up once installed.

This article covers EZ-LOK Thread Insert features and benefits, installation and removal instructions, and process animation video.

Custom Threaded Inserts

Industrial repair projects often require the use of thread inserts that are non commercially available.

Some factors that may crave a custom thread insert pattern include...

• Non-standard material of manufacture.
• Not-standard thread type and/or pitch.
• The dimensions of the required insert (wall thickness, diameter, or length) is not offered every bit a standard product.

What are the advantages and disadvantages of using threaded inserts? Advantages:

• The use of thread inserts tin can increment the strength of an assembly by distributing fastener clamping forces over a larger area of base textile.
• Thread inserts can increase the pull-out strength and vesture resistance capability of the thread, particularly when installed in softer materials.
• Thread inserts are designed to be hands replaced in the result of a stripped thread, cross-threaded, or worn thread situation. In fact, high-useage fixtures are often designed with thread inserts for this reason.
• Thread inserts are easily installed using readily available repair shop equipment.

Disadvantages:

• Depending of the design of the base material housing, the threaded fastener installation mounting hole may weaken the part as material is removed in a slender cantankerous-department.
• If non installed correctly, some types of thread inserts tin tend to work out of their base material mounting holes over time.

Thread Repair Project Custom Thread Insert - Drill Rig Awarding

This repair projection describes the step-by-step process of the pattern and installation of a custom thread insert in a Ability Take-Off (PTO) housing.

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Return to Thread Repair Flowchart

Impeller
Repair Project

Impeller Repair

This repair project describes the procedure of repairing a pump impeller drive hub and wear rings.

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Source: http://www.repairengineering.com/thread-repair.html

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