Best Thread Repair Kit

Contents

A Comprehensive Guide to Help You Choose the Best Thread Repair Kit for your Needs!

With over 30 years in the machining business I have had the occasion to repair many dozens of damaged threads. Consequently, every instance is different and requires a specialized thread repair tool to Different types of thread repair kitsdo the job correctly. Unfortunately, it’s not possible to know in advance just what size or type thread will require repairing so it makes sense to have the best thread repair kit available when the time comes.

Often times the original threads can be restored without removing any material which would weaken its holding ability. However, in many cases the threads will have been stripped or badly worn and require rethreading or replacing.

Fortunately, there are thread repair kits available that will enable you to either restore old threads or replace them with new full-strength threads.

What Type of Thread Repair Kit is Best for Restoring My Damaged Threads?

When a thread becomes damaged it can render an important and often times expensive part or piece of equipment inoperable.   Fortunately, there are multiple options for repairing or restoring damaged threads.  Since each instance is unique,  specialized tools and products have been developed to accommodate just about every possible scenario imaginable.

Certain products require only one tool to complete the job while others consist of a kit with threaded inserts and the tools necessary to install them.

In order to select the best option its important to consider whether the threads that require repairing are male or female, the extent of the damage, and the type of part the damaged threads are in or on.  Simply choose the Option in the BOX BELOW that best describes your thread repair scenario.

Types of Thread Damage

There are basically 4 ways threads become damaged: Wear, Stripping, Impact, and Cross-threading. Fortunately in most instances the damaged threads can be repaired or restored with the proper tools and knowledge.

Wear and Stripping

Any situation where you have threaded parts that are frequently installed and removed thread wear can occur, especially if no lubrication is present. When threads become worn the metal erodes away weakening the holding potential which often leads to stripping and part failure.

Worn or stripped threads must be replaced in order to restore the threaded parts to their design holding potential.

Worn or Stripped MALE Threads:

stud with stripped male threadsWhen male threads on a shaft, bolt, or stud become significantly worn or stripped the threads must be replaced in order to return it to original strength.  Unfortunately, there are no “Kits” available to restore male threads that have been stripped.

Larger diameter shafts can be welded and the threads re-cut in a metal working lathe.

Worn or Stripped FEMALE  Threads:

When a threaded hole becomes worn or stripped there are two highly effectivestripped female threads in casting options for restoring the threads to original holding potential.

  1. Install a Recoil Insert
  2. Install a Solid Threaded Insert

Both options work very well but choosing which one is best depends on the particular task.

SEE: Recoil Screw Thread Inserts (aka Heli-coil or Helical) Pros and Cons

..also

SEE: Solid Threaded Inserts-Pros and Cons

Impact and Cross-Threading Damage

Impact:

When the male threads on a bolt, stud, or threaded shaft become damaged as a result of impact they can usually be restored to their original strength.

Female threads typically are not prone to impact damage because they are by design protected.

Cross-Threading:

Cross-threading occurs when a female thread is misaligned when first started on a male thread or cross threading occurs when male and female threads are misalignedvisa versa.  When this happens the helix of the threads are not properly engaged causing the metal of the threads to become forced aside or distorted.

Once the threads are forced out of the helix it becomes very difficult or impossible to continue turning the nut or stud.  If turning is continued the threads are very likely to become ceased, destroying the male and female threads beyond repair. However, if there is minimal damage to the threads they can be restored to their original configuration and in most cases to original holding strength.

There are basically THREE methods for repairing or restoring threads that have been cross threaded:

  1. Swaging
  2. Chasing
  3. Filing
Swaging

Swaging is a thread restoration process that works by forcing damaged threads back into their original configuration.

Specially designed thread repair taps and dies feature several tapered threads called lead threads. These tapered threads are designed to engage the helix of the threads and progressively force (Swage) them back to the original helix form as you turn the tool.  Once the process has been completed the threads will be restored to near original strength.

Unlike threading taps and dies that are designed to cut and remove metal, swaging thread repair tools reshape threads that have already been cut.

SEE:  Swaging Tool Thread Repair Kits RECOMMENDATIONS

Chasing

Another highly effective method for restoring damaged threads is a process called “Chasing.” As the word suggests it means to follow. A thread repair chasing tool is designed to follow the repairing damaged thread with chasing toolhelix of the undamaged threads while forcing the damaged threads back to their original form.

A male thread chasing tool works similar to a “C” clamp. Two adjustable followers with 60 degree angles are designed to engage both damaged and undamaged thread. A V shape opposes the two follower arms and allows for the threaded stud, bolt, or shaft to nest securely in place while the chasing tool is turned. The follower arms are adjusted to exert high pressure in the thread valleys and force the damaged metal back in to the original thread helix.

A female thread chasing tool works the opposite of a male chasing tool.

One of the advantages of a thread chasing repair kit is that one tool or kit can be used for any diameter shaft within its adjustment range and any pitch. A thread chasing repair kit is an excellent choice for the auto repair business where all makes and models of vehicles with damaged threads require repair.

SEE:  Thread Chasing Repair Kits RECOMMENDATIONS

Thread Restoration Files

Some thread restoration kits include a set of thread restoration files with teeth that match specific thread pitches (distance between threads).   A common application would be if a threaded stud or shaft was dropped causing slight flattening of the thread crest.

Thread restoration files SHOULD ONLY BE USED where damage is minimal because they remove metal making the thread weaker.

SEE: Thread Restoring Files – Pros and Cons

Recoil Screw Thread Inserts (aka Heli-coil or Helical) – Pros and Cons

Recoil Screw Thread Inserts are basically a spring-looking item made with a unique wire that has a cross section resembling a diamond.  Heli-Coil is is the name of the company that developed the recoil screw thread insert repair system.   Multiple companies now manufacture Recoil Screw Thread Inserts that are basically identical to the Helicoil brand.

These unique inserts come in various thread sizes in both SAE and METRIC and in different lengths.  To install a Helicoil-type insert the damaged threaded hole must be drilled out to a larger diameter hole specified in the kit instructions.  Then, the freshly drilled hole is tapped using the special Tap also included in the kit.

Once thee hole has been tapped the Helicoil is inserted on the special installation tool and started in the tapped hole.

When the Helicoil has been screwed to the correct depth with the end of the coil just slightly below the surface of the tapped hole, the Tang of the coil is removed.  A Tang Breaker tool is included with some sets but  a punch, or screwdriver can also be used successfully.

Watch this Instructional VIDEO – Thread Repair with Helicoil Thread Insert

Pros

Helicoils are the best option if the damaged threaded hole is in a restricted area or if you want to retain as much of the original part as possible.  If the appearance is an issue such as restoring a vintage or antique piece of equipment a Helicoil-type insert is by far the best option.

Helicoil-type inserts are commonly used in the auto repair industry to perform highly effective as-new repairs.

A great application for Helicoils is to repair easily stripped threads in aluminum machined parts or castings creating stronger than original threads.

Cons

Installing a Heli-coil insert can be a bit tricky, even with experience.  However, when correctly installed the thread will be restored to as-new condition or stronger, especially in soft non-ferrous metals.

Recoil inserts require specialized tools adding to the cost of a kit.

To View Helicoil Thread Repair Kits Go HERE!

Recoil (Heli-Coil) Threaded Insert Repair Kit RECOMMENDATIONS

HHIP 1011-Series Helical STI Thread Repair Kit (Select Thread Size)

Features:

HHIP 1011-Series Helical STI Thread Repair Kit

  • Application :General purpose FEMALE thread repair in machined parts, dies, fixtures, farm equipment, home workshop
  • SAE (Fractional) Kit Sizes:  ¼”-20, 5/16”-18, 3/8”-16, and ½”-13
  • METRIC Kit Sizes: M5 x 0.80, M6 x 1.00, M8 x 1.25, M10 x 1.50, and M12 x 1.75
  • No. of Inserts: Varies per kit model
  • Tools:HS Steel Twist Drill, Coil Driver, Tang Breaker, L HEX Wrench, and Metal Case

Overview

The HHIP 1011-Series Helical STI Thread Repair Kit is available in specific Fractional and Metric thread sizes per each kit. Each kit includes the appropriate HSS drill bit and Tap plus a Coil Driver and a Tang Breaker.

Each component is nicely arranged in a metal case with a latch for secure storage.

The HHIP 1011-Series Helical STI Thread Repair Kit is an excellent cost-effective option if you are in the machine shop, commercial HVAC, millwright, or general maintenance business. Or for anyone in need of an inexpensive solution to repair a damaged thread.

You can select a kit with the specific thread size that requires repair as-needed or to keep one on hand for future thread repairs.  The

check price of HHIP 1011-Series Helical STI Thread Repair Kit at amazon

 

CO-Z 131 pc Stripped Thread Repair Kit, Recoil (Helicoil)

Features:

CO-Z 131 pc Stripped Thread Repair Kit, Recoil (Helicoil)

  • Application :General purpose FEMALE thread repair in machined parts, dies, fixtures, farm equipment, home equipment, etc.
  • Thread Size/s:M5x0.8×6.7 mm, M6x1.0x8.0 mm, M8x1.25×10.8 mm, M10x1.5×13.5 mm, and M12x1.75×16.3 mm long
  • No. of Inserts:110
  • Tools:(5) HS Steel Drill Bits, (5) Coil Drivers, (5) Tang Breaker, (2) L-HEX Wrenches, and Metal Case

Overview

The CO-Z 131 pc Stripped Thread Repair Kit is ideal for repairing damaged or stripped threads that cannot be restored. With recoil screw thread inserts ranging in sizes from M5 to M12 plus all the tools necessary to do a complete installation this is a versatile set to have on hand.

The quality of the tools in this kit is good and the coils are made from stainless steel so they will create a strong, long lasting thread repair.

I recommend the CO-Z 131 pc Stripped Thread Repair Kit for general machine shop, auto repair, farm equipment, commercial HVAC, plant maintenance, and DIY home repair projects.

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E-Z Lok Helical Threaded Insert Kit, SAE (Number and Fractional)

Features:

  • Application :General purpose repair of FEMALE threads in machined parts, dies, fixtures, farm equipment, home equipment, etc.
  • Thread Size/s: #4 -#12, and 1/4″-3/4″ Coarse and Fine Series
  • No. of Inserts: 5 to 10 per set
  • Tools: STI Tap and Combination Insert Tool/Tang Break Tool

Overview

E-Z Lok Helical Threaded Insert Kits are a cost-effective option when only one size thread needs to be repaired. This SERIES of E-Z Lok Sets is available in SAE Number sizes #4 to #12 Coarse and Fine series and 1/4″ to 3/4″ Fractional Coarse and Fine Series. NOTE: only ONE thread size per set.

There are 5 to 10 Helical inserts per set depending on which thread size and series option you select plus a choice of insert lengths.

A size-specific combination Insert Tool that doubles as a Tang Break Tool in included with each set. The appropriate STI Tap is also included; however the proper tap drill must be supplied by the user as noted in the included instructions. Refer to: STI Helical Coil Drill Size Chart

If you don’t own a set of drill bits, visit Best HSS Drill Bit Sets .  The only other tool you will need to install a helical insert is a Tap Wrench.

E-Z Lok Helical Inserts are the equivalent of the more expensive Heli-Coil brand and when installed correctly will hold equally as well. Each insert is made from 304 Stainless Steel that is harder and stronger than the material in which it is installed.  When you have a part or piece of equipment with a damaged female thread, the E-Z Lok Helical Insert Thread Repair Kit is one of the best available.

To select the appropriate SAE Number or Fractional size set, simply CLICK on the Drop-Down chart.

check price of E-Z Lok Helical Threaded Insert Kit (SAE and Metric Kits) at amazon

 

E-Z Lok Helical Threaded Insert Kit, METRIC

Features:

E-Z Lok Helical Threaded Insert Kit, METRIC

  • Application :General purpose repair of FEMALE threads in machined parts, dies, fixtures, farm equipment, home equipment, etc.
  • Thread Size/s:M3 to M20 Coarse and Fine Series
  • No. of Inserts: 5 to 10 per set
  • Tools: STI Tap and Combo Installation/Tang Break-off Tool

Overview

This E-Z Lok Helical Threaded Insert Kit Series covers METRIC thread sizes from M3 to M20 in both Coarse and Fine thread. Each set contains only ONE size set of metric inserts.

If you only have one size thread that needs to be repaired the E-Z Lok Helical Threaded Insert Kit is a smart choice. You only pay for the tools and inserts you need for the repair job at hand.

Each set includes 5 to 10 Helical inserts depending on which thread size and series you select. Different insert LENGTHs are also available.

These sets include a size-specific combination Insert Tool that doubles as a Tang Break Tool once the insert is installed. A size-specific STI tap is also included; however the user must supply the proper size drill which is noted in the instructions of each set.  Also SEE: STI Helical Coil Drill Size Chart (Bottom Chart)

If you don’t already own a set of drills, visit Best HSS Drill Bit Set.   A Tap Wrench is the only other tool you will need to make an installation.

E-Z Lok Helical Stainless Steel Inserts comply with the STI industry standards established by the more familiar Heli-Coil brand. When correctly installed they will have the same holding potential and their installation is identical. The repaired thread will actually be stronger than the original and have the added benefit of being rust and corrosion resistant.

Simply select the Metric thread size from the Drop-Down chart that needs repairing.

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Solid Threaded Inserts – Pros and Cons

Solid Threaded Inserts are an excellent option for repairing un-restorable female threads.  A solid threaded insert is machined from a solid piece of bar stock with both male and female threads.  The female thread matches the damaged thread that needs to be repaired.  Solid threaded inserts are available in both thin and thick wall and in various lengths and are available in carbon steel and stainless steel.

SEE: Best HSS Tap and Die Set

also..

SEE:  Best HSS Drill Bit Set

To install a solid threaded insert, simply drill out the damaged tapped hole with a standard size drill bit which is specified in the Kit Instructions.  Or, you can refer to this Tap Drill Chart after identifying the Diameter and Pitch of the Male thread of the insert.

SEE:  How to Determine Thread Pitch

Once you have drilled out the hole with the damaged thread, tap the hole with the correct sizeturn threaded insert until fluse using screwdriver or bolt and jam nut standard tap and you are ready to install the insert.

Using a HEX Head bolt with the same threads as the female threads of the threaded insert, run a hex nut up to the HEX head.  Thread the bolt into the threaded insert until it stops on the HEX nut.  Then, using a wrench, drive it into the freshly tapped hole until the top of the insert is flush with the top of the part.

Some Solid Threaded Insert Repair Kits contain inserts that have an adhesive or threadlocker type substance already applied.  So, once the insert is installed it can be used in 72 hours or less at full strength.  It there is no adhesive on the inserts use either Locktite RED 271 Threadlocker for a permanent installation.   Or, for a service-removable installation choose Locktite BLUE 242 Threadlocker depending on how permanent you want the repair to be.

Pros

A huge advantage of using a solid threaded insert is there are no specialized tools necessary for installation, assuming you  own the correct size tap and drill bit.

When correctly installed the provide an new threaded hole that is as strong or stronger than the original tapped hole

Cons

Installation of a solid threaded insert requires that the original tapped hole be drilled out to a larger diameter which could be relevant if appearance is an issue.

Solid Threaded Insert Thread Repair Kit RECOMMENDATIONS

E-Z LOK Solid Threaded Inserts for Metal, SAE or Metric Kit (Carbon or Stainless Steel)

Features:

E-Z LOK Threaded Inserts for Metal, SAE or Metric Kit (Carbon or Stainless Steel)

  • Application :General purpose FEMALE thread repair in mild steel, cast iron, aluminum, and other non-ferrous metals
  • Thread Size, SAE:Course and Fine Series – #10 to ½”
  • Thread Size, METRIC:Course and Fine Series – M3 to M16
  • No. of Inserts: 33 per set
  • Tools: NO Tools

Overview

The E-Z LOK Solid Threaded Insert Kit is a viable option for repairing damaged female threads in a variety of situations and metals.

If you are in the machine shop business, industrial maintenance, millwright, or farming operations valuable tooling and equipment can be come inoperable due to a damaged thread.  When time is of the essence and you need  to make a thread repair a solid threaded insert kit will get you back up and running quickly.

Each insert is machined from solid bar stock and is available in both Carbon Steel and Stainless.  Thick and Thin-Wall inserts are also an option.

One of the biggest advantages of using a solid threaded insert is you can use tools you may already have available instead of paying for new specialized tools.  Each Male thread is machined to a standard size in either SAE or Metric so you can use any good quality proper size tap.  SEE:  Best HSS Tap and Die Set

E-Z Lok Drive ToolOnce the hole has been drilled and tapped a simple blade screwdriver the appropriate width is the only tool required to install the insert.  Or, if you prefer, you can purchase a size-specific Insert Drive Tool that will fit the insert slots perfectly.

If you frequently experience damaged threads within a certain size range, the E-Z LOK Solid Threaded Insert Kit is an excellent product to keep on hand.

To choose a E-Z LOK Solid Threaded Insert Kit to fit your requirements simply CLICK on the Drop-Down Chart.

check price of E-Z LOK Solid Threaded Inserts for Metal, SAE or Metric Kit (Carbon or Stainless Steel) at amazon

 

E-Z LOK Solid Threaded Insert Kit (Select Thread Size)

Features:

E-Z LOK Solid Threaded Insert Kit (Select Thread Size)

  • Application :  General repair of FEMALE threads in mild and non-ferrous metals
  • Thread Size, SAE:  Course and Fine Series – #10 to ½”
  • Thread Size, METRIC:  METRIC: Course and Fine Series – M3 to M16
  • No. of Inserts: 10 per set
  • Tools:  Size-specific drill bit and tap, and Drive Tool

Overview

When you only need to repair one thread size this E-Z LOK Solid Threaded Insert Kit is the most cost-effective way to go.

Each kit includes a thread-size specific HSS drill bit, tap, Drive Tool, and (10) solid threaded inserts all the same size. The only other hand tool you will need for installation is a tap wrench.

The Male threads on the insert have a Threadlocker Adhesive pre-applied so once installed it will have full torque-out strength in about 72 hours.

These kits include Carbon Steel Inserts in both Standard and Thin Wall:
Standard Wall Sizes are designated as EZ-329
Thin Wall Sizes are designated as EZ-310

To select a kit with the appropriate thread size CLICK on the Drop-Down Menu at Amazon.com.

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Swaging Tool Thread Repair Kits RECOMMENDATIONS

CTA Tools 8240 Universal 53-Piece Thread Restoration Set

Features:

CTA Tools 8240 Universal 53-Piece Thread Restoration Set

  • Application : Restoration of damaged Male and Female threads in annealed steel and soft metals
  • METRIC Tap & Die Sizes: M6 x 1.00, M8 x 1.50, M10 x 1.00, M10 x 1.25, M10 x 1.50, M11 x 1.50, M12 x 1.25, M12 x 1.50, M12 x 1.75, and M14 x 1.50mm; – NC-USS – 1/4″ – 20, 5/16″ – 18, 3/8″ – 16, 7/16″ – 14, 1/2″ – 13, 9/16″ – 12 tpi; – NF-SAE – 1/4″ – 28, 5/16″ – 24, 3/8″ – 24, 7/16″ – 20, 1/2″ – 20, 9/16″ – 18 tpi
  • Dies ONLY: Metric – M6 x 1.25, M7 x 1.00, M8 x 1.00mm; – NC-USS – 5/8″ – 11 tpiX
  • No. of Taps and Dies:  (23) Taps and (28) Dies
  • Additional Tools:  (2) Rethreading Files
  • Storage Case:  Blow-Molded Plastic

Overview

When a male or female thread becomes damaged by cross-threading or from impact it can in most cases be restored with the proper tool. The CTA Tools 8240 Universal 53-Piece Thread Restoration Set contains all the tools necessary to restore just about any SAE (Fractional) or Metric size internal or external thread you may encounter.

A total of 23 Taps and 28 Dies are machined from high grade tool steel and heat treated to reform damaged threads. These tools are Color-Coded for easy identification. Each tap and die is HEX shaped so they can be turned with an appropriate box or open-ended wrench or an adjustable wrench.

It’s important to note that these taps and dies are NOT designed to cut new threads. They are made to re-structure threads back to their original form.   (For cutting new threads SEE: Best HSS Tap and Die Set)

(2) Rethreading files can be used to clean up lightly damaged male threads where minimal material removal is necessary.

The CTA Tools 8240 Universal 53-Piece Thread Restoration Set is proudly manufactured in the USA to the highest industry standards.  If you are in a business where you frequently encounter damaged threads, the CTA Tools 8240 is the best thread repair kit to have available.

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Lang 972 40 Piece Fractional and Metric Thread Restorer Kit

Features:

Lang 972 40 Piece Fractional and Metric Thread Restorer Kit

  • Application:  Repair and restoration of Male and Female threads
  • (7) SAE Coarse Taps and Dies:  Sizes – 1/4″-20, 5/16″-18, 3/8″-16, 7/16″-14, 1/2″-13, 9/16″-12, 5/8″-11
  • (7) SAE Fine Taps and Dies:  Sizes – 1/4″-28, 5/16″-24, 3/8″-24, 7/16″-20, 1/2″-20, 9/16″-18, 5/8″-18
  • (6) Metric Taps and Dies:  Sizes – M6-1.00, M8-1.25, M10-1.50, M12-1.2
  • Additional Tools:  (1) Metric File, and (1) SAE Rethreading File
  • Storage Case:  Blow-Molded Plastic

Overview

Rethreading tools are color- coded for quick visual identification
Highly tempered for strength and durability and are hex shaped for use with a socket or wrench
Made in the USA

The Lang 972 40 Piece Fractional and Metric Thread Restorer Kit is very practical option for restoring Fractional and Metric male or female threads. The tooling in this kit is very high quality and machined to ANSI Standards from heat-treated tool steel.

Each tap and die is color-coded for quick identification. Both are HEX-shaped and can be driven with an open-ended or box end wrench, socket, or an adjustable wrench.

A thread file is a tool that can be used for restoring damaged male threads on bolts and threaded studsIncluded in the set is (1) METRIC and (1) SAE Rethreading File for dressing those banged up male threads.

Keep in mind this set is NOT for cutting new threads. The taps or dies are designed to reform existing damaged threads without removing metal.

Any mechanical shop, garage, or maintenance department would benefit by having the Lang 972 40 Piece Fractional and Metric Thread Restorer Kit on hand. It’s sensibly priced and proudly made in the USA.

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Thread Chasing Repair Kits RECOMMENDATIONS

NES External Thread Chasing Repair Kit

Features:

NES External Thread Chasing Repair Kit NES1000

  • Application: Repair and restoration of MALE external threads
  • Thread Size/s: NES100 model 5/32″ to 1-1/2″ dia. , NES1300 model 5/32″ to 6″ dia.
  • No. of Inserts: (2) extra
  • Tools: 1 or 2 Thread Chasing Tool

Overview

The NES External Thread Repair Kit is an excellent option for restoring male threads that have become damaged from impact or cross-threading.

This well-designed tool is able to restore right or left-NES External Thread Chasing Repair Kit NES1300handed threads, both SAE and Metric coarse or fine.

Two different kits are available depending on the diameter range that requires repair: The NES1000 model will handle threaded bolts, shafts, and studs from 5/32” dia. to 1-1/2″ dia. This set contains 2 thread chasing tools with blades made from tungsten High Speed Steel hardened to 58 Rockwell ‘C’ scale for long life.

The chasing tools are very easy to use and adjust quickly to any thread pitch. Each blade follows the original thread while restoring the damaged thread as the tool is rotated.

The NES1300 model will work on male threads from 5/23” dia. all the way up to 6” dia. Two chasing tools are included to handle the smaller threads and the large-size threads. The kit comes with extra cutters and a deburring tool. Each piece is secured in a rugged plastic case

You will find the NES External Thread Repair Kit especially useful for auto repair and restoration or for use in a busy machine shop.

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Nes Internal Thread Chasing Repair Kit

Features:

Nes Internal Thread Chasing Repair Kit

  • Application: Repair and restoration of internal threads
  • Thread Size: NES1007 model 5/16” to 13/16″ dia., 3-Pieces ; NES1008 model 5/16″ to 1 1/4″ dia., 4-Pieces; NES1036 model 7/8” to 2-5/8″dia., 4-Piece
  • Extra Cutters:  (2)
  • Tools:  2 to 4 Internal Thread Chasing repair tools, sleeves, and extra cutters

Overview

The Nes Internal Thread Chasing Repair Kit is available in 3 different models that accommodate 3 different thread diameter ranges.

Each set contains all the necessary tools to repair or restore damaged internal threads easily and quickly. The thread chasing tools enable you to repair right or left-handed threads of course or fine series, Metric or Fractional (SAE) with one hand operation.

Quickly adjust from small to large sizes. Tungsten high speed steel (HSS) blades cut and shape any annealed steel while repairing the threads to original specs. Everything item necessary to do a professional thread repair comes with the kit including easy-to-follow instructions.

The Nes Internal Thread Chasing Repair Kit is professional grade and appropriate in any setting where internal threads require repair.

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Thread Restoring Files – Pros and Cons

If you are in a trade or business where you occasionally encounter damaged external threads a thread restoring file set is a must-have tool. Threaded shafts, studs, or bolts can be impossible to use if the threads are damaged.

A simple bolt that normally costs $5 could end up costing you a couple hours of down time to run to the big box store to buy a replacement. Or, shop online and then have to wait for the replacement to show up just because the threads got damaged when it was dropped.

If the threads are just flattened out or the crests bent over they can usually be restored to working condition with the proper size thread restoring file. In some cases where the threads were cross-threaded or even seized thread restoring file can the part serviceable again.

To repair a damaged male thread with a thread file does require some basic skill to do the job correctly. If a certain technique isn’t followed it could damage the threads even greater and beyond repair.

How to Use a Thread Restoring File

To repair a damaged external thread it is helpful if the shaft, stud, or bolt can be clamped in a table vice. The way a thread restoring file works is quite obvious by its appearance with rows of cutting teeth on the file face. Before starting the repair procedure its necessary to determine the Thread Pitch you are about to work on in order to select the correct file.

The reason its so important to identify the thread pitch correctly is because there are fractional and metric threads that are close to being the same. However, if you choose a thread restoration file with the wrong pitch you will end up damaging the threads even more.

SEE:  How to Determine Thread Pitch

Restore the Damaged Threads

Now that you have determined the correct pitch and selected the correct thread restoring file, begin by starting the file in undamaged threads just ahead of the damaged ones. While applying firm downward pressure on the file begin working the file with forward strokes while gradually advancing into the damaged threads with each stroke. Continue this technique until the damaged threads have been cleaned up and the file can track from one side of the damage to the other smoothly.

Once you have filed the threads to where the file tracks smoothly, try threading the nut on the thread or the stud in the threaded hole. The two parts should fit together without binding.

Although thread restoring files are an excellent way to repair damaged external threads there are some pros and cons you should be aware of.

Pros

Thread restoring files are an effective option for restoring damaged male threads. A set of thread restoring files are inexpensive and generally easy to learn to use.

Cons

Thread restoring files are designed to remove metal and if not used correctly can cause more thread damage.

Thread Restoring File Set RECOMMENDATIONS

CTA Tools 8230 SAE and METRIC Thread Restoring File Set (4 Piece)

Features:

CTA Tools 8230 SAE and METRIC Thread Restoring File Set

  • Application :Repair of External threads
  • Thread Pitch Size/s: (File number: 8231) Metric 0. 75, 1. 00, 1. 25, 1. 50, 1. 75, 2. 00, 2. 50, 3. 00-millimeters; (File number: 8233) SAE 11, 12, 13, 14, 16, 18, 20, 24 TPI (threads per-Inch); (File number: 8235) SAE 9, 10, 12, 16, 20, 27, 28, 32 TPI
  • Additional Tools: (3) Poly Handles, and 60 degree Universal Thread Restoring File

Overview

CTA Tools has become one of the top-rated USA tool manufactures. Their products are well-engineered and made from premium materials for professional use.

One of the reasons I recommend the CTA Tools 8230 Thread Restoring File Set is because it includes files for the most common SAE (fractional) and METRIC pitch threads. Each file is made from close grain heat treated tool steel for long lasting service. Heavy duty construction with sharp cutting points enables these tools to cut and restore damaged 60 degree threads with minimal effort.

The file faces are crosscut to full depth to prevent skipping when filing fine pitch threads. Each file in this set is 7/16” square and 8-3/8” long with cutting teeth on both ends and 8 different thread pitches per file.

A feature you will appreciate about this Thread Restoring File Set is it includes (3) Poly handles that will protect your hand while using the files. A 60 degree Universal Thread Restoring File is also included for those minor thread repair jobs.

The CTA Tools 8230 is one of the best thread restoring file sets available and they are reasonably priced.

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General Tools Thread Repair File (SAE or METRIC)

Features:

General Tools Thread Repair File

  • Application :Restore damaged EXTERNAL threads
  • Thread Pitch Sizes: (177-2) SAE Thread Pitches 9, 10, 12, 16, 20, 27, 28 and 32 T.P.I.; (177-1) SAE Thread Pitches 11,12,13,14,16,18,20,24, TPI; (177-8) METRIC Thread Pitches 0.75, 1.0, 1.25, 1.5, 1.75, 2.0, 2.5, 3.0mm
  • Additional Tools:N/A

Overview

General Tools one of the oldest USA tool manufactures with an extensive range of quality products for professional use.

The General Tools Thread Repair File is available in (3) different individual MODELS: 177-1, 177-2, and 177-8. Each model covers (8) different thread pitches in either SAE (Fractional) or METRIC.

These thread restoring files are quality made from tempered tool steel. The cutting faces are crosscut to minimize skipping or jumping while dressing fine threads.

The only issue with this tool is there is no handle to protect you hand while using. A piece of hose or a few wraps of insulating tape solves that minor problem.

If you need an inexpensive solution to damaged external threads this product is an excellent option. Select the MODEL that’s right for your thread repair job.

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How to Determine Thread Pitch

Thread PITCH refers to the distance between thread crests or valleys. SAE or Fractional threads SAE and Metric thread pitchare designated by TPI (threads per inch) which are easy to identify. Simply place a scale caliber on the threads and count the number of threads from one end of the scale to the inch hash mark.

Or, for fine threads you can simply count the threads to the 1/4 inch hash mark and then multiply by 4X.

METRIC threads are designated as the number of millimeters from one thread crest or valley to the next one. They can be a little trickier to identify, especially if you are dealing with a small diameter part with fine threads. If you happen to own a set of Digital Calibers with an Inch/Millimeter setting you can simply measure the distance from one thread crest to the next.  A more accurate method is to measure 4 to 6 threads and then divide the distance by the number of threads to get the correct pitch (Metric threads only).

If you don’t happen to own Metric calibers or scale, measure between the threads and divide the inch measurement by .03937.  This number will be the Metric Pitch of the threads.

A faster way to determine which thread restoring file to use is to check the threads with a Thread Gauge. Their not expensive and come in handy if you do mechanical work.

Another quick and easy to check the pitch of the damaged part is to compare it against another threaded part where the thread pitch is known.