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A rusty bolt or nut does not necessarily mean it has damaged threads. Sometimes all you need to do to make the fastener thread like a new one is to clean it and chase the threads. In this article, I share the 5 best thread chaser sets and how to use a thread chaser to clean and straighten up rusty, dirty, or slightly damaged threads on bolts or bolt holes.
What does it mean to “chase the threads”?
“Chasing the threads” is the process of cleaning the dirt and corrosion from the threads of a bolt or threaded hole. The aim is to eliminate resistance when reinstalling and removing the bolt and avoid cross-threading. Thread chasing also helps to straighten up slightly damaged threads without messing them up.
A thread chaser kit consists of specially designed bolts and nuts of different diameters and pitches. The bolts are for repairing threaded holes whereas the nuts are for bolts and studs.
What is the difference between tap and die and thread chaser?
A tap and die set is for cutting new threads whereas a thread chaser set is for cleaning up and restoring existing threads. In other words, thread chaser bolts and nuts are not made from hardened material like taps and dies. Therefore, they remove dirt and corrosion from threads without shaving off metal.
On the other hand, taps and dies are aggressive and tend to cut. Therefore, they are only good for retapping or creating new threads on a damaged bolt. If you try to use them for chasing threads, you are likely to create crooked threads that would lead to cross-threading.
How a thread chaser works
As I mentioned, a thread chaser kit consists of special bolts and nuts. The bolts are for use on threaded holes while the nuts are for bolts. These special nuts and bolts are of different diameters and pitches but are built the same. Their threads do not run continuously. There are vertical grooves that run across the radial threads. These grooves act as channels for expelling gunk and rust removed when cleaning and repairing threads.
To use a thread chaser, simply fasten it on a threaded hole or bolt as you would with regular bolts or nuts. Then, turn the chaser slowly down the gunky or slightly damaged threads. Be gentle to avoid causing more damage. As the chaser spins down the threads, it removes dirt and rust and expels it through the vertical channels. It also straightens up crooked threads on the bolt or bolt hole. You can also use the chaser to clean up a gunky nut of your truck.
Why is a thread chaser important and who needs it?
A thread chaser kit is one of the important tool kits you need when rebuilding anything that has bolts and nuts. It helps clean up and restore the threads on your fasteners to make them go back easily. Chasing threads also allow thread sealant to work effectively.
A thread chaser set is for anyone who takes things apart and reassembles them. But most importantly, it is a must-have kit for any auto mechanic for chasing threads on rusty fasteners and bolt holes on cylinder heads, engine blocks, and bodies of vehicles.
If you use it properly, you will not have to replace bolts and nuts every now and then. Also, thread chasing minimizes the chances of cross-threading when installing nuts and bolts because they go back easily and smoothly. Lastly, if you make chasing threads a habit you will hardly encounter corrosively “frozen” fasteners that take a lot of time and effort to remove.
Which are the best thread chaser sets?
Lang 972 40 Piece – Best Overall
- Contains 40 pieces
- Taps and Dies are hex shaped
- Highly tempered for strength and durability
- Both SAE and Metric
The Lang 972 is a USA-made thread restorer kit. It contains 40 pieces including 7 SAE coarse and fine dies, 6 SAE coarse and fine taps, 6 metric dies and taps, an 8-pitch SAE rethread file, and another 8-pitch metric rethread file. The kit comes in a blow-molded plastic carry case with a secure lid. The case keeps everything organized and makes it easy to transport all the dies and taps to and from the worksite.
The taps and dies in the kit are hardened for durability. They cover most passenger vehicles with right-hand threads. You can use them to clean up and rethread rusty lug nuts on vehicle wheels and the filthy bolts on the exhaust manifold. There are also two thread files that you can use to clean 8-pitch lug bolts.
A unique thing about the Lang 972 thread chaser set is that the taps and dies are color coded for easy identification. This helps you differentiate at a glance between coarse, fine, metric, and SAE chasers and dies. To top it off, there is a one-year warranty on this kit!
Overall, the Lang 40 pieces thread restorer kit is the best for both professional mechanics and weekend warriors who work on passenger vehicles and motorcycles. It is the exact same kit as the Snap-On but you don’t pay Snap On-prices for it!
Kastar 971 SAE and Metric Thread Restorer Kit – Best for technicians and Weekend Warriors
- Contains 48 pieces
- Includes both metric and SAE taps and dies
- Comes with a blow molded carry case
- Chasers and dies are hex shaped
Kastar 971 thread restoration kit looks very similar to the Lang 972 kit but it is made in China. However its quality is on par with store brands like Stanley and Craftsman.
The kit has a variety of taps and dies for working on different sizes of bolts and nuts. In fact, it has more metric taps and dies than the Lang 972 kit.
All the dies and taps in this kit have a hex shape to allow you to use a wrench or socket on them. This kit takes away the worry and effort out of reassembly projects.
CTA Tools 8240 53-Piece Rethreading set
- Has 53 pieces
- Includes both metric and SAE parts
- Hex-shaped bolt and hole chasers
The CTA Tools 53 piece thread chaser set is another rethreading kit from the U.S.A. It has all the bolt and hole chasers you would need for most of your restoration projects. Not only can you use the thread chasers to get rid of foreign materials from threads but also line up bent threads on aluminum bolts. Unfortunately, you cannot use the kit to straighten up bent threads on steel bolts.
In fact, one of the downsides of this thread chaser set is that the taps and dies are made of too soft metal which tends to wear out pretty easily when used on hardened fasteners and threaded holes. Also, the chasers are poorly labeled and the plastic carry case does not feel like the best quality. But you can make your kit last longer by applying thread oil on your workpiece every time you want to rethread or clean up crud from a fastener.
The CTA 53 piece thread restorer kit is a must-have for auto mechanics for chasing and repairing threads on engine bolts and nuts. It has all the sizes of chasers to cover all the bolts and nuts on a typical engine block and body of a passenger vehicle. It is the same exact kit as the Craftsman 48 piece master set with the advantage of not paying the tool truck price for it.
Normal Coarse -USS
Metric : 0.80, 1.00, 1.25, 1.50, 1.75, 2.00, 2.50, 3.00
SAE : 11, 12, 13, 14, 16, 18, 20, 24 tpi
Normal Fine – SAE
Key: T&D = Tap and Die, D=Die only
FJC 2755 Metric Thread Chaser kit – Best for AC repairs
- Metric thread chasers only
- Hex shaped
- 8 pieces
If you are an AC repairman dealing with heating and cooling systems, this compact FJC thread chaser kit should be in your toolbox. It contains different sizes of chasers that you would need to clean and fix internal and external threads on pipes, fasteners, and equipment. The kit is manufactured in Taiwan.
You can use the FJC kit to repair damaged threads on AC equipment including condensers, evaporators, and accumulators. It is a handy kit to have when you are servicing the heating and cooling systems on trucks and RVs.
The only limitations of the kit are that all the chasers are metric and you should not use them on stainless steel material. However, I did use one of the taps to fix galled threads on my truck’s steel ac line that goes to the evaporator and it did a perfect job. But I don’t recommend going against what the manufacturer recommends.
That being said, the FJC thread chaser set is a must-have for anyone working on all types of ACs. There is also an SAE version of it.
How to chase internal and external threads with thread chasers
Frequently Asked Questions (FAQs)
To avoid breaking taps when cleaning and rethreading lug holes, apply cutting oil. The oil helps to freshen up old holes and makes it easy to get rid of rust and debris from the threads.
Thread chasers remove any dirt and gunk from threads. This includes loctite and other thread-locking fluids.
A thread restoration kit can restore a lot of threads but cannot restore threads bent or damaged from overtightening.