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Oversize Thread Repair Kits - Top 3 Questions

Oversize Thread Repair Kits - Top 3 Questions

DennisB WiseAutoTools.com © Summary: How to determine the right oversize thread repair when a previous parts store type insert or Helicoil has failed making the hole bigger. This question answered and more. We help customers find the best kit when a Helicoil or some other similar type thread repair has failed. 

There's a lot of information online however it's hard to know who's opinion to trust. A recent customer said "Everyone's got an opinion on thread repair kits online". That's true. I worked as a Master Auto Tech for many years and have been selling thread repair kits since 2005. I used my first Time Sert thread repair kit in the early 2000's. I used Helicoil prior to that. Between my personal experience working on vehicles and my knowledge gained from helping our customers and getting great feedback; I am uniquely qualified to help in choosing the best oversize thread repair kits or first time kits for that matter.

Question - Can I use the same size bolt after a bigger thread repair has been used?

Answer - We get this question a lot. Some people think that using an oversize thread repair kit means you have to step up the size and use a bigger bolt. Not true with the Time Sert oversize thread repair kit which they call Big Sert. The Big Sert thread insert is a thicker insert which accepts the same size bolt. Big Sert Kits are used for  repairing threads which have been previously worked on using Helicoil, Perma-Coil, Uni-Coil, Recoil or any other similar coil or spring style insert that has failed. There has also been an onslaught recently of Chinese copies of these type kits, on the market that the Big Sert can also remedy. The kit sizes are the internal size of the insert, not the outside. So for example an M11x1.5 bolt would require an M11x1.5 Big Sert Kit.

Question - How do I know if the Big Sert will be big enough to fix my threads?

Answer - Typically if a coil type insert or first time type solid insert has failed the Big Sert is usually big enough to repair the hole properly. See the drill bit size chart below in case there's any doubt. This is a partial list. It's important to know that drill bits are in each kit and the other tooling is needed to do a proper installation, the list below is mainly for size reference.

BIG-SERT INCH KITS
DRILLC.BORETAP
SIZE  DRILL  SIZE  MIN. DIA  MIN. DEPTH MAJOR  DIA.
10-32 G .261 .340 .050 .300
1/4-20 7.8mm .307 .355 .050 .359
1/4-28 L .290 .330 .055 .330
5/16-18 13/32 .406 .474 .085 .474
5/16-24 13/32 .406 .474 .085 .474
3/8-16 31/64 .484 .552 .085 .552
3/8-24 31/64 .484 .552 .085 .552
7/16-14 37/64 .578 .634 .085 .634
7/16-20 37/64 .578 .634 .085 .634
1/2-13 41/64 .640 .701 .085 .701
1/2-20 41/64 .640 .701 .085 .701 
BIG-SERT METRIC KITS
DRILLC.BORETAP
SIZE  DRILL   SIZE   MIN. DIA  MIN. DEPTH MAJOR  DIA.
M5x0.8 D .246 .290 .050 .290
M6x1.0 L .290 .330 .055 .330
M7x1.0 U .368 .440 .075 .422
M8x1.0 13/32 .406 .474 .085 .474
M8x1.25 13/32 .406 .474 .085 .474
M10x1.0 31/64 .484 .552 .085 .552
M10x1.25 31/64 .484 .552 .085 .552
M10x1.5 31/64 .484 .552 .085 .552
M11x1.25 37/64 .578 .634 .085 .634
M12x1.5 37/64 .578 .634 .085 .634
M12x1.75 37/64 .578 .634 .085 .634 


Question - What makes the Big Sert better other brands?

Answer - Big Serts are a solid one piece insert that are able to be locked in place several ways. Since they are solid, thread locker on the outside threads is very effective. Also, Big Serts have a tiny pin embedded on the outside of the insert that acts as a locking pin after the final installation step is carried out. Which brings us to the final step. The install driver is used to finish the bottom threads; expands the bottom portion of the insert locking it into place. You see the bottom few internal threads are not completed on purpose. The install driver is like a thread tap which finishes the bottom threads. Not cutting them, but cold rolling and causing an expansion on the bottom of the insert which locks it. The embedded locking pin is pushed outwards causing a genius locking method that no other thread repair system implements.

We've been selling specialty tools and thread repair kits since 2005. Call for assistance in finding the best spark plug thread repair, head bolt thread repair, drain plug or other general thread repair kit for your application at 800-734-8665 x251 or provide your details by using our Contact Form.

30th May 2022 DennisB

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