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Helicoil Type Insert Technical Data Sheets

Data for helicoil type thread inserts and tapped hole sizes in Metric (ISO), UNC, UNF, BSW, BSF, BSPP or BSPF, NPT and BA is listed in the following pages. To access the data on each threadform, click for detailed index to the various different threadforms.

Helicoil Type Inserts.  Are Different Brand Names Interchangeable With Each Other?

Basically the answer is YES, but to answer this better, here's a bit of history. The word "Helicoil" is actually a brand name but has become generic for a certain type of thread insert like the word "Band-Aid" which is also often used to refer to any kind of sticking plaster bandage. The true generic names for helicoil type inserts are "wire thread insert" abbreviated "WTI" or "screw thread insert" abbreviated "STI".  Before World War 2 there were various forms of thread insert, but as far as we are aware, the first coil wound Screw Thread Insert "STI"  was  made around 1940 from pear shaped wire as in the diagram below left. The rounded threadform was known as "Aerothread". Then about 1950 Cross Manufacturing in the UK started making diamond shaped wire thread inserts with a standard "V" threadform as in the diagram below right.










Very soon afterwards an STI was made in competition with Cross's thread inserts under the brand name of "Helicoil". The competitor's STI was very well marketed and the "helicoil" name has stuck ever since as the generally know "generic" name for screw thread inserts. STI's soon became far more common and at first were not generally thought of as thread repair tools but were mainly used as original equipment threads.  In fact, many threads that were critical in leading edge technology such as in aircraft, nuclear installations and turbines were fitted with STI's from new.  This was because STI's spread loads far more evenly in both  parent materials and the fasteners.  This in turn greatly increases the "fatigue life" of a threaded assembly.


So much for initial "history".  Because STI's had become quite common it is obvious that just like ordinary nuts and bolts, this new type of fastener needed to be standardised.  And that's exactly what happened, so from somewhere about the late 1950's or early 1960's STI's in the  main threadforms that are world standards have generally been interchangeable between the main manufacturers of this type of insert. Hence our answer is, yes, almost all STI's made in the common threadforms are interchangeable no matter who makes them.

DIAMOND shaped wire thread inserts as is now the common standard

AEROTHREAD - The first form of wire STI

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