Taptite Trilobular Thread-Rolling Screw Thread Compatibility

[revilla]

Various places on the K VVC engine use Taptite thread-rolling screws to make their own threads during insertion (for ease of manufacture), typically when screwing onto aluminium castings (e.g. alternator tensioner adjuster, IACV and MAP sensor to plenum screws).

The original LYP101690 screws (used for the MAP sensor) are no longer available anywhere. I want to replace quite a few of these.

Similar pan head taptite torx screws are available from AccuScrews but only in multiples of 200 which seems a bit silly.

But I was reading this on a supplier website:

I read this as saying that Taptite screws roll a thread in the aluminium which is identical to or compatible with a standard metric thread. So once you've used a Taptite screw once, you can then replace it with a standard metric screw and it will go straight into the thread produced by the Taptite screw.

Can anyone confirm this? If this is true I can just replace them with standard pan head metric torx screws available anywhere.

[revilla]

I suppose one difference reading that is that the Taptite screw runs in the thread with no clearance and is probably less prone to working loose so a spot of threadlock might be advisable with a replacement metric screw with a working tolerance.

[Golf Juliet Tango]

I used Taptite screws for the assembly of theatrical lanterns back in the 1980s. They were inserted into purpose-sized cylindrical slots in aluminium extrusion and could certainly be replaced by non-Taptite machine screws. Arguably this is preferable as a standard screw will follow the existing thread; I think there is a danger (small but possible) that a Taptite would form a new thread.

P.S. I don't know (because I didn't ask) if we were working with a trilobular Taptite. They were only known as Taptite and certainly did the job.

[revilla]

Thank you, and makes sense. I'll check out exactly what metric thread they are and order some standard screws.

[revilla]

They seem to be M4 x 0.7 x 20mm with Torx TX20 pan heads. Easy enough to get hold of in small numbers. Ordered some.

[revilla]

Got the screws. Yes they fit the threads fine. They screw in with fingers until the last 1mm or so. I think because I ordered screws that were exactly the same length as the original Taptite screws, the last 1mm of thread probably isn't fully formed (it will only have seen the trilobular (sort of "rounded triangular") cutting bit of the the Taptite screw. This wasn't a problem, the screws nipped up with a Torx bit easily and this will provide some self-locking (a bit like an Aerotight nut). I was having second thoughts about using thread-lock on an M4 anyway, I didn't want to end up shearing it when removing. Sorted.

[Golf Juliet Tango]

Good. Taptites do have that slight taper at the front end; you probably made a good call to get the same length, it is certainly how we used them.