Thread size of safety-belt fitting bolts?

Are you sure that the thread is not filled with a tubular plastic plug? I have never seen a blank nut fitted, the nuts are tapped before being attached. The thread size is a peculiar old english size, I can check exactly what tomorrow, but I am fairly convinced the thread will already be there ! As to the torx size it is probably a 50.

Had one on the connector of my (£200) graphics card a couple of weeks ago - bastards - took a while to register

just thought you might like to know ... ATI - Ford of the computer world

More than likely they are all unthreaded from new, and they use thread cutting bolts when fitting the seats in the factory.

Despite metrification seat belts anchors have remained imperial

I don't know about Ford specifically, but I think everyone has been metric for quite a few years. The seatbelt reels on my Volvo V70 are held in with M14 bolts.

In the good old days, the standard size was 7/16" UNF which is what you're probably thinking of. It seems very unlikely that anyone is still using UNF threads on motor vehicles.

Er, it was, I prised it out. It was only when I felt the inside of the bore with a small screwdriver that I convinced myself that it was smooth and it wasn't just my eyesight missing a thread!

Never knew such things existed. Just had a quick Google around & found lots of info. Thanks for that, interesting.

For fixing into composites or interior trim then yes you might use thread forming fasteners, but in no way would that be acceptable for metal to metal fixings as it would compromise corrosion resistance.

As for using something similar for a seat belt mount. It's totally off limits, the possibility of process failure on a production line and the subsequent rework costs are just too high. It's not a case of fitting a nut and washer on the underside, or rewelding a new nut plate - it's a scrapped bodyshell, removal from the production line, plus all the work carried and components fitted.

To the OP, it's possible your threads are there, they might be filled in with excess primer/topcoat.

Don't think so, I ran a screwdriver over the bore and there wasn't a hint of a thread there. And the paint didn't look as if it had been trowelled on (would have been awaste of £0.00001 of paint and Ford would never have allowed that to happen :-/)

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember John Stumbles saying something like:

Costing is the answer. I bet it costs an extra 2cents per threaded nut over an unthreaded and Ford know exactly what seats are being fitted before a shell hits the line. In the vast majority of vans leaving the factory with a single passenger seat, a wider seat will never be fitted, so it's a waste of money using threaded nuts.

I would not be surprised if the following happens... For retro-fitting seats, the dealer will have a task sheet for the fitter to follow, including running a tap down the blank insert.

Why do you think the ar$e still rots out of transits? Was under a 56 plate last week, and it was already showing signs of rust.

It will probably be a self-tapping bolt. Best option is to go to the dealer and order the proper bolt, and then you'll know for sure what thread it is, and if it cuts it's own thread.

Correct. You guessed it right first time.

Just bought a double passenger seat for my 2000

Another correct guess.

This one is right too. The seat belt supplier supplies the belt assembly complete with Thread Rolling Bolts (TRBs) which are inserted with a driver. They form the thread on the way in. (All seat belts are subject to ES testing once the bolts are inserted. Removal of them may cause deformation to the nut insert)

Tip - when you insert the bolt, make sure you do it right first time! (Yes, I've worked for a seatbelt supplier and a co next to both European Transit plants...)

OTOH one from a dealer might actually be a 'replacement after it's been disturbed' bolt, hence *not* designed to self cut, but instead to maybe be a tighter fit in the already-cut threads..

Well that's the way its done, whether or not you think its not acceptable, or off limits!

That isn't true. Taptite thread rolling screws are used all over BT exchanges because they don't easily cause corrosion.

Don't confuse them with the difference between high tensile thread forming bolts & self tapping pan head screws, it'll get in the way of the rant. (Obviously it's not actually going to stop somebody tapping them out & using a 4.6 bolt to attach the seat because Ford want £12 for a set of the proper bolts)

I've just looked at the M6-ish bolts I took out and they do indeed look like tri-lobe thread-cutting types. That'll do for the smaller blank hole: I'll grease up one of the now-spare bolts and drive that in.

I'm not going to even try that on the seat-belt-sized one though: I've ordered the tap set that Mike pointed out for sale on ebay and I'll tap it out properly. Now if I can only find where I put my stash of seat-belt bits and pieces (including bolts) I tidied up a while back ...

Why would you want to tap it, that'll give you a weaker thread than rolling it?

Why would a cut thread with a normal bolt be weaker than one made with a thread-forming bolt?

But the reason I want to tap it is I don't have any thread-forming bolts of that size whereas I do have normal bolts (if I can find them) and a tap set (when it arrives).