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  View original topic: What thread are seatbelt bolts?
vanis13 Thu Jul 02, 2015 7:28 pm

What thread are seatbelt bolts?

Want to mount something in position F1 and F2 below. The seat belt bolts fit. Those bolts are not 10mm of 12mm. 7/16 x 20 seem to be the closest but still feel a little sloppy.

Anyone know for sure?

BTW if yo uwant to play - name that hole - http://www.thesamba.com/vw/forum/viewtopic.php?t=631339&highlight=


Merian Thu Jul 02, 2015 7:37 pm

7/16-20 UNF pitch thread for all cars on planet Earth

some people have shoehorned 11 mm taps into rusty receptacles - no idea how much that compromised safety

rmcd Thu Jul 02, 2015 7:42 pm

I can second that size. I just re tapped mine.

vanis13 Thu Jul 02, 2015 7:49 pm

nice!

thanks guys

vanagonjr Fri Jul 03, 2015 9:29 am

Merian wrote: 7/16-20 UNF pitch thread for all cars on planet Earth
For many cars on earth, not all. Plenty of cars use M12-1.75, virtually all modern Fords for instance. Lots of GM products use that size as well, although they have switched back to 7/16-20.
Merian wrote:
some people have shoehorned 11 mm taps into rusty receptacles - no idea how much that compromised safety
M11-1.25 is virtually identical to 7/16-20 size, from investigations we have done, I suspect that some Asian cars used M11-1.25, but it really does not matter.

If anyone needs to chase the threads, let me know and I can supply a 7/16-20 thread rolling bolt - these are used on the vast majority of seat belt bolts for US cars and plenty of European ones as well. Don't chase threads with a thread-cutting tap, if avoidable.

Merian Fri Jul 03, 2015 10:15 am

Metric threads are allowed only if "equivalent" - IIRC, the US 'forced' all other countries ot follow this spec. due to market size, etc. I'm sure there is an ISO on it.

US Dept ofTransportation : Federal Motor Carrier Safety Administration
section 571.209

(S4.1)(f) Attachment hardware. A seat belt assembly shall include all hardware necessary for installation in a motor vehicle in accordance with Society of Automotive Engineers Recommended Practice J800c, “Motor Vehicle Seat Belt Installation,” November 1973. However, seat belt assemblies designed for installation in motor vehicles equipped with seat belt assembly anchorages that do not require anchorage nuts, plates, or washers, need not have such hardware, but shall have 7/16-20 UNF-2A or 1/2-13UNC-2A attachment bolts or equivalent metric hardware. The hardware shall be designed to prevent attachment bolts and other parts from becoming disengaged from the vehicle while in service. Reinforcing plates or washers furnished for universal floor, installations shall be of steel, free from burrs and sharp edges on the peripheral edges adjacent to the vehicle, at least 1.5 mm in thickness and at least 2580 mm 2 in projected area. The distance between any edge of the plate and the edge of the bolt hole shall be at least 15 mm. Any corner shall be rounded to a radius of not less than 6 mm or cut so that no corner angle is less than 135° and no side is less than 6 mm in length.

http://cfr.regstoday.com/49cfr571.aspx#49_CFR_571p209
and
https://law.resource.org/pub/us/cfr/ibr/005/sae.j800c.1973.pdf


I'd be interested to hear of any deviations.



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