Seat belt anchorages on the roll cage

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Doug G
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Seat belt anchorages on the roll cage

Post by Doug G »

The roll cage anchorages have a hole ine the plate and a nut welded on behind it so you can screw the seatbelt bolts straight in.

But the bolts supplied with the seatbelts are slightly too big a diameter and have too fine a thread.

A 3/8" bolt is just too small a diameter.

Any suggestions on how to determine the thread size without continunial trial and error?
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Nigel(no top)Sykes
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Post by Nigel(no top)Sykes »

Before I answer - Do you have scrapyards over there ?
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Doug G
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Post by Doug G »

Nigel(no top)Sykes wrote:Before I answer - Do you have scrapyards over there ?
Yes . . . but they are really scrap yards ie fully canabalised.

NB There are no mini's etc there and the cars (mostly japanese origin) that are there will not have the same threads on the anchor bolts.
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Tim
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Re: Seat belt anchorages on the roll cage

Post by Tim »

Doug G wrote:The roll cage anchorages have a hole ine the plate and a nut welded on behind it so you can screw the seatbelt bolts straight in.

But the bolts supplied with the seatbelts are slightly too big a diameter and have too fine a thread.

A 3/8" bolt is just too small a diameter.

Any suggestions on how to determine the thread size without continunial trial and error?
Doug, to measure a thread you need a thread gauge, a pair of calipers and a thread reference chart (This site is brilliant : http://www.gewinde-normen.de/en/unified ... hread.html).
Image

You measure the diametr of the hole (this will be the minor diameter) and the use the gauge to measure TPI, then go through the charts until you get a match.

Didn't you think that you had a factory roll bar? Seatbelt bolts are meant to be 7/16 - 20 UNF so thats where I'd start looking (that means a major diameter of 7/16" and 20 threads per inch, unified fine thread form).

Tim
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Doug G
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Re: Seat belt anchorages on the roll cage

Post by Doug G »

[quote="TimDoug, to measure a thread you need a thread gauge, a pair of calipers and a thread reference chart
You measure the diametr of the hole (this will be the minor diameter) and the use the gauge to measure TPI, then go through the charts until you get a match.

Didn't you think that you had a factory roll bar? Seatbelt bolts are meant to be 7/16 - 20 UNF so thats where I'd start looking (that means a major diameter of 7/16" and 20 threads per inch, unified fine thread form).

Tim[/quote]

I have now worked out that it is 7/16. :D
The threads have a bit of paint on them, I am in the process scraping/cleaning that off.
Now would 20 threads per inch be regular or fine ? :?:
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Tim
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Post by Tim »

7/16 - 20 UNF is fine, 7/16 UNC is only 14 TPI according to that website.

Tim
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Doug G
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Post by Doug G »

Having cleaned the threads of paint etc.
I have now discovered that the thread is metric and have now fitted metric bolts and all is well and good in the rear seats.

However it appears that the floor anchor points for the front seats have to be drilled. :(

Oh well tomorrow is another day. 8)
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Tim
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Post by Tim »

Doug, unless the floor has been replaced the floor anchor points should already be there. They are in the hump in the centre, behind the crossbrace that the seats mount on.

Tim
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Doug G
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Post by Doug G »

Tim wrote:Doug, unless the floor has been replaced the floor anchor points should already be there. They are in the hump in the centre, behind the crossbrace that the seats mount on.

Tim
Thanks, Will have a look in daylight.
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