 | Home > Maintenance & Modifications > Tow bracket arms - tapered thread?? |
 
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| ppad Member Since: 16 Nov 2012 Location: now, UK S Coast Posts: 218   
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5 yrs ago the tow bracket was removed for a NATO hitch, needs to go back on. So, on the corner of the chassis is a threaded hole c/w captive nut on the back. But what came out all those years looks tapered and a new std bolt, when it reaches the nut - nope.
The pics are clear enough .. - where and what and how do I get new bolts for the tow bracket arms? Thanks experts.  Click image to enlarge Click image to enlarge Click image to enlarge Sold the much modified 110 2.8, in Oz Brought the 90 home from Switzerland ... |
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25th Jun 2020 4:08pm |
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| jst Member Since: 14 Jan 2008 Location: Taunton Posts: 7699 
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They are not tapered. As above that thread is just damaged. I expect the arm was under tension putting an angle on the bolt when it came out. Recut the thread in that captive nut. If you don't have a tap you can grind a taper onto a bolt and cut two longitudinal slots across the thread and tap with that. Just check thread pitch first. Are they not fine thread those nuts? I can't recall.
Other option is drill damaged thread completely out and use longer bolt with suitable washer and nut behind drilled out bolt. Cheers James 110 XS Utility 130 Puma Station wagon/camper (in the making) 90 Puma Hardtop |
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25th Jun 2020 5:13pm |
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| Pacha Member Since: 23 Feb 2020 Location: North Yorkshire Posts: 772 
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From memory they are M12 (std pitch) 40mm long (measure what came out) - high tensile. Rgds.
Chris |
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25th Jun 2020 6:32pm |
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| ppad Member Since: 16 Nov 2012 Location: now, UK S Coast Posts: 218
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Thanks for all the info.
The 'other option' I was tempted to do yesterday, just steadily clean it out and have something permanently different - so long as captive nut is securely welded, all OK. In the interests of learning, never too old, do you know of tap die sets at reasonable price? Screwfix is 20 quid to 100 ... - and that ain't worth it. Sold the much modified 110 2.8, in Oz Brought the 90 home from Switzerland ... |
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26th Jun 2020 12:01pm |
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| Philm Member Since: 19 Jun 2020 Location: Manchester Posts: 149
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Any decent garage or workshop will have a set, see if you can lend them, do it in their car park.
If you were closer, I would have lent you a set. |
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26th Jun 2020 12:19pm |
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| jst Member Since: 14 Jan 2008 Location: Taunton Posts: 7699
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^^^^ make one Cheers
James 110 XS Utility 130 Puma Station wagon/camper (in the making) 90 Puma Hardtop |
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26th Jun 2020 1:04pm |
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| Martin Site Admin Member Since: 02 Apr 2007 Location: Hook Norton Posts: 6485 
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Just to throw a curve ball at this.
It's the correct bolt, and it is tapered. On the genuine LR tow kit for a 90 Td5 or Puma, these M12 bolts are a form of self tapper into the corner of the fuel tank cradle. RYP501120
On aftermarket kits they use standard M12 bolts/screws and nyloc nuts inside, instructing you to drill out the hole in the corner of the cradle to 13mm. Link to aftermarket instructions: https://www.defender2.net/gallery/albums/userpics/10002/R28.pdf With the 110 genuine kit, you remove the lash down eyes, then refit through the arm. But the 90 is different. See step 8 of the fitting instructions, it is labelled as a "self tap" screw. Click image to enlarge PDF: https://www.defender2.net/gallery/albums/u...r%2090.pdf Either reuse (not really  ), replace the bolt (pn RYP501120)  or drill out the cut thread in the cradle and use a standard M12 replacement with a nyloc on the inside as per aftermarket fit. 1988 90 Td5 NAS soft top
2015 D90 XS SW |
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26th Jun 2020 1:32pm |
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| htb2 Member Since: 02 Nov 2018 Location: aberdeenshire Posts: 510 
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We stand corrected, will bow to the modern practice but will personally stick to old school techniques
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26th Jun 2020 4:11pm |
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| blackwolf Member Since: 03 Nov 2009 Location: South West England Posts: 16893 
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I think you'll find that the original screws (they're not bolts because they don't have an unthreaded portion) are a thread-forming type, probably Taptite®, although there are other makes. These are not strictly tapered, but have a special trilobular shape and threadform which rolls, rather than cuts, a thread in the hole. A rolled thread is stronger than a cut thread for a variety of reasons. Once assembled they are rather more "snug" and vibration-resistant than a conventional fastener.
They can be reused with care if they're in good condition (which the OP's are not) but you must be careful not to cross-thread them and roll a second destructive thread in the hole. Quite often it is easier to replace them once removed with a conventional set screw of a non-thread-forming type. Dont use them with conventional nuts, either. In this particular case I'd drill out the hole and use a nyloc on the back, assuming that there is room. |
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26th Jun 2020 4:56pm |
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| jst Member Since: 14 Jan 2008 Location: Taunton Posts: 7699
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I stand corrected Cheers
James 110 XS Utility 130 Puma Station wagon/camper (in the making) 90 Puma Hardtop |
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27th Jun 2020 12:57pm |
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| ARC99 Member Since: 19 Feb 2013 Location: North Yorkshire Posts: 1831 
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Come on Blackwolf you know that non engineers call everything a bolt that has a hex head and stop using technical terms they can't understand "trilobular shape". I had to get my reference books out.  Don't make old people mad.
We don't like being old in the first place, so it doesn't take much to  us off.
Richard |
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28th Jun 2020 10:42am |
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