Bolt size Defender rear step to crossmember

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wessexmike

Member
Posts
10
Location
Stroud
Hi folks
Recently got a 1994 Defender 110 300tdi. The seller said that the rear crossmember had been replaced at some point. He had not put the towbar back on, so I am planning to, plus add a rear folding step. There are 3 nuts welded underneath the crossmember that are used to attach the towbar and rear step. I tried using an M10 bolt, and found it became really tight after a few threads. So much so that on trying to remove one, it sheared :(
So, I don't know what age the crossmember is, but either the thread is full of waxoyl or something else, or the nuts are not metric, which is most likely.
Can anyone advise on what bolts I need? UNC/UNF/AF/Whitworth?
Thanks in advance! :)
 
M10, run a tap through the nuts first, with some oil ...
 
Thanks. Should be, but these are only going in 5-10mm before getting so tight they will shear (and one has...). Any other sized nuts used ever?
 
Well I used an M10 tap today which spun through quite feely. M10 bolts are still getting really tight after about 5mm in. They can't be metric nuts on this crossmember, but close to M10. Any thoughts on which bolts to try? Thanks in advance!
 
neilly said:
Silly question, did you use the same thread pitch for M10???

Cheers
Click to expand...
I assumed an M10 tap would have same thread pitch as M10 bolt. It went through the nut with no resistance, which is why it seems odd that any M10 bolts I try are not working. Halfords and Screwfix don't stock anything but metric, so can't buy a couple of different types to try unless I buy online and guess the size. On a happier note the gearbox and transfer box drain and fill plugs all behaved themselves..
 
IIRC a 'standard' M10 bolt has a 1.5mm pitch. I think you can also get M10 with 1.25mm pitch. Your tap will almost certainly have it stamped on like M10x1.5
You might have got your hands on some M10x1.25 bolts
What does your tap have stamped on it? You could lie one of your bolts along the top of the tap and see if the helix of the bolt drops evenly in to the tap, that way you can check if they have the same pitch.
 
Should someone be fitting a towbar if they are not compentant enough to wind correct threads into holes without resulting in them going so tight they shear off

This a safety critcical item, somebody messing with such areas of a motor vehicle should be completely confident before they attempt to achieve anything
 
Are you sure that it should be M10x1.5 and not 3/8UNC which has a thread pitch of 1.587mm?
UNC are still available in many car accessory shops ... or even off fleabay.
 
wessexmike said:
Hi folks
Recently got a 1994 Defender 110 300tdi. The seller said that the rear crossmember had been replaced at some point. He had not put the towbar back on, so I am planning to, plus add a rear folding step. There are 3 nuts welded underneath the crossmember that are used to attach the towbar and rear step. I tried using an M10 bolt, and found it became really tight after a few threads. So much so that on trying to remove one, it sheared :(
So, I don't know what age the crossmember is, but either the thread is full of waxoyl or something else, or the nuts are not metric, which is most likely.
Can anyone advise on what bolts I need? UNC/UNF/AF/Whitworth?
Thanks in advance! :)
Click to expand...

AF is not a thread form it is a spanner size. AF = Across flats.
 
Shirley the clue is that there are '3 nuts welded underneath the crossmember'!

As these have apparently been added at some late stage, might it just be possible that they may be UNC?

With them providing blind fastenings where the screw is trying to crossthread after a few turns also suggests the possibility UNC, because there is not a great deal of difference in pitch between M10 and 3/8UNC.

Is it possible to accurately measure the thiskness of the nuts, and the measurement across the flats if you can get to them?
 
Oldseadog said:
Shirley the clue is that there are '3 nuts welded underneath the crossmember'!

As these have apparently been added at some late stage, might it just be possible that they may be UNC?

With them providing blind fastenings where the screw is trying to crossthread after a few turns also suggests the possibility UNC, because there is not a great deal of difference in pitch between M10 and 3/8UNC.

Is it possible to accurately measure the thiskness of the nuts, and the measurement across the flats if you can get to them?
Click to expand...
Thanks. Have ordered a few 3/8" UNC bolts. It will at least rule these out if they don't fit...

Thanks Wammers, I'd never realised the AF meant 'across flats'.
 
If your tap winds in but not the bolts, then clearly you are not noticing something quite obvious, please let somebody else do this job for you
 
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