wessexmike · Aug 30, 2017

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!

jamesmartin · Aug 30, 2017

they should be m10

Paul D · Aug 30, 2017

M10, run a tap through the nuts first, with some oil ...

wessexmike · Aug 30, 2017

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?

jamesmartin · Aug 30, 2017

wessexmike said:
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?

some do as they are a blind hole

zeaphod · Aug 30, 2017

Drill and tap, gives you an excuse to buy more tools!

wessexmike · Aug 30, 2017

Thanks for all the replies

. Mm, will get a tap and die set, although will have to be a cheap one...

wessexmike · Sep 1, 2017

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 · Sep 1, 2017

Silly question, did you use the same thread pitch for M10???

Cheers

wessexmike · Sep 2, 2017

neilly said:
Silly question, did you use the same thread pitch for M10???

Cheers

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..

Wimblowdriver · Sep 2, 2017

Run your M10 die over the bolt; bolt might be over plated hence getting stuck.

wessexmike · Sep 2, 2017

Wimblowdriver said:
Run your M10 die over the bolt; bolt might be over plated hence getting stuck.

Thanks, will give that a go.

Al2O3 · Sep 2, 2017

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.

Grem · Sep 2, 2017

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

Oldseadog · Sep 3, 2017

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.

jamesmartin · Sep 3, 2017

unc or unf hasnt been used since when lr went metric

wammers · Sep 3, 2017

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!

AF is not a thread form it is a spanner size. AF = Across flats.

Oldseadog · Sep 3, 2017

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?

wessexmike · Sep 3, 2017

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?

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'.

Grem · Sep 4, 2017

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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Old, nackered 'n broke, but the Landy is fine . :)

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