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Lewis Buckle

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Hi, I'm fitting a tow hitch assembly, but the 4 off supplied DB bolts to the bottom of the cross member are too big. The two on the flip up step are slightly smaller than the metric versions supplied, and slightly more tpi. I suspect they're UNC?
Unfortunately I don't have a gauge, so if any one could help please...
Lewis
 
Hi, thanks for responding
It's not the hefty ones: there's a right angle steel support behind the tow plate that runs under the cross member. Two M16 bolts through the DB plate, and there's some smaller ones that bolt up into the cross member. It's these I need a size for. They supplied what looked to be M10, but these don't fit the threads in the cross members; too big. The ones in the step are correct, which are smaller and more tpi. Couple with this being an older 90, I'm wondering if these could be UNC not metric?
 
With the 90's replacing the Series III in the 1980's it is unlikely that they will be imperial threads and not metric.
However, I would be inclined to go along to a local nut and bolt sockist and ask them to measure it up, bearing in mind that there might be an outside chance that they are metric fine threads.
The angle steel bits, do they go out and bolt onto the sides of the chassis and onto the back of the drop plate?
A pic would be helpful.
 
No, there's a bent plate bolted to two rear facing rt angled struts that bolt to the chassis. Above that bent plate there's another, transverse rt angle about 12" long as described above.
 
Seems you select the write - not write then select...
 

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Finally, and if the memory of an old man serves correctly, the three bolts are M10 x 25, and I would be inclined to use 8.8 grade as minimum.
 
Ahh. Sadly not in this case, but as you're in accord with Dixon Bate, I'd anticipate they are supposed to be M10, as you say by 25mm. Good memory!
However, whether due to an after market replacement cross member or an older replacement made to fit; I now know the ones I have fitted are 3/8" UNC. Hence the supplied M10 are just a smidgen too big and won't even start in the holes. I've found one 3/8" UNC, had two (Grade 5), need five (fitting of a folding step). I have 5 nice bright shiny SS ones on the way, along with some Duralac green for galvanic corrosion protection.
Meantime, with the added one found, there are enough to secure the towbar. Good job too, I'm picking up a sheet metal rolling machine and an anvil & stand tomorrow...
Thanks for your help Oldseadog. You are a Gent.
 
Pleased to hear that you've got sorted!
I am surprised at them being UNC though, especiallly as you have a 90.
However we all learn something new every day :)
Good luck with your machine move.
 
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