A 1970's raleigh-type GB stem uses M8 x 1.00 (fine pitch) metric nuts and bolts. The bolt must be ground down (with a dremel) in order for it to fit snug against the stem. The bolt needs to lose about 1-2 mm on all six sides. I have at least 5x of these and for the past month i've been making the bolts i need for some stems that lack the bolts.
I have been unable to find anything like the tall nuts used for these bolts in M8 threading (coarse or fine threading). these nuts are approximately 11 mm across and 10 mm tall, which is about twice as tall as a normal nut. this is hard enough to find that i haven't been able to find any 10 mm tall nuts. These nuts also have a what I call a "skirt", e.g. a circular taper inward 2 mm from the bottom, and a circular (not hex) taper outward at 1 mm from the bottom.
Luckily, regular nuts _do_ fit behind the stem and can be turned, despite their larger diameter.
- Don Gillies
San Diego, CA