aeroprof
I agree with you, no substitution was made on Leah's stem.
What I meant was Nitto designed the stem for a Standard M6 hex nut (13mm
flats) some time before 2000 when I bought my 225mm Technomic with 80mm
stem. Some time between 2000 and 2010 Nitto made a design change to go to
a JIS M6 hex nut with 12mm flats.
The design change added 0.5mm of margin between the nut flat and the
ledge and is reasonable, but not as tolerate to the allowed tolerances in
the bolt hole location and the ledge shape/location.
I would guess they made a change if they were running into too many
problems with the clearance between the nut flat and ledge. All very
reasonable, but *only* Nitto can say for sure.
I think Leah's stem simply fell outside of the 6-sigma bell curve and was
not caught by Nitto.
I think she ought to return it to RBW, and if they want they can pursue it
with Nitto. Or maybe RBW/Nitto might say, " Ok it's 1 out X000's, which we
expected. Give the a new one"
John Hawrylak
Woodstown NJ
On Saturday, June 27, 2020 at 5:02:26 PM UTC-4, aeroperf wrote:
>
>
> John—
>
> No, I don’t think they substituted a JIS nut for a standard M8 nut in this
> particular unit. That was my first thought but my nut is close enough to
> the “step” that it looks like the design is for the JIS 12mm.
>
> My thought is more like #1 or #6 in Paul’s entry above, and your comment
> yesterday.
> Say the hole is drilled a little off, or at a very tiny angle, or
> something like that. You have to drill a hole a tiny bit oversized to
> account for manufacturing tolerance of the bolts, but just a little more
> and things can be off center.
> There is also the fact that the step has a “draft” - it has a slight
> radius, at least on mine. So the nut already may have an opportunity to
> misalign a little, and a very slightly misaligned or oversized hole would
> let it spin.
> Finally, Leah’s photo indicates that the bolt/nut was slightly offset from
> the center of the hole.
>
> We tend to think “It’s just a bicycle”, but it is really a collection of
> precision parts clamped in loose formation.
> Sometimes a part has a bad day in the manufacturing process and sometimes
> the quality inspectors don’t catch that.
>
>
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