"Tim+" wrote in message
...
Fredxx wrote:
On 25/02/2021 18:28, Tim+ wrote:

I happened to stumble upon an old Hayter electric start lawnmower
chucked
into the long grass by a road whilst out for a jog the other day so Ive
brought it home to see if its repairable or has any bits worth
salvaging.

I started stripping it down and all the bolts were regular metric sizes
until I came to remove the engine cooling cowling. 10mm socket too big,
9mm
too small.

It did occur to me that they might not be the original bolts so I tried
all
the AF and Whitworth spanners that I have. No joy.

Eventually dug out a cheap 9mm open ender spanner that could be forced
on
with a bit of percussive persuasion.

Im now inclined to think that they are original as they all match and
my
micrometer measures them up at 9.5mm. WTF is the point of that?? How
many
socket sets include a 9.5?

My 3/8" socket would be at least 9.525mm, likely larger for a little
clearance. If this was a 3/8" bolt I would be surprised you squeezed a
9mm socket onto it, unless it was a 12 sided socket?

I didnt squeeze a 9mm socket onto it. Re-read my post. A 3/8€� spanner
fits
rather loosely (but usably).


I cant believe that a designer decided that 9 mm would be too weak and
that a 10mm would be too cramped for space.

Briggs and Stratton has a US heritage so could well be imperial sizes.

But that wouldnt explain why all the other engine bolts are standard
metric sizes. Its just the engine cooling shroud retaining bolts that are
odd.

What are the other engine bolts ? There are some that
work fine with both metric and non metric spanners.