ETKA shows it as an M6 hex nut.  No pitch given so it must be a standard
thread.

Remember, when you're working with the wipers, that the wiper arm, where
it connects to the motor shaft, has soft metal inside so you don't ever
want to move the arm once it's on the shaft.  That will ream more of the
soft metal out.

You want to really clean the splines on the motor shaft.  Use a wire
brush in conjunction with a sharp knife and/or a pick.  Make sure that
all the old metal deposits are completely removed so that, when you put
the wiper arm back on, new grooves are cut into the arm's soft metal.
Sometimes, a small washer under the nut will allow you to get a little
more out of the arm.  Once the soft metal is all gone, it's new wiper
arm time.

Mike

Dan Barrett wrote:
> Volks:
>   Subject says it all: the nut holding the driver's side windshield
> wiper on has stripped.  Anyone know the diameter and thread pitch so I
> can hit my local hardware store for a replacement?
>
> Best,
> d.
> 1990 GL -- "Mudskipper"
>