[T3] 10mm Mirror bolt

[Jim Adney]

On 1 Feb 2012 at 18:01, Gary Forsmo wrote:

>    - *Question:  If the threads (O.D./major) of a 10mm bolt measures 5.97
>    mm (0.235"), what size (I.D./minor) hole do I DRILL for the 10mm tap?*

In about 1970, when I was first trying to rebuild an engine, I made 
this same mistake: I was calling out bolt sizes by the head dimension 
rather than by the thread dimension. It took a confused parts man at 
the VW dealership to straighten me out. You're talking about a 6 mm 
bolt, which happens to, by current DIN standards, have a 10 mm head.

Tap drill sizes are easy to determine for metric threads if you know 
the full thread description; it's the diameter minus the pitch. Since 
the most common 6 mm thread is the M6 x 1, the tap drill size is 6 
minus 1 = 5 mm. Looking at my handy drill chart, an 8 drill comes 
closest.
 
> *2.  Does anyone have a suggestion for a (Mid-West or other location)
> company that does "RE-SILVERING" of mirrors*

I think that's very unlikely. The closest you'll come will be a glass 
shop that can cut you a replacement from mirror stock. The problem 
remains of how to keep the mirroring from corroding over time. I 
think this got discussed recently, but I don't recall that anyone had 
a good solution.

> *3.  If I'm ever going to find a correct (Jim says: long arm) RHS, Type 3
> Door Mirror, what I've learned by "dissecting" this Type 1 mirror, may come
> in handy.*

I understand your desire to be original, but the later style, that I 
think came out around '70, was MUCH better. Anything replaced after 
that date would have been replaced with the later style, and since 
these break so often, I think your chances of finding a good early 
one are next to zilch.

The difference between early and late is not the length of the arm, 
it is in how difficult they are to adjust. On early ones, to adjust 
the vertical position, you have to loosen the locknut, turn the 
threaded portion that screws into the door, and retighten the 
locknut.

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Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA
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