# A 'good-enough' H960 |d|i|g|i|t|a|l| PDP11 masthead replica

Noel Chiappa jnc at mercury.lcs.mit.edu
Fri Jul 10 23:12:02 CDT 2015

```    > From: Pete Turnbull

> z = about 0.5mm - you're trying to measure the taper on the edge of
> the flange? Not easy to be accurate.

Ah, I've just realized I made a mistake in a previous message.

I thought 'z' was calling for the distance between the inner edge of what I'm
calling 'the flange' (i.e. the edge the left-hand arrow of 'x' is pointing
to), and the upright at the right end of what I'll call the 'bottom plate'
(when the piece is mounted on the H960, the bottom plate is in a plane
parallel to the ground - i.e. it's in a plane perpendicular to what I'm
calling 'the flange'). That upright is the vertical (in this picture) axis at
one end of 'z'.

Having called up a flat plate, and a square, to help measure accurately, the
width of the flange ('x') is 1.26 cm, and the distance from the outer edge of
the flange to the vertical at one end of 'z' (i.e. the end of the 'bottom
plate') is 1.57 cm at the 'bottom' of the plate (i.e. in this image), making
the distance from the inner edge of the flange to the vertical edge of the
bottom plate 3.1 mm - at the 'bottom' of the bottom plate.

At the _top_ of the bottom plate (i.e. the inner edge, when the unit is
mounted on an H960), the distance to the outer edge of the flange is 1.62cm,
making the 'flange inner edge' to 'bottom plate side' distance 3.6 mm, at the
'top' of the bottom plate.

So 'z', the variance between the two, is indeed 0.5 mm. Pete's spot on!

Noel
```