# Full PHP31-FIBER manual — design findings

Source: the user's photograph of the Graphtec PHP31-FIBER instructions, printed
reference 621589190. Preserved unchanged as
`../../reference/graphtec_php31_fiber_manual.jpg`.

## What the manual establishes

The holder uses a plunger body, removable plug and threaded end fitting. The pen
is inserted with the end fitting loose, then secured by tightening that fitting.
The drawings support the split-collet interpretation, but provide no sectioned
internal geometry, thread specification, taper angle, or dimensions.

A separate height adjustment tool establishes the pen's axial position. In the
manufacturer's sequence, the plunger is placed in that tool, its end fitting is
loosened, and the pen is inserted gently until its tip reaches the tool's bottom
surface. The fitting is then tightened and the assembly removed from the tool.
The manual also calls for straight, centered insertion, keeping the pen straight
during tightening, cleaning ink off the datum surface between pens, and retaining
the removable plug when the fitting is removed.

## Consequences for this experiment

- Treat the lower internal passage as clearance and guidance. The collet grips
  the barrel; a setting jig can establish height without relying on a different
  internal stop for every pen's nose profile. The outlet must still allow each
  intended pen to reach that position without nose interference.
- A matching jig is the next design candidate. Its datum would sit **33.12 mm
  below our flange's carriage-contact face**, using the user's target. That number
  is not supplied by the manual. The reference photo does not establish the
  original Graphtec jig's dimensions or confirm that it fits this custom body.
- Correct the earlier blanket instruction against tip contact: Graphtec expressly
  uses gentle contact with a setting surface. For our Copic experiment, contact
  should establish the datum without intentional nib deflection. Hold the barrel
  while tightening so cap motion does not add downward load; recheck height after
  tightening. This adaptation has not been physically tested.
- The manual strengthens the interpretation of the intended adjustment workflow.
  It does not validate our custom thread fit, 9.75–9.85 mm barrel range, finger
  flexibility, release behavior, or added upper-head clearance.

This update adds the reference and corrects the setup documentation. It does not
change the experimental STL geometry, the main holder, or either mounting datum.
No setting-jig model has been made in this update.