Monday, July 31, 2017

The extraction of lever-filler pressure bars

While most pen repair techniques have been given at least basic treatment online or in print, there is still next to nothing publicly available on how to remove a spring-loaded pressure bar from a lever-filler. What is to be found is generally either unhelpful or dangerous: pulling on the long end runs an unacceptably high risk of breaking off the short end (a risk that increases rapidly with the age of the pressure bar, with old one-piece "J-bars" being almost certain casualties), while pulling on the short end is often impossible, as its end has dug itself into the barrel wall and cannot be grabbed.


Dislodging the short end is nonetheless the key to safe pressure bar removal. This is best not done dry, since there is usually accumulated dirt, corrosion, and ink residue present. A little naphtha applied to the short end with a long-necked applicator will make things much easier. The short end must then be lifted slightly off the barrel wall to break its bond, and to free its end from any furrow it has gouged there. This generally cannot be done by approaching it from the front; instead, a piece of wire bent into a right-angled hook at the end can be used to apply pressure from the back.


As shown above, there is enough clearance to the side to insert the wire with the hooked end vertical. It is then rotated, placing the the hook behind and at the bottom of the short end. This will work even with a flat-bottomed barrel with the pressure bar pushed all the way against the barrel's end. Once it is in position, pulling on the hook will lift the short end while dragging it forward. Sometimes this will be enough to carry the pressure bar forward a substantial distance, but more often the hook will pass under the short end with an audible snap, dislodging it only partially. Not to worry, though -- you are almost there! Clamp the barrel in a padded vise so you can use both hands. Put the hook back into place, this time also grabbing hold of the long end of the pressure bar (locking hemostats are ideal). Now pull the hook a short distance, just far enough to lift the short end so it doesn't dig into the barrel wall. Then, holding both hook and hemostats together so as to maintain their relative position, pull them and the pressure bar the rest of the way out of the barrel.


Another tool that is even easier to use, albeit not always suitable, can be made by flattening the end of a piece of spring wire into the form of a gently curved, round-ended chisel. Once inserted under the short end as shown above, the long end can safely be pulled to extract the pressure bar, the short end riding smoothly atop the steel wire. This tool works best when the short end of the pressure bar is wide and flat, leaving a gap between its bottom and the curve of the barrel, or in those unusual cases where the short end terminates with an upwards bend. It does not work at all well when the short end is narrow, thin, or otherwise shaped to made it hard to dig under.

An alternative technique is to use the hooked wire to lift the short end just enough that the chisel-ended wire can be pushed in place. In this case the hook is not pulled through the rest of the way, but is then pushed back, turned, and withdrawn. The pressure bar can then be extracted by pulling on its long end as described above.

The tools described here are shown below. Hooks of different sizes can be handy: small hooks are necessary when clearances are tight, but a hook that is too short can slip out of place when there is more room and may end up lifting the short end unevenly. Basic instructions on heat-treating hobby-shop music wire can be found here.


Note that the methods discussed apply only to pressure bars held in place by a simple bent end. Bars that are anchored by C-shaped metal split rings as shown below require a different approach, in which pulling on the long end must be avoided entirely.


Finally, a point of terminology: the term "J-bar" is an old one with a specific and still-useful meaning, denoting a cheap one-piece pressure bar of the sort seen at bottom and center below.  Two-piece sprung bars of the sort shown on top were not called J-bars -- at the time, they were consistently referred to as "pressure bars".


NOTE: The discussion here is deliberately restricted to the use of tools that can be easily acquired or made. For while I have also designed more sophisticated tools (which I may yet have commercially manufactured), there is a special elegance to a minimalist solution.

1 comment:

menoeceus said...

Thanks for the very clear explanation and diagrams! If only most of the pressure bars didn't break almost immediately on attempted removal or weren't so fatigued that they couldn't be used even if not broken (yet)!