Some repair people will tell you that you never need to remove the front section when repairing a Parker “51”. I find that this is not true in most cases.  A lot of the Parker “51” owners used Parker “51” Ink or Superchrome Ink. Both of these inks dried up very quickly and tended to clog up a pen, especially after being stored for years without use. The best preventive maintenance is to remove all the parts and thoroughly clean them. To remove the shell,  you will need to apply heat to the shell area near the clutch ring. This can be done with a multiple setting heat gun or alternatively a hair blower.  Be careful because the hood is rather thin, and will deform easily.  Grip the hood and the barrel with two pieces of  rubber and twist clockwise.  Do not exert excessive force, or you risk cracking the hood.  If the hood does not give, apply some more heat.  Hoods are shellac-ed in place and you will need to soften it before the hood will unscrew.  Once the hood is off, soak the front collector and hood in cool water.  Do not attempt to twist the collector without soaking, as you will either crack it or break some fins.  Once the collector is off, remove the feed and nib.  You will need to make sure that the breather tube is clear.  This can be done by blowing at one end.  If clogged, insert a thin pin through one end of the breather tube to clean.

The next step is removing the filler.  This has to be done with a special threaded tool; either a vac wrench or vac block.  Again, it is essential that you apply heat around the filler area to soften the shellac often used.  Once the filler unscrews, use a wooden dowel that will fit in the front of the barrel to push the filler unit out.  Remove all leftover remnants of the petrified rubber, especially around the ring where the filler sits.  To replace the diaphgram, you will first need to remove the old pellet from the filler.  The pellets were made of either rubber, plastic or a hard substance that looks like glass.  Removal can be challenging, but in most instances, this can be done by either using a very thin dremel tool, or alternatively, heating a pin and inserting into the ball.  Let it cool down, and then slowly work it out.  Note that in a lot of cases the ball cup has become very brittle with age, and you run the risk of cracking it.  If it cracks, you can try to repair it, but you will probably need to find a new filler.  Before fitting the new diaphgram, first make sure it is cut to size, otherwise it will hit the breather tube when filling.  In most instances you will need to cut about 1/4″ from the factory length diaphgram.  Push the nipple with the pellet into the cup.  You may need a thin wood dowel to assist you.  After inserting the new diaphgram, fold it once upon itself until the leading edge covers the retainer ring.  Apply silicon or talcum powder over the diaphgram to make re-insertion into the barrel easier, otherwise you run the risk of twisting the diaphgram.   Once the unit is screwed back into the barrel, check for suction by putting a wet finger in the front opening and pumping.  The barrel should “hang-on” to your finger for 10 seconds, otherwise, you have a leak.  Make sure to align the blindcap by making small turns to the unit until you get a perfect fit.  This can be tricky and requires some time and practice.

Re-assemble the front section by aligning the hood first without the collector, in order to estimate the alignment of the nib.  Insert the collector, nib and feed.    Screw the hood to check alignment.  Repeat until perfectly aligned.  It should only require small adjustments.  The hood must be re-sealed, or you will get inky fingers.  You can use either rubber cement or shellac on the threads.  I prefer rubber cement for easy removal later on if necessary.

Let the front section dry for at least 30 minutes, and then test the pen by filling up with ink.  Ink flow can be regulated by spreading the tines very slightly or by molding the tip of the hood onto the nib, which has the same effect as spreading the tines.

Click Here to see a ca. 1944 Parker “51” Repair Kit

A lot of people will tell you that an Aerometric Filler “51” can be restored with just a good flush of water and nothing else.  Although this can be the case in some Aerometric Filler “51s”,  I find that this is not true in most cases.  A lot of the Parker “51” aerometric owners used Parker Superchrome Ink. These inks dried up very quickly and tended to clog up a pen, especially when the silver breather tube got corroded by these very alkaline inks.  The best preventive maintenance is to remove all the parts and thoroughly clean them. To remove the shell,  Parker used a tool to grip the treads when the barrel was off, in order to avoid twisting the metal filling case.  In any event, you will need to apply heat to the shell area near the clutch ring. This can be done with a multiple setting heat gun or alternatively a hair blower.  Be careful because the hood is rather thin, and will deform easily.  Grip the hood with a piece of  rubber and the barrel by the threads.  Do not exert excessive force, or you risk cracking the hood or ruining the filler.  If the hood does not give, apply some more heat.  Early hoods  were shellac-ed in place and later a rubber o-ring was used.  Once the hood is off, soak the front collector and hood in cool water.  Do not attempt to twist the collector without soaking, as you will either crack it or break some fins.  Once the collector is off, remove the feed and nib.  You will need to make sure that the breather tube is clear.  This can be done by blowing at one end.  If clogged, insert a thin pin through one end of the breather tube to clean.  Some of the silver tubes are beyond hope and will even break from so much corrosion.  If this happens, some people drill the broken piece out and replace them, but in most cases you will need a replacement part.

In the case of the Aerometric “51”, the filler itself will need little or no work, other than a good flush. Check the condition of the sac by putting a wet finger in the front opening and pressing.  You should get a good amount of suction.  The barrel should “hang-on” to your finger for 10 seconds, otherwise, you have a leak.  Re-assemble the front section by inserting the collector, nib and feed.  Align the hood first without the collector to estimate location.  Insert and try the hood again.  It should only then require only a small adjustment.  The hood must be re-sealed, or you will get inky fingers.  You can use either rubber cement or shellac on the threads.  I prefer rubber cement for easy removal later on.

Let the front section dry for at least 30 minutes, and then test the pen by filling up with ink.  Ink flow can be regulated by spreading the tines very slightly or by molding the tip of the hood onto the nib, which has the same effect as spreading he times.