Parker cap thread problem.

[CountryDoc]

Help, Parker fans. I have a vintage Vac, and the the pen itself works fine, but the cap will only twist on about 1/8 of a turn. There is a slight bulge in the barrel, but that is well below the barrel threads. I can't see any damage/cross-threading on the barrel or inside the cap. Has anyone else encountered this, or know who can fix it?

 

 

 

Thanks,

Tim

 

 

[Ron Z]

Wear to the threads is not uncommon.  Sometimes it's the cap, sometimes the barrel, or both.  The barrel threads can be stretched, but I wouldn't recommend that an amateur try it.  The room for error is thin, and it is easy to turn your pen into a celluloid flambe'.  The first clue that you have things to hot is the puff of acrid smoke as the celluloid ignites.  It's already too late when that happens.

[VacNut]

Is this a new condition or an existing problem? 

[dipper]

From the photos, that looks like a double-start thread? If so, that is good news. Two areas of 1/8 turn thread engagement, on opposite sides of the pen body.

 

Can you identify what it is that stops the cap rotating after 1/8th of a turn?

Could be .....

1) Mismatched thread pitches?

2) Pen and Cap are both slightly flattened. Round cross-sections have become elliptical with age?

3) Pen grip section end face hits a shoulder inside the cap?

4) Something else ...... ?

 

I have two Demi-size UK Duofolds.

When received, one pen had adequate cap rotation, the other had hardly any rotation at all.

 

Swaping the caps over - the problem followed the cap.

Looking deep inside the "bad" cap, and comparing with the "good" cap, and with caps of some other sizes of Duofold, it was clear that an internal machining stage had been omitted.

All the other caps had a sloping smooth internal shoulder that butted against the front of the grip section to create a sealed nib chamber, and define the limit of screw-in rotation.

The bad cap had a perpendicular faced shoulder, with a sharp internal corner, and machining marks visible on the face of the shoulder. There was also a scar on the front face of the pen grip section - caused by friction against the sharp corner of the unfinished cap shoulder. (That is issue #3 in my short list of possible causes given above.)

 

Having identified why the cap had hardly any rotation, and finding that it was not a thread problem, I was able to fix it.

(Smooth dowel rod shaped to be a free sliding fit in the cap nib space, and spun by hand. A collar of sandpaper bound onto the spinning dowel to grind and then polish the cap shoulder to approximately match the form of all the other caps.)

 

[Ron Z]

Vacumatic threads are triple lead.

 

Short rotation is usually caused by worn threads, so the threads don't engage farther down in the cap like they should.

[judo]

I'm sure with all the experience he has, that Ron Z is correct that it's mostly worn threads, but I had a similar experience to dipper where the cap wouldn't engage at all with the threads on a Parker Vac I'd just purchased a few weeks ago. On checking the pen, I found that the shoulder inside the cap was not as far down as my other Vacs and so I used a twist drill to take 1.5 mm off it and the cap now screws on as good as my other pens and there is still clearance for the nib. Worth a check anyway.

[Carguy]

I was getting ready to post this same issue with a Duovac/striped Duofold I just received. I can fix most any issues on Parker pens except this. 
 

Any suggestions on what I might be able to do?

[FarmBoy]

There are a few ways to fix this problem independent of the pen brand. 
 

I find it just isn’t worth the cost for most common pens. There are just to many pens in better condition that don’t need this level of work. 
 

 

[Carguy]

2 hours ago, FarmBoy said:

There are a few ways to fix this problem independent of the pen brand. 
 

I find it just isn’t worth the cost for most common pens. There are just to many pens in better condition that don’t need this level of work. 
 

 

That’s what I was afraid of….guess I will just help this one for parts then

[Ron Z]

I disagree with Todd.  Many pens can be saved when the threads are stretched.  The repair is often invisible.  With the number of pens and parts diminishing I like to save a pen if I can.

[FarmBoy]

I’ll clarify a bit. 3rd gen SJ wartime vac is pretty common. I see a nib, filler, and cap that can all save other pens that otherwise would hit the parts bin. I get a lot of requests for fillers and clips.  So much so that I rarely have enough that I’ll dip into the repair stock and sell them. 
 

If it wasn’t a common baseline pen I’d have a different approach. 

How you fix it depends a bit on what the cause is. 
 

In stream of thought order 

 

Stretch the barrel threads. Ron mentioned this. I’ll repeat it isn’t for the weak hearted as you can quickly end up with a cap and nib. 
 

Sleeve the cap and recut the threads. Fun but you really need to be proficient using a lathe. 
 

Try shortening the section and/or the inner cap to get to unworn threads.  Make sure the nib still clears.
 

Sometimes swapping two apparently alike  caps or grabbing one from the parts bin solves the problem. But Ron and I most likely would make this the last option since it is like mixing the jacket and pant from two hand tailored and fitted Italian suits.

[Ron Z]

Type is too small.....  Should be:

 

Make sure the nib still clears!

[es9]

22 hours ago, FarmBoy said:

since it is like mixing the jacket and pant from two hand tailored and fitted Italian suits.

Now *that* is a great metaphor. 

[VacNut]

Each their own, but I suspect they may have just swapped the caps when NOS caps were readily available in the shop. Unless the pen has sentimental value, isn’t the cap swap a less expensive option with less risk?