I like the P 51 aerometric pen, but prefer the vacumatic blue diamond caps. I know this might be pen heresey,but doesn anyone know if the vacumatic blue diamond pen cap fits on the aerometric pens?

Yes they do... except maybe the MK III which I believe is a thinner cap

Sparky

Don't take this as gospel, 'cause maybe other years aren't compatible but I just put a Blue Diamond cap from a '47 Canadian on a '48 Aero-- the clutch ring engaged, so no scratching that I can see.

But- cap swapping might have happened to these pens before I acquired them.
One could imagine that in the half century of life of either of these pens, a cap got trashed or lost, so the owner got a replacement from somwhere.

But if you go to sell the aero with a blue diamond cap you might loose credibility with a knowledgable buyer.

I say please yourself and swap away. If they fit, they fit; if they don't they don't.

It's not like you're drawing a mustache on the Mona Lisa!

Jack

I'm in accord with the above comments. Most blue-diamond caps should fit Aeros with no problem, and you should do what makes you happy. I think the 51 is a remarkable pen, but OldGriz is exactly right about the Mona Lisa thing - these are essentially tools to be used, not art.

I'd also reccomend keeping the orignal Aero cap around if you want to sell the pen - though there are many people out there just looking for a good user 51 - hisotrically accurate or not.

Actually, there are a couple of issues with the MK III caps.

Thinner is one of them, so the taper of the cap is different.

Parker also changed the clutch system in the cap, from closed ends to open fingers at the open end of the pen. They also changed the clutch ring on the pen. It's a little thinner, and also a little smaller in diameter. The fingers on a MK III cap will/can catch on the larger diameter clutch ring, or NOT (i.e. may be loose) if you're putting a standard cap on a MK III pen.

You can't just swap out a standard section and a MK III section - that thinner clutch ring means that a shoulder in the front of the front of the section (look down inside one and you'll see what I mean) is set in just a little deeper. That shoulder buts up against the end of the collector. To use an earlier section on a MK III one needs an end mill to shave a little of that shoulder in the front of the section.

But to answer the earlier question, yes vac and aero caps will swap out. Note that there are differences. Vac 51 caps (except the transition pens) had blue diamond clips, the aero caps have a tab that catches the clip to keep it from rotating on the cap.

My big objection to putting BD caps on aero pens is that not all BD caps are vented in such a way that the aero filler will do its job on an airplane. If you really want a BD clip on your aero pen, I recommend installing the clip on a proper aero cap. You will need to file down the tab that keeps the clip from rotating on the cap, as it's too wide to fit right under a BD clip.

Hi,

related to this issue, please take a look at my post "Parker, What is it ?" and help if possible.

thanks

rusty

Thank you for the information on cap switching... and the ""support" to go ahead and do it.