A Happy End To A Long Onoto Repair Story

July 21, 2017

I had all sorts of headaches repairing my Onoto 6233, throughout my learning experience. I made probably every possible mistake, first in extracting the plunger rod, which caused me to replace the rod with a new one, then, as a consequence, cutting the new rod too short, which prevented the vacuum release at the end of the downward stroke once the plunger was assembled, not to mention a few more. Finally, cutting the rod too long, which turned out to be the real cause for an irregular ink flow performance, as well as systematic drying out of the ink in the feed.

Determining the proper length of the plunger rod was the real issue and, after the first mistake of cutting the rod too short, I was mislead by the notion that the plunger had to rest directly against the end of the feed. This is not right: the correct rod length should allow for some space between the plunger and the feed.

I had always suspected this to be the cause for the feed running dry, but wasn't sure because the flow didn't seem to improve when I kept the knob slightly unscrewed. I definitely opened my eyes when I bought a second Onoto, a 3050 which I restored with the usual o-ring method (see Richard Binder's pages). I found out this pen to be exactly the same size as the 6233, apart from the cap and was able to exchange the sections.

When I fitted my 6233's section to the 3050's body, it performed flawlessly. I therefore decided to compare the length of the portion of the plunger protruding from the section: 11.5 mm (6233) vs 9.5 mm (3050). Rather than trying to disassemble the rod again and cut it shorter, at the risk of making my 5th order to Custom Pen Parts, I decided to sandpaper the plunger to size and reconstruct the tip by means of a graphite stick sharpener. The plunger on the 6233 still sticks out a little more than on the 3050, but the pen is now performing superbly. Gone is the drying problem and the filling performance is unaffected.

I am by no means a purist, therefore I never considered reinstalling cork washers, given the superior performance and durability of properly sized silicon o-rings, but, in fact, air-tightness in the packing was never an issue. The real difficulty I found out to be in determining the right rod length, I you have the misadventure to have to replace it: it is very difficult to find the correct position when the knob is loose and it's very easy to cut it too short or too long.

July 21, 2017

Hi

Happy to hear your pen is now back working ☺

Regarding getting the rod length right first time, did you read the guide i wrote in the rod detail on my site.

Very simply, assemble the full pen screw the rod into the plunger knob as far as it will go, screw the plunger knob back onto the pen and then by screwing the rod in it will eventually seat on the cone shutout. Drill and pin the rod and trim the rod to the top of the knob. Simple.

In order to ease adjustment of the rod, i always make the rods longer than needed so you can get hold to adjust, and like i say on my guide the rod should turn easily on the thread to feel when the rod is fully seated.

July 21, 2017

Good that you got your pen back in working order. I have a beautiful 6235 that is awaiting restoration. I would benifit from your experience as well the valuable advice of Custom Pen Parts.

Thank you to both of you.

Edited July 21, 2017 by mitto

July 21, 2017

Thanks. I think I did as you suggested if I remember correctly. In the end the plunger was sitting against the feed with the knob screwed in in place. The plunger had no room to go down any further. Yet I believe this was too tight a position and a little gap seems to improve the ink flow. There is no theory here, just my practical experience

July 21, 2017

Firstly, congratulations, that is excellent for you and interesting for any of us with an interest in Onotos.

I am reading your comments as being that with the cap fully closed the plunger should almost, but not quite, shut off the ink, leaving it like an ordinary pen which has an open feed channel from its ink reservoir. Presumably it would be aesthetics alone which might stop one from simply leaving the plunger knob slightly unscrewed, to the same effect? That way one could still shut it off for flying if that were a need (as it was for the buyer of a 5601 from me).

Some of my Onotos seem not to seal properly anyway, in that they will always write despite never opening the plunger knob. This may be the same solution as you found, with an even greater gap. It seems the plunger rod length is a critical item in Onoto restoration, depending on one's expectations.

July 22, 2017

Thanks, praxim, I think you hit the nail on the head. It is conceivable, imho, that the shutoff position may not be the same, say in a 6233 or in a Magna. For the simple reason that, in a wider girthed pen, owing to the ink's surface tension properties, a tight seal would be reqired, to prevent spillage. While, in slimmer pens, such as mine, a gap would be requred to ensure the correct flow. Luckily for me, I didn' t break the rod on the 3050 too, which had exactly the same section measurements as the 6233's, and was able to ascertain that the factory settings, in this case, allowed for a gap of 1-2 mm from the feed when the knob is fully closed.

July 25, 2017

I saw a very good work here, pal! It is really great

Edited July 25, 2017 by harrietboyd

October 24, 2017

I'm a little confused here about what's being discussed on setting a rod and feed.

I've always set the cone right up to the feed to prevent ink from leaking when the pen is not in use. Then when I want to use the pen I simply unscrew the end by about a half turn or so depending on the desired flow.

October 24, 2017

BTW the new peek rods 'rock'. They use this stuff in spinal fusion implants so you know it's got to be strong.

October 24, 2017

I wish the same could be said about the soft silicone washers. After a couple of months use, I noticed that my pen was not taking in much ink any more and realised that the washer had moved up the rod. In my humble opinion, the washers are too soft and prone to move from their position after some use. So, as an update, I am not very happy with my pen after all.

I wish the same could be said about the soft silicone washers. After a couple of months use, I noticed that my pen was not taking in much ink any more and realised that the washer had moved up the rod. In my humble opinion, the washers are too soft and prone to moving from their position after some use. So, as an update, I am not very happy with my pen after all.

Edited October 24, 2017 by pieemme

October 24, 2017

I'm a little confused here about what's being discussed on setting a rod and feed.

I've always set the cone right up to the feed to prevent ink from leaking when the pen is not in use. Then when I want to use the pen I simply unscrew the end by about a half turn or so depending on the desired flow.

The point I intended to make was that the opening or closing position (i.e. the distance between the plunger and the tip of the feed) would depend on the model and, ultimately, I would suppose, on its girth.