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Thread: A Radical Rebuild of a Most Unusual Onoto

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    Senior Member Cob's Avatar
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    Default A Radical Rebuild of a Most Unusual Onoto

    Preamble.
    As some of you may know, apart from being a pen enthusiast, I buy and sell vintage fountain pens, mostly on eBay.
    Except very rarely, I sell only pens that are in full working order, presentable and ready to fill and to write. It follows, therefore, that I have had to learn a considerable amount and acquire special tools etc., in order to achieve this: as I am sure you know, not all pens are simple lever-fillers that require only cleaning and the fitting of a new sac.

    ************************************************** ****
    Apart from Sheaffer Snorkels, Parker 51s, Ink-Vues, Swan Visofils, Osmias and (reluctantly) the terrible Vacumatic, I have had a lot to do with Onotos; I have repaired at least thirty, probably more, so therefore these have become pretty much routine – that is they were until this one turned up:

    Capped.jpg

    Even Steve Hull’s Onoto masterwork contains very little information about this model that he says dates from about 1949 (see P 253 of Mr Hull’s Onoto book). It carries no model number

    Everything about this pen is different: first it is shaped like no other Onoto, its “torpedo” shape resembling a post-war Swan or a pre-war Sheaffer Balance; note also the midway “waterfall” clip fitted to the cap – a feature that harks back to the Onoto Mammoths of the 1920s. The large bi-colour nib is mysteriously stamped 99 rather than “5” which is what it probably is.

    Torp 7.jpg

    The filling system is the classic Onoto plunger/vacuum system introduced in 1905, the invention of George Sweetser (an extraordinary character) and Edmund de la Rue, and thankfully it accepts the standard cup seals – a relief! There is a difference though: the piston rod in the standard pen is black hard rubber with a hard steel insert (probably piano wire) 3.2mm (1/8”) in diameter. This pen has a plain steel rod 2 mm in diameter. Fitted to the piston seal end was a small black hard rubber piece with the usual left hand 5BA thread to accept the seal holder, which is like that of an Onoto Minor – there is no ink shut-off feature. In their wisdom (?) Onoto made the rod or at least the extreme end, of plain steel which rusted, expanded and exploded this! I should have photographed this abortion, but failed to do so. Using 1.35mm and 2.8mm drills I modified a spare part from my stock and made up this rod:

    Old Rod Modified.jpg

    It won’t work because the sealing corks at the end of the barrel (new) are designed for the standard rod. The corks are vital to maintain the vacuum behind the piston seal and so originally the pen must have had special corks.

    This left three repair routes: try to source special corks, use O rings or make a new rod. I chose the latter route. The plunger knob is not of course LH 5BA threaded and pinned to the shaft as with the standard models: it is RH threaded. The ever-helpful Tracy Tools identified the thread: it is 2/56 UNC (major diameter 0.086”) and of course they had the dies on the shelf.

    A friend of mine has a lathe and turned down the last 10mm of the new 3.2mm brass rod to 2.2 mm. So all I had to do was cut a LH 5BA thread on the seal end and a 2/56 UNC RH thread on the other. Here's a snap showing the new rod with another blank and the original rod as modified by me.

    Torp 6.jpg

    I polished the rod carefully to avoid risking damaging the corks. The lock nut that secures the RH threaded knob is buried inside the cap – deep joy. This means that the cap has to be fitted before inserting the rod into the pen which means running a socket down to the end to tighten the nut. The rod is then inserted and the seal holder assembly fitted as per an Onoto Minor. However the larger rod required that I drilled out inside the barrel, the ledge that supports the corks to 3.5mm to permit the new rod to pass and similarly I had to drill out the cork-retaining threaded plug that screws into the end of the barrel and which also accepts the plunger knob.

    A 2/56 UNC nut is 3/16” AF (4.7mm) with the thickness of a socket this would be another problem. I solved this by having my friend turn down a 4mm Socket to about 6.5mm OD so it would go into the knob, and then rather naughtily, tapped a 2mm nut out to 2/56 UNC and finally all was done.

    Torp 3.jpgTorp 4.jpg

    The pen now fills and writes as an Onoto should!

    Torp 1.jpg

    Rgds

    Cob
    Attached Images Attached Images
    Last edited by Cob; April 14th, 2018 at 07:36 PM.
    Vive les chevaliers! A bas les têtes rondes!

  2. The Following 10 Users Say Thank You to Cob For This Useful Post:

    amk (November 11th, 2019), countrydirt (April 14th, 2018), da vinci (April 14th, 2018), fountainpenkid (April 15th, 2018), FredRydr (April 14th, 2018), gbryal (April 15th, 2018), Lady Onogaro (April 15th, 2018), penwash (April 14th, 2018), Robert (April 14th, 2018), Schaumburg_Swan (April 3rd, 2023)

  3. #2
    Senior Member FredRydr's Avatar
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    Default Re: A Radical Rebuild of a Most Unusual Onoto

    I love restoration stories, from a big classic phaeton to a little fountain pen.

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    Cob (April 14th, 2018)

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    Senior Member Cob's Avatar
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    Default Re: A Radical Rebuild of a Most Unusual Onoto

    Quote Originally Posted by FredRydr View Post
    I love restoration stories, from a big classic phaeton to a little fountain pen.
    Fred, actually it's quite a big pen!!

    Rgds

    C.
    Vive les chevaliers! A bas les têtes rondes!

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    Senior Member Deb's Avatar
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    Default Re: A Radical Rebuild of a Most Unusual Onoto

    Well done! That's an admirably technical and complex repair.
    Regards,
    Deb
    My Blog

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    Cob (April 14th, 2018)

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    Senior Member Cob's Avatar
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    Default Re: A Radical Rebuild of a Most Unusual Onoto

    Quote Originally Posted by Deb View Post
    Well done! That's an admirably technical and complex repair.
    Thanks Deb.

    Whilst the O ring route would have seemed to have been the "sensible" option, first I didn't like the fact that the original rod rusted and exploded the BHR end and second I liked the idea of using the original corks that are readily available.

    Rgds,

    Cob
    Vive les chevaliers! A bas les têtes rondes!

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    Default Re: A Radical Rebuild of a Most Unusual Onoto

    Well done Cob! Great read and glad to see the Onoto restored to working order!

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    Cob (April 14th, 2018)

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    Senior Member FredRydr's Avatar
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    Default Re: A Radical Rebuild of a Most Unusual Onoto

    Quote Originally Posted by Cob View Post
    ...the cap has to be fitted before inserting the rod into the pen which means running a socket down to the end to tighten the nut. The rod is then inserted and the seal holder assembly fitted as per an Onoto Minor....
    What were they thinking?!

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    Cob (April 14th, 2018)

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    Senior Member penwash's Avatar
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    Default Re: A Radical Rebuild of a Most Unusual Onoto

    Wonderful restoration record. Please know that your effort to do this is well appreciated.

    Due to its rarity here in the US, I have never had the chance to write with let alone restore an Onoto from the same era as this pen.
    - Will
    Unique and restored vintage pens: Redeem Pens

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    Cob (April 14th, 2018)

  15. #9
    Senior Member Cob's Avatar
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    Default Re: A Radical Rebuild of a Most Unusual Onoto

    Quote Originally Posted by FredRydr View Post
    Quote Originally Posted by Cob View Post
    ...the cap has to be fitted before inserting the rod into the pen which means running a socket down to the end to tighten the nut. The rod is then inserted and the seal holder assembly fitted as per an Onoto Minor....
    What were they thinking?!
    Indeed Fred!

    Well the Onoto Minor is similar but actually worse - the knob is actually glued to the rod! As for 'thinking' I was truly shocked to find ordinary steel inside a fountain pen. That's what made me think of brass. I suppose that I shall find out that brass reacts with ink! Actually someone else most likely will, as already a client wants to buy the pen, but I am hanging on to it for a bit.

    The point is that as it now uses standard corks and the seal is standard anyway it will be straightforward to overhaul should that become necessary.

    Rgds

    C.
    Vive les chevaliers! A bas les têtes rondes!

  16. #10
    Senior Member Cob's Avatar
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    Default Re: A Radical Rebuild of a Most Unusual Onoto

    Thanks for the kind words.

    Onotos come up all the time on English eBay and occasionally in other Commonwealth countries, a legacy of Empire I suppose.

    Cob.
    Vive les chevaliers! A bas les têtes rondes!

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    FPG Donor ♕ Chrissy's Avatar
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    Default Re: A Radical Rebuild of a Most Unusual Onoto

    Excellent. Good job Cob

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    Cob (April 15th, 2018)

  19. #12
    Senior Member Cob's Avatar
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    Default Re: A Radical Rebuild of a Most Unusual Onoto

    Quote Originally Posted by Chrissy View Post
    Excellent. Good job Cob
    Thanks Chrissy; how are things?

    Rgds
    C.
    Vive les chevaliers! A bas les têtes rondes!

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    Default Re: A Radical Rebuild of a Most Unusual Onoto

    Beautiful work Cob! Amazing and excellent skills to show us the sequential story of the restoration.

    regards.

  21. #14
    Senior Member Cob's Avatar
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    Default Re: A Radical Rebuild of a Most Unusual Onoto

    Quote Originally Posted by Cyril View Post
    Beautiful work Cob! Amazing and excellent skills to show us the sequential story of the restoration.

    regards.
    Thank you. A bit of a while ago this one. Everything since then has been routine really.

    C.
    Vive les chevaliers! A bas les têtes rondes!

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