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Piston Disassembly? Hardtmuth Airless

hardtmuth airless piston disassemble

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15 replies to this topic

#1 praxim

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Posted 24 May 2018 - 00:00

This is an unused L&C Hardtmuth Airless fountain pen I purchased recently (7000 lire in the 1950s, it seems, and over-priced today).

 

fpn_1527118729__hardtmuth__286_1_of_4.jp

 

The piston seal looks intact but is very stiff so I would like to grease it, whereon I discovered some interesting things on which I would like some advice. Pretty as it is, the pen itself has all indications of being something made for Hardtmuth by someone else, so in looking at further description and pictures, you may be able to relate it to something else German or East European, probably from the mid-1950s or a little earlier.

 

Close examination of the section through the semi-transparent barrel suggests that it is not threaded. However, heat and force to the limit I was prepared to take the thin celluloid showed no sign of give. I think it is glued.

 

I can chase removing the nib-feed assembly (it did not give easily) or try removing the piston. Before doing so, here are the curiosities (to me) and queries. The next two pictures show the piston knob under the blind cap (all pictures expand with suitable clicks):

fpn_1527118750__hardtmuth__288_3_of_4.jp

fpn_1527118764__hardtmuth__290_4_of_4.jp

From the second picture it appears that the knurled knob is not formed with the threaded part, yet when you turn the piston knob then the threaded part unscrews from the barrel as the piston extends. It is possible to work the piston fully (and very stiffly) by this means but it can hardly (to me) be intended operation because the celluloid into which it is threaded will surely soon wear and crack.

 

There is no flat or hole visible in the threaded or knob part, so if the inner knob is to release then it is simply a padded grip on the thread that would be needed while the knob is turned (after heating). I am expecting that the assembly is released by fully withdrawing the plunger using the inner knob (assuming it can be moved) then keeping it still while unscrewing the threaded portion from the barrel. By the way, knurling on the barrel is for effect only. Close loupe examination shows no join there.

 

Is anyone familiar with this piston mechanism, or seen the same in a better known pen? Do you think I should simply resort to trying to unscrew the nib and feed, returning to the piston assembly only as a last resort?

 

Thanking you for any assistance you may be able to offer. Edits for clarity.


Edited by praxim, 24 May 2018 - 00:03.

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#2 siamackz

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Posted 24 May 2018 - 01:04

Nice looking pen!

First, are you very sure that the section does unscrew? Do you see clear signs for that?

If the purpose is just to grease the piston then I would try getting in from the nib side - its safer. If the section isnt giving way, then I would try to simply take out the nib and feed - then use a toothpick with grease on the barrel insides.

I wonder if the threaded part of the piston actually unscrews from the barrel end or not. And if it does then is it friction fit or screwed? A vac tool might help? I have a C ring that can go onto most threads like that and then I use a wrench on the C ring. But the threads are plastic so I would be very careful.

Sorry, I dont have answers, but only questions :) I look forward to learning from your journey.

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#3 praxim

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Posted 24 May 2018 - 01:34

Thank you. I generally agree with you on your points although waiting for any other enlightenment which might be offered before I attack again.

 

Regarding the section not unscrewing, I am pretty confident about that. The brown striped barrel becomes transparent for an ink window, continuing through the cap threads. Looking through that one can see the striped in the section up under the cap threads, where it would nominally screw in. Now, the stripes on the barrel across the threads offer that slight sideways visual distortion one gets when looking at that sort of feature. Looking through the transparent part of the cap threads, the stripes from the section are dead flat, and very close to the surface -- the barrel is thin. So, I conclude from lack of underlying visual distortion and thinness of the barrel that the section is a friction fit and not screwed in. My guess it is glued comes entirely from the heat and force I have applied without success. I am unwilling to go further with that compared with trying the other two avenues we are discussing.

 

If the section proper is glued in, or even a formed part of the barrel despite my impression through a loupe, then there is probably an inner nib assembly which unscrews, like a Pelikan. That is the most promising route for greasing. However, it still leaves the oddity that I am sure the piston knob should turn while the threads remain steady, rather than both turning together, so one way or another I am likely to need to solve that.

 

By the way, the finned feed has a metal breather hole in its front ramp, in case that looks like other pens.


Edited by praxim, 24 May 2018 - 01:36.

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#4 tmenyc

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Posted 24 May 2018 - 15:02

To me, it seems more and more that the knob has to come off.  You're sure there are no retaining pinholes?  Assuming not, since none are visible in the photos, could the knob be counter-threaded, so that a bit of pressure clockwise when the piston is all the way down releases it?  

 

Tim



#5 siamackz

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Posted 24 May 2018 - 16:39

To me, it seems more and more that the knob has to come off.  You're sure there are no retaining pinholes?  Assuming not, since none are visible in the photos, could the knob be counter-threaded, so that a bit of pressure clockwise when the piston is all the way down releases it?  
 
Tim

If this is true then Praxim is in dangerous territory. How much pressure and which direction - when both these variables enter the equation together then it gets rather tricky!

Edited by siamackz, 24 May 2018 - 16:39.

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#6 tmenyc

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Posted 24 May 2018 - 23:06

Oh, agreed...but there are only two ends of the pen, and he's had no success gaining access to the piston from the nib end.  If there isn't a retaining pin and the knob isn't friction fit, it probably screws off.  I'm not advocating that Praxim turn the knob until it breaks, but with a little heat maybe he'll get some info to go on. 

 

 

More conservative, perhaps we can find out more about the pen first.  A post here from 2012, here , by a member named Khufu, who was active here within the past month, says: 

"But the prewar high-end brands as L&C Hardtmuth, Prestige (the most expensive prewar brand) and some Ripets (silver/amber oversized Ripet Hermetic with art-déco snake clip is something i have never seen anywhere else, really) were their own original conceptions/styles. Terrible and outstanding designs! Today extremely expensive pens." 

 

So if that's correct, then this pen was made by Hardtmuth, and further searching might yield an assembly chart.  

 

Tim



#7 praxim

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Posted 24 May 2018 - 23:37

Thank you people, for your continuing interest. I have some progress to report.

 

Just a bit of history. L&C Hardtmuth was an Austrian company which set up later in an area of the then Austro-Hungarian Empire which is now Czechia. So, I think it moot whether it is proper to call them Austrian, Czech, or both. This is before the Hardtmuth brand was subsumed by its own Koh-i-noor label under State control in the 1950s. I have searched images as well as brands on Google without finding a disassembly diagram.

 

I tackled the nib end again. The difficulty at that end is there are no keyways such as you have on a Montblanc so you are twisting the nib and feed. However, to my relief it moved and emerged, just like a Pelikan. From there I could grease the cylinder* successfully yet two problems remain:

  • Still quite stiff.
  • The fact the rear threaded portion moves with the knob, against the plastic walls of the barrel.

Further searching with picking and cleaning revealed definitely no flat part or pin hole. Mindful of the discussion above, I will warm that zone, place thin rubber sheet over the threads, grip them with Loggerhead pliers (love 'em) then try to turn the knob separately.

The outer threads have to unscrew normally, because that is how they are threaded. If the inner knob is supposed to turn within the outer threads (it makes sense) then normal action would also be counter-clockwise to extend the piston. So, plan is: with piston half way down the barrel through unscrewing the threaded portion, loosen knob then use it to withdraw the piston further, unwind the threaded portion further (which extends the piston again), repeat until all is free.

 

Be back in an hour or so to tell you what happened. :thumbup:  :yikes:

 

* by-note: we on FPN constantly refer to pistons but never to cylinders, the obvious adjunct, as being that in which they run. Never mind. :)


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#8 siamackz

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Posted 25 May 2018 - 00:46

Thank you people, for your continuing interest. I have some progress to report.
 
Just a bit of history. L&C Hardtmuth was an Austrian company which set up later in an area of the then Austro-Hungarian Empire which is now Czechia. So, I think it moot whether it is proper to call them Austrian, Czech, or both. This is before the Hardtmuth brand was subsumed by its own Koh-i-noor label under State control in the 1950s. I have searched images as well as brands on Google without finding a disassembly diagram.
 
I tackled the nib end again. The difficulty at that end is there are no keyways such as you have on a Montblanc so you are twisting the nib and feed. However, to my relief it moved and emerged, just like a Pelikan. From there I could grease the cylinder* successfully yet two problems remain:

  • Still quite stiff.
  • The fact the rear threaded portion moves with the knob, against the plastic walls of the barrel.
Further searching with picking and cleaning revealed definitely no flat part or pin hole. Mindful of the discussion above, I will warm that zone, place thin rubber sheet over the threads, grip them with Loggerhead pliers (love 'em) then try to turn the knob separately.
The outer threads have to unscrew normally, because that is how they are threaded. If the inner knob is supposed to turn within the outer threads (it makes sense) then normal action would also be counter-clockwise to extend the piston. So, plan is: with piston half way down the barrel through unscrewing the threaded portion, loosen knob then use it to withdraw the piston further, unwind the threaded portion further (which extends the piston again), repeat until all is free.
 
Be back in an hour or so to tell you what happened. :thumbup:  :yikes:
 
* by-note: we on FPN constantly refer to pistons but never to cylinders, the obvious adjunct, as being that in which they run. Never mind. :)

Its been an hour already :) howd it go?

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#9 praxim

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Posted 25 May 2018 - 01:44



Its been an hour already :) howd it go?

 

:D

 

Duties such as making espresso for morning coffee with one's wife intruded. ;)

 

The process worked, and this is the result so far: 

fpn_1527212128__hardtmuth__291_1_of_1.jp

You can see that the piston itself still sits inside the barrel. That is what resulted. Tugging and pushing encountered plenty of resistance, and it will certainly not come out the front. Given that despite greasing the piston remains extremely stiff to move inside the barrel, I want to complete the disassembly to check the nature of the seal.

 

My next step will be to put parts through the USC, see whether that frees action, then to focus on getting the piston seal out.

 

Incidentally, if I am being painfully slow about doing and describing the exploration it is because this is the first instance of which I am aware (of course, or we would not be in this thread) so I am trying not to destroy the pen while making it useful for the next discoverer of a Hardtmuth Airless.


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#10 praxim

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Posted 25 May 2018 - 01:50

Adding for clarity, yes the piston knob moves inside the threaded part. By the time of the photo I had already greased those parts to try to improve action. Maybe I should have stepped to the USC first. I have tested that the threaded portion can be tightened to the barrel and the piston knob moved as it should without the threaded portion turning as it did before.

 

The threaded nib section looks like it had a little shellac or similar on it. There are only a few threads on it, near the front.

 

Nothing more for hours or even tomorrow. We are flapping off off lunch with friends.


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#11 siamackz

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Posted 25 May 2018 - 03:53

Fantastic, well done, and all the best!

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#12 praxim

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Posted 25 May 2018 - 09:11

Probably all that is remaining for me to say on this.

 

After cleaning, I was still unable to get the piston seal out of the barrel. From the noises it makes I suspect it is intact but dry cork. I have added a couple of thin smears of silicone grease to the cylinder wall, working the piston a few times after each smear. There is nothing else I am willing to risk using at present. I will see how it develops with use.

 

Once it has been apart and cleaned, everything can be done finger-tight, no shellacs or rosins needed, so it becomes an easy pen on which to work. The translucent brown - gold stripe celluloid is very nice, gleaming in real life with more depth, the nib a decent size, fairly hard, smooth, the pen comfortable.

 

fpn_1527239314__hardtmuth__292_1_of_1.jp

Auto-enhancement and early writing make the black look much paler than it appears on paper.

 


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#13 tmenyc

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Posted 27 May 2018 - 23:36

Excellent job, congratulations!

 

Tim



#14 praxim

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Posted 06 June 2018 - 07:06

Re-opening this case. :)

 

I only partially filled the pen, so it soon ran out. I found then that I could no longer move the piston, again. The silicone grease was not enough. This meant I had to get out the piston which you can see still in the barrel in the picture in #9.  It did not want to budge. After some puzzling, I eventually resorted to the method described here, which worked remarkably well. Sure enough, the piston seal comprised two perished O-rings. After removing these, I was able to measure the size as a standard AS568-008 (ID 4.5 mm CS 1.8 mm). Buying unpackaged small O-rings around here is not easy but eventually I tracked down what appears to be the single nearby specialised supplier, who proved to sell them at half the price they were advertised by the major Oz small parts supplier on the internet! And that before postage.

 

The other thing to be noted by the legions of Hardtmuth repairers out there is that their barrel design incorporates an internal groove near the top. A lot of care and a little force are needed to push the siliconed-up O-rings past this because you do not have the grip position to use a twisting action. I used dowel and a small brass hammer with the pen section end resting against a firm rubber surface.

 

If anyone should tackle one of these pens, HTH.

 

edit:clarify


Edited by praxim, 06 June 2018 - 07:07.

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#15 stephanos

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Posted 28 August 2018 - 22:21

Thank you very much for this clear and detailed description.

 

I have a Bohler Original with a very similar-looking back end / piston knob. Now that I have finally found someone who has successfully managed to take this kind of construction apart, I am more confident in applying heat to my Bohler and trying to do the same.



#16 praxim

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Posted 29 August 2018 - 03:14

Some of these older pens can be quite stuck, not helped by use of some form of rubbery rosin by some manufacturers or later people working on them. A Soennecken I took apart recently took several bouts in a USC, of heat, of wetting lubricant, a dash of pen cleaner, 24 hours soaking, yet more USC and heat yet still a fair amount of pressure before it finally released. Patience is definitely a virtue! My preferred way of applying that pressure is to wrap the heated section (or piston retaining ring as the case may be) in rubber grip then use loggerhead pliers over that, with just my other hand holding the barrel close to the join so I can feel how much torque I am applying. So far, no shattered barrels or scrunched ends.

 

Good luck with yours. Do not hesitate to ask for help if you want. There are many professional and amateur repairers here far more experienced than I am.


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