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Mb149 Piston Spindle Replacement


viju

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Hi stoen,

Thanks for your reaction and rightful remark!

I will surely investigate in how far my tool can also be used to pull the cup bushing which holds the spindle on pens dating from the seventies.

Could imply some light changes on the tool,  but I expect it will work...

Francis 

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14 hours ago, fountainbel said:

I will surely investigate in how far my tool can also be used to pull the cup bushing which holds the spindle on pens dating from the seventies.

Hello, Everybody,

 

Thanks for your remark @fountainbel. This also applies to 60s resin MB149.

 

Please, observe that my comment was about knobs which have less than 8mm of broken spindle!

 

AFAICT, the brass cup bushing is either heat set or perhaps even glued in place and there is one tiny but sharp step to overcome. The drawings are not correct, as this step is not exactly where indicated, but ca 1mm lower. Once this step is overcome as described earlier, it can be pulled out by a metric machine screw, which screws through the bushing being turned clockwise, and by reaching the bottom by gradually applies pressure to the bottom of the blind cap by continuingly being turned, thus pulling the bushing out.

Only three things must be taken care of:

 

- that the bottom of the screw is filed and polished flat, with no sharp edges which could damage the plastic bottom of the cap.

 

-that the spindle debris is taken out before introducing the screw.

 

- that the pulling process damages neither the brass bushing nor the knob, so it can get functionally re-installed upon replacing the spindle.

 

I’ll post the drawing in a separate post.

Hope this can help.

Thanks for reading.

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Hi all,

And the story of the extractor tool continuous...

I've had a rightful remark that the “C” Ring was only used on the later "precious resin” MB pens.

On the earlier ones the lead spindle was secured with press fitted "cup ring', which is even more difficult to remove!

The extraction tool I've presented earlier works well to extract the “C” ring, but even then it looks somewhat borderline  in the end.... 

The pulling stroke needed to get the “C” ring out of its seat groove is 1.3mm

The radial engagement notch on the top of the lead spindle, mating with the notch inside the top of the filling knob being also 1,3mm, I’ve experienced the lead spindle occasionally starts to rotate before the “C” ring jumps out of its seat groove.

This occurs when the radial notches just start slipping over each other, resulting in the fact the partly extracted “C” ring occasionally jumps back in its seat groove…….

I’ve also evaluated the difference in removing the lead spindel by torsion or purely by axial pulling.

This learned me purely pulling extraction creates much less spindle breakage risks compared to applying torsion.

Given the rightful suggestion to create a tool which can be used as well for the “C” ring and the “Cup ring”, and my experience that purely pulling is beneficial, I went back to the drawing board and designed a combined tool allowing both “C” ring and  “cup ring extraction.

Extracting the “cup ring” out of its seat requires however a pulling stroke of 4.5mm, so the lead spindle would start to rotate after 1.2mm, as soon as the radial  engagement of both radial notches is gone…..

After unsuccessfully trying different alternatives avoiding the spindle to rotate during extraction,  I finally decided to make and  install a threaded "left hand" brass “ 5BA die” on the top of  the pulling shaft.

The female threads can be screwed -anti clockwise!- over the broken lead spindle and provide a secure axial fixation.

This tool is however  not as simple as the earlier presented version, but it works like a charm for both versions !

Took me 4 days, but I’m very happy.

Complementary benefit is that even short broken lead spindles  - having a remaining thread length of 5- even 4 mm - can be extracted.

On “C” ring equipped pens were the remaining  spindle thread length is below 4 mm the only alternative is trying to pull it out with a hook tool after drilling a 2.5mm hole  through the remaining  spindle part  inside the knob so one can get underneath  the "C" ring 

On “Cup ring” equipped pens one can also drill a 2.5 mm  through the remaining  spindle part  inside the knob so one can get underneath the cup ring to pull it out .

Note however the thickness of the cup base is only 0.3 mm, so pulling asymmetrical  with a hook one can easily damage the cup base!

In both situations this works when the spindle threads are broken at the end of the threads, however if the remaining spindle part is longer this is not an easy task !

Another alternative  is drilling cap a 1.0-1.5mm central bore through the cap top and knock the spindle and “cup ring" through … A black plug can be installed afterwards.

On the attached pictures you can see the tool used for pulling  the “C”ring and the “Cup ring” out, on a broken spindle which has only 4.5mm thread left....

Note the tool uses an eccentric cam which backs-up against the base ring  which  is screwed in the filling knob, resulting in a purely axial pulling movement.

Note I strongly recommend to install the superior "Peek" lead spindle  made by Custom pen parts in the UK. ( no affiliation just a very happy user !)

As always your comments, critique  and thoughts are most welcome !

Francis

IMG_2509(1).JPG?width=1920&height=1080&f

IMG_2510.JPG?width=1920&height=1080&fit=

IMG_2511.JPG?width=1920&height=1080&fit=

IMG_2512.JPG?width=1920&height=1080&fit=IMG_2513.JPG?width=1920&height=1080&fit=

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Hello, @fountainbel,

Hello, Everybody,

 

I am impressed at your engineering efforts in devising a universal tool for extracting c-ring and cup from MB mechanisms.

Congratulations for allowing for an even shorter part of the spindle to be good enough in making the tool work.

 

Will it ever become commercially available, or at least available for the forum members?

 

Last but not least, I still have a problem with drilling holes in the knob and knocking out the cup ring. I’m sure that a still more elegant solution could exist.

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Excellent example of evolution theorie, the need makes creative and the added cam makes it easy and powerful !

Even I was not aware about the cup ring back-up, only new C so far...

Though this is no longer a selfmade tool for majority, will it be available, I'm interested !

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Thanks for your reactions PENrob & Stoen !

And Stoen, I strongly doubt any other alternative to get the "cup ring" out can be found...

Best,

Francis

 

 

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On 10/2/2021 at 9:05 PM, fountainbel said:

I strongly doubt any other alternative to get the "cup ring" out can be found...

Thanks for your remark, @fountainbel.

I already have an alternative method I’ve described, which isn’t elegant, isn’t 100% fail-safe and wouldn’t therefore recommend it to others.

On the other hand, what’s your point in saying that your unavailable prototype tool is the only such tool available?

Please, make it available, than it would make sense.

 

Best regards!

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6 hours ago, stoen said:

Thanks for your remark, @fountainbel.

I already have an alternative method I’ve described, which isn’t elegant, isn’t 100% fail-safe and wouldn’t therefore recommend it to others.

On the other hand, what’s your point in saying that your unavailable prototype tool is the only such tool available?

Please, make it available, than it would make sense.

 

Best regards!

Sorry Stoen, I did not want to suggest my tool is the only option!

However the tool can directly extract both "C"ring & "Cup" ring equipped knobs - no need to for any delicate preliminary work .

Drilling the remaining threads out to get under the "C" or "Cup" ring is easy when the spindle was sheared in the diameter transition between lead spindle threads and the spindle head.

However - according my experiences -  95%of the spindles are sheared leaving 4 to 8 mm of the threads inside the filling knob.

Given the broken spindle sits radially un-centered, drilling this part away looks very delicate to me.

Not aware an alternative tool already exists... 

I'll evaluate the possibilities to get the tool available

Best,

Francis

 

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16 hours ago, fountainbel said:

I'll evaluate the possibilities to get the tool available

Good success in evaluating both: getting the tool available as well as the functionality of the prototype itself. 

🙂

Please keep us posted.

Thanks in advance!

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On 9/30/2021 at 10:33 AM, fountainbel said:

 

Hi all,

And the story of the extractor tool continuous...

I've had a rightful remark that the “C” Ring was only used on the later "precious resin” MB pens.

On the earlier ones the lead spindle was secured with press fitted "cup ring', which is even more difficult to remove!

The extraction tool I've presented earlier works well to extract the “C” ring, but even then it looks somewhat borderline  in the end.... 

The pulling stroke needed to get the “C” ring out of its seat groove is 1.3mm

The radial engagement notch on the top of the lead spindle, mating with the notch inside the top of the filling knob being also 1,3mm, I’ve experienced the lead spindle occasionally starts to rotate before the “C” ring jumps out of its seat groove.

This occurs when the radial notches just start slipping over each other, resulting in the fact the partly extracted “C” ring occasionally jumps back in its seat groove…….

I’ve also evaluated the difference in removing the lead spindel by torsion or purely by axial pulling.

This learned me purely pulling extraction creates much less spindle breakage risks compared to applying torsion.

Given the rightful suggestion to create a tool which can be used as well for the “C” ring and the “Cup ring”, and my experience that purely pulling is beneficial, I went back to the drawing board and designed a combined tool allowing both “C” ring and  “cup ring extraction.

Extracting the “cup ring” out of its seat requires however a pulling stroke of 4.5mm, so the lead spindle would start to rotate after 1.2mm, as soon as the radial  engagement of both radial notches is gone…..

After unsuccessfully trying different alternatives avoiding the spindle to rotate during extraction,  I finally decided to make and  install a threaded "left hand" brass “ 5BA die” on the top of  the pulling shaft.

The female threads can be screwed -anti clockwise!- over the broken lead spindle and provide a secure axial fixation.

This tool is however  not as simple as the earlier presented version, but it works like a charm for both versions !

Took me 4 days, but I’m very happy.

Complementary benefit is that even short broken lead spindles  - having a remaining thread length of 5- even 4 mm - can be extracted.

On “C” ring equipped pens were the remaining  spindle thread length is below 4 mm the only alternative is trying to pull it out with a hook tool after drilling a 2.5mm hole  through the remaining  spindle part  inside the knob so one can get underneath  the "C" ring 

On “Cup ring” equipped pens one can also drill a 2.5 mm  through the remaining  spindle part  inside the knob so one can get underneath the cup ring to pull it out .

Note however the thickness of the cup base is only 0.3 mm, so pulling asymmetrical  with a hook one can easily damage the cup base!

In both situations this works when the spindle threads are broken at the end of the threads, however if the remaining spindle part is longer this is not an easy task !

Another alternative  is drilling cap a 1.0-1.5mm central bore through the cap top and knock the spindle and “cup ring" through … A black plug can be installed afterwards.

On the attached pictures you can see the tool used for pulling  the “C”ring and the “Cup ring” out, on a broken spindle which has only 4.5mm thread left....

Note the tool uses an eccentric cam which backs-up against the base ring  which  is screwed in the filling knob, resulting in a purely axial pulling movement.

Note I strongly recommend to install the superior "Peek" lead spindle  made by Custom pen parts in the UK. ( no affiliation just a very happy user !)

As always your comments, critique  and thoughts are most welcome !

Francis

IMG_2509(1).JPG?width=1920&height=1080&f

IMG_2510.JPG?width=1920&height=1080&fit=

IMG_2511.JPG?width=1920&height=1080&fit=

IMG_2512.JPG?width=1920&height=1080&fit=IMG_2513.JPG?width=1920&height=1080&fit=

QUIck fix if the helix threads are too long you could do a through hole design on the tool too allow any length to work??

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1 hour ago, GWT1 said:

QUIck fix if the helix threads are too long you could do a through hole design on the tool too allow any length to work??

Practical experience learned me the thread spindles shear-off at a remaining length of 5-8 mm

However the extraction shaft being completely drilled through, any length should work...

Best,

Francis

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Hello,

 

Aside from the topic about which spindle rest length satisfies for an elegant tool application, I’ll give a quick report on ring extraction itself.

 

Hope it can be useful when the spindle restbis too short. 

 

The “C ring” extraction is fairly straightforward, simple, non-destructive and safe, providing such a “dentist tool” as shown in the picture above.

 

The “cup ring” extraction, on the contrary makes quite a challenge, with the success rate of ca. 90%, using a method of hand drilling through the spindle rest, applying some gentle heat, ultrasound cleaning, a “dentist tool” and the improvised tool as shown in the picture below. The process is tricky and requiring much patience. 

 

Devising a more elegant tool, whoch wouldn’t depend on how many mm of spindle is left would be much appreciated.

🙂

8044F384-8915-4922-A610-2E29BCE19581.jpeg.8589007fbe44a8a5377a9db4f8190c1c.jpeg

 

 

 

 

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Hello, again!

 

Here’s my 3€ improvised tool for extracting the cup ring, when the spindle is broken at the very end, thus leaving less than 3mm stretching out.

 

First the 1mm hole has to be drilled in the center of the rest of the spindle, then gradually widened to 1.5, 2, 2.5 and 3 mm. Then a 4mm thread tap is used to prepare the hole in the cup ring. I do this all by hand to have full controll. A dentist tool helps removing the scrap debris.

 

Finally, using some gentle heat, the “tool” is applied. Once the screw is firmly in the “cup ring”, the counter-nut and washer tightening action provide the pure axial movement which eventually pulls the cup ring out. The washer distributes the axial pressure to the knob rim evenly.

5051A5F2-E4FF-4E74-9225-A1FFE629A7C0.jpeg.661bf08721f65fa375d7582842275165.jpeg

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