Section mandrel - A safe way to produce sections

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Sri Pens

Member
Joined
Mar 11, 2024
Messages
102
Location
India
I came up with this idea since I could not get a mandrel with an 0.6MM pitch cut on a lathe locally . This would have helped to hold the section internally . Also for bock 6 nib , I was working with an a tap of M7.9x0.6 since I did not have a die . These dies are not available in India and for an import it's any up to 3-4 weeks . This compelled me to device a way to produce sections safely since holding it externally by the section threads broke a few .

My procedure is as follows

1. I cut a blank of 32.7 mm and cut a tenon of 8 MM on which M10x1 is threaded .
2. I then drill a hole of 7.3 Mm through the section.
3. Then I drill a hole of 8.2 for 17.8 MM . This is to accommodate the nib housing portion without the threading .
4. After this i Cut threads of M7.9x0.6 on the 7.3 hole beyond the 17.8 MM distance .
5. Then I load the drilled and tapped section on to the mandrel and turn it comfortably and finish it .
6. As a last step I hold the section thread In a M 10x1 Mandrel and finish the nib side .
7. The entire process did not take more than 15 minutes to finish the section safely without an iota any fear .
 

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Interesting and ingenious idea. Thank you for sharing.

I think all of us turning the section while holding it by the 10mm threads have experienced a few (or more) failures.

Question for you... do you bring a live center in to support the nib end of the section while turning it? I find that makes a big difference.

For me, I find the Bock #6 sections to be even more fragile because the threads are closer to the threaded tenon. See the picture below for comparison between Jowo #6 and Bock #6 and their thread locations within the section. This creates a weak(er) spot right where the nib threads end and section threads begin.

635A0CEF-88E0-403F-9360-618455BE150B_1_105_c.jpeg
 
In the past ( i am just 10 sections young ) , I held the 10 MM threads and used a live centre ( pic 1) . With my new idea , I use a live centre ( pic 2) . The M3 bolt head sits snug in the live centre groove .

Just reverse work the dimensions on the nib housing . I kept a negative 0.5 MM tolerance for the threaded portion not to foul with the mandrel , while the non threaded portion a 0.1 MM for the section to have its support strong .

It will be a pleasure , if few experiences are shared .
 

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