Difficult Plunger Pins In Onoto 6233

[praxim]

I am progressing with repair of an Onoto 6233 which arrived solid with ink, with a fossilised cup washer, and the rod broken at the blind cap.

 

My last tasks in disassembly are to remove the pins in the plunger and in the blind cap. Trying to punch them out has proven difficult. I was using a dowel with a short length of stiff 0.8 mm wire embedded in its end, and light taps with a small hammer.

 

Before I get a bigger hammer, I was wondering whether I might not be better off simply drilling them out, using a drill press?

 

I have not tried heat at this point, being a little doubtful of how useful it would be. I could also try the USC as a loosener except the blind cap is BHR which I do not want to immerse too long in water.

 

Of course, I could simply re-use the existing rod by gluing its end into the cap (thus not having to disassemble that part) but the pen would then become difficult to disassemble again without worsening problems. The purist in me does not like that but the practical in me wants a working pen.

 

So, at the moment I am leaning toward drilling out, as I will have new pins anyway. Any thoughts or suggestions on that, or effective things to try which do not require quite the same precision?

[northlodge]

I would agree that gluing the piston rod is not the way to go; a short term solution that will be regretted further down the road.

 

Assuming you have identified the securing rod (and occasionally that is difficult) then a little heat will help in its removal. So long as someone has not gone before you with a tube of glue, then heat will normally make the difference. Occasionally I have come across a rod that had been broken and was then glued in from both ends (??? ). As far as I can see the only choice here was to drill it out.

[fountainbel]

Drilling the dowel pin out will be very difficult

Both the dowel pin and the part it holds are made from hard rubber, and chances are high you will end with an enlarged and/or bad aligned bore.

Drilling out would be no problem If the dowel pin would be much softer compared to the material of the part it secures

Drilling out a dowel made from brass or steel looks completely impossible to me, the drill will wander away and search for the "easy way through"and migrate drilling to the hard rubber.

I use a little V block to clamp the part in , so the part can at least not rotate when i knock the dowel pin through.

Makes it much easier to align the tool pin .

Just my 2 euro cents….

Francis

[praxim]

Thank you. I will have another try with the aid of heat.

 

I am not too worried about the drill wandering. It won't be my hands holding it but a machine, and I can drill down to 0.3 mm (probably 0.8 mm for this). However, increasing (by offset) the hole would happen on the slightest mis-alignment so that is definitely something holding me back from that approach.

[fountainbel]

Thank you. I will have another try with the aid of heat.

 

I am not too worried about the drill wandering. It won't be my hands holding it but a machine, and I can drill down to 0.3 mm (probably 0.8 mm for this). However, increasing (by offset) the hole would happen on the slightest mis-alignment so that is definitely something holding me back from that approach.

"Wandering" is perhaps not the right expression .

I wanted to say risks are high the drill will slightly bend-off during the drilling operation when the drill is not exactly centered on the brass pin, i.e, the drill will always search for" the less resistant way to go through"

[pieemme]

Thank you. I will have another try with the aid of heat.

 

I am not too worried about the drill wandering. It won't be my hands holding it but a machine, and I can drill down to 0.3 mm (probably 0.8 mm for this). However, increasing (by offset) the hole would happen on the slightest mis-alignment so that is definitely something holding me back from that approach.

Hello praxim, I had a hard time repairing my 6233. I made my mistakes, especially with the plunger assembly. I've come to realise that the cup washers supplied by Roger Wolfe, customspareparts.co.uk are too soft and get easily unseated. However, concerning the removal and replacement of the fixing pin, I've found a satisfactory DIY solution. I use small carbon fiber rods, which can be found as kite spare parts (had bought them at Decathlon). I insert these rods in my drill as a bit and sandpaper them to size.

[northlodge]

Hello praxim, I had a hard time repairing my 6233. I made my mistakes, especially with the plunger assembly. I've come to realise that the cup washers supplied by Roger Wolfe, customspareparts.co.uk are too soft and get easily unseated. However, concerning the removal and replacement of the fixing pin, I've found a satisfactory DIY soluti)on. I use small carbon fiber rods, which can be found as kite spare parts (had bought them at Decathlon. I insert these rods in my drill as a bit and sandpaper them to size.

 

I've come to realise that the cup washers supplied by Roger Wolfe, customspareparts.co.uk are too soft and get easily unseated

 

Not my experience, and I have used a number over the past 4 - 5 years.

I use small carbon fiber rods, which can be found as kite spare parts (had bought them at Decathlon

 

useful tip, thank you.

[praxim]

Thanks for the idea, pieemmee. I had better bring things up to date. I decided that my biggest problem was holding the pen, not wanting to clamp its non-cylindrical shape and not having a V-block to hold it at the right angle. While coming up with that I switched to making the MB tool then everything was packed in boxes for the house sale and move, where it stays until we unpack in the new one late this year. By then it will be well over a year just to knock one pin out, so to speak.

 

Gives me time to pick up some carbon rod at my leisure though.

[Custom Pen Parts]

I think your experience of unseating the cup washer i wholly down to the bore in the barrel not being clean. If the surface is sticky at all, then as the washer progresses along it will tend to drag which will try to invert the cup and in extreme circumstances drag the washer from its mount.

The softness of the rubber is designed to compress against the bore as pressure increases due to the vacuum which in turn gives a progessively tighter fit needed to withstand filling forces.

Hope this helps

[pieemme]

Yes, I think it makes sense. I applied the silicon grease too generously and am wondering if silicon oil rather than silicon grease should be recoomendable. At any rate, I've ordered 5 additional cup washers for my further testing, in spite of their jewellery prices:-)