Doric Plunger Seals

April 28, 2016

Hi Gang,

Does anyone have a source for original size, Doric plunger seals with the 3 micro holes?

In looking into this there appears to be 2 sizes of original Doric seal.

0.320" (~8.13mm) lady/junior sized pens

0.365" (~9.27mm) standard and senior sized pens

The reason I ask, is that I've been playing around with this for some time and I haven't been able to find a solution that will reliably work.

Using the Shaeffer sized large seals that are widely available, and after sanding them down to the right size (~9.3mm), I've found that these washers are not reliable in that they don't always generate the required vacuum. My thinking is that:

They're too thin and so usually distort as the initial vacuum is generated which releases the vacuum and the pen doesn't fill
The hole in the centre is too large and so it's possible that is where the vacuum is lost.

It frustrating as every time it looks like I've got one working and use it to fill my pen, it lets me down on the next fill.

I've also gone down the totally customised path with a thicker sheet of rubber. That certainly solves the generating of vacuum problem, but when I try and flush the pen, the thicker seal doesn't let the ink/water past on the up stroke and so ink/water is forced past the barrel seal.

I've come to the conclusion that the only reliable solution is the original size, 3 hole seal that was originally developed by Wahl Eversharp.

So, does anyone know of a source that can supply these little gems, or perhaps an alternative solution?

Cheers,

Noel

Melbourne, Australia

May 10, 2016

...bump......anyone?

Cheers,

Noel

May 11, 2016

Try Syd.

May 24, 2016

Hi Gang,

I came to the conclusion that nobody makes factory original replacement Doric 0.365" plunger seals, like they do for Shaeffer vac fill pens.

So, I ponied up for a sheet of Nitrile rubber.

and an Ez Tools 3/8" circle punch

I used a pair a callipers and measured the tiny post that the washer sits on to be ~2.5mm

It's very unlikely to be metric so it's probably meant to be either 3/32 (2.38mm) or 7/64 (2.77mm)

Using a Dremel I ran a 2.5mm hole through the centre and, 3x 1mm holes around the centre hole.

Here's an early draft copy (left) that didn't turn out so well, next to an original seal that's now cracked, very brittle and shrunken (right).

Using higher magnification glasses I was able to make a couple of better versions that are now in my pens.

In my standard size Doric I'm measuring the fill at ~2 grams and the Senior size pen at ~2.5 grams of ink.

Those fill level aren't perfect, but probably say more about the barrel seal than the plunger seal.

Time will tell, but they're now both repeatedly filling well, and ink isn't being forced past the barrel seal when flushing.

So, what have I learned?

The EZ Tools circle punch is a gem! The rubber doesn't easily fit in the punch but if you stretch the sheet you can convince it to go in.

That's actually good news as if there was play in there the rubber would distort and the seal would come out slightly oval in shape.

The resulting washer came out somewhere around 0.375" (~9.5mm), the original washer should be 0.365" (~9.3mm).

I didn't sand it down further as I'm ok with a seal that's 0.01" (~0.25mm) oversize.

The peripheral holes are too small. I don't think that it makes a huge amount of difference when flushing but if were to do it again I'd try 1.5mm.

A standard drill is no good as it's too slow. For these sizes and the flexibility of the rubber, a standard drill doesn't make a round hole.

Instead it sort of forces it's way through and makes a kind of pinhole, mush instead of a clean hole.

That said, don't go too fast with the Dremel. I cranked it to over 20k rpm and had the seals literally smoking.

Under 20k seamed about right.

Anyway, if you're up for it give it go, but remember with respect to the Nitrile sheet and the punch, this is a sample size of 1 and so your mileage may vary.

Cheers,

Noel

May 29, 2016

Nice work. Yes we all make our own seals and gaskets as none are ready made as far as I know. The thickness and pliability of the rubber sheet is important too. Looks like you lucked out. The EZ tool looks to have performed well enough. I use spent .380 bullet casings. The inner diameter is just right. The smaller dorics however require yet another size. The ink shutoff gaskets are a lot smaller but a 22-250 spent bullet casing does that job well. Bullet calibers vary in size as you go up in bullet size by very small increments and this shells that hold the bullets run a nice game of sized for gasket work. Also the little vent holes on the factory gaskets were a nice touch to relieve pressure on the out stroke when the pen has ink in it, but the supple rubbers today work fine without the holes.

Syd

May 30, 2016

Thanks Syd. Spent bullet casings is a GREAT idea! .....and if you leave the primer in you have an easy way to get the seal out.... :-)

Anyway, I couldn't help myself and had another round of making seals. Under the loupe, the EZ Tool leaves the circumference edge of the seal slightly scalloped, so I ran it over some 1200 grit wet & dry paper with the Dremel and that squared it right up. I now get around 2.7g of ink in the Senior, which is just great!

Also, even with modern rubber I think the vent holes are worthwhile as they significantly reduce ink blow by when flushing in my pens (which probably need new barrel seals).

Cheers

Noel

PS I'm sure you get this all the time, but your Decoband Collection is just gorgeous!

PPS I'm sure you also get this all the time, but is an oversize Doric on your drawing board?....

Edited May 30, 2016 by DuckMcF

May 30, 2016

I would recommend punching rather than drilling the holes, both the center hole and the surrounding vent holes. For the vent holes, you can use stainless steel hypodermic tubing.

May 30, 2016

Thanks David. I (eventually) came to the same conclusion. Under the loupe, the edges of the drilled holes look quite ragged which probably leads to a level of vacuum leak for the 1mm vent holes.

Also, thanks very much for your suggestion to use stainless steel hypodermic tubing for the vent holes. That's a great idea!

Cheers,

Noel