Several weeks ago, I lost my other TWSBI 580 (technically, the 580 ALR) which meant that I didn’t have any EF nibs left1.

Through the process of sourcing nibs, I learned a lot about the details so:

You can buy “nib units” from TWSBI for around $20. This is the standard replacement part. This includes a (EF|F|M) nib, already fit on a feed (the plastic thing with fins), and the plastic housing that holds the nib and feed together, and that screws into the pen.

The TWSBI replacement unit also comes in a small threaded storage case, which the nib + feed + housing comes threaded into, and the little upper metal grip section between the grip proper and nib on the 580 that fits around the housing. We will come back to this crucial point later.

It turns out that the TWSBI is one of the many companies that makes the pen, but not the nibs– the TWSBI 580 uses the Jowo #5 nib + feed + housing. That is, the 580 uses stock Jowo #5 nibs with the Jowo #5 compatible feeds and housings, and the pen body is threaded to fit a Jowo #5 nib/feed housing.

So you can use any replacement Jowo #5 nib, but the reason I don’t say that the 580 uses the stock Jowo #5 housings is that the TWSBI housings actually have small grooves that align with the upper metal grip section.

I had gotten a Jowo #5 nib + feed + housing from Franklin-Christoph to make sure that the TWSBI replacement unit is just the same thing, but the Franklin-Christoph housing doesn’t have the grooves.

So when you try to screw the nib unit into the pen, the upper grip section rotates by itself and you can’t completely screw the nib in.

This means that while eg you can take the nib off the Franklin-Christoph nib unit and fit it onto an existing TWSBI feed + housing, you can’t directly use the Franklin-Christoph nib unit in the 580.

I think aside from the small grooves, the nib units are otherwise identical, so you could swap just the feeds between the housings but this is probably unnecessary.

Unfortunately I forget where I saw this advice while I saw looking into all this last month, but the man in the youtube video suggested to always keep feeds and housings, since those are more often going to be specific to the pen. Unless the feed itself somehow breaks, you can always mate it with a new nib if you damage the old one, which is more standard.

Actually I might’ve misremembered the reason he gave, but definitely always keep old feeds around.

  1. TWSBI F nibs are more like a M, so you need a EF if you want a F. ↩