Using calipers to achieve consistant in arch in your EMF nib collection.
If you have calipers, you can measure across the nib, perpendicular to the long axis (see diagram). This measurement will allow you to gauge how much you have ground off, and how much further you have to go. Use the knife-like tips of your calipers to get a true measurement of the material remaining between the highest part of the arch and the top of the nib. One leg of the calipers goes over the top of the nib; the other leg is positioned spanning the 2 bottom sides of the nib at the thinnest part of the arches. The measurement won't tell you if you are grinding symmetrically, rather it gives you an average of the 2 arches since you are measuring both simultaneously.
Suggested measuring procedure (and grinding goals) for the Ahab/Konrad EMF mod:
1. Draw the arch on your nib with a marker pen. Measure the depth of the un-ground nib at the place you expect the top of your arch to be.
For my un-ground Noodler's stiff nib, this depth = 0.105" (2.67mm)
Notes: 1) This is the measurement of the depth of a Noodler’s stiff nib. By the time I thought of using calipers, I'd already EMF'ed all my Noodler's Flex nibs, so I don't know what the depth was in an original flex nib. However, holding the stiff and the flex nib together, they appear to be the same size.
2) Since the nib bottom edges are not parallel to the nib top, and since each grind will likely place the top of the arch in a slightly different position relative to the length of the nib, it's impossible to define a universal value for the original depth. Wherever you decide to place the top of your arch is the value you should record.
2. Decide how much metal you wish to leave un-ground at the top of the arch. I originally left about 0.050" (1.27mm) of metal (measured depth). While this increased the flex over the un-ground nib, I decided to re-grind the arch, removing more metal, to get more flex. Measuring my nine already-ground nibs, I found unexpected variation in the arch (0.044-0.052" left). The most flexible nib, and the most pleasant one to use, had a top arch thickness of 0.044".I decided to shoot for a top arch value of 0.045" (1.14mm) in my other nibs. The reground nibs were noticeably more flexible. A little change made a big difference to the good.
3. If you subtract the remaining arch value (found in step 2) from the original thickness, you will know how much metal you removed. Recording this value may help you achieve uniform flex across your pen collection. For my reground nibs, total metal removal was 0.060" (1.52mm). In Pterodactylus' first post, he suggests removing 2.0mm. Possibly the top of my arch is farther from the tip than Pterodactylus' arch, which would account for the difference. Or, maybe I simply have not ground off as much as Pterodactylus - I'll write a while with the 1.52mm nibs, and see if they flex enough for my style of writing.
4. If you modify a stiff nib into a flex nib using the "slot" method I discuss in another thread, be aware that the slot will remove metal too. This means a slotted nib will be more flexible than a Noodler's flex nib even though both might have the same EMF arch.
5. Others have reported flex variation between unmodified Noodler's flex nibs. So, attaining uniform flex across your collection of pens may not be as straight-forward as I implied :-/ However, with the measurement method I suggest here, you will have a baseline to which you can refer when you shoot for consistency.
I also rounded the tip of the triangle, removing about 0.5 mm or so. This was mainly done to reduce stress risers, which can cause cracks in the metal. I think it's important to leave the most of the triangle, though (or "angel wings" as some call them). Removing the wings entirely would make the nib more flexible, but at the cost of increased complexity in adjusting the tines. Leaving the wings also makes the tines more resistant to over-flexing. As we produce nibs with more and more flex, we risk the over-flex problem vintage gold nib users experience (reported by Richard Binder and Nathan Tardif).
It's helpful to have the horizontal gap be zero at the tips (the tips should touch). This allows capillary action to get the ink out to the tip, where it needs to be to start writing. The wings make adjusting the horizontal gap between the tips easy. To close the gap, simply bend tines down; To open the gap, bend the tines up. The wings convert some of the up/down motion into in/out motion. If the tines don't have wings, then adjusting horizontal spacing would require more complex bending and twisting of the tines. I like to keep adjustments mechanically simple :-). Of course, if you end up with "Grand Canyon" or "Inverse Grand Canyon" problems at the tips, then twisting will be required. But for simple horizontal gap adjustment, the wings will make adjustment easier.
Diagram: Where to measure arch with calipers, and my target thickness of top of arch. Also shows triangle grind.
Photo: Calipers measuring the arch.
Edited by Brooks MT, 14 February 2014 - 19:01.