Manufacturing process for a new Blickensderfer type wheel 407

How to make a new type wheel for the Blickensderfer; in this case a reproduction 'Small Roman' type wheel catalogue number 407, codename 'Table'.

To start with, take a 3D-model of the type wheel. This 3D-model is designed for 3D printing in PLA material on an FDM printer. The overhang-angles and outer contour are designed for the FDM process with a small nozzle (0.2 mm) and best printed with a fine layer-height of ~0.080 mm. The model does not require any supports.

The 3D model can be downloaded here.

After printing, the wheel needs some finishing to be usable - the top 'stub' that holds the spring-clip is far too weak to withstand any use and the important surfaces will need fine-tuning. The tools needed for this are a round file (small, ~3mm diameter), cyanoacrylate glue, a toothpick and a bit of scrap card.

To strengthen the stub on top, place a drop of cyanoacrylate on the toothpick and bring it to where the stub meets the top-plane. Cyanoacrylate will fill remaining gaps between the deposited filament layers. Use the toothpick to bring the drop all-around the stub, also in the corners of the spring-clip notch. Use the scrap-card to absorb any excess and wipe clean/flat the cyanoacrylate over the top face of the wheel. Then give the part a few hours, say 10, to let the cyanoacrylate set - do not disturb during hardening.

Any stringing or z-seam artefacts on the bearing-surfaces in the central hole can then be made smooth with the round file. The mounting-rod on the typewriter is ~ 3.2 mm diameter, the type wheel should fit on this rod without any friction and ideally without play. Any friction when rotating on the rod will cause the Blickensderfer to 'jam' or cause the typing-head to not come back up completely after a keypress.

Any cyanoacrylate that got into the central hole can also be filed away after setting. In case a hole turns out to be too large, an even application of some cyanoacrylate with the toothpick round the inner-surface can again reduce the diameter a fraction of a mm. A thin application of cyanoacrylate on the inner-surface of the central hole may be good anyways - it gives it a very hard and low-friction surface compared to plain PLA.

In case the square take-up hole is too tight, it can be filed wider. Note that the actual dimension of a printed part can vary slightly per individual 3D printer and also per filament used (and the condition, how well dried etc.) 

The spring-clip that fixes the wheel in-position can be formed from spring-steel wire of 0.020 gauge (approximately 0.5mm diameter). E.g. plain-steel guitar-string of 0.020 gauge is a good source of a practical length of suitable wire.

A few nails driven in a scrap bit of wood serves as a jig to create several clips. As always, taking care with springy wire that has sharp ends. Small pliers help to bend a new clip into shape.

The spring-clip is simply snapped on the stub - and the new type wheel is ready to be used on the Blickensderfer! 

The machine can now be typed on without fear of damaging an original vulcanite type wheel, even with rock-hard platen. An extra backing-sheet is a good idea anyways, also helps with the quality of the impression.

* Note that when actually using a Blickensderfer, it quickly becomes obvious that type wheels get covered in ink - especially the top where the ink-roller is pushed to when the type hits the paper. This makes swapping typefaces without getting ink all over your fingers tricky. Best to use a patch of tissue or waxed-paper to handle a type wheel when putting it on or taking it off the typewriter -and to wrap it in when stored in its wooden box.

* Note that on original vulcanite type wheels, the central tube is brass. It is a brass tube of ~4 mm with a ~3.4 mm (?) hole that is the wheel's bearing/mounting on the machine. This reproduction is all-plastic, but of course a reproduction could be designed to take a brass tube with a machined slot for the holding-clip.

* Note that the alignment of characters is from their position on the type wheel, so should be good. However, any play of the type-wheel on the shaft or with the take-up vane will result in alignment deviations. Also a loose or badly-fitting spring-clip can cause alignment irregularities.

* Note that the FDM printing process is not as high-resolution as a DLP resin-printing process would be, but it is good enough for typing and the material is much stronger and impact-resistant than a resin print. Another benefit is that FDM prints are much easier/cheaper to make - less hassle with unpleasant chemicals and this part should take about 4.6 grammes of PLA. For FDM process, the PLA material is a good one - compared to e.g. ABS or PET it is easier and usually gives a superior surface finish.

* Note that the baselines of the three rows of text do not seem to have an immediately obvious spacing. It is not like e.g. the Mignon that is spaced in tenths of an Inch (i.e. 2/10ths between rows). Comparing test-wheels with the typing from original wheels, the three rows baselines were set at experimentally derived distances from the top-face of the wheel. The current values seemed to work fine, but may not be correct or optimal for all Blickensderfer machines.