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Voyage of Discovery

A while ago I saw a post on a local Facebook page saying

Help wanted from any local knitting group. One of the ladies in our sight loss club with sight loss is in need of help to carry on with her knitting. She had a gauge with Braille capability that enabled her to identify the size of the needles but unfortunately it broke and she has not been able to find a source of getting a replacement. She’s tried RNIB & Sight Cymru to no avail. If by any chance anyone has a spare/ unwanted one she would be happy to pay for it. Or if anyone could suggest where she may be able to get one she would be most grateful.”

I suggested that I could help if they could not find anyone else, not because I knew exactly what to do, but because I had a rough idea. Nobody had a solution, so I started experimenting. First solution was based on an idea (copied) that using lumps you could count might work (first lump =1mm, 2nd lump = 2 mm etc), so I drew up this in Inkscape (left hand side is 1mm increments and right hand side is 1.5mm, 2.5mm, 3.5mm etc)

 I cut it out on a laser cutter using RDWorks. (My first design on Inkscape, my first use of RDWorks and my first lasercut). First cut was done on cardboard and then followed by one in 3mm plywood.

I didn’t have the power quite high enough on the cardboard version, thats why its not cut through all holes. The wood one worked fine except I hadn’t learnt about ‘kerf”. ‘Kerf’ is the bit of material you loose when you cut something e.g. if you cut a 20cm piece of wood in the middle with a saw that is 1mm thick, you will end up with one piece of wood 10cm long and another piece 9.9cm long (and 1mm worth of sawdust). Back to the needle gauge, all my holes were the wrong size because I hadn’t allowed for the (approx) 0.1mm you loose because of the thickness of the laser beam. Anyway, lesson learnt and drawings amended to fix this error. I changed the design to that there were slots for the needles rather than holes as I thought it would be easier for a blind person to slide a needle into a slot rather than find a small hole.

Next issue was to try and make Braille numbers. Standard UK Braille is quite precise in terms of dimensions, so I sketched up accurate numbers 0 to 9 in Inkscape

Plan was to etch away the surface of the gauge to create the raised Braille letters. I tried various speeds and power on the laser to get the desired height of the Braille bumps. This worked on a small scale so I tried it on a full size version. The version on plywood looked OK, but the wood warped, either because of the heat from the laser cutting away the surface or because of tension within the plywood after 20% of it was removed.

My intention was to make the final version in acrylic (more dimensionably stable that wood) so I tried that next. Small scale experiments were promising, (two passes at 150mm/s and 25% power, one in x direction and one in y direction) but again I think the heat from etching away so much material left behind a less than perfect finish.

My final solution was to etch small holes where the Braille dots were to be and then glue in small (1.5mm diameter) ball bearings (from a nail art supplier !). This is how it is sometimes done commercially for Braille signs

Superglue is not ideal as any overspill slightly marks the acrylic. Contact adhesive was a bit too stringy and I ended up using epoxy glue. Below is the finished gauge. Not perfect, but should do the job and I need to find a new project

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