Focusing ground glass.

[landstrykere]

so I bought a Toyo Field Special, the 60's/70's one primarily for half-plate japanese holders. The back lacks the focusing glas:



on this one tolerance around the edges is tight, like 1,5mm. After the black metal strip holders left and right are removed, measurement:



I cut a piece of thick paper as exactly as possible, to fit inside. This is my template: 12x16,5cm



buy at a cheap store the cheapest picture frame, 15x20cm. (check it has a glass not acrylic). And I grab the glass cutter:



strip the frame, keep the glass, position the paper template with tape. There will be two cuts.



check the margin between the blade of the cutter and the outer edge of its holder. Btw i prefer this kind of cutters because the large flat shape of the blade holder. Easy to slide against a guide when cutting:



I position whatever thick enough straight length along the edge of the paper template, as per the measured margin. Use tape to secure it. Check it's ok all the length:





a dip of the cutter in white spirit/terebenthine/terpentine/etc for lubrication is not vital but good:



first cut, and because this is thin glass sheet (~1,5mm) I sandwich it and hold to avoid irregular uneven pressures that could cause break. Put something under the glass to have it a bit lifted, and the cut line aligned by the edge. Grab a piece of wood or MDF or whatever to distribute the push lengthwise, and give a clean straight push with the hand.



I have reached the 10 pictures by comment, so follow on next one.