ChevyEFI.
The broaches are used primarily to create a bearing hole in brass, so that the slow moving shafts get a low friction surface. The drilled hole is broached first from one side so that the shaft can enter abt halfway thru. Turn part over and broach from other side so that shaft just slides thru. Play is around 0,005 mm when correctly done. The shaft is lubed with "hoof oil" , and only a very small fraction of a drop is enough for many years.
The broaches are great for other purposes too, and can be used in normal steel also at a thickness up to 1,5 mm. They are perfect for adjusting a worn out( elliptical) hole in a watch part. The design makes them self center so that the origo of the widened hole remains, which is quite astonishing.
One non-watch task at which they excel is to ream up holes in a thru-plated PCB. When replacing components, it is quite common that the new part has a larger dia pin. Drilling up say 0,1 mm *****. With a broach like this it is easy and the risk to damage the thru-plated hole is zero!
The design of the broaches is intricate. They are made of spring steel that is polished after grinding. The penta-shape is asymmetrical, each ridge is a few degrees off of 72 degrees. This helps the broach to make a very round hole.
They are made in Switzerland and the label in the box is in French, German and English.
As to eyesight, a pair of dentists glasses ( with built in "microscope" ) that has an astonishing depth of field and perfect three-D view would be perfect. However , they start at US$ 3k, so I guess I wait until I stumble over a brown envelope somewhere.
Ola
