I am trying to find out what this vintage woodworkng tool is called. It holds a small file. It seems to be cast iron. It does have screws to open & change files. Any ideas? PAT. Jan. ? 1891 No makers marks.
You have there what's called a saw jointer. The one below is very similar. The site linked as the source says it's similar to a Stearn's model, so that might be what you have.
These are used to joint (flatten) the teeth of a hand saw to one level. After jointing, one would then sharpen each individual tooth such that the points are now at the same level as just jointed.
I'd say that it's a cross-cut saw sharpening tool.