Does anybody have some old timer stories about how to grind and dress the tips of spring ID or OD calipers? Was there ever and sort of standard for this? The quality of newly made ones seems really, really poor.
Does anybody have some old timer stories about how to grind and dress the tips of spring ID or OD calipers? Was there ever and sort of standard for this? The quality of newly made ones seems really, really poor.
------------------------
A belt sander with the platen carefully squared to the table does a nice job of squaring hardened steel. You can lightly close the tips on sandpaper to cut them parallel. Like grinding HSS lathe bits it requires some user skill and practice. I've learned to grind broken taps and screwdrivers to a conical or pyramidal point, which is useful to salvage them into scribes, drifts and reamers. The shape of the tip, pointed or flattened, gives immediate feedback to how symmetrical it is.
It's said that Henry Royce could file a brass hubcap into a perfect octagon by eye. Rolls was the businessman, Royce the engineer.
I practiced holding partly ground lathe bits and other tools against the motor housing to develop the skill of keeping them steady in position and grinding the entire surface all at once. When I took a night class in machine shop the instructor was annoyed that my practice lathe bit looked better than his.
Checked some old texts in my stash and didn't find anything on that specific subject...
From this old Machinery's Reference book it seems like it wasn't uncommon to bend them into different shapes and dress the tips to fit a certain job🤷
Checked some old texts in my stash and didn't find anything on that specific subject...
From this old Machinery's Reference book it seems like it wasn't uncommon to bend them into different shapes and dress the tips to fit a certain job🤷
---------------------
I have one that a previous owner reground from possibly inside to a conical point and a rounded sharp edge for scribing circles.
For the flat style, do you just leave the tips completely parallel like wire nippers, or round the edges a bit? The ones I was using were of the round type, with round tips, never had and issues. Now that I have access to larger lathe, I can use the larger ones made from flat stock, and they feel terrible.
Nice.
For the flat style, do you just leave the tips completely parallel like wire nippers, or round the edges a bit? The ones I was using were of the round type, with round tips, never had and issues. Now that I have access to larger lathe, I can use the larger ones made from flat stock, and they feel terrible.
--------------------------
I should have mentioned that sanding the contact surfaces parallel refers only to outside calipers, and tweezers for fine work such as handling tiny surface mount components.
My 8" Starrett dividers which are flat stock and apparently unmodified have the tips ground conical at an angle that lets the tips touch. For scribing circles I prefer the modified dividers with one point conical and the other flattened like a duck bill, so it has the longer curved edge of an Ulu knife.
PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.