For some time now I had wanted to make a squareness comparator. You know, the conventional kind with a large radius on the base, which rides on a surface plate and carries an indicator. This was partly my motivation behind lapping in my own cylinder square (I will try to clean up and merge those threads later).
On question bothered me for months: how to check squareness when only one surface is accessible? Most comparators depend on the principle of reversal: test the backside of the part and note the difference to the front. But what if your part is such that you cannot use the reversal technique? What if part geometry only allows testing *one* plane?
I concluded that the only way, is to have a disc-shaped base with the indicator held centrally, and be able to vary its height with no tilt in any direction. My project isn't quite that perfect yet but it's getting there.
Next question was what to use? The only steel pieces I had were way too large. I do have a pair of indicators that mount on the back with a threaded hole. And I have the pistons left over from when I rebuilt my welder -- nice and round already, and just the right radius for my rear-mount indicators! All I had to do was cut off the piston top and flatten it on the plate. drill and tap, and make up a selection of "height rods".
Pics:


On question bothered me for months: how to check squareness when only one surface is accessible? Most comparators depend on the principle of reversal: test the backside of the part and note the difference to the front. But what if your part is such that you cannot use the reversal technique? What if part geometry only allows testing *one* plane?
I concluded that the only way, is to have a disc-shaped base with the indicator held centrally, and be able to vary its height with no tilt in any direction. My project isn't quite that perfect yet but it's getting there.
Next question was what to use? The only steel pieces I had were way too large. I do have a pair of indicators that mount on the back with a threaded hole. And I have the pistons left over from when I rebuilt my welder -- nice and round already, and just the right radius for my rear-mount indicators! All I had to do was cut off the piston top and flatten it on the plate. drill and tap, and make up a selection of "height rods".
Pics:
Comment