Bruce Griffing
Titanium
- Joined
- Jan 1, 2003
- Location
- Temple, Texas
I recently read a post that made reference to a Planekator - a device for checking the flatness of a flat. The real live device has a calibrated granite straight edge and an indicator that will read 20 millionths of an inch. You can set the planekator up on a flat with its two supports and measure the space between the straightedge and the surface of the flat. By doing this in several orientations, you can build up a map of the surface height. There are some details in the math, in that all of the measurements are relative, but I am not worried about the mathematics of that. Having recently discovered an affordable electronic indicator that reads 50 millionths or 1 micron, I am encouraged to build my own Planekator equivalent.
http://www.shars.com/Online_catalog.htm?sec=126&lang=1033
(indicator on page 23 on this quirky catalog)
I believe that I can do this, but I have two questions. The first is building the bearing surface on the supports for the straight edge. My first idea is to use a hardened rod sitting in a vee way on a part with a scraped flat base and vee way. The straight edge would be supported by two of these parts. I also thought of a knife edge, but thought that that would damage the straight edge. I would be interested in other ideas for the supports. The second question relates to the lapping of the plate to remove high spots. I have done lapping in the past with a variety of abrasives. I assume this is done with diamond paste. But I sure would like to read a good reference on this process. Any thoughts on this would also be helpful.
http://www.shars.com/Online_catalog.htm?sec=126&lang=1033
(indicator on page 23 on this quirky catalog)
I believe that I can do this, but I have two questions. The first is building the bearing surface on the supports for the straight edge. My first idea is to use a hardened rod sitting in a vee way on a part with a scraped flat base and vee way. The straight edge would be supported by two of these parts. I also thought of a knife edge, but thought that that would damage the straight edge. I would be interested in other ideas for the supports. The second question relates to the lapping of the plate to remove high spots. I have done lapping in the past with a variety of abrasives. I assume this is done with diamond paste. But I sure would like to read a good reference on this process. Any thoughts on this would also be helpful.