Very good video. I was a surface plate technician for 7 years. I calibrated them with an Optodyne LDDM laser system. We had a fixture made to support the laser and 3 detachable extensions to allow us to calibrate granite from 6x6 to 96x72. I was averaging calibrating 30-40 surface plates a week thanks to this technology. And of course we used the Repeat-O-Meter. I also resurfaced them using a cast iron lap with fine diamond, many as big as 48x72 with holes as deep as .003 , most shops do not treat them properly, as you can imagine. I just thought I would share, the skills behind keeping these surface plates in good shape is hard to find. It's always refreshing to see different takes on the calibration process.
...Treat them properly.......Something like using them for a workbench and hammering new studs into brake discs for cars.....or laying out steel plates and center punching with a 4# sledge......
This makes me wonder, Is a surface plate technician a part in the quality trade career path? I am curious about this work. The fact that you said skills are hard to find and have in use consistently pique my interest as a challenge to master and thrive. who knows if you still use this account, but I am curious to learn more even as a potential learning point. I think it is worth the effort to reply and share. 👍
@@dougankrum3328 oh God no. get a piece of wood. use it. not the surface plate. A previous production manager said that a few guys played bones on a surface plate for some time. had to resurface a bunch of it. I forget the number, but it was a lot of material to remove to get flat. I now know that there are several factors in surface plate acceptability and not just flatness. It is very, very interesting.
When talking about the resurfacing process Craig mentioned it is a "heavy job". The worn spot is a "hole" of course, so the whole rest of the plate has to be brought down it it's level.
that thing with the paper is incorrect. A piece of paper is .004 or 4000 micro inches. tolerances on surface plates can be around .0004" which as you can see is 10 times smaller than a piece of paper. 400 micro inches is .0004"
we are looking at adding phys d to our calibration capabilities, i have been looking at used plates and have seen different colors, is there a standard for hardness and durability..i.e.. the black granite is typically harder then the pink granite?
The flatness is the plane or the means of the surface plate like what he is showing you.The repeatability is like if you were to place a height gauge on the table, zero it, and move it around everywhere on the plate,then you end at where you started at zero, the total tolerance you got would be the repeatability.
8:32 Umm how did you get 28,000,000th of a degree? 60 arc minutes in a degree, 60 arc seconds in 1 arcminute, so 0.1 arcseconds is 1/36,000 of a degree.
@@ghffrsfygdhfjkjiysdz Where I got confused was that he said 0.1 arc-seconds was the resolution which is 28 millionths of a degree, but when he went to the board to do the calculation, he had written 1 arc-sec = 0.00028 which is 280 millionths of a degree. He was right both times. I was afraid with all of his arm waving that he was going to knock the levels over onto the surface plate. I was always worried that would happen to ours, so I would lay them down on the plate when we were in-between measurements. Our lab didn't have a Repeat-O-Meter and I don't remember it being required in the procedure we used. We also didn't have a simple flatness gage for small surface plates. I can see now that we needed both of them..
NOTE: The ONLY reason he levels ("has to level") the plate is because of the design (limitations) of his testing equipment. It is VERY rare that a surface plate method requires a "level" plate. Associate Degree in "Quality Technology", 16+ years in "the business" including 4 yrs. in a NAVLAP accredited cal lab. In practical use, as long as your gages /accessories do not roll around /off, you are good.
Another very good reason to level the surface plate first is so that you don't have to adjust the feet of the differential levels to keep the reading on the scale when you change directions. The most sensitive range is 200 arc-seconds. And, I'm sure they swing better when they're not leaning..
At my company they are training me to be an quality control tech, however I can tel that they already have no idea what they are doing. I was wonder if you have a demonstration on how to test for Warp or if you could sens me a link to where I can learn. My company uses a surface plate and this hand tool with metal slices that are each a different thickness.
The hand tool is most likely a feeler gauge, it's *a* way of testing for flatness vs. a known flat surface or straight edge. I have a Suzuki workshop manual that describes the process for checking the flatness of heads and block mating surfaces as laying a straightedge over them and checking if you can fit a feeler gauge under it anywhere. It all depends on the level of accuracy that's required.
They measure milliarcseconds but you eyeball them 4" at a time? What would happen if the software thought you moved them 4" but you really moved them 3 15/16"?
I suppose you'd have a 1.56% error (0.0625/4x100) for that one spot, but it's hard to stop exactly on each spot. You're only checking the plate every 4 inches anyway. That's why you need to run the Repeat-O-Meter over it. If you look at the Moody graph afterwards and the lines have peaks and valleys in them, you might need to check the plate for foreign objects..
