Well I've gathered stuff to practice scraping.

Before doing any scraping, get one of the guys check your "free" surface plate against theirs. If you don't, you could be chasing your tail on tyring to get something flat or even determining if something is flat. Both these guys would be a great mentor for you! Ken

I need all the help I can get with learning! :)
 
Honestly I might be embarrassed to allow anyone to see this granite block. I have no idea where it's been other than it was found being a door stop at a house where I guy used to make knives. He was no longer around to explain... There are no identifying marks on it..it's a black granite? If it got close to other nicer plates it might upset them. :)

Have you got anything you know to be relatively flat of some considerable size? If you do, put a thin skim of that Prussian blue on it and gently float it over that surface plate. Hardly NIST stuff, but under a strong backlight it will suggest what you're dealing with.
 
Honestly I might be embarrassed to allow anyone to see this granite block. I have no idea where it's been other than it was found being a door stop at a house where I guy used to make knives. He was no longer around to explain... There are no identifying marks on it..it's a black granite? If it got close to other nicer plates it might upset them. :)
Surface plates have nothing to do with beauty contests. They just need to be flat, damned flat! Eyeballs are worthless at checking them. A single test is worth a lot of opinions... Bring it on! We can also put it on top of one of our calibrated surface plates and chase a tenths indicator around the top surface, then turn it over and check the other side. If done a few times on different parts of my plate, and we get the same results, I think you could keep the results in mind while you use it until you can get it calibrated properly or replaced.
 
Surface plates have nothing to do with beauty contests. They just need to be flat, damned flat! Eyeballs are worthless at checking them. A single test is worth a lot of opinions... Bring it on! We can also put it on top of one of our calibrated surface plates and chase a tenths indicator around the top surface, then turn it over and check the other side. If done a few times on different parts of my plate, and we get the same results, I think you could keep the results in mind while you use it until you can get it calibrated properly or replaced.

Oddly the bottom side of the thing is rough cut and even has a big saw mark and is unfinished. I think it can certainly be looked at by you guys. It's portable enough. If nothing else I can be told it needs to go back to holding a door. Either way there would be a result and that's a start.
 
Have you got anything you know to be relatively flat of some considerable size? If you do, put a thin skim of that Prussian blue on it and gently float it over that surface plate. Hardly NIST stuff, but under a strong backlight it will suggest what you're dealing with.

I honestly don't have anything else even close to flat. It would at least tell me if there was a huge dip through the center.
 
I totally blew off the fact that the bottom of surface plates are rough cut, and useless for anything beyond holding up the top surface. Still, we can level the top surface with shims underneath and then indicate the top to look for dish or crown or other issues. What size is the plate? A lot of checking parts and comparing stuff is done with small plates like a comparator uses. I wish I had one...

Edit: Maybe we could put Ulma Doctor's .00005" (that is 50 millionths) DTI to work...
 
I honestly don't have anything else even close to flat. It would at least tell me if there was a huge dip through the center.

A good piece of plate glass would give you an idea of what you're working with. No clue what kind of tolerances modern glass is made to, but it's pretty flat. I used to have a 1/2" thick piece that I'd lay on a cast iron surface plate to serve as a backing plate for a sheet of wet or dry sandpaper. Real handy for cosmetic flattening and producing that matte swirled finish on material prior to engraving. Just a thought...
 
Plate glass is ground and polished and it is pretty flat, but certainly not calibrated surface plate flat, it is not designed or made for that purpose. Float glass, less so, but not really bad. Same with granite counter tops. Ordinary window glass, you can see the ripples in it...
 
Back
Top