billiard table surface plate???

[stepperhead]

hello out there,

I have been looking for something to use for a suitable surface plate. I was hoping that I could come up with something that was sort of laying around as somebodies 'garbage' and lo and behold I was gifted a slate from an old pool table. now I need to test it to see how flat it is. I want to know what is the best low cost method for testing flatness? I have a level that is probably close although it is not a very expensive level, shining light from behind shows a fairly flat surface. would that do? I am curious what kind of tolerance slate for pool tables are? the thing is very heavy and I can not move it by myself, so moving it is not an option that I would prefer. I just got dave gingerys books and I am going to start to make his lathe. so that is what I am going to use it for.
What do you guys think??

thanks,
mac

[wildwestpat]

Hi Mac

Good scrap harvest however slate is both porus and relatively soft compared with steel. If you envisage using the 'slate surface' to slide metal jobs and measuring tools about on then it will wear rapidly.

You might be able to find a suitable bit of plate glass to make a wear surface by bonding the glass to the slate. The slate pool table bed would make a good support for the glass and avoid the glass flexing.

Good hunting

Pat

[stepperhead]

well thanks for the advice. It just so happens that I have a piece of tempered glass that fit the slate. It is 1/4 inch and kind of flexible but when I put it on the slate it conformed to the dead flat state. I checked the slate with winding sticks and It is very flat to my eye. it does not bend at all, which should be great for its purpose.
Just one question though, how should I check the surface?? my level does not rock at all, and I can see a very even surface of light at the contact point. In fact I can see the dust that it is sitting on! Am I done? is this good enough?? I sure hope it is but I guess I can not be absolutely sure until I check against a standard.

the tempered glass should have a excellent wear surface as you were right the slate is very soft. thanks again, should be great for blueing up and flattening my bed casting for the gingery lathe.


mac

[Delw]

you could stick 3 precisly cut douglas firr 4x4's on a smooth garage floor, the lay the slate top side down on the 4x4s , get a good heavy duty indicator base and run a indicator under the slate.

this is a 3 point check for flatness, what ever your reading is, is what the flatness of the slate is.


Delw