Well Brian a big welcome to the family. It sure is great to have another couple as members and Canadian too.
I will make sure to add the tags to this post cause it sure is gonna come in handy all the info you provided here. With my gray hair i have to rely on search and tags.
While i am at it seeing as how you a glass man, do you have any idea just how flat glass really is. Sounds like a crazy question but i would like to order a piece of glass that is say around 10 or more millimeters thick to use for sharpening my woodworking tools. But i was wondering if glass that thick is uniform flat across say 20 inches by 18 inches. What would be the nearest standard thickness for this kind of glass.
Hi Rob,
Many thanks for the welcome and apologies for the slow reply.
Commonly available float glass, (as opposed to the old fashioned polished plate glass), should work very well for a sharpening surface plate. It is manufactured by drawing the glass over a bed of molten tin. Some literature I dug out of my files indicates that the flatness is 1 or 2 microns per inch maximum deviation, and not cumulative over a longer dimension. As a micron is one millionth of a meter, or 40 millionths of an inch, the max. deviation from perfectly flat is 80 millionths of an inch per inch of glass surface.
I would suggest using min. 12mm, (1/2"), thick float glass. Having it tempered would reduce the chance of it breaking if you dropped a heavy tool on it, but non-tempered, (annealed), should work fine. Ideally when not using it, it should be stored on edge, upright. When using it to sharpen, I would lay it flat on some 4" strips of masking tape spaced about 4" to 6" apart.
Float glass is readily availalable in 3mm, 4mm, 5, 6 10 and 12mm. Especially if you go to a shop that makes glass table tops, etc. They may even have some 19mm, (3/4"), kicking around which would be even better. The 12mm weighs about 6.4 lbs. per sq.ft. so if your surface was 18" square, about 15 lbs. total.
Regardless of the thickness or tempered/annealed, I would suggest ordering it with flat polished edges, (i.e. with 2 small bevels at top & bottom of flat edges), or pencil polished, (slightly rounded).
Thanks a lot Rob; now you've gone and got Cynthia nagging on me for the one of these things.
Cheers,
Brian