View Full Version : Surface plates
08-24-2010, 03:53 PM
Another nutty question -
Anyone use a granite floor tile as a cheapie surface and/or lapping plate?
They are about 3/8 inch thick and seem quite consistent for flatness - and cheap.
08-24-2010, 04:27 PM
I did before I bought a proper granite surface plate.
08-24-2010, 08:42 PM
Find yourself a place that does stone countertops.
You can buy the cutout for a sink dirt cheep.
The material is much thinker so it's more stable.
08-24-2010, 09:47 PM
i got a countertop cutoff for free. its not square but it seems to be very flat. plenty good for my amateurish,self educated efforts at layout work .more than good enough for my chinese mill/drill. until i get a better machine,i dont need a better tool.
Go to a glass shop and ask for a piece of 1/2" glass plate. They are quite flat.
08-25-2010, 08:41 AM
Doesn't enco have surface plates for 30 bucks? Then use the free shipping option and you're set.
09-04-2010, 02:06 PM
I took a 1911 class from Bob Marvel this past summer at Montgomery Community College in NC. He used the heck out of a piece of granite counter top about 6 inches wide and 20 inches long. He puts two different grits of 3 inch wide, self sticking automotive sandpaper on there and it is like a very low cost surface grinder. In past classes when building a 1911, I have set up the frame in a jig plate and then used a surface grinder to take down the top of the frame to get it to fit with the slide. Using the counter top was faster (no set up time), but you have to be carefull to keep the cut level. It really is not hard to do. A couple of passes, measure and now a little more pressure on the front (or rear or left or right).
09-06-2010, 09:26 PM
Went to a stone tile shop, got a 12 x18 x1 1/4 polished one side granite slab for free!
Thx for the info!
09-07-2010, 02:43 AM
Just a story about granite plates:
In "my German forum", someone tried to make his own granite surface plate. All the lapping with diamond etc.
The result was, that the plate changed shape over and over again. At evening after correcting it, it was OK, the next day it was warped again. And it was really thick enough!
He found an explanation. He used granite that was quite big grained. Granite contains quartz that is a piezo crystal. When working the plate, the crystals were charged and expanded. To some extend, he was able to release the charge with a slap of a mallet.
Can't tell wether his findings/explanation are true.
Anyhow, he gave up and bought one. :D
Here in Germany, "granite plates" are not made out of granite, but a special stone coming from Africa (forgot the name). They are much finer grained.
09-07-2010, 03:13 AM
I need to find a slab drop for under my digital powder measure. That'll be a good use for a 4" thick chunk.
Surface condition won't matter much - just uses the mass to damp vibrations and keep the grains of powder from dropping off after the motor has stopped.
09-08-2010, 09:49 PM
I'm a knifemaker in Oregon and we use Plate glass, and The pro granite slabs. I find that the plate glass serves most of my needs, but the granite slab I got from Grizzly is helpful as well.