Surface Plate without paying out the A55

Wallace Mutt

Wallace Mutt

Joined
Jan 24, 2016
Messages
503
I live in a small town and I'm having trouble finding a flat surface plate locally and having one shipped is expensive for a grade B. I do have the option of having one made at a local granite top supplier for a good price. My question is, can I expect that the flatness from a granite shop to be good enough for getting stuff flat?
 
How accurate will they guarantee it to be ?
How precise do you need ?
Fwiw, I use a wall slab from a demolished building. I dont make parts for NASA, its plenty accurate for what I do.
 
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Haha yeah, I just need something a little better than eyeballing it and thought if I can get it locally for the price of a couple of coffees. I have no experience with granite shops but those are some good questions I could ask.
 
A scrap from a granite counter shop will work. Also, check out gravestone places, they sometimes have small flat pieces.

If there is a Woodcraft Supply near you, you can pick up a 9X12 plate for $30.
They also sell a 18X6 plate, which is great for knives, for $50 with free shipping.
Both are A grade.
 
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Granite fabricators will get you a sink cut out for cheap or free, I found a bunch dumped in the woods once. I have one of those for gluing up liners. I use a granite umbrella base that I liberated from a patio set that I use for layout and scribe lines with a height gauge . For flatening scales, I have a small "real" surface plate that I got off amazon for around 40 bucks.
 
Maybe glass is better and cheaper then granite ? I was surrounded by granite and marble mines and factories .One of best marble in world come from my place . I have granite plate but I like more glass ..........

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I bought a 18”x18” granite tile from Home Depot for about $6. Ordered it online with their “free ship to store” and picked it up about 5 days later.
 
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Countertop granite and thick architectural glass (meaning 1/2" or more) are both a lot flatter than you would expect. Unless you are doing actual machine shop work either might serve your needs.

And if you have a good quality straightedge that you can take with you when shopping for a piece, you can check out the flatness pretty easily. Flashlight and eyeball for most purposes; use a thin feeler gauge if you need to get really serious about it. Make sure to use the straightedge in various positions/angles.

I have a granite sink cutout in my basement shop, and for woodworking purposes it has been very useful. Found it on a jobsite trash pile for zero $.

Window glass that is thick enough to be rigid ends up remarkably flat as a result of the manufacturing process used to make it. I don't know much about how they make granite countertops, but they seem very flat based on what I have seen.
 
Glass is reasonably flat. Just like any body of water, The liquid tin bath its molded upon follows curvature of the earth.:thumbsup:
 
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Lieblad said:
Glass is reasonably flat. Just like any body of water, The liquid tin bath its molded upon follows curvature of the earth.:thumbsup:
Click to expand...

Exactly! A float plant is an amazing thing to see.
I was visiting an AFG plant up in NC and they had a 3ft by 6ft by 6" slab that the maintenance people actually USED as a surface plate.
 
Thanks glass guys, I'll call around for some glass sources or just order some. All I can find online is 3d printer glass.
 
The plate glass used for coffee and end tables works fine. Check the local thrift stores for a cheap glass top accent table.
 
I used a glass shelf out of a old fridge for a couple yrs until I could get my granite plate.

I did even it up with my coarse diamond sharpening stone, just knocked off the high spots.
 
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