Granite Surface Plate Usage Rules

Machine Shop
1

Hi Everyone,

I seem to remember the machine shop had a granite surface plate. Would I be allowed to temporarily glue some sandpaper on it (using 3M 77 Super spray adhesive)? I’m restoring a Stanley no. 6 jointer plane and I don’t have a flat enough, long enough surface at home. Will this damage the granite surface? What’s the best way to clean in after?

Also, does anyone know (roughly) what the dimensions of the granite plate are?

Thanks!

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2

I don’t know the rules for the granite plate, but I recommend a sheet of float glass as your under layer. Glass is incredibly flat and it makes a great sanding surface (when it’s supported by another surface).

EDIT: In fact, I keep a small piece of glass in my workshop as a sanding base. FWIW, thicker is better.

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one may often find glass free on CL:

e.g.
https://dallas.craigslist.org/mdf/zip/d/euless-storm-windows/7312603830.html
https://dallas.craigslist.org/dal/zip/d/allen-shelf-unit/7312576941.html
https://dallas.craigslist.org/ndf/zip/d/argyle-window-glass/7312556120.html
https://dallas.craigslist.org/dal/zip/d/keller-34-x-16-dual-pane-window/7312312423.html

I’m not saying all of those are suitable but they’re free glass, and depending on your needs, MIGHT be.

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Please don’t do this on the Machine shop surface plate. While the wear is small, it’s enough to throw delicate instruments out over time.

There is a “cheap” granite surface plate in the woodshop annex on the sharpening table which will fit 2 full sheets of sandpaper on it and can / has been used for this purpose many times before.

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5

I have a small surface plate at home and you can spray the surface plate with water to stick the sandpaper to it. With glue you are unlikely to get a flat surface because there will be variations in the glue thickness

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Thanks, understood.

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Machine shop has a cast iron surface plate that would work wonderfully and has been used like you want to use it.

The granite surface plate should properly only be used for layout and inspection.

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Thanks, I didn’t know about this. Do you know where it is and what it looks like? I haven’t been to the machine shop since the expansion.

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Usually on the Blue metal table. It has wooden cover for it like the granite. I’d guess it is 12" x 18" or maybe a little bigger.

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The steel surface plate was on the turret drill press Saturday evening.

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In other words - Hell to the No. The large surface plate is a precision instrument with flatness generally rated in the .0000x" range over the span of the plate. General cost is in the $3500 range for an A grade. So even the glue residue will throw it off.

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Got it! Thanks for all the help everyone.

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Plus, if you should use a sheet of glass on top (although it sounds like you shouldn’t need that for the other surfaces??), then I could get you a sheet of window/float glass.

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Thanks, I’m going to try my luck with the granite plate in the woodshop first.

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15

How funny, I’m restoring a #6 myself right now and need to flatten the bed too

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