I got a small granite surface plate so I could lap things as

You could probably get away with a layer of water and press down on it. Should stick decently well.

>>1128728
This is what I do. Works best with fine sandpaper

>>1128718
>using a surface plate to hold sandpaper down for "flatness"
Holy fuck no, you will destroy that poor plate. If all you need is something reasonably flat then use glass as a backing.

>>1128728
>>1128730
I've noticed that the problem with this is that repeated rubbing literally stretches the sandpaper out on the grit side and it's not long before the sheet starts curling up.

>>1128732
I'm not using the plate to take precise measurements and calibrate sensitive metalworking tools. I'm talking about flattening things that are not so critical, like lapping CPU heat spreaders, heatsinks, soles of hand planes, etc.

>>1128780
>I'm not using the plate to take precise measurements and calibrate sensitive metalworking tools.
Then why the fuck did you buy a surface plate? If you're using sandpaper as the final step you don't need anything near that flat because the paper itself will be far less accurate. Sell the plate to someone who will use it properly and get a fucking glass plate.

modge podge should come off with water or simple cleaners

Don't they sell sandpaper holders specifically for this with little plastic clips on the top of it so you can keep the sandpaper taut over it like the felt on a pool table?

>>1128788
if the OP didn't get it for free or dirt cheap, yeah - a piece of glass will work fine

>>1128928
I bought a single marble tile at homo depot and have been using that. Works awesome.

>>1128718
I usually use a spray adhesive, but that does leave a little residue. Try a thin firlm of water and weighting/clamping the corners/edges.

As others have said, a surface plate isn't for doing work on, its essentially a reference tool to measure and indicate a flat surface.

The first few times you use it will be fine for lapping, after that and it won't be flat and you won't be lapping very well; only producing shiny surfaces with convex or concave imperfections.

See if you can replace it and buy a cheaper pane of glass for lapping.

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>>1128718
If you need to just hold sandpaper on a flat surface, use pic related, they are cheap and work on both sides so you can keep it flat or curved depending on what you want to do.
They also sell flat-only versions that are much stronger if you absolutely need flatness of the surface the paper is resting upon.

Much more convenient than using a granite brick and gluing sandpaper to it.

If you are that determined to use your granite block, you can try to cut two slots on its sides so it somewhat replicates the functionality of pic related.

Granite can't be black
that's gabbro/norite
you fuck

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>>1128718
>2 clamps
>2 bits of timber
Sandpaper over the top of the granite
Timber clamps to the sandpaper going over the edges, clamp it up

>>1129346
Yes it can you stupid shit, the black plates are a very specific kind of granite.

>>1129482
What fucking feldspar is black

>>1129483
It's the quartz in it that's black. Black granite has a shit ton of quartz compared to pink ones that are more feldspar.

>>1129346
>>1129482
It's actually diabase.

>Today most surface plates continue to be made of black granite, more accurately referred to as black diabase

https://en.wikipedia.org/wiki/Surface_plate#Granite

>>1129484
quartz is clear, or smoky when it's really mineralised, it's the amphibole that makes up the black spots on other granites. Remember, quartz is the last thing to form out of a melt, when most or all of the metal is used up, which is where the black colour comes from.
>>1129486
Diabase I can deal with, or diorite, but both of those are mafic, which granite sure as shit ain't

>>1129487
"Granite plate" is one of those things like Kleenex or Band-Aid. They're not always made of granite but back in the day most of them were and a lot still are so they get wrapped together since they perform the same function.

>>1129494
Yeah I know, but it's wrong to call it granite

>>1128718
Honestly, the easiest way is to just use sandpaper with an adhesive backing. Then when you need to remove it, just use a bit of lacquer thinner or solvent to dissolve the adhesive for a quick and easy removal.

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>>1129176
Your full of shit. I do lapping at work in the aerospace industry. We check our stones regularly and have never had one go out of flat.

You probably don't even realize that you don't use lapping compound on a stone, you use lapping film and that is what the OP is talking about.

>>1130785
Are they certified to A or AA? I highly doubt they're certified at AAA and I'm calling your bluff.

Nobody smart uses the actual surface plate to do heavy duty work on, but they do infact get worn in certain areas, and depending on how flat you want a stone, they can go out of spec. There are even different materials for a surface plate which have different hardnesses, and getting it to within a few millionths of flatness isn't easy.

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>>1130794

Manufacturer of the worlds best solenoid and other elector-mechanical actuators and valves. I've had my fingerprints on parts for fighter jets, nuclear capable missiles, rockets, satellites and man rated space vehicles.

>>1130785
Which goes on a lapping plate you stupid fuck, not an inspection plate. The ONLY thing you do on an inspection plate anything at all like this is dying it and doing rubs for hand scraping.

>>1130794
Plates don't go to millionths unless you spend out the ass for some kind of lab grade one. Best you get without spending five figures+ is tenths.

>>1131043
Kill yourself, he bought it he can do whatever he wants with it. Its a flat piece of fucking rock.

https://www.woodcraft.com/products/granite-surface-plate-9-x-12-x-2-a-grade
I would bet this is the exact product OP bought. It's marketed for what he wants to do, and isn't very expensive. I really don't understand the autism attack ITT

https://www.youtube.com/watch?v=cwdoUjynpEk&t=1161s

granite countertop works fine for lapping tho.
use cheap valve lapping compound.

>>1131563
>$36
>grade A
lol no

>>1131717
it could be for a small plate like that, but who's going to pay to have a $36 surface plate calibrated and resurfaced?

>>1131734
No, a Grade A plate of that size is a good $200. It's probably a B grade at best.

>>1131739

who usually uses small grade A plates?

>>1131770
That size is what you'd find actually out in a shop for doing on the fly inspection and calibration or in a smaller inspection room. We have one or two floating around the shop I work at.

>>1130813
And yet here you are, right down with the rest if us.

Oh how the mighty fall.

>>1131708
Thanks m8. I'm now watching the whole series.