How to Clean a Granite Surface Plate?

[Tecnico]

I picked up a black granite surface plate today and have a few questions about maintaining it. I see suggestions about pricy $tarrett cleaner, ammonia, alcohol and even Windex, what are you folks out there using on yours that works?

Also, how shiny should the surface be when it’s cleaned? Shiny? Matte? Sorta shiny?

For what it’s worth it didn’t come with a cal certificate but to the inexperienced eye there aren’t any obvious defects so it’ll probably do do what I’ll ask of it.

Oh, it’t going to get a cover so I can incorporate it in my sedimentary filing system, I hear that’s a key part of its use.

D

 

[140mower]

Oh, it’t going to get a cover so I can incorporate it in my sedimentary filing system, I hear that’s a key part of its use.

....yes, a solid foundation is the key to a successful shop stack up, and a surface plate fits the anchoring bill nicely.
In my hill billy shop, Windex is what I have been using...... So, that is probably not going to be the right answer.

 

[Dusty]

@Tecnico this is the process I use works great. Just saying!

 

[Tecnico]

@Tecnico this is the process I use works great. Just saying!

Is it the PB or the jam that’s the secret ingredient?

D

 

[Tecnico]

....yes, a solid foundation is the key to a successful shop stack up, and a surface plate fits the anchoring bill nicely.
In my hill billy shop, Windex is what I have been using...... So, that is probably not going to be the right answer.

Oh, Windex…but there’s the argument for and against the version with ammonia!?

Yah, the surface plate will make a really solid foundation…..cus it’s not going to move anywhere any time soon now that it’s down the stairs and in the basement - solo I might add….

D

 

[Susquatch]

what are you folks out there using on yours that works?

Mitutoyo recommends denatured alcohol. That's what I use. My current plate is too small - I can't get a reasonable sized pile of stuff on it.

How big is it Dave? I'd love a 24 x 32 or 36. But so far I have not been able to find one that was certified and has been properly cared for.

Are the three mounting points on yours clearly evident?

 

[Tecnico]

Mitutoyo recommends denatured alcohol. That's what I use. My current plate is too small - I can't get a reasonable sized pile of stuff on it.

How big is it Dave? I'd love a 24 x 32 or 36. But so far I have not been able to find one that was certified and has been properly cared for.

Are the three mounting points on yours clearly evident?

Mine is an 18 x 24 x 3 and that’s at least heavy enough! No certs but anything that’s more than a year old would be out of the cal cycle. If it wasn’t hobby use since new then all bets are off on whether it’d pass.

I’ll probably noodle around a bit to see if I can figure out how the “old guys” calibrated them before the fancy electronic gear was invented.

Any suggestions out there?

What are the three mounting points you speak of?

Bottom line though it’ll be miles better than the cast iron top of my table saw so it’s worth it!

D

 

[Tecnico]

What about the surface finish?

Shiny?

Matte?

Sorta shiny/sorta matte?

D

 

[Tomc938]

Is it the PB or the jam that’s the secret ingredient?

D

If you use crunchy peanut butter it helps fill in chips on the surface.

 

[justin1]

I picked up a black granite surface plate today and have a few questions about maintaining it.

I've been using isopropyl alcohol for a quick wipe and I used Windex to clean blueing off

 

[mickeyf]

...so I can incorporate it in my sedimentary filing system

Wait - what? You're going to clean it off first and then put sediment on it?

 

[Susquatch]

I’ll probably noodle around a bit to see if I can figure out how the “old guys” calibrated them before the fancy electronic gear was invented.

I'm keenly interested in this too! Please share as you learn.

I'd WAG that they just relapped them each and every time and that was their cert method.

What are the three mounting points you speak of?

I don't think it applies to a stone that size. It's very important for big stones. But have a good look at the bottom anyway. It won't hurt to use them if they are marked.

When they are lapped, they are set on three points to provide consistent support for the stone. Even stones bend under their own weight. To hold calibration, they have to be used sitting on the same points that supported the stone when it was lapped.

 

[Tecnico]

Wait - what? You're going to clean it off first and then put sediment on it?

Sure, you have to get a good clean start!

Ok, let’s be fair, the first layer will be a wooden cover, then let the filing begin! The cover serves two purposes, protect the plate and as a carrier for the sediments above it when ya just gotta get at the plate.

D

 

[Susquatch]

Sure, you have to get a good clean start!

Ok, let’s be fair, the first layer will be a wooden cover, then let the filing begin! The cover serves two purposes, protect the plate and as a carrier for the sediments above it when ya just gotta get at the plate.

D

That's how my 18x24 is setup and for exactly the same reasons. I have a thin sheet of kitchen cutting board plastic laying on the surface too. That way I can even use the stone for small non-critical work without fear of scratching it or chipping it.

When and if I ever find a Grade A 24 x 32 or 36, it will get the same protection.

 

[Tecnico]

I'm keenly interested in this too! Please share as you learn.

I'd WAG that they just relapped them each and every time and that was their cert method.



I don't think it applies to a stone that size. It's very important for big stones. But have a good look at the bottom anyway. It won't hurt to use them if they are marked.

When they are lapped, they are set on three points to provide consistent support for the stone. Even stones bend under their own weight. To hold calibration, they have to be used sitting on the same points that supported the stone when it was lapped.

I had a look at the bottom and I didn’t notice any evident mount points. I would imagine they trued out 3 or 4 corners so it would sit on a plane without rocking. Interesting point.

I don’t know about the re-lapping as certification. Even if you re-lap you’d need to know how flat you achieved. I say this based on (just) one video I looked at yesterday where the guy started with a crown in the centre and after first lap it was overall better but now it had a hollow in the centre. He eventually tweaked until they were all happy about just how good it was.

This guy had an electronic tilt measuring device that compensated for everything but the phase of the moon which would have an influence on a bigger plate…….. His other tool was a mechanical (local) flatness gauge, basically a super precise DTI on a flat plane apparatus.

EDIT: the tool is called a repeat-o-meter.

I see where a guy mimicked one of those using a chunk of cast iron etc. I suppose it would give you an idea whether any inaccuracies were local but not over a long span. The guy did seem to be using it as a first pass measure of how good the lap job was.

The lap was interesting, it was an iron casting, scraped and he rolled diamond dust onto it to embed it for the lapping. He said the more he used it the flatter it got.

I would expect one could get a plate lapped for ‘way less than gearing up to do it.

D

 

[skippyelwell]

@Tecnico this is the process I use works great. Just saying!

Did you notice the size of those cylindrical squares on that surface table?

I use Iso or Methyl Hydrate to clean my surface plate.

 

[Susquatch]

I would expect one could get a plate lapped for ‘way less than gearing up to do it.

I wasn't so much interested in how hobbiests do it today or how they do it at the factory. I'd like to know what the old guys did before modern metrology.

As far as how they do it today, I understand that they use 3 stones - each makes up for the other two and you work your way toward flat for all three. I can't imagine doing that with the bigger stones though. And I don't think a cast iron lap will ring the bell.

I guess it depends on what you are after.

Ya, I didn't think your stone would have three points on it, but no harm in checking. If you know who made it you could try asking them what they would recommend. I'd think a reasonably flat surface would be better than using edges. Or maybe use the math for 3 points and try it both ways to see what is best. But maybe your needs (and your stone) are just fine sitting flat on a workbench. I did the math for a big stone and was quite surprised at how much a stone can bend. Everything is rubber. A small stone doesn't weigh enough to bend it much.

Myself, I would not even try to fix a stone. I'd just accept whatever it was and live with that. Maybe map it so I understand it's geometry. If I really wanted it to be factory flat, I'd hire a guy who does that for a living. There is a guy in Michigan who travels around certifying stones.

I lean toward buying a used A-Grade stone hoping it would meet B in my shop. It seems there are lots of stones for sale out there, but the minute I see they are not mounted properly, I lose all interest. Who knows how someone treated an A grade stone if they don't even know enough to mount it properly.......

 

[Tecnico]

I wasn't so much interested in how hobbiests do it today or how they do it at the factory. I'd like to know what the old guys did before modern metrology.

Same here, speaking of measuring flatness that is.

As far as how they do it today, I understand that they use 3 stones - each makes up for the other two and you work your way toward flat for all three. I can't imagine doing that with the bigger stones though. And I don't think a cast iron lap will ring the bell.

Dunno, that’s not the impression I got. The guy with the CI lap seemed to think he got better than AA with it by mapping the SP and concentrating on bringing the highs down to meet the lows thus making it all planar. Craftsmanship in action. Apparently the black granite cuts very well compared to pink. The lap was about 1 ft square on what looked like about a 2 x 3 stone.

I’m not going there anyhow.

Ya, I didn't think your stone would have three points on it, but no harm in checking. If you know who made it you could try asking them what they would recommend. I'd think a reasonably flat surface would be better than using edges. Or maybe use the math for 3 points and try it both ways to see what is best. But maybe your needs (and your stone) are just fine sitting flat on a workbench. I did the math for a big stone and was quite surprised at how much a stone can bend. Everything is rubber. A small stone doesn't weigh enough to bend it much.

No name so it’s up to me to decide how to handle it. I suppose if I put it on high durometer rubber it’d find its natural shape better than on a hard table. Maybe it needs the rigidity of the table? Gotta think about that a bit. Maybe it doesn’t’t matter.

What’s under your 18 x 24?

Myself, I would not even try to fix a stone. I'd just accept whatever it was and live with that. Maybe map it so I understand it's geometry.

That’s about as far as I can see going unless I really needed it and there’s someone local that does lapping. There are enough shops with SPs and CMMs around here so I wouldn’t be surprised.

As far as mapping it, so far it looks like a repeat-o-meter can tell you if your stone is flat (I.e. it shows no variation) but if you do have variation then it’s harder to quantify how much overall without the more sophisticated tool$.

Even a repeat-o-meter is $$$ even if it’s shop made because the 1u measuring indicator is $$$ so that’s back burner until I really need to know how how flat the stone is. FWIW, I saw a graded stone, I think at KBC, for less than the price on an indicator so that pretty well tells the tale.

D

 

[Susquatch]

What’s under your 18 x 24?

Sorry, old memory is good for shit sometimes. Mine is actually 12x18, not 18 x 24. It just sits on a flat heavy work bench with a heavy foam mat between them to take up any irregularities. My math says that anything 18x24 or smaller doesn't really matter.

 

[Mcgyver]

sorry, was still editing and the window closed ..... you can delete the previous post. You'd get better posts from me and cleaned up posts if I could edit them whenever

Same here, speaking of measuring flatness that is.

No measurement necessary with Whitworth's original three plate method. It's iterative and comparative and you end up flatness to with the depth cut, say a tenth.

Be extremely careful in introducing lapping into it. Most of internet is wrong, you cannot get three plates or stones flat with this by lapping, at least as many suggest lapping to be. That is throw loose abrasive between two items (which except for cylindrical work which is self correcting, is NOT imo lapping). Lapping uses a lap, a cutting tool made by embedding abrasive.

The three plate method depends on the piece of you just worked, becoming the master or record for the next step. e.g. A is scrapped to match B. A is then the master and C is scraped to A, and so on. This cannot work if you just throw abrasive in between as there is no master, both plates wear

Where lapping works using the three plate method is the specific high sports are identified and then lapped with a charged lap - you know exact which is the master and work (which changes each iteration) and you know where you are removing material. In other words a lap used instead of a scraper