Anyone own a Starrett crystal pink surface plate?

[alfadan]

I bought one of a guy on craigslist a few years ago and have always wondered something.
The surface is nice and smooth of course, except there are little, I guess, voids all over it, including the sides. Everything glides smooth across it and near as I can tell is flat; at least flat enough for hobby use.

Are these little "nicks" normal for a Crystal Pink stone?

 

[American Locomotive]

I've used them before, don't recall any kind of voids. It's not uncommon for surface plates to get little chips and dings from use.

 

[Firebrick43]

I bought one of a guy on craigslist a few years ago and have always wondered something.
The surface is nice and smooth of course, except there are little, I guess, voids all over it, including the sides. Everything glides smooth across it and near as I can tell is flat; at least flat enough for hobby use.

Are these little "nicks" normal for a Crystal Pink stone?

Used a couple at work without voids.

 

[alfadan]

Interesting. It's like there are chips all over it, but without any roughness, almost like it's the nature of this piece of granite, even on the sides and I think the bottom and need to check on that.

 

[RoninB4]

Are these little "nicks" normal for a Crystal Pink stone?

=That would depend upon the size/depth of the "voids". Almost every granite surface plate has tiny pores in it that can be easily seen with magnification. You can almost see them with the naked eye too. If you can sink the tip of a ball point pen into them then that's a pothole and no that isn't normal for pink, black, or any other color. Granite is far more fragile than most people think and lots of idiots use the surface plate for all sorts of idiotic things that damage them. Careless handling of objects on the surface plate often results in a small chip/ding to the surface. One large tow truck maker (name omitted) I contracted at stored a wooden board atop the surface plate for long enough that some sort of fungus was growing on the plate. Despite my repeated attempts to clean it there was always a shadow. Photos with a reference object would help.

 

[alfadan]

I'll try to get a good picture tonight. If I remember right, this came from a Baldor plant out of Arkansas and has an inspection sticker from a couple years before I bought it.

I don't think these nicks affect any measurements I take, as long as the part is large enough to bridge over the nicks; just a homegamer anyway.

 

[WAS Jr]

I had a 12 x 12 Starrett pink surface plate recertified locally here in the Cle area years ago. I believe part of the rehab process was filling small voids and gouges with an epoxy and flattening them. I too believe your voids are probably normal wear.
bill s

 

[pelletman]

Anyone know the difference between pink and black surface plates?

 

[seber]

Pink granite is softer than black granite due to the color coming from feldspar instead of hornblende. Might explain the chips.

 

[CallumRD1]

Broadly speaking, pink granite has a higher quartz content and so is on average harder and thus much more slowly wearing. For plates in constant use where accuracy matters, pink granite can be preferable. For most applications the difference will never be seen.

Starrett Crystal Pink surface plates are used as very high-quality references surfaces that can be used for far longer than black granite before needing resurfaced.

 

[rlitman]

Pink granite is softer than black granite due to the color coming from feldspar instead of hornblende. Might explain the chips.

Pink granite has a higher quartz content, and the quartz crystals are significantly larger than those found in black granite. And if whole crystal chunks pop out, you'll end up with more visible chipping in pink, even though it retains more flatness.

 

[slowtwitch73]

That the nice thing about a granite plate as opposed to cast iron.. you get a chip with a dead flat surface all around it as opposed to a ding/dent with a raised area around it.

 

[seber]

Pink granite has a higher quartz content, and the quartz crystals are significantly larger than those found in black granite. And if whole crystal chunks pop out, you'll end up with more visible chipping in pink, even though it retains more flatness.

Actually, black granite generally contains more quartz than pink. Also quartz is the hardest component of granite.

 

[isb cornbinder]

I missed an opportunity to buy a big Pink Starrett surface plate. I think the size was something like 4'X8'. It was on Craigslist, 3-4 years ago. The seller lowered the price a few times until he was asking under a grand. About the time that I made up my mind to buy the surface plate, I was hauled away to the hospital. After 6 weeks in ICU and rehab the surface plate was gone.
My shop is crowded and fitting it in would be a tight fit, BUT, you know how these things can find and follow a person home.
On top of the purchase price would be pick up and delivery. The estimate I was given was a fluid $500-$1000. Has anyone ever been told, "that was an estimate." the final price is $1250?
I paid $400 cash to have my South Bend delivered and that was 2 kilometers,

 

[rlitman]

Actually, black granite generally contains more quartz than pink. Also quartz is the hardest component of granite.

Actually, information about black granite in general is not all that relevant when it comes to surface plates that use very specific sources, and I stand by what I said above. The black rock used in surface plates has less quartz than the pink. Probably because it is really diabase and not granite. My understanding of the selection of stones used for surface plates is that the most important thing is homogeneity, because the interesting looking stones we put on our kitchen countertops would flex too unpredictably to be useful at surface plate tolerances.

Here's a slightly dated reference by Starrett comparing the pink vs black plates.

https://www.gagesite.com/documents/Granite%20Surface%20Plates.pdf

 

[alfadan]

Here is a pic. It's kinda hard to get a good picture of something like this, but all the nicks are in the dark spots in the stone.
It's last calibration was grade A in 2018. Good enough for me. 18x24x4 stone BTW.

 

[alfadan]

Thanks for all the replies guys

 

[RoninB4]

I wouldn't want or expect to see that on a NEW plate from Starrett but it's a used one and it's about par for normal/careless wear-n-tear. Get a thin sheet of Plexiglass, make a lightweight frame, and keep the plate covered. The Plexiglass can now serve as a protectant cover and provide a fairly flat surface for some work. I have an 800 lb. hunk of black rock in the basement that stays covered. Congratulations on the purchase.

 

[Byrdnyrd]

Voids are common in Starett Pink surface plates, but they don’t affect “Flatness” as they are voids!
pink is the Lowest grade, Black is the highest! Depending on the size most Starrett surface plates are “Flat” to
.0002 ( two tenths) across the diagonals.

cheers,
BN

 

[2oolhound]

That would make pink granite surface plates avoidable however one shouldn't avoid their use when a high degree of precision is required. Pink granite surface plates are quite unavoidable in that case.

Check the tolerances in this AA Pink Granite Surface Plate.

 

[Firebrick43]

Voids are common in Starett Pink surface plates, but they don’t affect “Flatness” as they are voids!
pink is the Lowest grade, Black is the highest! Depending on the size most Starrett surface plates are “Flat” to
.0002 ( two tenths) across the diagonals.

cheers,
BN

Um, no. Grade is independent of the color. You can buy AA, A, or B grade in all three colors that starrett sells.

Pink plates have more quartz and therefore more wear resistance and black plates absorb less water. Older Herman “pink” plates (starrett bought Herman in the 70’s were more of a gray to tan color.

As veins of specific colors have played out they have had to open/buy other quarry’s for the granite characteristics they desired which is why color has varied somewhat over time

And starrett (at least for a decade) doesn’t advertise black currently but have red granite (black with red quartz) which is according to their promotional literature is superior to both.

 

[neophyte]

I have no clue whether it applies to the stone Starrett uses, but I believe all stone from Vermont can technically be labelled “Granite” even if it is not actually “Granite”.
This was from one of the early Great Courses lectures on geology, and I was only partially interested at the time, so maybe I’m wrong.

 

[2oolhound]

I'd expect Starrett, Mitutoyo or any makers of surface plates would be extremely stringent in selecting granite for this purpose. It wouldn't matter what quarry owners or anyone called it, it would have to pass the test.

 

[slowtwitch73]

I have a 3x4' 5" thick black granite plate on cast iron legs.. story is it came from General Dynamics, but there is no proof.

I'd like to get it flattened someday.. don't know if it will ever happen, and it suits my needs at this point.

 

[2oolhound]

I've seen a number of incorrectly mounted SPs. People think they can just make an angle iron frame with legs and sit it in that but they should be mounted level on 3 points. Suppliers provide proper mounting instructions.

 

[PCustoms]

I have no clue whether it applies to the stone Starrett uses, but I believe all stone from Vermont can technically be labelled “Granite” even if it is not actually “Granite”.
This was from one of the early Great Courses lectures on geology, and I was only partially interested at the time, so maybe I’m wrong.

Well I've certainly dug rocks out of my yard that are not granite, so I'm pretty sure you're wrong.

How would limestone, feldspar or sandstone be called granite just because it came from VT?

Ever hear of VT marble?

 

[PCustoms]

I've seen a number of incorrectly mounted SPs. People think they can just make an angle iron frame with legs and sit it in that but they should be mounted level on 3 points. Suppliers provide proper mounting instructions.

There's a reason good stools are 3 legged....

 

[chevy.stroker]

OK I hate to go off topic, but you 3 legged guys started it! I'm from the automotive world.

I see machinist jacks often sold in a set of four but used in 3's. My assumption is it is easier to level 3 points than four?

 

[PCustoms]

OK I hate to go off topic, but you 3 legged guys started it! I'm from the automotive world.

I see machinist jacks often sold in a set of four but used in 3's. My assumption is it is easier to level 3 points than four?

3 points make a plane.

Think about it, two points and an object can teeter totter, add a 3rd point and it stabilizes.

 

[chevy.stroker]

3 points make a plane.

Think about it, two points and an object can teeter totter, add a 3rd point and it stabilizes.

I figured it was easier to level between 3 points than 4. Less measurements.

 

[AEAdam]

Pink granite is softer than black granite due to the color coming from feldspar instead of hornblende. Might explain the chips.

Wrong.

Your other post was wrong too. I suspect you’ve got hardness, density, and strength mixed up.

 

[AEAdam]

What you are seeing is normal, but it’s a natural product and stones vary. I have one and it looks just like yours. Mine is small, 12x18” grade B.

Pink stones are HARD, but not as dense as granite and not as strong. So they are always thicker than the black granite stones. I also have a larger AA grade Doall, which is my main inspection plate 24x18, maybe only 3” thick. even tho it’s a bigger plate, it’s thinner than my Starrett, which I think is 4” thick.

The chief advantage of the Starrett crystal pink stones is their hardness and slow wearing, making them outstanding buys second hand. I wish I had a 24”x36” but I dont have the gear I need to move one. Tho the Starrett crystal pink stones have a lower density than black or gray granite, the typically weigh as much as a comparable stone because they are made thicker.

 

[AEAdam]

I've seen a number of incorrectly mounted SPs. People think they can just make an angle iron frame with legs and sit it in that but they should be mounted level on 3 points. Suppliers provide proper mounting instructions.

They are called “Airy“ points. I would guess most US makers complied with them during manufacture and you are safe to mount your US (or Canada) made stones using the formula. No need to consult the manufacturer.

 

[AEAdam]

OK I hate to go off topic, but you 3 legged guys started it! I'm from the automotive world.

I see machinist jacks often sold in a set of four but used in 3's. My assumption is it is easier to level 3 points than four?

Starrett sells them only individually. S#190 and #191. I’ve never seen them sold in sets anywhere. They are commonly used to support long stock that overhangs your vise. If you are mounting irregularly shaped castings on your mill you might need multiples.

Like all machinist clamping and fixturing, clever people combine basic fixturing tools to solve complex problems.

 

[vanapplebomb]

In general, the pink ones have bigger grains than the dark grey/black stones. The quartz is extremely hard and chips out easier with larger grains in the pink. Mine has lots of little voids you could catch a fingernail on when scratched, but it doesn’t matter. That is what separates all granite from cast iron. Cast iron will always raise a burr when dinged which screws up everything. Granite just chips and leaves voides. Many of the voides and micro chipping is from the manufacturing process. Perfectly normal.

 

[Hephaestus29]

We have some Starrett Pink Granite at work, I don't recall that many voids.


I saw. BLOOD RED Granite Plate one time, not sure of the hardness or quality but it was Awesome, I wanted it bad but couldn't buy it at the time. I still want one.

 

[Beerhippie]

Anyone know the difference between pink and black surface plates?

After carefully reading the educated and in-depth replies above, I can synopsize: One is pink and the other is black.

 

[Beerhippie]

After carefully reading the educated replies above, I can synopsize: One is pink and the other is black.

And black is the only proper color for shop use.