# 3-Plate Method, Surface Plates?



## middle.road (Jun 21, 2020)

OK, so, I going to open up a discussion on this far-fetched thought. (Blame the Cerveza...  "
I case you haven't seen 'The Haul' click -=- HERE -=-

With so many at my disposal. . .
Is it possible to true up surface plates using the 3-plate method?
A 'brief' review of YouTube last night and I'm not sure this is possible, but it makes sense to my addled mind.

First - there is the matter of picking up and 'flipping' one plate onto another.
Secondly, there is the matter of picking up and 'flipping' one plate onto another.
Thirdly, there is Honey's patience with this entire fiasco...

But I'm curious, what do y'all think? 

Back in the day when I needed to get plates calibrated I'd just call a service, and then stand there watching as they worked their magic.
Of course this time around I don't have a company that is paying the charges.

Last Thursday morning I submitted requests for surface plate calibration to two companies that have locations in Nashville and Chattanooga .
Have not heard back from them...


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## matthewsx (Jun 21, 2020)

I saw those plates, I'd pay a fair amount to avoid having to "flip them over"

John


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## Bob Korves (Jun 21, 2020)

It is entirely "possible" to make a flat plate using the 3 plate method.  It is also fussy and will take you forever from scratch, at least to do it right.  The first accurate plates were made using that method.  Then they mostly stopped using it, at least for getting something done, not just proving a concept.  These days, there is no reason for using the three plate method for any useful reason, but rather only to prove it can be done.  Instead, use an autocollimator and repeat-o-meter, along with the necessary skills, and then get on to your REAL project, whatever you want to make flat...


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## middle.road (Jun 21, 2020)

Bob Korves said:


> It is entirely "possible" to make a flat plate using the 3 plate method.  It is also fussy and will take you forever from scratch, at least to do it right.  The first accurate plates were made using that method.  Then they mostly stopped using it, at least for getting something done, not just proving a concept.  These days, there is no reason for using the three plate method for any useful reason, but rather only to prove it can be done.  Instead, use an autocollimator and repeat-o-meter, along with the necessary skills, and then get on to your REAL project, whatever you want to make flat...


The problem is that I don't have access to an autocollimator or a repeat-o-meter...    Wish I did!
There's not even a calibration service in East TN that I could find.
Now if I could run down to Tifton, GA and visit Keith, then maybe. . .
Or else if I was located near you guys in central CA.  (What a weekend get-together project that would make!)

It was just a thought I had before I picked them up on Tuesday given what I have to work with. 
But then after tossing them around this week. . .


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## matthewsx (Jun 22, 2020)

How flat do they need to be for your shop? If it were me I'd be inclined to use them as-is until I came upon a project where I knew they needed to be better. 

John


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## Aukai (Jun 22, 2020)

Last December the wife, and I spent a week in Nashville, and had a blast, I even remember most of it.....continue on....


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## Bob Korves (Jun 22, 2020)

You might start out by checking out these companies, just the start of looking at this search:  "surface plate calibration east tennessee"






						calibration and resurfacing service of granite surface plates - Cleveland OH, Chicago IL
					

Your granite surface plate (granite block, granite table) is the foundation of all accurate measurements, Optimal Calibration has the ability to achieve extremely tight tolerances to ensure that your are getting the most precise measurements possible.




					optimalcalibration.com
				








						Certified Service calibration, repair, resurfacing. Granite plate, granite table, granite master angle, granite block
					

Certified metrologists,over 40 years experience,ISO 10275 Accredited providing granite plate, granite block, granite table, granite master angle, calibration, repair and resurfacing services. We come to you- on-site, your plant. Certified Service Company has years in this industry, proud of its...




					www.certifiedservicecompany.com
				











						On-Site Calibration Services - Cross Precision Measurement
					

Offering a range of ISO 17025 & NIST traceable calibration services on site at your facility. Schedule a service call today! CrossCo Precision Measurement




					www.jaking.com


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## middle.road (Jun 22, 2020)

Strange how Google works sometimes.
I had done the almost the same syntax, but I had inputted 'East Tennessee surface plate calibration service'
Neither Optimal nor Certified showed up. J.A. King did though, they're one of the two that I submitted a request to.
Doesn't look like there are any in the Knoxville area, though there is one up near the Tri-Cities, but they don't list surface plates on their site.
Perhaps I'll get lucky and find a service out of Nashville or Chattanogga that combines trips.
Of course first, I have to get the one(s) I'm keeping mounted properly and not on a dollie.

Here's a funny one. I was checking out one service that came up in searching and here's their list:

Threaded Ring Gauges 
Dial Indicators
Optical Comparitors
Snap Gauges
Depth Gauges
Comparitors?   




Bob Korves said:


> You might start out by checking out these companies, just the start of looking at this search:  "surface plate calibration east tennessee"
> 
> 
> 
> ...


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## Janderso (Jun 22, 2020)

How did the Egyptians create giant flat one piece stones? They must have used the three rock method (Flintstones)
Or had help from ET.
There was a Youtube on the 3 plate method recently.


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## middle.road (Jun 22, 2020)

This had to have been a fun gathering:







Bob Korves said:


> You might start out by checking out these companies, just the start of looking at this search:  "surface plate calibration east tennessee"
> 
> 
> 
> ...


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## Bob Korves (Jun 22, 2020)

This was the fun gathering at my former shop, Randy Richard was there with his plate:








						Surface Plate Calibration Collaboration (or Plate Fest)
					

Four machinists got involved in this collaboration at my shop.  It was time to get those plates flat and certified, and known quantities.  Randy Richard (RR in the Shop--YouTube), Mike Walton (Ulma Doctor on H-M), Ray "Razor Ray" Goff, and I.  Five plates total.  We had Standridge Granite from...




					www.hobby-machinist.com


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## middle.road (Jun 22, 2020)

Company out of Michigan showing prices...





						International Certification Measurements, Inc. | Dimensional Calibration Services
					






					icmcal.com


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## vocatexas (Jun 22, 2020)

I would love to have one of those 24x36 plates, but I'll bet shipping would be astronomical! Great haul you got there!


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## Bob Korves (Jun 23, 2020)

Surface plate calibration seems reasonable:





						International Certification Measurements, Inc. | Dimensional Calibration Services
					






					icmcal.com


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## NCjeeper (Jun 23, 2020)

Bob Korves said:


> Surface plate calibration seems reasonable:
> 
> 
> 
> ...


That is what I was thinking


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## middle.road (Jun 29, 2020)

So while trying to repair the engine hoist and dealing with the 90° weather we're having I remembered a few things from my Metrology days.
With the temp here bouncing between 90° during the day and the high 60's at night the plates can't normalize. 
I'm going to have to install some sort of A/C in the shop, make some more room, and then wheel these granite slabs in and let them sit.
It'll more than likely have to be one or two at time and then let them soak and acclimate and then start to measure and check them out.
Not enough floor space and too many slabs.   
I did asked my Better Half if I could move them into the living room... Since I do not have the new floor installed - yet.


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## NCjeeper (Jun 29, 2020)

You could lay them out and play "twister."


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## westerner (Jun 29, 2020)

I believe I do not regret NOT having the need or patience for this level of accuracy.....
If I have to acclimate my great huge chunks of granite to achieve the level of precision I need, it will feel more like a job than a hobby to me.


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## Bob Korves (Jun 29, 2020)

If you let the shop air easily get to all the surfaces of the plate, the plate will have equal temperatures from that aspect.  Radiated heat coming from something like a hot tin roof above and a cold floor below can mess it up, so insulate or otherwise make the floor and the ceiling show the same temperatures to the plate top and bottom -- at least as good as possible with what you can cobble together...


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## middle.road (Jun 30, 2020)

Had a brainstorm of an idea this morning over coffee.
The 36' car hauler _storage _trailer we have has an RV type A/C unit on it.
So....
Went out to the trailer and of course it doesn't work. -hehe


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## NCjeeper (Jun 30, 2020)

Did any of the local companies get back to you on calibrating them?


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## middle.road (Jun 30, 2020)

NCjeeper said:


> Did any of the local companies get back to you on calibrating them?


Nope.  Wish we were near SoCal about now, I know where I'd go...
And if you watch Stan's BarZ shop tour of Standridge out in SoCal from (5) years ago, The dude Mike made an interesting comment
about some companies that offer 'calibration' services... So time to do a bit more in-depth research.

What I would like to find, is a couple of those hooks he's using when placing the plate on the SG.


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## Weldo (Jul 2, 2020)

I'm fairly ignorant when it comes to surface plates but how does a giant chunk of granite go out of calibration?


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## Bob Korves (Jul 2, 2020)

Weldo said:


> I'm fairly ignorant when it comes to surface plates but how does a giant chunk of granite go out of calibration?


By use.  If used carefully and kept clean and the grit kept cleaned off the plate, it will stay in calibration for a long time.  Temperature warps the plated, but will return to true when the temperature returns to the same as before.  Grit will wear the surface.  If the top of the plate is warmer than the bottom, it will warp out of true, but will return to the previous shape when the temperatures change back to the same gradients.  In clean rooms that do do high accuracy work and testing, they are quite anal about controlling all the things that can change the size and shapes of the measuring equipment.  In a home hobby shop it is a lot more difficult to make the environment stabilized, and we will need to settle for a lower tolerance, even if we are quite careful with our setups and work.


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## Weldo (Jul 3, 2020)

For something as hard and stable as granite to warp or wear, I'm guessing we're talking about tenths of thousandths of an inch, right?  I'd imagine the wearing and warping to very miniscule.


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## middle.road (Jul 3, 2020)

Weldo said:


> For something as hard and stable as granite to warp or wear, I'm guessing we're talking about tenths of thousandths of an inch, right?  I'd imagine the wearing and warping to very miniscule.


_Wearing _can get pretty bad. Have a look at ROBRENZ's video. He scored a large Starrett pink for nothing because it had wore beyond the point of being economically feasible to bring it back into tolerance.
Temp changes, as Bob mentions, straighten out after the plate has 'soaked' at the temp it was certified at.

(never did see a Part II...)


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## middle.road (Jul 3, 2020)

From the 'Just when you think you've got it clean dept.'
I took one of the 24x36"ers last night after the sun had set and wheeled it to the end of my apron.
('wheeling' these around is a bit challenging...)
Sprayed some Dawn on it and let it soak for half-a-Cerveza. 
Made up a bucket and used a soft brush on it and gave it a good cleaning. Figured that Dawn is good for cleaning injured wildlife, oughta work for granite... 
Rinsed it down with a pressure nozzle, and let it run off for the other half-a-Cerveza.
Took a clean white bath towel and dried it off, and _still_ it had a light brown tint to it. 
I believe that shows how embedded the dirt and grime can become when they are not maintained properly.


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## Weldo (Jul 3, 2020)

Wow, this is all very surprising to me!  Thanks for the education.  I know some surface plates are cast iron, any benefit or detriments to cast over granite?


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## middle.road (Jul 3, 2020)

Weldo said:


> Wow, this is all very surprising to me!  Thanks for the education.  I know some surface plates are cast iron, any benefit or detriments to cast over granite?


Cast Iron ruled the roost until WWII. When metal was needed elsewhere granite became more prevalent.
Granite is more stable than CI and lasts longer - if maintained properly. There's the catch, as I have found out this past month. 
Just as with most anything, it as to be taken care of.


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## Weldo (Jul 4, 2020)

I watched some of the video you posted and I was amazed to see how the precision level actually showed a change when he slid the counter balance weight from side to side.  I would have never guessed in a million years that moving a 10lb chunk of steel across an 8" thick slab of granite would cause any change whatsoever.  Interesting stuff!


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## Asm109 (Jul 4, 2020)

Best argument for granite:  dropping items on it cause chips that have minimal effects on accuracy.
Argument against cast iron:  Dropping items raises up a mini volcano that affects accuracy until you locate them and stone them flat.


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## Weldo (Jul 4, 2020)

I'm shocked at the level of accuracy capable from a surface plate.  In the video the guy was even standing in the same place on the floor to take readings because he said there could be some deflection!  Holy cow!  On that stone he had about 0.001" of concavity over 4 feet and considered it unacceptable.  I find that fascinating!


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## Cooter Brown (Jul 4, 2020)

I just got My surface plates lapped, it took me a while to find someone to do it for me..... I found him by calling local tool & die machine shops and asking them who does their plates.... Didn't take me very long to get a phone number to a local company, he came to my shop and knocked them out very quickly.... Did two 24x36" plates in less than an hour.... Within .00008" now.....


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## Bob Korves (Jul 4, 2020)

A friend bought a very nice looking pink Starrett 24x36" surface plate,  I told him it was nice, but make sure it is tested and calibrated as necessary.  He finally did so, and it had a .005" low area in the middle of the plate.  A proper test is worth a million expert opinions...


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## Cooter Brown (Jul 4, 2020)

Bob Korves said:


> A friend bought a very nice looking pink Starrett 24x36" surface plate,  I told him it was nice, but make sure it is tested and calibrated as necessary.  He finally did so, and it had a .005" low area in the middle of the plate.  A proper test is worth a million expert opinions...



That's called a soap dish.....


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## middle.road (Jul 4, 2020)

Bob Korves said:


> A friend bought a very nice looking pink Starrett 24x36" surface plate,  I told him it was nice, but make sure it is tested and calibrated as necessary.  He finally did so, and it had a .005" low area in the middle of the plate.  A proper test is worth a million expert opinions...


A good straightedge and a flashlight would show that.
Was it able to be lapped out and get it into 'A' or 'B'?


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## Bob Korves (Jul 4, 2020)

Cooter Brown said:


> That's called a soap dish.....


Or a lake...


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## Bob Korves (Jul 4, 2020)

middle.road said:


> A good straightedge and a flashlight would show that.
> Was it able to be lapped out and get it into 'A' or 'B'?


Yes, it was put back into grade A condition by Standridge Granite.  Not such a big deal for them, everyday work.  This is not something that can be tested or re-calibrated by the typical hobby machinist, or even a pro machinist.  An unknown surface plate is just that, and we are just guessing.  The brand name on it and the calibration label only show what it was when it was last calibrated.  Unless it has been under your personal control since that date, it is pretty much just a Wild A$$ guess what you have, rated only as a potential tombstone...


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## middle.road (Jul 5, 2020)

Bob Korves said:


> Yes, it was put back into grade A condition by Standridge Granite.  Not such a big deal for them, everyday work.  This is not something that can be tested or re-calibrated by the typical hobby machinist, or even a pro machinist.  An unknown surface plate is just that, and we are just guessing.  The brand name on it and the calibration label only show what it was when it was last calibrated.  Unless it has been under your personal control since that date, it is pretty much just a Wild A$$ guess what you have, rated only as a potential tombstone...


We have two definite tombstones in the recent batch. They resemble the surface of the moon. Looks like a toddler went at them with a mini rock hammer...
Found a sticker on one for a company between Knoxville and Nashville that had not showed up in searches.
They at least mention lapping and have pictures on their website which is more than some of the others.
I'll have to get in contact with them after the holiday.

I wonder if Starrett over in Mount Airy, NC does maintenance... That's only (4) hours away.


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## Weldo (Jul 5, 2020)

Is it possible that a plate can be lapped flat even though there's chips through-out the surface?  A surface gauge would have a big enough base to float over at least some chips, right?


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## NCjeeper (Jul 5, 2020)

middle.road said:


> I wonder if Starrett over in Mount Airy, NC does maintenance... That's only (4) hours away.


 If they do and you make a road trip stop by and pick me up.


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## Bob Korves (Jul 5, 2020)

Weldo said:


> Is it possible that a plate can be lapped flat even though there's chips through-out the surface?  A surface gauge would have a big enough base to float over at least some chips, right?


Low spots do not cause problems by themselves, if they are small enough for the test item to bridge the low spots.  Also, granite does not get burrs on it sticking up like what can happen to metal surface plates, the granite chips break clean.  Dings and other low spots can cause real problems if they fill up with swarf or other junk, but we are supposed to clean the plate and the work well before using it.  A bunch of small dings should be no problem at all for a hobby shop, and might be bought for a large discount from 'pretty' plates.


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## Bob Korves (Jul 5, 2020)

Deleted duplicate post...


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## middle.road (Jul 8, 2020)

NCjeeper said:


> If they do and you make a road trip stop by and pick me up.


It would appear, judging by Starrett's FAQ, that they perform reconditioning at their Tru-Stone division which is up in Waite Park, Minnesota

Section 13,





						Precision Granite FAQs
					






					www.starrett.com


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## NCjeeper (Jul 8, 2020)

I wonder if you could drop them off at the Mt. Airy location and they could send them to Minnesota?


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