# Surface Plate Calibration Collaboration (or Plate Fest)



## Bob Korves (Apr 7, 2016)

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 Southern California drop by on one of their road trips.

If we had done this separately it would have cost each of us $175 mileage charge plus $165 minimum invoice charge.  This way, my 18x24 plate cost me $60 for the work and $43.75 for my quarter share of the mileage charge.  What would have cost me $340 doing it alone became $103.75 doing it as a group.  That is less than 1/3 the cost of going it alone, and saves the cost of shipping it for calibration and back again, which is expensive and there is also a fair chance of the plate being damaged or ruined in transit.

The plates are all now calibrated to AA standards, none of them have more than 40 millionths repeatability, and some are within 20 millionths.  These techs are highly skilled, care about what they do, go way past the minimum requirements, have pride in their work, and are absolutely pleasant to deal with.  Three techs came, and they were done and gone in less than an hour and a half, on to their next job.

Getting together with the other machinists was also great fun, as usual.


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## NCjeeper (Apr 7, 2016)

Very cool.


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## extropic (Apr 7, 2016)

What a great idea.

It looks like one tech is using a cast iron flat to lap a granite plate.

I'm wondering how bad the worst granite was, before lapping. That is, did they improve a "B" plate into a "AA" in such a short period of time?

Thanks for sharing.


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## kvt (Apr 7, 2016)

Good idea,   Thanks for the pics and info.


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## LucknowKen (Apr 7, 2016)

Good thinking. Good pictures. Also interesting post. Thanks


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## brino (Apr 7, 2016)

Thanks for the pictures. -brino


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## CraigB1960 (Apr 7, 2016)

Excellent idea!  Thanks for posting the photos.


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## Bob Korves (Apr 7, 2016)

extropic said:


> What a great idea.
> 
> It looks like one tech is using a cast iron flat to lap a granite plate.
> 
> ...


Yes, Meehanite cast iron laps and diamond powder of various grits.

Mine was the worst, at 1.5 thousands out, a "bowl" in the center.  I had guessed that, having bought it off a rack behind a machine shop, covered with dirt and grime and then chasing a tenths indicator around it.  It took about 20 minutes to half an hour to calibrate.  Ulma Doctor's two  plates were good enough that they would have passed class B as they were, and they finished at 20 millionths after 15 minutes work.  The smallest plate actually took longer because the lapping plates being larger than the surface plate causes overhang which makes the work more fussy.  The larger 24x36 plates were fairly flat, but one of them had a twist in it (see writing on plate), and that one also took longer.  All the surfacing was done with cast iron lapping plates.


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## Ulma Doctor (Apr 7, 2016)

i wish i didn't have to go to San Luis Obispo yesterday and miss the party!
thank you very much Bob for coming up with the great idea of joining forces to get this done.
now the real fun begins!


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## Catfish6945 (Apr 7, 2016)

Bob Korves said:


> 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 Southern California drop by on one of their road trips.
> 
> If we had done this separately it would have cost each of us $175 mileage charge plus $165 minimum invoice charge.  This way, my 18x24 plate cost me $60 for the work and $43.75 for my quarter share of the mileage charge.  What would have cost me $340 doing it alone became $103.75 doing it as a group.  That is less than 1/3 the cost of going it alone, and saves the cost of shipping it for calibration and back again, which is expensive and there is also a fair chance of the plate being damaged or ruined in transit.
> 
> ...



Great time Bob, Thank you for hosting.  Plates sure came out nice.


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## Catfish6945 (Apr 7, 2016)

Ulma Doctor said:


> i wish i didn't have to go to San Luis Obispo yesterday and miss the party!
> thank you very much Bob for coming up with the great idea of joining forces to get this done.
> now the real fun begins!


Mike,
You missed it.  I left you Scribe with your plates.  I had to give one to Bob so he wouldn't take yours.


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## eeler1 (Apr 7, 2016)

I've been to your 'shop', where did you get all that open space?  Really nice project.  Wish I had a beat up surface plate to fix.


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## Bob Korves (Apr 7, 2016)

eeler1 said:


> I've been to your 'shop', where did you get all that open space?  Really nice project.  Wish I had a beat up surface plate to fix.


Hi Jon,
It's a three car garage, just kicked my ONE car out for the plate fest.  I did realize that I never posted any pics of the rest of the shop and the machines, maybe next time...


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## extropic (Apr 8, 2016)

Bob Korves said:


> Yes, Meehanite cast iron laps and diamond powder of various grits.
> 
> Mine was the worst, at 1.5 thousands out, a "bowl" in the center.  I had guessed that, having bought it off a rack behind a machine shop, covered with dirt and grime and then chasing a tenths indicator around it.  It took about 20 minutes to half an hour to calibrate.  Ulma Doctor's two  plates were good enough that they would have passed class B as they were, and they finished at 20 millionths after 15 minutes work.  The smallest plate actually took longer because the lapping plates being larger than the surface plate causes overhang which makes the work more fussy.  The larger 24x36 plates were fairly flat, but one of them had a twist in it (see writing on plate), and that one also took longer.  All the surfacing was done with cast iron lapping plates.



Thank Bob,

And thanks again for posting about the "plate fest" idea. It's perfect for those of us who would like to save some $$ where we can.


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## itsme_Bernie (Apr 18, 2016)

Holy crap what an Awesome idea!!!   I have to reread your first message, but I'd like to learn how do I arrange for this in Northern New Jersey! I'm totally up for having a surface plate calibration event!


Sent from my iPhone using Tapatalk


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## Ulma Doctor (Apr 20, 2016)

here's a video Randy Richard made from the experience!





i'm sorry i had to work and was not present for the surface plate re-calibration party.
Thanks again Bob for the great idea!
(pictures 1,3, & 10 show my surface plates  , a 12x18 Escondido Blue Granite and a 18x24 Escondido Black Granite)


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## bfd (Dec 21, 2016)

I always assumed that my plate is ok. I have one of the $88 18 x 12 plate from enco. never really used it. but it is a really good idea bill


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## Bob Korves (Dec 22, 2016)

bfd said:


> I always assumed that my plate is ok. I have one of the $88 18 x 12 plate from enco. never really used it. but it is a really good idea bill


Bring it over, Bill, and we can spot it in to my newly calibrated plate by using some spotting ink for scraping.  That will likely tell the tale, at least pretty well...


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