Surface Plate Calibration Collaboration (or Plate Fest)

Bob Korves

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Rest In Peace
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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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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.
 
Good idea, Thanks for the pics and info.
 
Good thinking. Good pictures. Also interesting post. Thanks
 
Thanks for the pictures. -brino
 
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.
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.
 
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!
 
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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Great time Bob, Thank you for hosting. Plates sure came out nice.
 
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