Inspecting & Lapping a Granite Surface Plate

My friend Lance brought along his electronic differential leveling system so he could do some inspection on a few granite surface plates at our buddy John's shop during the week of the scraping class. The granite plate in this video is a 36"x36" that John bought at an auction. It was not bad but still needed some attention. I'll have some more of this working on my own granite place coming up pretty soon.

My second YouTube channel that covers our fun explorations and traveling.

[t.d.mich.]

I remember one time back in 1973, I set a 100 lb. large cast iron angle plate on the 8x14 ft. granite plate. I turned around momentarily to grab something else, and out of the corner of my eye, I saw the angle plate floating over to the far side of the surface plate. After a quick Oh S#$!, I ran around the other side and stopped it just in time! I had forgotten about this until I watched your cool vid!

[Olliemm]

Eating Oreos while measuring millionths doesn’t seem like it should happen at the same time haha.

[ROBRENZ]

Awesome work Lance and Adam! Love the differential levels. Thanks for the shout out.
ATB, Robin

[thatoneguy]

Back probably 45 years ago my Uncle worked at the Fiat-Allis experimental lab & he took me thru the place & they had a surface plate there that was as big as a king size bed of course as a 16 year old kid I didn't really understand when my Uncle told me it was really flat & used to test how flat a part was. But after watching this & your last video I'm amazed with the process of getting such accuracy. Thanks for putting out such informational vidoes.

[bobbendt]

Enjoyed this video because I worked in calibration for almost 25 yrs and had always heard how they did this but never had actually seen this process. Thanks Adam and Lance.

[khjbbsl]

Hellow m. Lance m. Adam.
Fantastic.... amazin job.
I was working 45 years in machine shops the Last 30 in aerospace industry in Greece
I make thousands parts dificault parts with close tolerance this video is near too me
Congratulations.
John Grizopoylos retired machinist From Greece

[Airtight]

@ROBRENZ Getting a mention, I love it. No reason he shouldn't hit a 100k subs by the end of the week. Lord knows he and his knowledge certainly deserve it. If you don't follow him and you value precision, you're doing yourself a disservice.

[paulrusnak]

Hi Adam, I am a retired film sound recordist with almost 50 years experience. I think that the problem you are having is in the mini connector on the GoPro. There is a switch that is activated in the connector so that when you plug the connector in it disconnects the internal mic so there aren’t two signals going into the camera. The switch is just a metal whisker inside the connector that is very delicate and is easily bent so that there is no connection for either signal. This happens all the time and in a professional situation we just threw them away and got a new one. Is the Hero9 new enough that you can return it for a new one? The GoPros are great when they work but are notoriously unreliable for sound. I would suggest that when you get a working GoPro plug the mini connector in, tape it securely, and leave it plugged in permanently. My dad was a career machinist and watching your videos reminds me of going to the shop he worked in after school and hanging out. Please feel free to contact me if you have any other questions

[mareknetzel]

Thanks Adam for sharing this, really inspiring... I felt like watching Discovery Channel back when it was worth something...

[caseysmith]

I love that every few months to once a year we get these kinds of videos of Lance doing things like this or of scraping, etc. Really shows the science behind the machine shop. Lance truly is one of the brightest!

[steveschumacher]

pretty cool, wish I was born with that kind of patience. Thanks Adam & Lance & John

[pchurchill]

Great episode again. Learn something on your channel very time. Thank you to all

[chieft]

Thanks for allowing us to see what has to be done to get a granite plate up to "A" grade. WOW!!

[DracoOmnia]

lol, "air hockey" at the end with what must be a 20-30 lb cast iron lap was pretty cool

[timmallard]

Great video! My 4 year old now knows what a differential level and repeat o meter look like! That level setup looks slick! Thanks for sharing!

[vp]

.00008" concave across that much surface, not bad; a well taken care of plate. As a Tool and Die Maker who specializes in Tungsten Carbide, .00008" is a football field in size and can make or break a precision fit, just like thermal expansion plays into the finished Dim. First video I've seen of a surface plate being resurfaced. I always look forward to my annual plate inspec/resurface. It is an old craft, usually passed from grandfather, to father, to son, and it's still done by the decades old process of the flat plate and silicon carbide. Not many companies out there doing this type of Craftsmanship. Of course, although not mentioned in the video, that granite plate quarried in the USA is a much better quality and harder plate than the "import" (without naming the sole source country of origin) plate. Great video Adam!

[timothyforney]

That stuff is so amazing, the kind of stuff Tom Lipton would drool over. I enjoyed that.

[millomweb]

I reckon your surface plates should be in a climate controlled room at 20°C for 7 days before they were measured or worked on.

You need 3 flat surfaces to ensure flatness. 2 flat surfaces may be equally curved - one concave, the other convex. The third plate is used to remove that curvature.

[AlmostMachining]

Thanks for sharing this Adam! Awesome equipment Lance. It doesn't seem like much to doing this but the precision of the laps, abrasive used, and most importantly having the inspection equipment to gage the work brings it all together. Robin was able to use his repeatometer the moment he had a proven surface in that optical flat. Great work you guys, Thank you! Phil

[bradthayer]

Complex yet surprisingly straightforward process—with the right tools.