Author Topic: Granite surface plate..has come to me!  (Read 11296 times)

Online steamer

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Re: Granite surface plate..has come to me!
« Reply #15 on: May 17, 2013, 04:25:43 PM »
Well....gotta be better than what is smells like now! :lolb:

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Offline 90LX_Notch

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Re: Granite surface plate..has come to me!
« Reply #16 on: May 17, 2013, 04:38:52 PM »
Based on the above posts, I'll bet the "conditioner" in the Starrett solution is lanolin. 

I should note that the alcohol we used was denatured.

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Offline mklotz

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Re: Granite surface plate..has come to me!
« Reply #17 on: May 17, 2013, 04:40:00 PM »
And don't forget the fragrant orange bouquet wafting through the shop too 

Just wait until I start extolling the benefits of camellia oil as a lubricant.  Oh, and rose water as a coolant.
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Offline MuellerNick

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Re: Granite surface plate..has come to me!
« Reply #18 on: May 17, 2013, 05:27:17 PM »
Quote
For minimum sag and distortion a beam like your surface plate should be supported at its Airy points.  These are two points located symmetrically a distance of:


That's the theory.
Practice is, that the plate should have the feet already installed or marked, exactly at the points where it sat while being ground. In practice, that won't be the Airy points nor the Bessel points.




Nick

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Re: Granite surface plate..has come to me!
« Reply #19 on: May 17, 2013, 05:29:46 PM »
Quote
For minimum sag and distortion a beam like your surface plate should be supported at its Airy points.  These are two points located symmetrically a distance of:


That's the theory.
Practice is, that the plate should have the feet already installed or marked, exactly at the points where it sat while being ground. In practice, that won't be the Airy points nor the Bessel points.




Nick


Good point Nick!

"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

Offline Jo

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Re: Granite surface plate..has come to me!
« Reply #20 on: May 17, 2013, 05:45:30 PM »
In practice, that won't be the Airy points nor the Bessel points.

Forgive my ignorance: Could someone explain these terms to me  :)

Jo
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Offline mklotz

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Re: Granite surface plate..has come to me!
« Reply #21 on: May 17, 2013, 05:47:05 PM »
Quote
For minimum sag and distortion a beam like your surface plate should be supported at its Airy points.  These are two points located symmetrically a distance of:


That's the theory.
Practice is, that the plate should have the feet already installed or marked, exactly at the points where it sat while being ground. In practice, that won't be the Airy points nor the Bessel points.

Interesting.  My plate (certainly not a met standard) had no mounting points indicated.

Why would they support a precision plate anywhere other than the Airy/Bessel points while grinding?  Certainly they must know that if the plate is mounted on these non-Airy... points later, its gravitational distortion will be more than the minimum achieved by Airy mounting?  Inquiring minds want to know.
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Offline MuellerNick

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Re: Granite surface plate..has come to me!
« Reply #22 on: May 17, 2013, 06:07:51 PM »
Quote
Why would they support a precision plate anywhere other than the Airy/Bessel points while grinding?


That is a good question!
But first, those Airy and Bessel points are only good for a beam, and not a slab. You would need 4 points, but that would be a contradiction to all the efforts to NOT influence the plate by the table it sits on.


But things are much simpler: It won't make a difference. I didn't calculate that, but I simply called the manufacturer and asked him exactly that question. In production, they do mark where the plate sat while grinding and then stick their rubber feet at that place. If they do have to hand-finish them, they already sit on their three feet.
There is also a very practical reason to have the feet more near the end: It won't tilt that easy with a heavy load on it.




BTW calling the manufacturer:
After a year of having it bought, I had a question. I was connected to the right person. He asked me for the serial number and had the protocol on his screen after a few seconds. Question was answered. That is the back-tracability required by the standards. Try that with your manufacturer (in case you even know him).




Nick

Offline kevin45

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Re: Granite surface plate..has come to me!
« Reply #23 on: May 26, 2013, 01:15:19 PM »
We always use Starrett cleaner on our surface plate at work and personally, I don't think it was anything more than liquid wax. I did find about the best thing to clean the surface plate though was good ole WD-40. It will pull dirt up off of the plate that other cleaners won't touch. Plus any tools (angle plates, 1-2-3 blocks) won't pull moisture from the plate and will keep your tools from staining. That was bad where I worked as in the summer the humidity would be great, and then having a cooler surface plate did not do the precision tools any good.

Online steamer

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Re: Granite surface plate..has come to me!
« Reply #24 on: May 26, 2013, 01:48:41 PM »
Hi Kevin,

I know it's expensive...but I use WD 40 also...but then again..I only have a 12 x 18 plate :shrug:

Dave
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Damned ijjit!

Offline Mosey

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Re: Granite surface plate..has come to me!
« Reply #25 on: May 26, 2013, 02:10:57 PM »
I walked into MSC's retail outlet one fine day about 10 years ago, and on the closeout table was an 18 x 24" black granite surface plate, $15.00. It had a small chip in one edge. I think it is grade B, certainly exceeds anything I'll ever need. It sits on it's own bench, and she made a nice vinyl cover with thin plywood plate for it (free). I guess I better remount it on it's airey-fairey points, whatever they are. I clean it with alcohol every couple of years whether it needs it or not. I don't scrape. It is the center of my metrology department.
Mosey
PS, They also had a Starrett flexible indicator magnetic base, new in the box on closeout for $20.00. I bought it. Never could find anything wrong with it.

And, Marv, I suggest the clock in your shop might be multi-torbillon to avoid gravitational distortion of the time while laying out on the surface plate.
« Last Edit: May 26, 2013, 02:20:02 PM by Mosey »

Offline kevin45

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Re: Granite surface plate..has come to me!
« Reply #26 on: May 28, 2013, 02:34:50 PM »
Hi Kevin,

I know it's expensive...but I use WD 40 also...but then again..I only have a 12 x 18 plate :shrug:

Dave

Dave......order it by the gallon and it's a lot cheaper then put it in your own pump bottle or pick up a WD-40 pump bottle. ANd don't forget to read the back of the can. There are a lot of uses for WD-40. I don't even think they list surface plate  :Lol: I use it to spritz down mo lathe and mill when I'm not using them. In Ohio, it can be dusty dry one minute, then the next minute we can have 100% humidity which machines and tools DO NOT like very well.