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Care and Feeding of a Cast-iron Surface Plate?

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kb3guy

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Hey all,
I had quite a find recently, which I will add to my small collection of formerly abused and neglected machine tools. I needed a vibration-resistant, heavy table for an optics project I'm working on, and I found a 18x36, cast iron surface plate for cheaper than I could get a granite tombstone of the same size. It's had a hard life, pretty clearly - it's got dings, and weld pits, and came caked in grease (way more than in the photos.) But once I got it cleaned up, the name "Brown and Sharpe" came out from under the layers of grime.

Now I'm curious about how much I can expect from this plate - I'm really tickled that I happened upon this piece of industrial history, but can I restore it to the point where it will be a valuable reference flat for scraping? What would be my options in that regard - lapping, planing, or knocking off the burrs and leaving well-enough alone? I'm curious what the experienced scraper hands here have to say about it. Even if it's doomed to boat-anchor status, it is a very nice boat anchor.

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benmychree

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I'd think about, first getting it Blanchard ground to remove the pits and dings and get it close to flat, then get a scraped bridge straightedge at least as long as the plate, and another scraped plat at least as wide as the plate and start learning to scrape. Only thing I would be concerned about is the weld pits, they could be quite hard and perhaps very hard to scrape. Otherwise, you could just remove the high spots and use it as it is, if it is accurate enough for your present needs. It may be possible that at least some areas on it are still reasonably accurate for some classes of work, but most likely far from accuracy needed for use as a scraping master. It would seem to be a blank canvas at this point, it has potential.
 

Bob Korves

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The real question is "What do you want to use it for, and how do you want to use it?" I am not so sure that cast iron surface plates are vibration deadening. If you hang them from a rope and and hit them with a hammer, they ring like a bell. If not, they are cracked or otherwise not correct. They have a relatively high modulus, not as high as steel, but still vibrate.
 

Rooster

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Greetings, what about having it surface ground.
 

Janderso

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It's pretty rough, is it worth it?
There are cast iron surface plates out there in better shape just looking for a good home.
You got my $.02
 

Bob Korves

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Greetings, what about having it surface ground.
Surface grinding can leave the surface 'toughened', and it can be nasty to scrape on until you get below the tough "skin." Dealing with that toughness can also make for an uneven surface after roughing. That has been my experience with scraping surface ground mild steel. I have not tried scraping on surface ground cast iron. I took a fly cutter to mine on the mill, only took a short time and I was down to a flat surface of clean, nice metal. Regardless of the method, it needs to be flat within .001" or so over all the surface if you do not want to spend the rest of your life scraping the plate to a flat and finished state.
 

Richard King 2

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If your going to use it as a stand and not a surface plate mount your parts and paint the rest. Or if you can live with the gouges have someone give it a Chicago scrape job.
 

Richard King 2

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I see your in Maryland. Down in Easton MD there is a private museum, they have a planner that could clean up the plate. You may have to donate some time as a volunteer or a 100.00 or so. They have an museum of all belt driven machine tools and steam farm equipment. I taught a scraping class there a few years ago.
https://tuckahoesteam.org/collectionspages/collectionsmachine.html or message me and I can give you the email of one of the machine shop volunteers.
 

DiscoDan

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Richard, I am in Maryland too and I know Jeff Greenblatt, one of the volunteers. I donated some items to them and he gave me a tour and I saw a scraping project someone was working on. No doubt helped along by your class!! What an awesome machine shop. I plan on volunteering after car show season ends. I am headed there Saturday for the big steam and gas show.
 
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matthewsx

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If you're looking for an optical isolation plate why not get that instead of this surface plate? I've seen them at auction with almost no interest.

John
 

Latinrascalrg1

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From the thread title I thought It was gonna be about the new diet and care instructions for someones shop Pets named "Cast Iron and Surface Plate!"
 

DiscoDan

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Richard King, I was at Tuckahoe today and got to watch Paolo (?) scraping the ways on a lathe as a demonstration. Very interesting. Never witnessed it in person before.
 

Richard King 2

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He is a scraper, a quick learner too. Plus he is probably the one who would plane the surface plate. Next time you see him say hi from me. I taught them to scrape down there. Paolo is the guy with the camera.
 

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mmcmdl

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I'll make it down one of these days on the way to OC ! Looks like a cool place Dan .
 
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