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Checking a cast iron surface plate (Video Included)

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ThunderDog

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#1
Hi all,

Continuing my exploration and understanding of scraping and measurement, I am trying to identify if my used tools are acceptable to begin some small practice scraping projects.
I am referring to Connelly's text, section 9.12 for this video. As I posted a video over on the Sheldon sub-forum a few weeks ago, it became apparent to me that I needed to identify whether or not these tools were acceptable for usage. I hope this video serves as a constructive platform for everyone to learn from my experience. If this is totally wrong, please say something. If you see something that needs tweaking or brought to the attention of potential viewer's, please provide feedback so that we all may learn from it. I guess I'm just saying that I made this video so people can arm-chair quarterback. I'm willing to be the test dummy, lol. Enjoy!!:grin big:

 

Rooster

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#2
Well done video, i look forward too more. I've checked my cheapo 12"x 18" x 3" by using a .0001 test indicator mounted to a surface gauge and swinging it from various points on the plate (poor man's repeat-o- meter ). I was surprised at how dead on the readings were.
 

Richard King 2

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#3
It's late ..will edit tomorrow if I have any typo's.
Did I miss something (apologize if I did) does the surface plate have 3 legs under it? (3 Points). Is your table it's sitting on sturdy?

If it is and you have a precision level like a Starrett 198 .0005"/12 accuracy or one of the $99.00 Polish levels they sell on Ebay.

I have pictures of how to test a plate. Rooster's way is like the Don Bailey on You Tube<How to determine surface plate is out of tolerance>
I would have linked to it, but not sure I could, so I just wrote down the title so the readers can look it up.

The scraping points look good and percentage of contact is good too. I would recommend you wipe the plate and SE with your hand to check for dirt in the blue. Also set them down slow and "listen" for a sand under shoe sound. Thats dirt getting squished. Dirt under a straight-edge can scratch the plate and or SE. The reason the camel back is probably high on the ends at first is you rubbed it on a shorter plate and the ends did hit properly. It probably looked good but you got false readings. The test across diagonally is better.

The long scratches or line are probably from when the SE was planed and the operator figured it would be scraped out but wasn't and he saw the PPI and POP and was weary and said "good enough" . It was going to be his SE, If he had planed on selling it,he would have had to scrape it a few more passes. If you or anyone else wants a new copy for the Connelly book I sell the 23rd printing, 2013. I cherish a like new, 2nd addition 1955 I have been thinking of selling for a Premium price. My Dad met Edward Connelly and I used to buy books from him and his late brother Ray. I now buy books from his estate. I will write more about more about that and other products on my own thread soon. For a youngster you look pretty good...who taught you to scrape? I have a class in April in Springfield, VT and if your looking for a job I know a Journeyman Rebuilder out there looking to hire people.
 
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Richard King 2

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#4
I just sent a job to my friend and student Daryl, member name Ugly Dog who also lives in MN about an hour from me, hopefully he does a show and can share it here too.
 
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#5
Premium Price is putting it mildly Rich. There was only on on ebay last week and it was $500.00.

"Billy G"
 

ThunderDog

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For a youngster you look pretty good...who taught you to scrape? I have a class in April in Springfield, VT and if your looking for a job I know a Journeyman Rebuilder out there looking to hire people.
Sir, I don't think I've earned that compliment. But, that just gave me a glimmer of hope that I can do this.:grin::grin:
I have NO formal training regarding anything related to machining. It's all self-taught through books and hands-on practice with a hint of having fun mixed into the equation. I'm saving my pennies in hopes of taking one of your classes.

Did I miss something (apologize if I did) does the surface plate have 3 legs under it? (3 Points). Is your table it's sitting on sturdy?
Yes, it has 3 legs only. The table it's sitting on is very stout. I built it specifically for the plate.

I have an 8" Starrett 98. I will take a look at the video you suggested later today.

One small newbie question, you said
he saw the PPI and POP
. PPI is points per inch, right? What is POP?
 

Richard King 2

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#7
PPI - Points per 1 inch & POP - Percentage of points in one inch. I was looking at your plastic gage...looks smaller then 1" x 1" lol?

Bill check out Amazon, someone had one on there for $2000.00

I hate to get rid of it, as it's so special. I bought it from an estate sale. The fellow wrote his name and address and he bought it on 1/27/56 for $10.75. I sell the new ones on Ebay for $139.00
 
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