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Laughing Jaguar
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Join Date: Jul 2008
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Fingernail Scratch Plate for Estimating Surface Finish

09/08/2009 2:43 PM

Back in the 60's I had a small metal plate whose surface was divided into a number of zones with different textures. A machinist could scratch a metal part with his finger nail, then scratch zones in the Scratch Plate until he got a similar sound. When he did, he could read the surface finish. They were low cost, simple to use and were remarkably accurate.

I have an idea that they were manufactured by the HeliCoil company but after 50 years, I don't trust any memory that comes from an area with so many cobwebs.

Does anyone recognize this tool and know where they can be purchased?

Thanks

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ronseto
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Technical Fields - Technical Writing - New Member Engineering Fields - Marine Engineering - New Member

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Location: Vancleave, Ms about 30 miles inland from Biloxi and the coast
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#1

Re: Fingernail Scratch Plate for estimating surface finish

09/08/2009 3:12 PM

This is what you are looking for.

http://www.engineersedge.com/catalog/product_info.php/products_id/142/language/en

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Laughing Jaguar
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#2
In reply to #1

Re: Fingernail Scratch Plate for estimating surface finish

09/08/2009 3:23 PM

Ron, that's it!

The one you pointed to has a far greater number of textures than what I recall. far more than what is needed in the average machine shop. and the asking price reflects it.

Thanks. I know what to look for now, in a more modest version.

L.J.

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TVP45
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Join Date: Jul 2007
Posts: 4448
Good Answers: 143
#3

Re: Fingernail Scratch Plate for Estimating Surface Finish

09/08/2009 3:50 PM

Here you go. Look at the 10.99 economy one; that's what I have.

http://www.mcmaster.com/#surface-finish-comparators/=3jn78n

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cwarner7_11
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#6
In reply to #3

Re: Fingernail Scratch Plate for Estimating Surface Finish

09/09/2009 12:06 PM

I have one of the plastic economy models, and it works for me, although I am not doing "certified" inspections- only use it to help specify surface finishes on parts I design.
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Street Preacher
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Join Date: Sep 2009
Location: Coachella, CA
Posts: 11
#4

Re: Fingernail Scratch Plate for Estimating Surface Finish

09/08/2009 4:57 PM

Does this look familiar?

The website this came from is http://store.flexbar.com/merchant2/merchant.mvc?Screen=CTGY_IM&Store_Code=FLX&Category_Code=Suf-Rough.
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Ti QE
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Engineering Fields - Manufacturing Engineering - New Member Engineering Fields - Mechanical Engineering - New Member

Join Date: Apr 2008
Location: USA
Posts: 113
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#5

Re: Fingernail Scratch Plate for Estimating Surface Finish

09/09/2009 9:39 AM

skip the middle men and go directly to

Info [info@garelectroforming.com]; they manufacture various types (milling, grinding, blasting) and can be purchased as a certified set (NIST certs).
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Previous in Forum: Annular Cylinder - Barrel and Piston Clearance   Next in Forum: How to Strengthen Tubing Mechanically

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