Author Topic: Scraper's block?  (Read 728 times)

Offline PekkaNF

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Scraper's block?
« on: December 30, 2016, 02:37:04 PM »
There is a nifty gadget used to bridge over "rough" scraped surface or granite surface plate when indicator is used. Indicators have typically very small stylys.

BOOK: Foundations of mechanical accuracy: Wayne R. Moore page 29 kuva ja tekstissä lyhyt selostus Scraper's block of hardened nitralloy steel lapped flat and parallel....is used as a gaging point when inspecting scraped surfaces.

Description goes something like this:
Scraper's block of hardened nitralloy steel lapped flat and parallel....is used as a gaging point when inspecting scraped surfaces.

Tried to google that thinggy, but much stuff from scrapbooks, concrete stuff etc...no luck with this gadget.

Is there something readymade substitution or other piece that could be used for this?

Pekka

Got two sided cast iron lapping plate that looks pretty good when clocked, wonder how fine and parallel surface could be reached.


Offline PekkaNF

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Re: Scraper's block?
« Reply #1 on: December 31, 2016, 02:49:48 PM »
I'm wondering would standard gage block do? Unbelievable accurate into nominal direction, often other dimenssional accuracies are not mentioned. Should be plenty good?

Pekka

Offline PekkaNF

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Re: Scraper's block?
« Reply #2 on: December 31, 2016, 04:50:04 PM »
I checked some of the gauge blocks and they seem to be very flat and smooth on other surfaces than gage planes too. I used 0,001 mm resolution DTI and it indicated that the gauge side was whole lot smoother than cast iron paralles and other stuff I had.

Pekka

Offline PekkaNF

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Re: Scraper's block?
« Reply #3 on: January 01, 2017, 05:49:22 AM »
Influenza has got the best of me. Between shivering and sweating I remembered that my brother gave me some mystery parts years ago. One part was a reject comparator table.

Almost perfect. It has even nice camfer on the edge, helps if you get sloppy with DTI stylys. Top is very good, it has minor scratch in it, probably it's the reason it was rejected. Top and bottom are very parallel and best thing is that bottom does not stick.

Pekka

Offline PekkaNF

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Re: Scraper's block?
« Reply #4 on: January 02, 2017, 10:17:32 AM »
Gage block is used in this video:
https://youtu.be/-TIh8K-f8EM?t=903

I tested the one camelback with coparator table. I blued the camelback and tried to measure it. Not sure. Think that the old secondhand (or fifthand?) surface plate has a dip on the middle and on the front.

Pekka