[gingery_machines] Re: new article: How Accurate is Your Micrometer?

Rick,

In your article you state:

"After the initial publication of this article, JR Williams pointed me to an optical instrument that tests the parallelism of the mic's anvil and spindle contact surfaces. You can see this amazing instrument at http://www.mitutoyo.com/TerminalMerchandisingGroup.aspx?group=1534"

The link points to a single optical flat (Mitutoyo Series 158). This will show the flatness of an anvil, spindle or gauge block but to truly check the parallelism you need a set of four (Mitutoyo Series 157). Different sets are needed for inch and metric micrometers as well as different sizes.

See page 3 of this PDF for an explanation:
http://mticatlive.ctt-inc.com/catalog/pdf/T-26.pdf
<http://mticatlive.ctt-inc.com/catalog/pdf/T-26.pdf>

Catalog listing of available sets:
Catalogue - Accessory Micrometer - MITUTOYO - (Version JPG) - 3
<http://pdf.directindustry.com/pdf/mitutoyo/accessory-micrometer/4906-14442-_3.html>

Craig

--- In gingery_machines@yahoogroups.com, "Rick Sparber" <rgsparber@...> wrote:
>
> Dave,
>
> Both of these articles are very good. No reason to duplicate any of the
> text. I just included the URLs in my article along with an additional
> acknowledgment.
>
> You say "stacking gage blocks to achieve an accurate dimension for testing
> will also give incorrect results". I'm not sure what you mean by
> "incorrect". The entire point of having gage blocks is so you can stack
> them. I do understand that each block contributes an uncertainty to the
> total. By knowing the total uncertainty, I can judge how much to trust the
> testing result.
>
> I was just playing around with my spacer blocks and my HF caliper. After
> zeroing, I took out a 1.000" spacer and the caliper read 1.000". I then took
> out a 0.5000" spacer and the caliper read 0.5000". I know that the caliper
> only reads 0 or 1/2 thou in the right most digit. So I conclude that within
> the displayed value on the caliper, it is damn good at 0.5000" and 1.000". I
> won't venture a guess as to the accuracy at any other values.
>
> These calipers don't have a threaded rod and threaded sleeve but they do
> have a pattern on the body and a pattern on the pick up so I expect have
> similar error sources.
>
> Rick
>
> -----Original Message-----
> From: gingery_machines@yahoogroups.com
> [mailto:gingery_machines@yahoogroups.com] On Behalf Of Dave
> Sent: Monday, January 24, 2011 4:50 PM
> To: gingery_machines@yahoogroups.com
> Subject: [gingery_machines] Re: new article: How Accurate is Your
> Micrometer?
>
>
> Rick this might help on your article
> http://www.starrett.com/download/222_p1_5.pdf
> http://www.angrave.com/catalog/GageBlocks.html
> but testing the accuracy of any measuring tool in an uncontrolled area will
> give you incorrect results. stacking gage blocks to achive an accurate
> dimension for testing will also give incorrect results. Gage blocks have a
> +/- tolerance, although small will effect the measurment in an uncontrolled
> enviroment.
> For the average hobbist +/- .001 is close enough, and doesn't need to worry
> about the accuracy of the tool , just the repeatability.
>
> Dave
>

__._,_.___

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