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

Dave,

Ah, now I see. I was thinking in the range of 1" while you were up there at 6". I agree with what you are saying. When I get above 2", I have no choice but to use a caliper or my DRO which has a lot of error compared to my spacer blocks. Most of this error on the mic is from user technique. On my DRO, the error is strictly from the error component related to total distance.

I have written about this:

http://rick.sparber.org/Articles/PAC/PAC3.pdf

Rick

-----Original Message-----
From: gingery_machines@yahoogroups.com [mailto:gingery_machines@yahoogroups.com] On Behalf Of David Patterson
Sent: Monday, January 24, 2011 9:55 PM
To: gingery_machines@yahoogroups.com
Subject: RE: [gingery_machines] Re: new article: How Accurate is Your Micrometer?

Lets assume,I know bad me to assume,you have to stack 6 blocks to reach 6". At +/- .0001 for each block, that would be +.0005" if all the were +.0001. Your micrometer has a tolerance of +/- .0001. if that runs to the full side your now at .0006. Don't know about your eyes but I can loose sight by +/- 2 to 3 marks by looking too long at the vernier scale, if I'm lucky I can get to +/- 1 mark. So now I have a possible error of about .0008 to .0009. That's assuming everything is to the plus side, it could also be the same to the low side, meaning tolerance band of .0016 to .0018, that is just for measuring the part. To get to +/- .002 for making a part is even harder. Because to hit an actual dimension of say 6.0000" +/- .0002 is near impossible for the home shop, because you can't measure that close to an actual dimension, nor can your machine cut a part that close, the graduations are .001 and the slop in the machine is probably .002"+, if you have
a good machine. so yeah I'm more than happy to work to .002 or +/-.001". Guaranteed you pass your part, that you measured, to someone else to measure with a different micrometer the will get a different dimension than you, if you try to measure to .0001".

Dave Patterson

__._,_.___

Reply to sender | Reply to group | Reply via web post | Start a New Topic

Messages in this topic (28)

Recent Activity:

New Members 7
New Photos 6

Visit Your Group

<*> Member map - Who and where we are. Please add yourself so members can find each other.
http://groups.yahoo.com/group/gingery_machines/app/peoplemap/view/map

MARKETPLACE

Stay on top of your group activity without leaving the page you're on - Get the Yahoo! Toolbar now.

Get great advice about dogs and cats. Visit the Dog & Cat Answers Center.