[Shop-talk] Micrometers

[pethier at comcast.net]

But they can skip.  My old instructor kept one in his toolbox.  It was smack on when used to measure a 1" block and off when used on a 2" block.  He insisted on vernier calipers.  

I'd go straight from a vernier to an electronic (skipping over the dial-type) if I was in the trade.

Phil Ethier West Side Saint Paul Minnesota USA
1962 Triumph TR4 CT2846L   1979 Caterham 7
1993 Suburban  1994 Miata C-package  2007 Saturn Ion 3 2.4
http://www.triumphtransamerica.org.uk
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----- "Mark Andy" <marka at maracing.com> wrote:

> From: "Mark Andy" <marka at maracing.com>
> To: shop-talk at autox.team.net
> Sent: Thursday, October 29, 2009 12:17:59 PM GMT -06:00 US/Canada Central
> Subject: Re: [Shop-talk] Micrometers
>
> Howdy,
> 
> On Thu, 29 Oct 2009, David Scheidt wrote:
> > Yes.  No moving parts.  There's a printed pattern on two printed
> circuit 
> > boards.  A sensor detects the change of capacitance as the two parts
> 
> > move relative to each other.  With standard PCB fabrication methods,
> you 
> > can get something like a tenth (one 10,000th of an inch) accuracy in
> 6" 
> > board.  Some apparently use induction, but the idea is the same. 
> The 
> > circuit involved is about a second semester project these days. 
> Only 
> > precision machining the caliper needs is to make sure it runs
> square. 
> > A cheap digital caliper (assuming it's not bent or something) is
> more 
> > accurate than an expensive non-digital one.  Progress is cool, 
> > sometimes.
> 
> That's cool to hear.  Thanks!
> 
> I will say there's one advantage to a dial caliper... If you're like
> me 
> and it might sit six months before you grab it to measure something,
> its 
> unlikely to have a dead battery.
> 
> :-)
> 
> Mark