# Methods for acheiving RCH accuracy in joinery?

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• posted on November 10, 2007, 2:40 am
I know this is a basic question, but I'm hoping I'll read some alternatives I hadn't considered.
I need to make a T, which is a simple butt joint against the 'centre' of another piece of wood. the depth of the short leg of the T should be 5.234567 (exaggerated) within one RCH. I thought I would clamp two blocks 5.234567 wide to the edge of the wood, then glue and tack the long leg of my T using the blocks as a guide. Once my gap was filled with the 5.234567" filler wood I would sand to within 1 RCH>
Any better thoughts on achieving RCH accuracy, especially squareness.
TIA
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• posted on November 10, 2007, 1:35 pm

Many years ago, Edward Deming (father of quality control), made the claim that sometimes it isn't the workers' fault, the fault is in the system. To fix a recurring conformance design problem, the design and the system of manufacturing may have to be changed.
For example: - you are working with wood, the nature of the material is not steel. - Since you are asking this question, I presume you are using home-owner class tools. - your power tools don't weigh thousands of pounds. - your power tools aren't bolted to the floor - woodworking sometimes requires skills, not only book learning, but years of experience with the tools. - any fabrication needs an error tolerance calculation due to fabrication process. What are your + / - errors allowed? (have you allowed for wood compression?)
Nobody can measure anything beyond three digits (0.000) with any meaning as the tools for measuring become inaccurate and the results meaningless. With wood, three digit precision limit is cause for laughter. You are asking for SIX digit accuracy. (The deflection of the wood by the pressure of your hands squeezing it will negate any attempt at SIX digit accuracy.)
In short, your "plan" or design is in error if you attempt to fabricate to such accuracy. Even trying to custom fit with sanding is going to get you high blood pressure. (sanding will many times cause loss of square in 3D of parts, as hand sanding is very, very in-accurate; one place always gets sanded more than another leaving a slight dip in the surface.)
Re-think your design, remember you are working in wood.
For FOUR digit accuracy, the Newsgroup you want is rec.metalworking. Their toys are a bit more \$\$\$\$\$.
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• posted on November 10, 2007, 1:51 pm

To be fair - he did state the six digits was an exaggeration. He's really asking about RCH accuracy.
--

-Mike-
snipped-for-privacy@alltel.net
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• posted on November 10, 2007, 7:20 pm

[...]>
What is RCH??
Tim w
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• posted on November 10, 2007, 8:12 pm
Tim W wrote:

Similar to BCH but red instead of blonde (or brunette).
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____________________________
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• posted on November 10, 2007, 9:59 pm
"Tim W" wrote:

Lew
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• posted on November 10, 2007, 10:07 pm
On Sat, 10 Nov 2007 13:59:36 -0800, "Lew Hodgett"

Is this it?
<http://www.wrch.com/
--------------------------------------------- ** http://www.bburke.com/woodworking.html ** ---------------------------------------------
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• posted on November 11, 2007, 1:29 am
wrote:

No straight answers here then? So now have to go to bed thinking... Royal College of Hairdressers? Registered Caliper Handlers? Roughly Calculated Hairsbreadth?
I am setting the pub quiz tomorrow night. I could ask this question.
Tim w
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• posted on November 11, 2007, 2:21 am

Somebody's gotta put you out of your misery before you do that...
RCH = Red [pudendum] Hair
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Regards,
Doug Miller (alphageek at milmac dot com)
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• posted on November 11, 2007, 2:57 am
On Sun, 11 Nov 2007 02:21:55 GMT, snipped-for-privacy@milmac.com (Doug Miller) wrote:

I had to laugh at this thread, wondering how long it would be before someone asked. I think I was introduced to the phrase when I was about 16 working in a hardware store among nothing but ancient (to a 16 year old) men.
--
LRod

Master Woodbutcher and seasoned termite
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• posted on November 11, 2007, 12:49 pm
wrote:

[...]
Ohhh! LOL. Silly me. I have never heard that one. I will leave it out of the quiz I think.
Tim W
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• posted on November 12, 2007, 2:11 pm

Excellent Idea Tim.
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-Mike-
snipped-for-privacy@alltel.net
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• posted on November 12, 2007, 1:49 am
Doug Miller wrote:

Doug:
I'm nominating you to be our next Secretary of State! You definitely belong in the Diplomatic Corp - so adeptly avoiding the Polictally Incorrect "C" word.
Well done - SIR.
charlie b
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• posted on November 11, 2007, 3:41 am
Tim W wrote:

Will guarantee you get the answer from the pub in less than 20 seconds
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If you're going to be dumb, you better be tough

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• posted on November 11, 2007, 3:52 pm
wrote:

H stands for hair. Not a consistent measurement.
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• posted on November 11, 2007, 5:54 pm
Guess everyone probably has it figured by now but just in case try http://www.m-w.com/cgi-bin/dictionary?pudenda . BTW clicking on "Show pudenda on a map" won't take you to a map :) :) :) :)
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• posted on November 12, 2007, 1:56 am
Mike in Arkansas wrote:

Now we need a dictionary to find out what one of the words referenced to explain an acronym is? This is getting funnier and funnier!
After a day at a slow woodworking show I really did need a thread like this one. Four out loud laughs so far - and I'm only half way through the postings. This is great!
charlie b
BTW the H in question is not limited to the location you provided - especially in France I'm guessing ; )
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• posted on November 12, 2007, 1:52 am
Leon wrote:

Did a lot of research did you? Did you publish the results? I'd really enjoy studying your sampling technique. Have you had your paper go through peer review?
charlie b
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• posted on November 12, 2007, 10:43 am

You'd be _surprised_ -- if not 'startled' -- at the data available under the heading of "forensic science'.

He uses only the traditional/classical methodologies -- no power equipment/ tools/automation whatsoever.
Some things _are_, quite simply better, when done by hand. (thoroughly documented in an 'automation' newsgroup, when somebody transposed the last letters of the first word in their request for a design for a "bar code reader")

Rumor has it that -he- was the one doing the peering.
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• posted on November 11, 2007, 3:40 am
B A R R Y wrote:

Oh, that's evil. ;-)
--
If you're going to be dumb, you better be tough