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

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


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 $$$$$.

"Phil-In-Mich." wrote in message
...


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



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.)


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

--

-Mike-

"Mike Marlow" wrote in message
...

[...]
.... He's really asking about RCH accuracy.

What is RCH??

Tim w

Tim W wrote:
"Mike Marlow" wrote in message
...

[...]
.... He's really asking about RCH accuracy.

What is RCH??

Similar to BCH but red instead of blonde (or brunette).


--

dadiOH
____________________________

dadiOH's dandies v3.06...
....a help file of info about MP3s, recording from
LP/cassette and tips & tricks on this and that.
Get it at http://mysite.verizon.net/xico

"Tim W" wrote:

What is RCH??

Ask your Daddy.

Lew

On Sat, 10 Nov 2007 13:59:36 -0800, "Lew Hodgett"
wrote:


"Tim W" wrote:

What is RCH??

Ask your Daddy.


Is this it?

http://www.wrch.com/

---------------------------------------------
** http://www.bburke.com/woodworking.html **
---------------------------------------------

On Nov 10, 7:35 am, "Phil-In-Mich."
wrote:
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.

Ideally, the skill of the worker includes his/her choice of tooling,
fixturing, and processing - essentially the "system of manufacturing".

For example:
- you are working with wood, the nature of the material is not steel.

Very true.

- Since you are asking this question, I presume you are using home-owner
class tools.

He probably is. This is not necessarily a problem. In 2003 I held an
accuracy contest here in the wreck. The idea was prompted by a guy
who claimed that he could work wood in the ten-thousandths of an inch
range on his "super tuned" contractor's saw (throughly de-bunked).
Here's the thread with the results:

http://groups.google.com/group/rec.w...7a6e7e35004e30

Sorry, the official results on my web site have long since been
deleted. The winner (Owen Lowe) cut acrylic samples to within 0.005"
using the stock miter gauge on a Unisaw (sold to home shop woodworkers
everywhere in the US). He aligned his saw using a "feel the rub"
technique. The best wood samples came in at 0.011" (hard maple).
Probably could have done better with lignum vitae. Not a chance with
pine, oak, or walnut. The thread includes my take on why it's hard to
do much better with wood. My benchmark on a Unisaw cutting aluminum
using the stock miter gauge was about 0.001".

- your power tools don't weigh thousands of pounds.

The Unisaw doesn't weigh thousands of pounds.

- your power tools aren't bolted to the floor

My Unisaw is on wheels. I can do work to about 20 millionths in steel
on my surface grinder. It's not bolted to the floor either. But it
does weigh about 2500 lbs.

- woodworking sometimes requires skills, not only book learning, but years
of experience with the tools.

Absolutely. Experience is required to achieve such results or even
comment on their feasibility.

- any fabrication needs an error tolerance calculation due to fabrication
process. What are your + / - errors allowed? (have you allowed for wood
compression?)

He probably hasn't. Sounds like he's doing emperical work.

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.)

Hmmmm....

Just call me "Nobody"!

Please feel free to stop by my shop anytime and I'll show you reliable
and repeatable linear measurements to within millionths of an inch and
angular measurements to less than an arc second. Yes, that's six
digits. No, it has nothing to do with wood. But, depending on the
species, and the direction of measurement (along the grain, not across
the grain) it's possible to work wood to less than 0.005" - all day
long, any day of the week. Measuring it is no problem. I wouldn't be
willing to claim anything better.

You did say "nobody" can measure "anything" beyond 3 digit
accuracy. ;-) I think it's safe to say that we don't need to consider
Hisenberg uncertainty or the observer effect for this sort of work.

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.)

I would liken hand sanding to hand scraping bed ways. Considerable
skill is required but I don't doubt the feasibility. I wouldn't try
it but there are guys who can scrape machine bed ways to within ten-
thousandths of an inch with a hand held scraper.

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 $$$$$.

I assume you mean rec.crafts.metalworking. I think a fairly decent
manual mill can be had for the cost of a 3hp unisaw. I would like to
learn more about Bill's application and needs. Perhaps there are
better ways for him to solve the problem.

Ed Bennett


Submit your work to the Gallery:
http://www.ts-aligner.com/gallery.htm

Ed:

You're taking this thing WAY TOO SERIOUSLY.

I know you think in machinist terms - I vividly recall the
"interaction" between you and Strickland - but lighten
up a little and you'll get at least a smile out of where
this thread has gone - probably the intent of the original
poster.

When was the last time you saw the word "pudenda"
in a woodworking - or even a machinist - forum?

charlie b

ps - I really like my TS-Aligner Jr. Deluxe. Great set
up tool - at a reasonable price and very high quality.
It, along with a good 3' straight edge, a set of feeler
gauges, a mallet and some special jigs made it POSSIBLE
to tune my Robland X-31. Wasn't easy by any means,
but possible - with your TS-Aligner's help. Thanks - again.

On Nov 11, 7:04 pm, charlieb wrote:
Ed:

You're taking this thing WAY TOO SERIOUSLY.

I know you think in machinist terms - I vividly recall the
"interaction" between you and Strickland - but lighten
up a little and you'll get at least a smile out of where
this thread has gone - probably the intent of the original
poster.

When was the last time you saw the word "pudenda"
in a woodworking - or even a machinist - forum?

charlie b

ps - I really like my TS-Aligner Jr. Deluxe. Great set
up tool - at a reasonable price and very high quality.
It, along with a good 3' straight edge, a set of feeler
gauges, a mallet and some special jigs made it POSSIBLE
to tune my Robland X-31. Wasn't easy by any means,
but possible - with your TS-Aligner's help. Thanks - again.

Hi Charlie,

Sorry if it seems like I'm out of step with where the thread has gone,
but you have to understand that none of that had happened when I
replied. I was commenting on what "Phil-In-Mich" said (a somewhat
misguided treatise on Edward Demming and the "futility" of accuracy in
woodworking). At the time, his was the only response to Bill's post.
I have no problem with how the thread has evolved. I almost suggested
that Tim do a Google search on "RCH" but that would have spoiled the
fun.

Thanks for the good words. Glad to hear from yet another happy
customer!

Ed Bennett


Submit your work to the Gallery:
http://www.ts-aligner.com/gallery.htm

"Phil-In-Mich." wrote in message
...


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


Many years ago, Edward Deming (father of quality control),

schnip

So who's the mother? Is she the one the RCH came from?

B.