The question:
Do we expect too much of our machines
and
not enough of ourselves
An earlier thread on combination machines like the Robland X31,
Mini-Max and Felder, got into the advantages of dedicated,
stand alone machines over combination machines (table saw
with rip fence, joiner with fence and planer). One major
difference was that with combination machines, you lose
your last set up for each operation and don't with dedicated,
stand alone machines. Another noted difference were the
rip fences. U.S. market fences typically go all the way
to the back of the saw table and often are secured front
and back, while combi fences typically only lock down in
the front and some only extend just beyond the back of
the saw blade.
But the difference that led to this post was the difference
in setting the rip fence. With a combi you typically
use a tape, or piece of wood the width you want, to set the
fence. With a US market rip fence you just set the cursor
to the deisred width on the fence's measuring tape.
With the latter, the assumption are:
a) that the tape for the fence is accurate to the precision
it implies by its smallest gradation - 1/32nd or
even 1/64ths
b) that the implied accuracy noted in "a" is good
for most of, if not the entire length of, the tape
c) that when you lock the fence down it won't
move - at all.
d) the tape only need to be set to the saw blade once
and will be accurate forever after (amen)
We expect these assumptions to be true - even though,
if you think about it - they're not. "a", "b" and "c"
have some slop. And if you change blades to best
suit the material you're working with, or have
tilted the blade for a bevel cut and then broght it
back to it's vertical "stop" then "d" may not be
true either.
Do you keep a good try square or starrett four
inch double square in your shop aproan and
check for square on stock you're prepping?
Do you keep a good caliper in your shop apron
to check the thickness of the stock you're
planing? Or do you just expect the machine
you're using to be as accurate as you think
it is?
charlie b
(now I'm going out to the shop to route
some mortises using my Micro Fence
which lets me dial in - in thousandths!
I've got a mini/midi lathe bench to build.
Another "quick and dirty" that'll likely
get away from me and end up with inlaid
legs and maybe some nice beading. Now if
I can just remember where I put all that
ebony - maccassar of course)
Wed, Feb 15, 2006, 9:55am (EST-3) [email protected] (charlie=A0b)
doth wonder:
The question:
Do we expect too much of our machines and not enough of ourselves
<snip>
Check my thread on, Full List Of Tools For Boatbuilding.
JOAT
IThere is no vaccine against stupidity!
Except for the fence on a table saw if we're talking Beismeyer, Unifence,
(1/64th accuracy) or other top-end fence systems or the digital read-out on
the Powermatic 15" planer if set up properly.
"W Canaday" <[email protected]> wrote in message
news:[email protected]...
> On Wed, 15 Feb 2006 09:55:44 -0800, charlie b wrote:
>
> > The question:
> >
> > Do we expect too much of our machines
> > and
> > not enough of ourselves
> For a number of years I earned my living as first a machinist and then a
> tool & die maker.
>
> As far as I am concerned, a scale (tape ... rule) on a machine is no more
> than a starting point. Ditto for a dial and so on.
>
> Bill
On Wed, 15 Feb 2006 09:55:44 -0800, charlie b wrote:
> The question:
>
> Do we expect too much of our machines
> and
> not enough of ourselves
For a number of years I earned my living as first a machinist and then a
tool & die maker.
As far as I am concerned, a scale (tape ... rule) on a machine is no more
than a starting point. Ditto for a dial and so on.
Bill
On Fri, 17 Feb 2006 06:37:44 +0000, Max Mahanke wrote:
> Except for the fence on a table saw if we're talking Beismeyer,
> Unifence, (1/64th accuracy) or other top-end fence systems or the
> digital read-out on the Powermatic 15" planer if set up properly.
>
Sorry, but being accurate to within 1/64" just isn't all that impressive.
Less than an hour ago I re-sawed a piece of 3/4" x 3" x 41" tamarind on
my Craftsman TS with the original fence and a sacrifical piece of mdf
subfence, and held ~.009" parrallelism. That's mighty close to 1/128".
It only took a couple minutes to set up for the cut, not much longer than
a top-end fence system would. The funny thing is that I really didn't need
that much accuracy for this cut. It's going to be part of a glue-up for a
cane that will be ripped and re-glued a couple more times before ending up
on the lathe. However, since I did an extremely good job tuning the saw
when I first started using it last year, that level of accuracy simply
comes automatically.(*)
Even if I had a DRO on every piece of equipment in the shop I'd still take
a measurement with another, known good, tool before making a final pass on
a critical part. In this case, I used a .325" jo-block stack to set the
distance between the fence and the blade and then measured the sawn pieces
with dial calipers (decimal inch). I really only got one shot at this cut.
Except for making endless test cuts, it's the only 'gotcha' insurance I
know of.
Sometimes a 64th is 'close enough', other times it's not. But if you don't
take a measurement with another tool, how can you be certain that you held
even that tolerance?
Is that why we woodworkers need to know so much about sandpaper and
scrapers?
Bill
(*) I can't be certain that there is any error at all in the relationship
between the saw arbor and the miter slots / fence face. My dial indictaor
showed about .002" error but there could have been other causes of this
error such as inconsistent pressure being applied to the indicator base,
poor finish / uneven wear patterns on the inside of the miter channel and
so on.
charlie b wrote:
> The question:
>
> Do we expect too much of our machines
> and
> not enough of ourselves
[shnibble]
> Do you keep a good try square or starrett four
> inch double square in your shop aproan and
> check for square on stock you're prepping?
> Do you keep a good caliper in your shop apron
> to check the thickness of the stock you're
> planing? Or do you just expect the machine
> you're using to be as accurate as you think
> it is?
I don't have any nice equipment like that, so I guess I'm totally
dependent on me.
I do find myself checking everything three times, though. And because
I'm inexperienced, I'm also reviewing whether I'm following all the
layout rules... measuring from the reference edge, etc.
I'm also accumulating a lot of tools to facilitate that, as well: I
wasn't satisfied that my cheapol protractor was accurate, so I got a
cheapol dial protractor, and tested them against eachother, and my work
against them to find they are all identically (in)accurate. I also have
engineers squares, and am jonesing for an engineer's level. I threw up
my hands when I couldn't get agreement between two rulers (er, one
bought on a weekend in Mexico), a tape, and a pad of graph paper: one
of those "all imperial" rulers resolved that with sufficient agreement
with the paper.
I put together some marking tools that I can live with.
In fact, so far I'm not making much outside of (good enough) tools, and
buying more! It's all good, I think.
er
--
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