| |
Main
Date: 28 Aug 2006 20:06:02
From:
Subject: How to measure tilt
|
I'm interested in measuring the alignment of an object relative to a
fixed plane.
As it happens, it's my saw blade relative to the saw table, but that
shouldn't matter much.
The dagnabbed setting circle that came with the saw is imprecise and
loses calibration easily. And nowadays we have cheap lasers and such,
but I'm not sure how to use 'em.
One approach would be to fix a laser to the tilting element, then use
it to direct a spot onto a screen. This, I'm familiar with (it's like
how we used to aim Howitzers at my old job...), but it seems..
inelegant.
Another would be to polarize a tilt-axis-parallel light source and as
the source polarization rotates, observe its null in an analyzer
mounted in a good setting circle. The saw axis of rotation isn't a
clear optical path, so the analyzer would have to be broad enough to
capture the arc of gyration of the source, and scanning for the null
would interfere with the other operation (cranking the tilt control).
A third might be to use a cheap scanner and read out a random speckle
pattern that tilts with the blade, using a mouse-grade scan chip.
You'd have to do some FFT tricks and have a BIG calibration table, but
it'd be accurate!
Does the amateur astronomy community have any slick way to work around
inadequate setting circles?
|
|
| |
Date: 29 Aug 2006 04:55:11
From: William Hamblen
Subject: Re: How to measure tilt
|
On 28 Aug 2006 20:06:02 -0700, whit3rd@gmail.com wrote:
>As it happens, it's my saw blade relative to the saw table, but that
>shouldn't matter much.
Use an adjustable square.
Bud
--
The night is just the shadow of the Earth.
|
| |
Date:
From: Martin Brown
Subject: Re: How to measure tilt
|
|
| |
Date: 29 Aug 2006 20:39:27
From: starburst
Subject: Re: How to measure tilt
|
whit3rd@gmail.com wrote:
> I'm interested in measuring the alignment of an object relative to a
> fixed plane.
> As it happens, it's my saw blade relative to the saw table, but that
> shouldn't matter much.
> The dagnabbed setting circle that came with the saw is imprecise and
> loses calibration easily. And nowadays we have cheap lasers and such,
> but I'm not sure how to use 'em.
>
>
Difficult things snipped<
The easiest way I know to get reasonable precision is to use a bevel
gauge. With the saw blade at vertical, lay a framing square along the
tilting side, so that the vertex is around the middle of the blade. Then
draw a pencil line on the table top along the perpendicular, so you have
a mark perpendicular to the blade. Set the bevel to the desired angle
using a protractor. When it's right, tighten the gauge. Stand it on the
table perpendicular to the blade so that the gauge shows where the blade
needs to be, tilt to the desired angle (when you sight down the blade it
will be easy to see the point where the light from behind the bevel
blacks out), tighten the knob, and you're good to go.
Be advised that for some common angles (like 45 degrees for instance)
you can buy nice metal mechanics squares that will stand up by
themselves on the table top. I got a nice Japanese one at woodcrafters
years ago.
I don't think you'll ever get decent precision using the scale on your
saw - whenever you set the marker it's only a matter of time until it
goes out of true. It's easiest just to set the angle properly for each cut.
Best o'luck from a former cabinetmaker-
Chris
|
| |
Date: 29 Aug 2006 19:15:56
From: J McBride
Subject: Re: How to measure tilt
|
Cut a piece of wood and measure the angle....than make the some marks for
the positions on your adjustment scale.
Joe
<whit3rd@gmail.com > wrote in message
news:1156820762.199503.25280@i3g2000cwc.googlegroups.com...
> I'm interested in measuring the alignment of an object relative to a
> fixed plane.
> As it happens, it's my saw blade relative to the saw table, but that
> shouldn't matter much.
> The dagnabbed setting circle that came with the saw is imprecise and
> loses calibration easily. And nowadays we have cheap lasers and such,
> but I'm not sure how to use 'em.
>
> One approach would be to fix a laser to the tilting element, then use
> it to direct a spot onto a screen. This, I'm familiar with (it's like
> how we used to aim Howitzers at my old job...), but it seems..
> inelegant.
>
> Another would be to polarize a tilt-axis-parallel light source and as
> the source polarization rotates, observe its null in an analyzer
> mounted in a good setting circle. The saw axis of rotation isn't a
> clear optical path, so the analyzer would have to be broad enough to
> capture the arc of gyration of the source, and scanning for the null
> would interfere with the other operation (cranking the tilt control).
>
> A third might be to use a cheap scanner and read out a random speckle
> pattern that tilts with the blade, using a mouse-grade scan chip.
> You'd have to do some FFT tricks and have a BIG calibration table, but
> it'd be accurate!
>
> Does the amateur astronomy community have any slick way to work around
> inadequate setting circles?
>
|
| |
Date: 30 Aug 2006 04:12:41
From: John Carruthers
Subject: Re: How to measure tilt
|
starburst wrote:
> whit3rd@gmail.com wrote:
> > I'm interested in measuring the alignment of an object relative to a
> > fixed plane.
> > As it happens, it's my saw blade relative to the saw table, but that
> > shouldn't matter much.
> > The dagnabbed setting circle that came with the saw is imprecise and
> > loses calibration easily. And nowadays we have cheap lasers and such,
> > but I'm not sure how to use 'em.
> >
> >
>
> Difficult things snipped<
>
> The easiest way I know to get reasonable precision is to use a bevel
> gauge. With the saw blade at vertical, lay a framing square along the
> tilting side, so that the vertex is around the middle of the blade. Then
> Best o'luck from a former cabinetmaker-
> Chris
I've had sucess using old prisms as test blocks, they're usually
cheaper and more accurate. You can get chipped prisms for nothing in
the usual 30, 45, 60, 90 degrees.
You can also use them in combination with a small laser as an optical
lever. Over 10 feet you would exceed the spec for any timber job I'll
bet.
jc
|
|
