phil on sat 31 jul 10
Hi Michael,
If one needs to...one can use a Straight Pin...'Silk Pin' or the likes...
Phil
Lv
----- Original Message -----
From: "Michael Wendt"
>I had an inquiry recently from a potter who wanted to know
> if I could think of a way to measure wall thickness on a
> trim ready pot so he could get it just right.
> He stated the mouth was fairly small so calipers would be
> difficult.
> Today I think I found the solution. My question is:
>
> Does anyone else need such a device?
>
> I can't see any reason to pursue it if there is no demand.
> I measure wall thickness during the throwing stage myself.
> Do any of you find you trim too thickly to avoid cutting
> through or do you often wind up with super thin spots that
> ruin the pot?
>
> Responses?
> Regards,
> Michael Wendt
gayle bair on sat 31 jul 10
MIchael,
I have already come up with a device just for this purpose. It's 1 1/2" =
=3D
off the eraser end of a pencil with a fairly thin sewing needle inserted =
=3D
into the eraser. I cut off the eye of the needle and sanded the tip. The =
=3D
needle can be adjusted with a small pliers to whatever thickness is =3D
preferred.=3D20
Poking it into various sections of the pot gives a quick & easy idea of =3D
wall thickness. If the neck is narrow all one has to do is look inside =3D
the pot and poke the pot with needle from the outside. =3D20
I came up with this solution because I have trouble hearing the tone =3D
when thumping my pots.
Hoping this makes sense.. I had a long, hard but productive day and am =3D
trying not to fall asleep as I sit in front of the computer.
Best regards,
Gayle Bair
Bainbridge Island WA
Tucson AZ
gayle@claybair.com
www.claybair.com
On Jul 31, 2010, at 4:21 PM, Michael Wendt wrote:
> I had an inquiry recently from a potter who wanted to know
> if I could think of a way to measure wall thickness on a
> trim ready pot so he could get it just right.
> He stated the mouth was fairly small so calipers would be
> difficult.
> Today I think I found the solution. My question is:
>=3D20
> Does anyone else need such a device?
>=3D20
> I can't see any reason to pursue it if there is no demand.
> I measure wall thickness during the throwing stage myself.
> Do any of you find you trim too thickly to avoid cutting
> through or do you often wind up with super thin spots that
> ruin the pot?
>=3D20
> Responses?
> Regards,
> Michael Wendt
Vince Pitelka on sat 31 jul 10
Michael Wendt wrote:
"I had an inquiry recently from a potter who wanted to know if I could thin=
k
of a way to measure wall thickness on a trim ready pot so he could get it
just right. He stated the mouth was fairly small so calipers would be
difficult. I can't see any reason to pursue it if there is no demand. I
measure wall thickness during the throwing stage myself. Do any of you find
you trim too thickly to avoid cutting through or do you often wind up with
super thin spots that ruin the pot?
Michael -
It is evident that you have a special ability to design and create superior
tools and equipment, and I have no doubt that you could come with such a
tool that would work well. My own curmudgeonly attitude is that the use of
such a tool would retard development of an intuitive feel for the thickness
of the pot. When a potter ruins a series of pots by trimming them too thin=
,
it teaches a very valuable lesson. My advice to my students is "trust your
eyes and your hands." I am also opposed to those clear plastic divider
disks used to divide a pot up into segments for decoration. If potters
trusts their eyes/hands for that task, then they will soon develop a good
feeling for eyeballing the divisions of space, and will never need to rely
on such a device. Same goes for trimming. It doesn't take that long to
develop a real intuitive feeling for the inside shape of the pot versus the
outside, to ensure that there are no excessively thick or thin places when
you finish trimming.
On the other hand, after almost ten years of writing the Tool-Times column,
I can vouch for the fact that many tools I consider to be entirely
unnecessary and/or highly impractical have become popular and sold very
well.
- Vince
Vince Pitelka
Appalachian Center for Craft
Tennessee Tech University
vpitelka@dtccom.net; wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka
Michael Wendt on sat 31 jul 10
I had an inquiry recently from a potter who wanted to know
if I could think of a way to measure wall thickness on a
trim ready pot so he could get it just right.
He stated the mouth was fairly small so calipers would be
difficult.
Today I think I found the solution. My question is:
Does anyone else need such a device?
I can't see any reason to pursue it if there is no demand.
I measure wall thickness during the throwing stage myself.
Do any of you find you trim too thickly to avoid cutting
through or do you often wind up with super thin spots that
ruin the pot?
Responses?
Regards,
Michael Wendt
Lee Love on sun 1 aug 10
The push pin is good for this. You can snip the tip to the thickness
you want and to keep from getting poked.
--
=3DA0Lee, a Mashiko potter in Minneapolis
http://mingeisota.blogspot.com/
=3D93Observe the wonders as they occur around you. Don't claim them. Feel
the artistry moving through and be silent.=3D94 --Rumi
William & Susan Schran User on sun 1 aug 10
On 7/31/10 7:21 PM, "Michael Wendt" wrote:
> I had an inquiry recently from a potter who wanted to know
> if I could think of a way to measure wall thickness on a
> trim ready pot so he could get it just right.
> He stated the mouth was fairly small so calipers would be
> difficult.
> Today I think I found the solution. My question is:
>
> Does anyone else need such a device?
>
> I can't see any reason to pursue it if there is no demand.
> I measure wall thickness during the throwing stage myself.
> Do any of you find you trim too thickly to avoid cutting
> through or do you often wind up with super thin spots that
> ruin the pot?
>
> Responses?
> Regards,
> Michael Wendt
To help my beginning throwing students, I suggest they check bottom
thickness with needle, then record on paper. I also have them use calipers
to measure bottom inside diameter and record on paper, before they close in
the form. Both measurements help to visualize thickness of the clay.
I find the problem the students have are trimming through the bottom more
than the wall.
I would not buy a device, but I could see beginning potters, learning on
their own or with minimum instruction, who are unwilling to slice open many
pots to see what they thought the thickness to be, wanting such an aid.
Did you figure out how to make Superman x-ray glasses?
Bill
--
William "Bill" Schran
wschran@cox.net
wschran@nvcc.edu
http://www.creativecreekartisans.com
Marcia Selsor on sun 1 aug 10
I had a student show me using a thumb tack , head inside the pot. He =3D
would hit the point on the outside and know the thickness.
I don't like such things in the clay classroom. They end up in the slip =3D
bucket.=3D20
I agree with Vince....let the force be with you. I usually tap the =3D
bottom before trimming and judge by the sound. Feel the walls in a =3D
throwing position to "know" the thickness.
Marcia
On Aug 1, 2010, at 1:52 AM, Vince Pitelka wrote:
> Michael Wendt wrote:
> "I had an inquiry recently from a potter who wanted to know if I could =
=3D
think
> of a way to measure wall thickness on a trim ready pot so he could get =
=3D
it
> just right. He stated the mouth was fairly small so calipers would be
> difficult. I can't see any reason to pursue it if there is no demand. =3D
I
> measure wall thickness during the throwing stage myself. Do any of you =
=3D
find
> you trim too thickly to avoid cutting through or do you often wind up =3D
with
> super thin spots that ruin the pot?
>=3D20
> Michael -
> It is evident that you have a special ability to design and create =3D
superior
> tools and equipment, and I have no doubt that you could come with such =
=3D
a
> tool that would work well. My own curmudgeonly attitude is that the =3D
use of
> such a tool would retard development of an intuitive feel for the =3D
thickness
> of the pot. When a potter ruins a series of pots by trimming them too =
=3D
thin,
> it teaches a very valuable lesson. My advice to my students is "trust =
=3D
your
> eyes and your hands." I am also opposed to those clear plastic =3D
divider
> disks used to divide a pot up into segments for decoration. If =3D
potters
> trusts their eyes/hands for that task, then they will soon develop a =3D
good
> feeling for eyeballing the divisions of space, and will never need to =3D
rely
> on such a device. Same goes for trimming. It doesn't take that long =3D
to
> develop a real intuitive feeling for the inside shape of the pot =3D
versus the
> outside, to ensure that there are no excessively thick or thin places =3D
when
> you finish trimming.
>=3D20
> On the other hand, after almost ten years of writing the Tool-Times =3D
column,
> I can vouch for the fact that many tools I consider to be entirely
> unnecessary and/or highly impractical have become popular and sold =3D
very
> well.
> - Vince
>=3D20
> Vince Pitelka
> Appalachian Center for Craft
> Tennessee Tech University
> vpitelka@dtccom.net; wpitelka@tntech.edu
> http://iweb.tntech.edu/wpitelka
>=3D20
Marcia Selsor
http://www.marciaselsor.com
Snail Scott on sun 1 aug 10
On Aug 1, 2010, at 1:52 AM, Vince Pitelka wrote:
> Michael Wendt wrote:
> "I had an inquiry recently from a potter who wanted to know if I
> could think
> of a way to measure wall thickness on a trim ready pot so he could
> get it
> just right. He stated the mouth was fairly small so calipers would be
> difficult...
Aside from pottery, have you considered its
usefulness in hollowing out solid-built sculpture,
whose convolutions can make it rather difficult to
accurately judge thickness at any given point?
Tangentially-related digression:
The exhibition of sculpture from the tomb of Jean
sans Peur (John the Fearless, the 15th c. Duke of
Burgundy) just came to St. Louis while they do
restoration on the structure of the tomb. I've always
been a huge fan of these, so I went down right
away to see - didn't even wait for 'Free Friday'!
Unlike seeing them in situ, you can actually see
the backs of the figures in this presentation.
Marvelous stone carving, but I noticed (after about
two hours of looking) that on one figure's hood,
the folds on the inside and outside didn't match up,
and as a result, the sculptor has accidentally carved
right through in one spot. (oops.)
We are fortunate to work in a medium that allows
us to test for thickness by poking holes through it
experimentally, and to be able to add on extra
thickness at need, not just remove material.
-Snail
Lee Love on sun 1 aug 10
On Sun, Aug 1, 2010 at 8:17 AM, Marcia Selsor wrote:
> I had a student show me using a thumb tack , head inside the pot. He woul=
=3D
d hit the point on the outside and know the thickness.
> I don't like such things in the clay classroom. They end up in the slip b=
=3D
ucket.
You can always put the pin in a cork if you have trouble keeping
track of your tools.
--
=3DA0Lee, a Mashiko potter in Minneapolis
http://mingeisota.blogspot.com/
=3D93Observe the wonders as they occur around you. Don't claim them. Feel
the artistry moving through and be silent.=3D94 --Rumi
Steve Mills on sun 1 aug 10
A lot of the vessels I make are narrow necked, so pins, needles etc. are
pretty much useless.
What I do is feel the thickness of the wall near the neck, and listen to th=
=3D
e
sound it makes when I tap it with one finger. I then trim the rest of the
piece until it sounds like the neck area.
Those that I have taught this technique to get the hang of it quite quickly=
=3D
.
For me, it does help that I play various stringed instruments which I tune
by ear.
Steve Mills
On 1 August 2010 13:51, Lee Love wrote:
> The push pin is good for this. You can snip the tip to the thickness
> you want and to keep from getting poked.
>
> --
> Lee, a Mashiko potter in Minneapolis
> http://mingeisota.blogspot.com/
>
> =3D93Observe the wonders as they occur around you. Don't claim them. Feel
> the artistry moving through and be silent.=3D94 --Rumi
>
--=3D20
Steve
Bath
UK
www.mudslinger.me.uk
Growing old is inevitable, growing up is optional!
Lee Love on sun 1 aug 10
On Sun, Aug 1, 2010 at 5:05 PM, Steve Mills
wrote:
> A lot of the vessels I make are narrow necked, so pins, needles etc. are
> pretty much useless.
You can use a throwing stick to place them. Just put some clay on the
end of the stick and then the pin. When you hit it, you can poke it
out from the outside with a needle tool.
--
=3DA0Lee, a Mashiko potter in Minneapolis
http://mingeisota.blogspot.com/
=3D93Observe the wonders as they occur around you. Don't claim them. Feel
the artistry moving through and be silent.=3D94 --Rumi
Ric Swenson on mon 2 aug 10
experience teaches....thump it.......measure it....by needle if necessary..=
. learn the sounds....
ruin few and you will learn..
eyes will teach you....
Distance contanstancy
my ex did her PhD in that...
so I learned it well..over 18 years...of her disseration....
or maybe 25 years totally...ahhhh....
Ric
"...then fiery expedition be my wing, ..."
-Wm. Shakespeare, RICHARD III, Act IV Scene III
Richard H. ("Ric") Swenson, Teacher,
Office of International Cooperation and Exchange of Jingdezhen Ceramic Inst=
itute,
TaoYang Road, Eastern Suburb, Jingdezhen City.
JiangXi Province, P.R. of China.
Postal code 333001.
Mobile/cellular phone : 86 13767818872
< RicSwenson0823@hotmail.com>
http://www.jci.jx.cn
> Date: Sun, 1 Aug 2010 08:52:36 -0400
> From: wschran@COX.NET
> Subject: Re: measuring wall thickness through the wall for trimming
> To: Clayart@LSV.CERAMICS.ORG
>
> On 7/31/10 7:21 PM, "Michael Wendt" wrote:
>
> > I had an inquiry recently from a potter who wanted to know
> > if I could think of a way to measure wall thickness on a
> > trim ready pot so he could get it just right.
> > He stated the mouth was fairly small so calipers would be
> > difficult.
> > Today I think I found the solution. My question is:
> >
> > Does anyone else need such a device?
> >
> > I can't see any reason to pursue it if there is no demand.
> > I measure wall thickness during the throwing stage myself.
> > Do any of you find you trim too thickly to avoid cutting
> > through or do you often wind up with super thin spots that
> > ruin the pot?
> >
> > Responses?
> > Regards,
> > Michael Wendt
>
> To help my beginning throwing students, I suggest they check bottom
> thickness with needle, then record on paper. I also have them use caliper=
s
> to measure bottom inside diameter and record on paper, before they close =
in
> the form. Both measurements help to visualize thickness of the clay.
>
> I find the problem the students have are trimming through the bottom more
> than the wall.
>
> I would not buy a device, but I could see beginning potters, learning on
> their own or with minimum instruction, who are unwilling to slice open ma=
ny
> pots to see what they thought the thickness to be, wanting such an aid.
>
> Did you figure out how to make Superman x-ray glasses?
>
> Bill
>
> --
> William "Bill" Schran
> wschran@cox.net
> wschran@nvcc.edu
> http://www.creativecreekartisans.com
Ric Swenson on mon 2 aug 10
or you can see the measurement in your head.....distance constancy.......
ric
just a measurement you can learn.....
Ric
"...then fiery expedition be my wing, ..."
-Wm. Shakespeare, RICHARD III, Act IV Scene III
Richard H. ("Ric") Swenson, Teacher,
Office of International Cooperation and Exchange of Jingdezhen Ceramic Inst=
itute,
TaoYang Road, Eastern Suburb, Jingdezhen City.
JiangXi Province, P.R. of China.
Postal code 333001.
Mobile/cellular phone : 86 13767818872
< RicSwenson0823@hotmail.com>
http://www.jci.jx.cn
> Date: Sun, 1 Aug 2010 11:10:46 -0500
> From: cwiddershins@GMAIL.COM
> Subject: Re: measuring wall thickness through the wall for trimming
> To: Clayart@LSV.CERAMICS.ORG
>
> On Sun, Aug 1, 2010 at 8:17 AM, Marcia Selsor wrote:
> > I had a student show me using a thumb tack , head inside the pot. He wo=
uld hit the point on the outside and know the thickness.
> > I don't like such things in the clay classroom. They end up in the slip=
bucket.
>
> You can always put the pin in a cork if you have trouble keeping
> track of your tools.
> --
> Lee, a Mashiko potter in Minneapolis
> http://mingeisota.blogspot.com/
>
> =A1=B0Observe the wonders as they occur around you. Don't claim them. Fee=
l
> the artistry moving through and be silent.=A1=B1 --Rumi
Michael Wendt on mon 9 aug 10
If you hate new things and new ideas, don't read this and be
sure to delete it!
For people who struggle with trimming thickness...
A simple idea:
Non penetrating, non marring thickness measurement
You need:
Inside component
obtain a small, high strength rare earth magnet and fasten
it to the end of a wooden dowel rod long enough to reach the
bottom of your tallest planned bottles or jars.. Choose an
angle that will be easy to place flat against the inside of
the pot or make a swivel that lets you change the angle as
needed..
Once you build the sensor part, you may need to experiment
with angle and direction of the magnetic field to get the
best couple with the sensor.
Outside component
The sensor array
Get an Oral-B battery powered electric tooth brush ($3-5).
Make a small rectangle of very thin iron (like a steel can a
magnet will stick to) that just spans the round brush head
and overwrap it with a single layer of scotch tape. Wind
about 100 turns of the finest lacquer coated magnet wire you
can find at Radio Shack. Slip it into the rotating part of
the brush so that the core and the wires are centered in the
brush and glue it in with a dab of silicone rubber caulking.
Leave plenty of excess wire hanging out one sides for
connecting to an analog voltage meter set to millivolts. You
will need to install either a small diode or a bridge
rectifier in between the meter and the rotating sender since
the signal will be A-C due to the back and forth movement
(analog panel voltage meters are D-C). Also, if you get the
polarity wrong, the meter will try to move downscale so just
switch the leads and try it again.
Note:
You will need to construct a small aluminum guard around the
brush head to assure the rotating metal and wire parts do
not contact the pot. An aluminum beverage can is easy to cut
and shape for this purpose.This also assures the accuracy
because the couple distance will then depend solely on the
wall thickness of the pot as the sensor is placed directly
on the outside of the pot where the magnet is on the inside.
Also, aluminum is non-magnetic so it doesn't alter the
signal strength.
How it works:
If you have ever owned an A-C welder (which is a voltage
dropping transformer), you have used this principle.
The A-C welder separates the primary and secondary coils by
cranking a handle that moves them farther apart to lower the
couple or closer together for more couple..
This wall thickness tester will work on the same principle;
If the wall is thick, there is less couple and the meter
registers a lower milivolt reading.
As the wall becomes thinner, the amount of couple increases
resulting in a higher milivolt reading.
All you need to do is switch the tooth brush on and
calibrate it with clay tiles you have made of differing
thicknesses and use colored sharpies to mark tick marks on
the volt meter where the needle points that correspond to
the thicknesses. Color code the thicknesses to eliminate
errors. Check the calibration at the beginning of each use
session and again at the end to see when the tooth brush
batteries are becoming low as this will skew your results.
Use:
Since the goal is to obtain an even trim, mapping the
thickness before you begin to trim is the first step. I use
Crayola washable markers with great success on trimmable
greenware. Color code each wall thickness mapped at the
level on the pot it occurs, then turn on the wheel and color
code the thicknesses with a colored lines all the way around
the pot as a trim guides.
Construct special trim tools that have a travel stop that
only allows them to cut to a specific depth. This depth
needs to be the amount you need to remove to reach the
desired final wall thickness. Color code these to match the
mapped thicknesses and use the correct color for the line
being cut.
By leaving a small ring of uncut clay between each of the
depth defining grooves it is possible to precisely cut the
grooves to the correct depth because of the trim stops.
Once all the grooves are cut, use a wider flat faced trim
tool to cut away the high spots until they just reach the
bottoms of the grooves you cut as guides.
Finally, refined the shape very lightly so as not to
overthin the clay and you can be sure the wall is the same
thickness everywhere.
This is the trim strategy I use for thousands of plates
every year and it always works.
Best of Luck and
Happy Trimming,
Regards,
Michael Wendt
Michael Wendt on thu 12 aug 10
What's this all about?
Suppose you ruin 1 in 20 pots by trimming through.
Is that acceptable?
Is leaving the wall needlessly thick so that the pot is
clunky acceptable?
It takes years to get a really good feel for wall thickness
at a low volume production level and it may never happen at
the hobby level.
Enter the non-invasive magnetic couple through the wall
measuring tool you can build and use yourself at very little
cost and with ordinary household tools.
Early yesterday I made the little iron armature core
wrapped with 75 turns of magnet wire and fastened it to the
Oral-B electric tooth brush with silicone rubber.
It took 15 minutes to cut, shape and wind the armature and a
few more minutes to glue it into the brush head.
After work when the rubber was cured, I hooked the armature
wires up to my digital multimeter and set the scale to A-C
milivolts.
I switche the toothbrush on.
Then the fun began!
With my magnet, it works out to 1/2" distance!
At 1/2" it showed 1 milivolt. At the closest I could get
without hitting the armature it read 25 milivolts.
It is very sensitive so it offers an accurate picture of
thickness.
Amendments to the design:
1) For ease of use and improved accuracy, the magnet must be
firmly attached to a measuring arm and a hinge or pivot
along with a second arm is needed to keep the orientation of
the armature the same at all times with respect to the
magnet.
Reason:
Some positions and orientations produced a far lower voltage
which makes the measurement meaningless if not oriented
exactly the same at all times..
2) A digital multimeter is easier to use than an analog
meter even though you would need to make a chart of
thicknesses the first time for tool selection. After that
you would simply number the tools and use the tool that
matches the number to mapped onto the pot surface.
I will take photos of the process and post them to the
clayart page on my web site when time permits.
Regards,
Michael Wendt
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