While fiddling with my RedNeck lathe I came across an interesting problem:

I am trying to clean up the outside of a steel ring: 5.5" OD, 3.25" ID,
0.25" thick.

I clamp it in the 4-jaw chuck (inside the hole) and am trying to center it
using an indicator. However, the outside edge of the ring is so pitted and
irregular that the indicator jumps about to the point where the readings are
hard to interpret let alone use to center the work-piece.

Now I do not need great accuracy: The inner hole and the outer edge should
be concentric as far as possible but I am not quibbling of a 0.001" or two.
Yet this way it is hard to get it confidently within 0.010"!

Clearly the obvious answer to this is "Get a 3-jaw chuck" and I have one
already, 4" with two sets of jaws, the only problem is getting the adapter
to 1"-8 spindle and turning it down to size. But this may have to happen (in
fact if this thing merits further expense it will happen).

However, given what I got now, I wonder how others would approach this
problem.

--
Michael Koblic,
Campbell River, BC

On Thu, 28 May 2009 16:30:41 -0700, Michael Koblic wrote:

While fiddling with my RedNeck lathe I came across an interesting problem:

I am trying to clean up the outside of a steel ring: 5.5" OD, 3.25" ID,
0.25" thick.

I clamp it in the 4-jaw chuck (inside the hole) and am trying to center it
using an indicator. However, the outside edge of the ring is so pitted and
irregular that the indicator jumps about to the point where the readings are
hard to interpret let alone use to center the work-piece.

Now I do not need great accuracy: The inner hole and the outer edge should
be concentric as far as possible but I am not quibbling of a 0.001" or two.
Yet this way it is hard to get it confidently within 0.010"!

Clearly the obvious answer to this is "Get a 3-jaw chuck" and I have one
already, 4" with two sets of jaws, the only problem is getting the adapter
to 1"-8 spindle and turning it down to size. But this may have to happen (in
fact if this thing merits further expense it will happen).

However, given what I got now, I wonder how others would approach this
problem.

Turn a mandrel to a snug fit on the ID, drill and tap it on the end in a
couple or three places, cut a circle of thickish sheet bigger than the ID
and smaller than the OD, and drill clearance holes in the same places as
the ones in the mandrel.

Chuck the mandrel with a hair less than the thickness of the ring proud of
the jaws, indicate the mandrel, slide the ring on, hold the ring with the
sheet bolted to the mandrel.

In article ,
"Michael Koblic" wrote:

However, given what I got now, I wonder how others would approach this
problem.

Indicate the inner bore. Or indicate the chuck jaws. Ignore the outer if
the outer is crap - you'll turn the outer clean, no? Just need to get
the inner lined up - therefore, indicate what you want to line up...

--
Cats, coffee, chocolate...vices to live by

On May 28, 7:54*pm, Ecnerwal
wrote:
In article ,
*"Michael Koblic" wrote:

However, given what I got now, I wonder how others would approach this
problem.

Indicate the inner bore. Or indicate the chuck jaws. Ignore the outer if
the outer is crap - you'll turn the outer clean, no? Just need to get
the inner lined up - therefore, indicate what you want to line up...

--
Cats, coffee, chocolate...vices to live by

Hold a feeler gauge, say .005" thick or so, between the indicator tip
and the work piece.

Wolfgang

Checking the jaws for and adjusting for very close to concentric would be a
good check.
With the center hole centered, trimming the circumference will get you an
equal width for 360 degrees.

Making a convex shoe for indicator stems has seemed like a very good idea,
numerous times when indicating something with a rough surface, but I haven't
done it yet.
It wouldn't be a difficult piece to make, though. The only critical aspect
would be that the shoe doesn't rotate around the indicator stem's axis..
otherwise, it would be an accurate indication of the OD.
The larger contact area would indicate the high spots, without popping into
every low spot/pit/valley.

--
WB
..........
metalworking projects
www.kwagmire.com/metal_proj.html


"Michael Koblic" wrote in message
...
While fiddling with my RedNeck lathe I came across an interesting problem:

I am trying to clean up the outside of a steel ring: 5.5" OD, 3.25" ID,
0.25" thick.

I clamp it in the 4-jaw chuck (inside the hole) and am trying to center it
using an indicator. However, the outside edge of the ring is so pitted and
irregular that the indicator jumps about to the point where the readings
are hard to interpret let alone use to center the work-piece.

Now I do not need great accuracy: The inner hole and the outer edge should
be concentric as far as possible but I am not quibbling of a 0.001" or
two. Yet this way it is hard to get it confidently within 0.010"!

Clearly the obvious answer to this is "Get a 3-jaw chuck" and I have one
already, 4" with two sets of jaws, the only problem is getting the adapter
to 1"-8 spindle and turning it down to size. But this may have to happen
(in fact if this thing merits further expense it will happen).

However, given what I got now, I wonder how others would approach this
problem.

--
Michael Koblic,
Campbell River, BC

Uhmmm, convex should've been concave



"Wild_Bill" wrote in message
...
Checking the jaws for and adjusting for very close to concentric would be
a good check.
With the center hole centered, trimming the circumference will get you an
equal width for 360 degrees.

Making a ****convex**** shoe for indicator stems has seemed like a very
good idea, numerous times when indicating something with a rough surface,
but I haven't done it yet.

WB
.........
metalworking projects
www.kwagmire.com/metal_proj.html

On Thu, 28 May 2009 23:42:50 -0400, "Wild_Bill"
wrote:

Uhmmm, convex should've been concave

Flat works.

Indicate on the jaws. Turn the OD. Reset; indicate on the OD, and
clean up the ID.
JR
Dweller in the cellar

On Thu, 28 May 2009 16:30:41 -0700, "Michael Koblic"
wrote:

While fiddling with my RedNeck lathe I came across an interesting problem:

I am trying to clean up the outside of a steel ring: 5.5" OD, 3.25" ID,
0.25" thick.

I clamp it in the 4-jaw chuck (inside the hole) and am trying to center it
using an indicator. However, the outside edge of the ring is so pitted and
irregular that the indicator jumps about to the point where the readings are
hard to interpret let alone use to center the work-piece.

Now I do not need great accuracy: The inner hole and the outer edge should
be concentric as far as possible but I am not quibbling of a 0.001" or two.
Yet this way it is hard to get it confidently within 0.010"!

Clearly the obvious answer to this is "Get a 3-jaw chuck" and I have one
already, 4" with two sets of jaws, the only problem is getting the adapter
to 1"-8 spindle and turning it down to size. But this may have to happen (in
fact if this thing merits further expense it will happen).

However, given what I got now, I wonder how others would approach this
problem.
--------------------------------------------------------------
Home Page: http://www.seanet.com/~jasonrnorth
If you're not the lead dog, the view never changes
Doubt yourself, and the real world will eat you alive
The world doesn't revolve around you, it revolves around me
No skeletons in the closet; just decomposing corpses
--------------------------------------------------------------
Dependence is Vulnerability:
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"Open the Pod Bay Doors please, Hal"
"I'm sorry, Dave, I'm afraid I can't do that.."

JR North wrote:
Indicate on the jaws. Turn the OD. Reset; indicate on the OD, and
clean up the ID.

Thanks everyone for so many suggestions how to skin this particular cat.
Unfortunately the way the ring is clamped there is no way to get at the jaws
but the feeler gauge method worked just fine.

--
Michael Koblic,
Campbell River, BC

On May 30, 11:41*pm, "Michael Koblic" wrote:
JR North wrote:
Indicate on the jaws. Turn the OD. Reset; indicate on the OD, and
clean up the ID.

Thanks everyone for so many suggestions how to skin this particular cat.
Unfortunately the way the ring is clamped there is no way to get at the jaws
but the feeler gauge method worked just fine.

--
Michael Koblic,
Campbell River, BC

You can indicate on any part of the jaws, not just where they grab the
work.

jsw

"Jim Wilkins" wrote in message
...

You can indicate on any part of the jaws, not just where they grab the
work.

I understand that, but they were kind of buried in the hole - no way to get
the indicator on them.

On May 31, 9:03*pm, "Michael Koblic" wrote:
"Jim Wilkins" wrote in message

...

You can indicate on any part of the jaws, not just where they grab the

work.

I understand that, but they were kind of buried in the hole - no way to get
the indicator on them.

Once upon a time they made a pivoted lever attachment that clamped to
a dial indicator and reached into a small hole to indicate the ID. The
turned ones are better than the stamped ones but I wouldn't pass up
either type.

jsw