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The raised land on my spindle plate measures 2.154 rather than 2.165
as given on the mini-lathe site. Sure enough, the recess in the chuck
measures 2.165.

In order to mount my 3 jaw chuck I first snug the nuts slightly, put
a rod in the chuck, and use an indicator on the rod. I rotate the
chuck so the high point is up and tap the chuck on the top with a
block of wood; this is not a well controlled process so it typically
takes several minutes to get TIR between 1 and 2 mils, when I tighten
the nuts.

Is there a better way to center the chuck?

Is the mis-match between the land and the recess common? I expected
the chuck to center itself on the spindle land but this mis-match
apparently precludes that.

John

John,
I have not heard of this problem before, but I am new
to the hobby, and if any lathes had this problem I would
have expected it on mine ( 8^) or 8^( - don't know which).

I would want this to be accurate, especially if removing
and mounting the chuck regularly. If under warranty I
would request a new spindle. If not under warranty a
new spindle is available from www.littlemachineshop.com
for $29.95. Alternatively, an adapter plate similar to
those necessary for a four inch chuck could be made.

Craig

--- In 7x12minilathe@..., "John <moran03@e...>"
<moran03@e...> wrote:

The raised land on my spindle plate measures 2.154 rather than 2.165
as given on the mini-lathe site. Sure enough, the recess in the

chuck

measures 2.165.

In order to mount my 3 jaw chuck I first snug the nuts slightly, put
a rod in the chuck, and use an indicator on the rod. I rotate the
chuck so the high point is up and tap the chuck on the top with a
block of wood; this is not a well controlled process so it typically
takes several minutes to get TIR between 1 and 2 mils, when I

tighten

the nuts.

Is there a better way to center the chuck?

Is the mis-match between the land and the recess common? I expected
the chuck to center itself on the spindle land but this mis-match
apparently precludes that.

John

Even if the land/recess match closely, 3-jaw chucks are not
precise. An adjustable backplate solves both problems:



Roy
--- In 7x12minilathe@..., "John <moran03@e...>"
<moran03@e...> wrote:

The raised land on my spindle plate measures 2.154 rather than

2.165

as given on the mini-lathe site. Sure enough, the recess in the

chuck

measures 2.165.

In order to mount my 3 jaw chuck I first snug the nuts slightly,

put

a rod in the chuck, and use an indicator on the rod. I rotate the
chuck so the high point is up and tap the chuck on the top with a
block of wood; this is not a well controlled process so it

typically

takes several minutes to get TIR between 1 and 2 mils, when I

tighten

the nuts.

Is there a better way to center the chuck?

Is the mis-match between the land and the recess common? I expected
the chuck to center itself on the spindle land but this mis-match
apparently precludes that.

John

Something to keep in mind: a little runout of the
chuck, say .002 or .003 won't affect most projects as
long as you don't remove the workpiece from the chuck
until all operations are completed.

The reason is that as soon as you turn the workpiece
down by more than .004, the resulting workpiece is
exactly concentric with the lathe axis within the
accuracy of the spindle bearings (typically .0002 -
.0005 on the minilathes).

This is why I was able to turn a piece of brass down
to .034 dia. and then drill a .016 hole through it.



More recently, I needed some test pins for making
temporary connections to a tiny DIN connector on a
video camera. I turned the pins from brass to a dia.
of .020. They were concentric even though the 4" chuck
holding the 1/8 brass stock I started with probably
has about .003 runout.

Frank Hoose


--- "Craig C. Hopewell
<chopewel@...>"
<chopewel@...> wrote:

John,
I have not heard of this problem before, but I am
new
to the hobby, and if any lathes had this problem I
would
have expected it on mine ( 8^) or 8^( - don't know
which).

I would want this to be accurate, especially if
removing
and mounting the chuck regularly. If under
warranty I
would request a new spindle. If not under warranty
a
new spindle is available from
www.littlemachineshop.com
for $29.95. Alternatively, an adapter plate
similar to
those necessary for a four inch chuck could be
made.

Craig

--- In 7x12minilathe@..., "John
<moran03@e...>"
<moran03@e...> wrote:

The raised land on my spindle plate measures 2.154

rather than 2.165

as given on the mini-lathe site. Sure enough, the

recess in the
chuck

measures 2.165.

In order to mount my 3 jaw chuck I first snug the

nuts slightly, put

a rod in the chuck, and use an indicator on the

rod. I rotate the

chuck so the high point is up and tap the chuck on

the top with a

block of wood; this is not a well controlled

process so it typically

takes several minutes to get TIR between 1 and 2

mils, when I
tighten

the nuts.

Is there a better way to center the chuck?

Is the mis-match between the land and the recess

common? I expected

the chuck to center itself on the spindle land but

this mis-match

apparently precludes that.

John

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Roy, I saw Rick Kruger about a month ago and one of the intresting
things in his shop is the adjustable backplate. The idea and
execution were clever and well done. I am going to make one for a 4"
3jaw I have. His was nice looking, the concept is simple enough that
it should be reasonably easy to do.

Al Day
.--- In 7x12minilathe@..., "roylowenthal
<roylowenthal@y...>" <roylowenthal@y...> wrote:

Al,
I agree; I'm in the process of making the same one!

Roy
--- In 7x12minilathe@..., "fromday2 <aldayis@a...>"
<aldayis@a...> wrote:

Roy, I saw Rick Kruger about a month ago and one of the intresting
things in his shop is the adjustable backplate. The idea and
execution were clever and well done. I am going to make one for a

4"

3jaw I have. His was nice looking, the concept is simple enough

that

it should be reasonably easy to do.

Al Day
.--- In 7x12minilathe@..., "roylowenthal
<roylowenthal@y...>" <roylowenthal@y...> wrote:

Even if the land/recess match closely, 3-jaw chucks are not
precise. An adjustable backplate solves both problems:

OTOH, when you're doing repairs/mods to existing stuff, the lack
of concentricity is a problem. I'm using the 4 jaw until I finish
the Rick Kruger style adjustable backplate (I'm too cheap to go the
collet route.)

Roy
--- In 7x12minilathe@..., Frank Hoose <fhoose@y...> wrote:

Something to keep in mind: a little runout of the
chuck, say .002 or .003 won't affect most projects as
long as you don't remove the workpiece from the chuck
until all operations are completed.

The reason is that as soon as you turn the workpiece
down by more than .004, the resulting workpiece is
exactly concentric with the lathe axis within the
accuracy of the spindle bearings (typically .0002 -
.0005 on the minilathes).

This is why I was able to turn a piece of brass down
to .034 dia. and then drill a .016 hole through it.

lathe.com/Mini_lathe/Capabilities/Capabilities.htm#tiny

More recently, I needed some test pins for making
temporary connections to a tiny DIN connector on a
video camera. I turned the pins from brass to a dia.
of .020. They were concentric even though the 4" chuck
holding the 1/8 brass stock I started with probably
has about .003 runout.

Frank Hoose


--- "Craig C. Hopewell
<chopewel@r...>"
<chopewel@r...> wrote:

John,
I have not heard of this problem before, but I am
new
to the hobby, and if any lathes had this problem I
would
have expected it on mine ( 8^) or 8^( - don't know
which).

I would want this to be accurate, especially if
removing
and mounting the chuck regularly. If under
warranty I
would request a new spindle. If not under warranty
a
new spindle is available from
www.littlemachineshop.com
for $29.95. Alternatively, an adapter plate
similar to
those necessary for a four inch chuck could be
made.

Craig

--- In 7x12minilathe@..., "John
<moran03@e...>"
<moran03@e...> wrote:

The raised land on my spindle plate measures 2.154

rather than 2.165

as given on the mini-lathe site. Sure enough, the

recess in the
chuck

measures 2.165.

In order to mount my 3 jaw chuck I first snug the

nuts slightly, put

a rod in the chuck, and use an indicator on the

rod. I rotate the

chuck so the high point is up and tap the chuck on

the top with a

block of wood; this is not a well controlled

process so it typically

takes several minutes to get TIR between 1 and 2

mils, when I
tighten

the nuts.

Is there a better way to center the chuck?

Is the mis-match between the land and the recess

common? I expected

the chuck to center itself on the spindle land but

this mis-match

apparently precludes that.

John

To unsubscribe from this group, send an email to:
7x12minilathe-unsubscribe@...



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Thanks to all who replied to my query. As suggested, I looked at
Rick's design for an adjustable backplate and realized that part of
his solution is a deliberate mis-match between the sizes of the land
and the recess. Given that I had this mis-match already what I
needed was a more controlled method of adjustment rather than my
crude tapping technique -- my lazy man's approach is to use the cross
slide as the adjusting screw for centering the chuck.

What I did was put a large (5/8) center drill in the chuck to use as
a shaft for measuring runout, chucked so it extended enough to allow
access to its HSS shaft. The indicator was set up to measure runout
at the rear of this shaft; the chuck was turned to place the low
point at the rear, thus placing the high point toward the front
(where a tool in the toolpost would contact it).

With the nuts on the chuck barely snug I placed a 1/2" square piece
of mild steel in the tool holder and attempted to use this to push on
the shaft of the center drill to slide the chuck to center. This
didn't work initially, apparently because the force is too far from
the backplate. However, by applying enough force via the cross slide
to move the indicator to the desired reading then loosening and
tightening each chuck nut in succession I was able to set the TIR to
better than .001 fairly quickly on each of several tries. Much more
controlled than my original "thump it" approach.

John



--- In 7x12minilathe@..., "John <moran03@e...>"
<moran03@e...> wrote:

The raised land on my spindle plate measures 2.154 rather than

2.165

as given on the mini-lathe site. Sure enough, the recess in the

chuck

measures 2.165.

In order to mount my 3 jaw chuck I first snug the nuts slightly,

put

a rod in the chuck, and use an indicator on the rod. I rotate the
chuck so the high point is up and tap the chuck on the top with a
block of wood; this is not a well controlled process so it

typically

takes several minutes to get TIR between 1 and 2 mils, when I

tighten

the nuts.

Is there a better way to center the chuck?

Is the mis-match between the land and the recess common? I expected
the chuck to center itself on the spindle land but this mis-match
apparently precludes that.

John

Roy and Al:
I'm making an adjustable backplate too. One thing I question
in Rick's otherwise great design is the amount of adjustment
he built in. .050" oversize on the diameter seems like too much
to me.
I can't imagine needing to adjust more than a few thou. Wouldn't
a .005 to .010" oversize diameter give a person enough adjustment?
Regards,
B Flint


--- In 7x12minilathe@..., "roylowenthal
<roylowenthal@y...>" <roylowenthal@y...> wrote:

Al,
I agree; I'm in the process of making the same one!

Roy
--- In 7x12minilathe@..., "fromday2 <aldayis@a...>"
<aldayis@a...> wrote:

Roy, I saw Rick Kruger about a month ago and one of the

intresting

things in his shop is the adjustable backplate. The idea and
execution were clever and well done. I am going to make one
for a 4" 3jaw I have. His was nice looking, the concept is
simple enough that it should be reasonably easy to do.

Al Day

I have not made the adjustable back plate so I cannot speak from
experience but I would guess you are right. It would seem that .010
would be enough adjustment for a chuck that does not have other
serious problems and would likely not be accurate at different
openings. The particular chuck I have that is a problem has .003
runout. HTH

Al Day


--- In 7x12minilathe@..., "bbftx <bflint@a...>"
<bflint@a...> wrote:

Roy and Al:
I'm making an adjustable backplate too. One thing I question
in Rick's otherwise great design is the amount of adjustment
he built in. .050" oversize on the diameter seems like too much
to me.
I can't imagine needing to adjust more than a few thou. Wouldn't
a .005 to .010" oversize diameter give a person enough adjustment?
Regards,
B Flint


--- In 7x12minilathe@..., "roylowenthal
<roylowenthal@y...>" <roylowenthal@y...> wrote:

Al,
I agree; I'm in the process of making the same one!

Roy
--- In 7x12minilathe@..., "fromday2 <aldayis@a...>"
<aldayis@a...> wrote:

Roy, I saw Rick Kruger about a month ago and one of the

intresting

things in his shop is the adjustable backplate. The idea and
execution were clever and well done. I am going to make one
for a 4" 3jaw I have. His was nice looking, the concept is
simple enough that it should be reasonably easy to do.

Al Day

I think it's an arbitrary amount. If you make too much adjustment
range, there's no particular downside; if you make too little
adjustment range, it's easy to increase. At some point, the mounting
studs hit the sides of the spindle holes, setting an upper limit for
adjustment.
My plan was to make the maximum adjustment range possible, on the
theory that I've never regretted having more adjustment capacity on
anything.

Roy
--- In 7x12minilathe@..., "bbftx <bflint@a...>"
<bflint@a...> wrote:

Roy and Al:
I'm making an adjustable backplate too. One thing I question
in Rick's otherwise great design is the amount of adjustment
he built in. .050" oversize on the diameter seems like too much
to me.
I can't imagine needing to adjust more than a few thou. Wouldn't
a .005 to .010" oversize diameter give a person enough adjustment?
Regards,
B Flint


--- In 7x12minilathe@..., "roylowenthal
<roylowenthal@y...>" <roylowenthal@y...> wrote:

Al,
I agree; I'm in the process of making the same one!

Roy
--- In 7x12minilathe@..., "fromday2 <aldayis@a...>"
<aldayis@a...> wrote:

Roy, I saw Rick Kruger about a month ago and one of the

intresting

things in his shop is the adjustable backplate. The idea and
execution were clever and well done. I am going to make one
for a 4" 3jaw I have. His was nice looking, the concept is
simple enough that it should be reasonably easy to do.

Al Day

True enough. I use the 4-jaw when I need absolute
concentricity on an existing workpiece. Not to put
down Rick's idea - I think it's great and will
probably make one someday.

Frank Hoose


--- "roylowenthal <roylowenthal@...>"
<roylowenthal@...> wrote:

OTOH, when you're doing repairs/mods to existing
stuff, the lack
of concentricity is a problem. I'm using the 4 jaw
until I finish
the Rick Kruger style adjustable backplate (I'm too
cheap to go the
collet route.)

Roy
--- In 7x12minilathe@..., Frank Hoose
<fhoose@y...> wrote:

Something to keep in mind: a little runout of the
chuck, say .002 or .003 won't affect most projects

as

long as you don't remove the workpiece from the

chuck

until all operations are completed.

The reason is that as soon as you turn the

workpiece

down by more than .004, the resulting workpiece is
exactly concentric with the lathe axis within the
accuracy of the spindle bearings (typically .0002

-

.0005 on the minilathes).

This is why I was able to turn a piece of brass

down

to .034 dia. and then drill a .016 hole through

it.

lathe.com/Mini_lathe/Capabilities/Capabilities.htm#tiny

More recently, I needed some test pins for making
temporary connections to a tiny DIN connector on a
video camera. I turned the pins from brass to a

dia.

of .020. They were concentric even though the 4"

chuck

holding the 1/8 brass stock I started with

probably

has about .003 runout.

Frank Hoose


--- "Craig C. Hopewell
<chopewel@r...>"
<chopewel@r...> wrote:

John,
I have not heard of this problem before, but I

am

new
to the hobby, and if any lathes had this

problem I

would
have expected it on mine ( 8^) or 8^( - don't

know

which).

I would want this to be accurate, especially if
removing
and mounting the chuck regularly. If under
warranty I
would request a new spindle. If not under

warranty

a
new spindle is available from
www.littlemachineshop.com
for $29.95. Alternatively, an adapter plate
similar to
those necessary for a four inch chuck could be
made.

Craig

--- In 7x12minilathe@..., "John
<moran03@e...>"
<moran03@e...> wrote:

The raised land on my spindle plate measures

2.154

rather than 2.165

as given on the mini-lathe site. Sure enough,

the

recess in the
chuck

measures 2.165.

In order to mount my 3 jaw chuck I first snug

the

nuts slightly, put

a rod in the chuck, and use an indicator on

the

rod. I rotate the

chuck so the high point is up and tap the

chuck on

the top with a

block of wood; this is not a well controlled

process so it typically

takes several minutes to get TIR between 1 and

2

mils, when I
tighten

the nuts.

Is there a better way to center the chuck?

Is the mis-match between the land and the

recess

common? I expected

the chuck to center itself on the spindle land

but

this mis-match

apparently precludes that.

John

To unsubscribe from this group, send an email

to:

7x12minilathe-unsubscribe@...



Your use of Yahoo! Groups is subject to

__________________________________________________
Do you Yahoo!?
Yahoo! Shopping - Send Flowers for Valentine's Day

To unsubscribe from this group, send an email to:
7x12minilathe-unsubscribe@...



Your use of Yahoo! Groups is subject to

__________________________________________________
Do you Yahoo!?
Yahoo! Shopping - Send Flowers for Valentine's Day