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Hi Folks,

If I can poll the collective wisdom on this I'd appreciate it.

I'm not sure I have a problem, but I think so.

Turning down a rod I get a 0.015" difference over 5.5", please see:



I would guess that would turn into 0.030" over 11"?

If I turn a cone in the chuck and pull up the tailstock, they appear
to match up as near as I can tell.

My failed laser edge finder drew a circle around the the tailstock
center that looked centered to me.

I get this just turning a reasonably robust rod just clamped in the
chuck too (measurable difference between ends, forget what the value
is now).

I'm really lost on this, only thing I can think of (SWAG) is (horrors)
that the bed is crooked or perhaps the saddle is crooked?!???

I'm really out of ideas, am I expecting too much of the 7x12?

Thanks & take care, Vikki.

Go read this,


This should get you in the right direction.


RC


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

Hi Folks,

If I can poll the collective wisdom on this I'd appreciate it.

I'm not sure I have a problem, but I think so.

Turning down a rod I get a 0.015" difference over 5.5", please see:



I would guess that would turn into 0.030" over 11"?

If I turn a cone in the chuck and pull up the tailstock, they appear
to match up as near as I can tell.

My failed laser edge finder drew a circle around the the tailstock
center that looked centered to me.

I get this just turning a reasonably robust rod just clamped in the
chuck too (measurable difference between ends, forget what the value
is now).

I'm really lost on this, only thing I can think of (SWAG) is

(horrors)

that the bed is crooked or perhaps the saddle is crooked?!???

I'm really out of ideas, am I expecting too much of the 7x12?

Thanks & take care, Vikki.

You well more than likely find the TS off set a bit. If your using a
three jaw chuck you have some run out at that end also. The best
either of my tree jaw chucks well do is .0015-.002. With a four jaw,
or collets, you can get dead on.
Some good info here

and gadgetbuilder is great also.
I spent the first two months I owned my 7X working on it to improve
accuracy. This is the first mod I did

followed by tapered gibs. I ended up putting a 14in bed on it. I
happy with the results. I still want to add bearing to the saddle
hand wheel and gears, a hand crank on the lead screw and headstock.
Here is more eye and head candy

Guys that should know, tell me that a lathe bed has almost no resistance
to twist. You need to beg, borrow, or steal a machinist's precision
level and check the bed, both at the headstock and near the tailstock to
make sure that the level reads exactly the same in both places. If your
bench is solid, you may need to add shims beneath the legs on the lathe,
then clamp it back to the bench. If your table is not completely rigid,
you can adjust the feet of the table to impart some twist to the table,
and thus to the lathe bed. It surprised me; just how much a small shim
will de-twist the bed. A twisted bed will exhibit exactly the symptoms
you describe.

Ed B

I have read that some folks have had a twist problem. Both my 10 and
14 in beds checked out good. I also use a piece of 24X6X3/8 steel
plate to mount the bed to, with the wide feet under that. Help cut
down on chatter when parting.

Leveling is the normal way (pun) that larger lathes are set up but the
minilathe is relatively stiffer due to its small size. Although the
castings aren't "aged", they are generally ground accurately so there
isn't any twist in the typical minilathe. Unless it is firmly bolted
down -- this can induce a twist, especially if bolted to something
that changes with humidity (wood) or temperature (metal) at a rate
different from the lathe bed itself. The simple rubber feet work well
because the lathe is light enough so it doesn't twist under its own
weight (as large machines may). (Hardinge made a large "portable"
lathe with wheels that was quite accurate so there is some precedence
for lathes not being bolted down.)

More commonly, tapers occurring in work held in the chuck (not between
centers) arise from poor alignment between the spindle and the ways.
This can be corrected by the owner with simple techniques but takes
several hours: Once
aligned the machine seems to remain aligned so this is a one-time
effort, i.e. the castings don't seem to "age" and twist.

John

Thanks to all that responded to this query.

OK, I am *totally* intimidated after going through some of the websites
suggested :-(.

It is going to take a LOT more experience and especially more
understanding than I have before I start tearing down the lathe to that
degree.

Of interest, I dug out that bolster bar I made out of the 1" stainless
rod and measured that at each end (3") and it is only off by 0.001.
Chucked on one end, center drilled and supported by the live center in
the tailstock.

Wonder if my problem is flex in the workpiece, as in I am hogging it?
It would see that would make it off in the middle were it is unsupported
though.

Yep, I am totally confused about what is going on here.

The item that was off the 0.015 was wood and I am now wondering if the
centers being slightly off from the center marks (assuming they were
perfect) would cause that much difference? I would think that turning
that down would result in it being symmetrical / consistent from end to
end once it was turned down far enough?

Starting to think I really need a mentor or at least a decent course
about all this.

Thanks & take care, Vikki (The Massively Confuzed).

G'day Vikki
Your site shows you have a dial indicator. Mount it on the cross
slide and extend the tail stock quill out to the limit of its travel
and clamp it. Run the dial indicator along the side and top of the
quill. You may well find the dial indicator moves during the travers
indicating that the quill is not parallel to the bed axis. Unless you
have spent time working over the tailstock you will find that it is
too high by up to 20 thou and the the quill alignment is out by up to
the same amount. I spent yesterday finally getting my tailstock to
near "perfect" alignment and height yesterday, this has taken me 10
months of intermittent effort. I moved the clamping screw from under
to above the foot.
Don't use the rolling centre when making alignment; for critical work
use a dead centre with the tip lubricated with molebdenum grease. I
use the method which holds a shim between the centre to verify
alignment.
BTW. It turning between centres the alignment of the headstock will
not effect the job. If the tailstock quill is not aligned then the
alignment with the headstock will differ as the quill is extended.

Keep up the work on the laser centre and edge finder, it looks a
great project.

One good turn deserves another.
Regards,
Ian

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

Hi Folks,

If I can poll the collective wisdom on this I'd appreciate it.

I'm not sure I have a problem, but I think so.

Turning down a rod I get a 0.015" difference over 5.5", please see:



I would guess that would turn into 0.030" over 11"?

If I turn a cone in the chuck and pull up the tailstock, they appear
to match up as near as I can tell.

My failed laser edge finder drew a circle around the the tailstock
center that looked centered to me.

I get this just turning a reasonably robust rod just clamped in the
chuck too (measurable difference between ends, forget what the value
is now).

I'm really lost on this, only thing I can think of (SWAG) is

(horrors)

that the bed is crooked or perhaps the saddle is crooked?!???

I'm really out of ideas, am I expecting too much of the 7x12?

Thanks & take care, Vikki.

No twist in my bed but the headstock was off by 0.015 in 8" when I got it.

After aligning using "Rollie's Dad's Method", my DTI (0.0005) doesn't twitch over the same distance. I can turn a 3" length and have it come out with no taper as measured with a good (? Starret) micrometer.

Aaron

Okay, it's not a complex deal although it appears to be. First off, find an old dot matrix printer and rob all the rods out of it. Take the larger one that the print carrige rides on and chuck it up. Drill a centering hole at one end if it doesn't already have one and then put that in the tailstock center. Mount a dial test indicator on the carriage of the lathe so that the test probe contacts the FRONT of the bar and reads. Run the carriage back and forth while watching the dial. This will tell you how much you're off either at the tailstock or the headstock / spindle. To eliminate chuck runout, turn the spindle 90 degrees and repeat. If your readings change, your chuck isn't centered. Repeat the whole process on the TOP of the bar to find out what your error is in tailstock HEIGHT.

Chris Bailey



wrlabs wrote:

Hi Ian,

Thanks for the response!

--- In 7x12minilathe@..., "steam4ian" <fosterscons@...>
wrote:

G'day Vikki
Your site shows you have a dial indicator. Mount it on the cross
slide and extend the tail stock quill out to the limit of its travel
and clamp it. Run the dial indicator along the side and top of the
quill. You may well find the dial indicator moves during the travers
indicating that the quill is not parallel to the bed axis. Unless you
have spent time working over the tailstock you will find that it is
too high by up to 20 thou and the the quill alignment is out by up to
the same amount.

That was the easy part :). Spent most of the evening working at
following these directions and I am still not sure I got this right.

If you would please look at:



The first 4 are checking the quill on the tailstock and it seems to look
pretty good, Up by 0.001 in the back and toward the rear of the lathe
by 0.0025 (closest to the tailstock, front of quill was used as zero).

I spent yesterday finally getting my tailstock to
near "perfect" alignment and height yesterday, this has taken me 10
months of intermittent effort.

I can understand that after tonight :-). Made the measurements several
different ways and many different times and got somewhat different
values. Still confused, but somewhat less so (I think :-).

Measuring the dead center with the DI clamped in the chuck, you see the
results. I tried it using the quill end (just get the ball up on it)
and got a different set of values:

Ball sitting on top (rear of ball touching) rather than front touching
as in the pix referenced above:

<pre>
Ball back resting on top of quill, dial up............: reference zero.
Ball back resting on front of quill, dial front......: -0.008 / -0.0085
Ball back resting on bottom of quill, dial down..: -0.0035 / -0.004
Ball back resting on back of quill, dial rea.........: -0.005
</pre>

Pretending I am getting a clue here, that would make the back end of
the work closer to the front of the lathe which would cut the workpiece
thinner than the front (chuck end).

Many different variations in the different pieces, certainly a challenge
to get them all working the right way. Starting to think this little
7x12 is rather amazing for as good as it is out of the box after being
shipped halfway across the planet!

I moved the clamping screw from under
to above the foot.

Need to figure out how to do that one, not clear to me why it is on the
bottom in the first place, just seems wrong to me. So far what tapers I
needed were short enough to do the math and set the compound
accordingly.

Don't use the rolling centre when making alignment;

Did indeed use the dead center that came with the lathe.

for critical work
use a dead centre with the tip lubricated with molebdenum grease.

Understand, thanks.

use the method which holds a shim between the centre to verify
alignment.

Do you mean crush (dent) the shim between a pointed rod in the chuck
against the center in the tailstock to see if they match up?

BTW. It turning between centres the alignment of the headstock will
not effect the job. If the tailstock quill is not aligned then the
alignment with the headstock will differ as the quill is extended.

With it having been fully extended to get space to work, I was getting
all it has to give :).

Keep up the work on the laser centre and edge finder, it looks a
great project.

Problem with using cheap laser pointers to do that is that NONE of them
(that I have tried so far) project a decent dot, if a dot at all. One
can get a donut pretty easily, but that requires better eyeballs than I
have to use. I looked into decent laser modules (Digikey, IIRC) and the
folks offering them for $40-$60 are one fantastic deal. Of the 5 I have
tried so far, none was significantly better than the first one I did
:-/. If there are decent laser modules at affordable prices out there,
I have been unable to locate them :-(.

Thanks very much & take care, Vikki.

Vikki
Here is some more tail stock info.

This can be a bit mind boggling at the start, just keep reading and
learning. Mr Kruger's pages help me a LOT. My TS is repeatable to
.0003 after 8-10 hours of work (head scratching).

G'day Vikki.
Looking at the comprehensive readings you have taken it appears as if
you tailstock is 8thou to the front, this would account for the
15thou taper you were getting.
Your quill alignment is good, IMHO i wouldn't do anything with that
until you have used the lathe for a while. BTW this is very good for
out of the box.
IMHO generally it is unwise to get into tuning up the lathe first off
short of cleaning up and making general adjustments eg gibs. Use the
lathe to allow surfaces to bed-in. The longer you leave it the more
time the bed has to normalise and stress relieve. Ultimately you will
get sick of working around the alignment inaccuracies and then it is
time for serious tuning.
I note that you mounted the DTI in the 3 jaw chuck. It is not safe to
assume the chuck is truely concentric, they are OK for general work,
but precision work should be either turned between centres or mounted
in a 4 jaw chuck with careful centering.
Here in Ox we have a bird called a Bower Bird. The male builds a
bower out of grass and twigs and then collect shiny objects to place
in the bower. When complete he invites females in to see his
collection, a bit like inviting girls back to see his etching. Your
colection of "shiny things" reminds me of that. Is your bower working?
I am impressed by your site.

One good turn deserves another.
Regards,
Ian
--- In 7x12minilathe@..., "wrlabs" <wrlabs@...> wrote:

Hi Ian,

Thanks for the response!

--- In 7x12minilathe@..., "steam4ian" <fosterscons@>
wrote:

G'day Vikki
Your site shows you have a dial indicator. Mount it on the cross
slide and extend the tail stock quill out to the limit of its

travel

and clamp it. Run the dial indicator along the side and top of the
quill. You may well find the dial indicator moves during the

travers

indicating that the quill is not parallel to the bed axis. Unless

you

have spent time working over the tailstock you will find that it

is

too high by up to 20 thou and the the quill alignment is out by

up to

the same amount.

That was the easy part :). Spent most of the evening working at
following these directions and I am still not sure I got this right.

If you would please look at:



The first 4 are checking the quill on the tailstock and it seems to

look

pretty good, Up by 0.001 in the back and toward the rear of the

lathe

by 0.0025 (closest to the tailstock, front of quill was used as

zero).

I spent yesterday finally getting my tailstock to
near "perfect" alignment and height yesterday, this has taken me

10

months of intermittent effort.

I can understand that after tonight :-). Made the measurements

several

different ways and many different times and got somewhat different
values. Still confused, but somewhat less so (I think :-).

Measuring the dead center with the DI clamped in the chuck, you see

the

results. I tried it using the quill end (just get the ball up on

it)

and got a different set of values:

Ball sitting on top (rear of ball touching) rather than front

touching

as in the pix referenced above:

<pre>
Ball back resting on top of quill, dial up............: reference

zero.

Ball back resting on front of quill, dial front......: -0.008 / -

0.0085

Ball back resting on bottom of quill, dial down..: -0.0035 / -0.004
Ball back resting on back of quill, dial rea.........: -0.005
</pre>

Pretending I am getting a clue here, that would make the back end

of

the work closer to the front of the lathe which would cut the

workpiece

thinner than the front (chuck end).

Many different variations in the different pieces, certainly a

challenge

to get them all working the right way. Starting to think this

little

7x12 is rather amazing for as good as it is out of the box after

being

shipped halfway across the planet!

I moved the clamping screw from under
to above the foot.

Need to figure out how to do that one, not clear to me why it is on

the

bottom in the first place, just seems wrong to me. So far what

tapers I

needed were short enough to do the math and set the compound
accordingly.

Don't use the rolling centre when making alignment;

Did indeed use the dead center that came with the lathe.

for critical work
use a dead centre with the tip lubricated with molebdenum grease.

Understand, thanks.

use the method which holds a shim between the centre to verify
alignment.

Do you mean crush (dent) the shim between a pointed rod in the chuck
against the center in the tailstock to see if they match up?

BTW. It turning between centres the alignment of the headstock

will

not effect the job. If the tailstock quill is not aligned then the
alignment with the headstock will differ as the quill is extended.

With it having been fully extended to get space to work, I was

getting

all it has to give :).

Keep up the work on the laser centre and edge finder, it looks a
great project.

Problem with using cheap laser pointers to do that is that NONE of

them

(that I have tried so far) project a decent dot, if a dot at all.

One

can get a donut pretty easily, but that requires better eyeballs

than I

have to use. I looked into decent laser modules (Digikey, IIRC)

and the

folks offering them for $40-$60 are one fantastic deal. Of the 5 I

have

tried so far, none was significantly better than the first one I did
:-/. If there are decent laser modules at affordable prices out

there,

I have been unable to locate them :-(.

Thanks very much & take care, Vikki.

Hi Ian,

Vikki's use of the DTI mounted in the 3 jaw to assess the tailstock
offset by indicating on a dead center is accurate and the result is
not affected by runout of the 3 jaw. Error arising from this source
is a common misconception covered on my site in the alignment section.

It is easily proved that chuck runout doesn't affect the results:
Record values with the DTI shaft gripped directly by the chuck. Then,
add a 30 thou or so shim between one jaw and the DTI shaft (to cause
serious runout) and record values again. The average (or difference)
for the front/back or top/bottom readings will be the same for both
conditions. This isn't really obvious and I had to go to the shop and
actually perform the experiment when I first realized how it worked --
so you're not alone :-)

John


--- In 7x12minilathe@..., "steam4ian" <fosterscons@...> wrote:

G'day Vikki.

<snip>

I note that you mounted the DTI in the 3 jaw chuck. It is not safe to
assume the chuck is truely concentric, they are OK for general work,
but precision work should be either turned between centres or mounted
in a 4 jaw chuck with careful centering.

<snip>

One good turn deserves another.
Regards,
Ian
--- In 7x12minilathe@..., "wrlabs" <wrlabs@> wrote:

Hi Ian,

Thanks for the response!

--- In 7x12minilathe@..., "steam4ian" <fosterscons@>
wrote:

G'day Vikki
Your site shows you have a dial indicator. Mount it on the cross
slide and extend the tail stock quill out to the limit of its

travel

and clamp it. Run the dial indicator along the side and top of the
quill. You may well find the dial indicator moves during the

travers

indicating that the quill is not parallel to the bed axis. Unless

you

have spent time working over the tailstock you will find that it

is

too high by up to 20 thou and the the quill alignment is out by

up to

the same amount.

That was the easy part :). Spent most of the evening working at
following these directions and I am still not sure I got this right.

If you would please look at:



The first 4 are checking the quill on the tailstock and it seems to

look

pretty good, Up by 0.001 in the back and toward the rear of the

lathe

by 0.0025 (closest to the tailstock, front of quill was used as

zero).

I spent yesterday finally getting my tailstock to
near "perfect" alignment and height yesterday, this has taken me

10

months of intermittent effort.

I can understand that after tonight :-). Made the measurements

several

different ways and many different times and got somewhat different
values. Still confused, but somewhat less so (I think :-).

Measuring the dead center with the DI clamped in the chuck, you see

the

results. I tried it using the quill end (just get the ball up on

it)

and got a different set of values:

Ball sitting on top (rear of ball touching) rather than front

touching

as in the pix referenced above:

<pre>
Ball back resting on top of quill, dial up............: reference

zero.

Ball back resting on front of quill, dial front......: -0.008 / -

0.0085

Ball back resting on bottom of quill, dial down..: -0.0035 / -0.004
Ball back resting on back of quill, dial rea.........: -0.005
</pre>

Pretending I am getting a clue here, that would make the back end

of

the work closer to the front of the lathe which would cut the

workpiece

thinner than the front (chuck end).

Many different variations in the different pieces, certainly a

challenge

to get them all working the right way. Starting to think this

little

7x12 is rather amazing for as good as it is out of the box after

being

shipped halfway across the planet!

I moved the clamping screw from under
to above the foot.

Need to figure out how to do that one, not clear to me why it is on

the

bottom in the first place, just seems wrong to me. So far what

tapers I

needed were short enough to do the math and set the compound
accordingly.

Don't use the rolling centre when making alignment;

Did indeed use the dead center that came with the lathe.

for critical work
use a dead centre with the tip lubricated with molebdenum grease.

Understand, thanks.

use the method which holds a shim between the centre to verify
alignment.

Do you mean crush (dent) the shim between a pointed rod in the chuck
against the center in the tailstock to see if they match up?

BTW. It turning between centres the alignment of the headstock

will

not effect the job. If the tailstock quill is not aligned then the
alignment with the headstock will differ as the quill is extended.

With it having been fully extended to get space to work, I was

getting

all it has to give :).

Keep up the work on the laser centre and edge finder, it looks a
great project.

Problem with using cheap laser pointers to do that is that NONE of

them

(that I have tried so far) project a decent dot, if a dot at all.

One

can get a donut pretty easily, but that requires better eyeballs

than I

have to use. I looked into decent laser modules (Digikey, IIRC)

and the

folks offering them for $40-$60 are one fantastic deal. Of the 5 I

have

tried so far, none was significantly better than the first one I did
:-/. If there are decent laser modules at affordable prices out

there,

I have been unable to locate them :-(.

Thanks very much & take care, Vikki.

Hi Ian,

Thanks for the response, I find it most encouraging!

--- In 7x12minilathe@..., "steam4ian" <fosterscons@...>
wrote:

G'day Vikki.
Looking at the comprehensive readings you have taken it appears as if
you tailstock is 8thou to the front, this would account for the
15thou taper you were getting.
Your quill alignment is good, IMHO i wouldn't do anything with that
until you have used the lathe for a while. BTW this is very good for
out of the box.

Most encouraging, thank you!

IMHO generally it is unwise to get into tuning up the lathe first off
short of cleaning up and making general adjustments eg gibs. Use the
lathe to allow surfaces to bed-in. The longer you leave it the more
time the bed has to normalise and stress relieve. Ultimately you will
get sick of working around the alignment inaccuracies and then it is
time for serious tuning.

I think I am getting over some of the intimidation at this point to even
start to approach this :-). Mostly thanks to everyone here who has
helped me understand what all this is about! The intimidation factor
has accomplished that, I have just been using it and not doing any
tuning so far :). As I learn more I am less afraid to tackle things
that were scary before.

I note that you mounted the DTI in the 3 jaw chuck. It is not safe to
assume the chuck is truely concentric, they are OK for general work,
but precision work should be either turned between centres or mounted
in a 4 jaw chuck with careful centering.

Read John's response to this a bit further along. Glad :-)! I'll have
to try the suggested experiment to really understand it though. I am
starting to realize that I do need a 4 jaw chuck, probably bigger than
3", just which one is going to be a learning experience :-).

Here in Ox we have a bird called a Bower Bird. The male builds a
bower out of grass and twigs and then collect shiny objects to place
in the bower. When complete he invites females in to see his
collection, a bit like inviting girls back to see his etching. Your
colection of "shiny things" reminds me of that. Is your bower working?

LOL, dunno about that, but I am learning and, most amazing to me,
starting to be able to make things out of metal which has always seemed
like magic(k?) to me :-).

So far all it has attracted is my landlord who wants much for nothing,
probably not a good result :). He doesn't like me having this stuff in
the apartment, but he sure doesn't mind when I use it for him :-). Will
probably result in having to move eventually, which is not a bad thing.

Perhaps it is that strange attraction for .au that I have had as long
as I can remember that leads me that way :-)! Have a net.friend in
Adelaide (electronics tech) who is trying to teach me Austrailian :-).
And another mate (see ;-) there who is a helo pilot who is also into
flight simulation :-).

I am impressed by your site.

Thanks for the kind words! Just trying to document what I am doing on
the off chance it might help someone else. I have gotten a lot of help
/ understanding from folks who have done this. Mine is by no means as
good as many, but if it helps anyone I'll be happy. That I have an
excuse to get a decent digital camera (Cannon S2 IS) and to putz with
using the linux tools to make web pages is just icing on the cake :-).

One good turn deserves another.

Indeed it does Sir!

I'm going to get brave and try to figure out how to square up the
tailstock today :-). That locking screw being on the bottom concerns
me, but we'll see.

Thanks so very much!

Take care, Vikki.

G'day John & Vikki.
John's right regarding the DTI mounting in the 3 jaw chuck.
But for centering a work piece my comments still stands. It is handy
for turning eccentric cams to put a packer under one jaw to off set
the work piece.

Regarding the swarf tray: How do you get photos on this site? My
workshop is not very photogenic at the moment so here is an excuse to
tidy it up. John, like Eddie Murphy "Coming to America" I do
have "wipers" but why let the s.....* fall there in the first place?

Must rush to a meeting.
One good turn deserves another.
Regards,
Ian

*swarf, you thought I meant something else!

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

Hi Ian,

Vikki's use of the DTI mounted in the 3 jaw to assess the tailstock
offset by indicating on a dead center is accurate and the result is
not affected by runout of the 3 jaw. Error arising from this source
is a common misconception covered on my site in the alignment

section.

It is easily proved that chuck runout doesn't affect the results:
Record values with the DTI shaft gripped directly by the chuck.

Then,

add a 30 thou or so shim between one jaw and the DTI shaft (to cause
serious runout) and record values again. The average (or

difference)

for the front/back or top/bottom readings will be the same for both
conditions. This isn't really obvious and I had to go to the shop

and

actually perform the experiment when I first realized how it

worked --

so you're not alone :-)

John

--- In 7x12minilathe@..., "steam4ian" <fosterscons@...> wrote:

G'day John & Vikki.
John's right regarding the DTI mounting in the 3 jaw chuck.
But for centering a work piece my comments still stands. It is handy
for turning eccentric cams to put a packer under one jaw to off set
the work piece.

I got to try that experiment, seems that it should be relative for
aligning the tailstock though. I figure that when I am confused as I
am at the moment, I must be on the verge of understanding something
LOL :).

Regarding the swarf tray: How do you get photos on this site? My
workshop is not very photogenic at the moment so here is an excuse to
tidy it up. John, like Eddie Murphy "Coming to America" I do
have "wipers" but why let the s.....* fall there in the first place?

NOW I am going to be self-conscious when taking pix in that mess here :-).

Don't know, but if you can't for some reason, let me know and I can
put them up here.

I started on aligning the tailstock and already have a disaster :-) on
my hands. Tapping it with a (nylon) jewelers hammer to move it back
seems to have moved it a LOT in both planes :-/. Just came back in
here for a break and a cup of coffee before hitting it again. Maybe
that should be breathing on it :).

I can figure out what the socket head screw on the bottom is for, but
what is the little slotted one on the back of the tailstock for, can't
just be another locking screw can it (so one could secure it to some
degree while taking the tailstock off to tighten the one on the bottom)?

I *AM* about to order the cam lock kit, so far I have spent more time
spinning a wrench on the hold down nut than I have anything else...
Really frustrating...

Fun, fun fun :-).

Take care, Vikki.

There's some more TS info in the "links" section at:



There are several different mods floating around to eliminate the
clamp screw on the underside of the TS & some that provide actual
controlled adjustment. Until you modify it, you can center it easier
off the lathe.

Once you figure how far off center it is, you can remove it to access
the bottom screw. Before loosening things, measure the relative
horizontal position of the upper & lower parts of the base. After
you've done that, it's relatively easy to move it a controlled
distance to center it.

Roy

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

Hi Folks,

If I can poll the collective wisdom on this I'd appreciate it.

I'm not sure I have a problem, but I think so.

Turning down a rod I get a 0.015" difference over 5.5", please see:



I would guess that would turn into 0.030" over 11"?

If I turn a cone in the chuck and pull up the tailstock, they appear
to match up as near as I can tell.

My failed laser edge finder drew a circle around the the tailstock
center that looked centered to me.

I get this just turning a reasonably robust rod just clamped in the
chuck too (measurable difference between ends, forget what the value
is now).

I'm really lost on this, only thing I can think of (SWAG) is

(horrors)

that the bed is crooked or perhaps the saddle is crooked?!???

I'm really out of ideas, am I expecting too much of the 7x12?

Thanks & take care, Vikki.

Hi folks,

Update...

I hath created a monster, I think :).

After loosening the socket head screw under the tailstock I discover the
top of the tailstock flops in the X and Y axis. Raised section on the
base and the slot in the tailstock itself are mismatched by (guess) at
least 1/8", lotsa twist there.

Apparently that little slot head set screw on the back of the tailstock
is for adjusting the Z (?rotational) orientation. If it was ever
tightened down, it worked loose over time.

I'm not sure what I am seeing here, but I get top and bottom of the
quill to read zero (top set as reference zero) but the front (toward
operator) and back are both around 13 (plus to front, minus to rear),
depending on the tap of the moment.

I was using the dead center for this and I thought that it was
elliptical (flattened top to bottom). So, just to see what happened, I
rotated the dead center 90 degrees expecting the top / bottom to
increase and the front / rear to decrease. Values did not change ?!?

Tried this using the inside and outside of the quill and get the same
kind of results.

I'm perplexed!

Putting this away for today, tired of cranking on that lock nut :-).

One another note. I was thinking it might be nice to have a place were
folks could chat live, I put together a channel on chat.freenode.net:
#vmmst

Standing for: Virtual Micro and Mini-Machine Shop Tavern :-).

Any IRC client will get you there set up for the network
(chat.freenode.net) and the channel (#vmmst).

IRC has gotten a bad rep for obnoxious jerks, but the exception to this
I have found is freenode, my personal channel is there and I have yet
(in years now) to have any problem with jerks.

Only rule I have for the channel is that folks treat it like my (or
your) living room and act accordingly. I do not and will not tolerate
rude / obnoxious people. Enough said.

It's there if folks want a place to chat live, I'm there when I am up
although I may be doing other things and not notice right away.

Thought it might be a nice resource.

It;s been an exciting day!

Take care, Vikki.

I'm not sure what I am seeing here, but I get top and bottom of the
quill to read zero (top set as reference zero) but the front (toward
operator) and back are both around 13 (plus to front, minus to rear),
depending on the tap of the moment.

That indicates that while you have the tailstock pretty well centred
properly up and down, it is either not pointing straight at the
headstock, or it is off centre. Most likely it's a bit of both. If
you extend the quill further, you'll probably find that difference
will drift one way or the other. Think of in in the extreme - think
of what the indicator would read if the tailstock was pointing 10
degrees or so off centre.

You must start by setting the tailstock straight - what John
(gadgetbuilder) calls angular alignment. Then you know the error
you're seeing with the DTI is all parallel alignment and you can
adjust to correct it.

For setting the straightness, I extend the quill about 1.5"-2", lock
it down, set the indicator in the toolpost and measure along the
outside body of the quill. For maintaining centre, this should be
adjusted so there is no variance along the length.

----

As a side note, with most folks mini-lathes there comes a point where
aligning the tailstock becomes a trade-off. Often, the tapered part
of the quill is not quite concentric with the outside barrel. So you
reach a point where you're deciding to go for taper straightness
(better for drilling/tapping/reaming) or for barrel straightness
(centre remains on centre no matter how far the quill is extended).

On my minilathe, the taper mismatches the barrel by about .002 per
inch. I have the tailstock adjusted for barrel straightness. With 5"
of chuck and drill bit sticking out of the tailstock, the tip of the
drill bit is .010" off centre. This causes it to drill oversized and
tapered holes. But the benefit is if I turn something between
centres, it'll not be tapered no matter how far the quill is extended.

Aligning the tailstock with the DTI-in-chuck method will cause you to
setup the tailstock for taper straightness. To setup for barrel
straightness you need a centre-drilled test bar and the DTI mounted in
the toolpost. Use RDM (Rollie's Dad's Method) on both ends and adjust
'till equal.

----

Aligning the mini-lathe tailstock can be very frustrating, even with
the various aids people have created. I like John's (gadgetbuilder's)
one best. Using shims rather than pushing against a set-screw makes
things a lot more repeatable, and dialing in the last .0005" is much
easier by torquing down a screw "just a bit tighter".

Finally, there's no point in going nuts about tailstock alignment if
the headstock hasn't been aligned yet. Eventually you'll want to do
that and it'll throw your tailstock alignment out (and all your hard
work!). For a quick an dirty alignment, setup the headstock and
tailstock with centres. A live tailstock is fine if it's a decent
one. Then bring the points together with a thin piece of metal
between them until they just touch lightly - you don't want to crush
them. Use a thin razor-blade or thin shim: the thinner, the more
easily the error will be seen. If the tailstock is well aligned, the
shim will be held square to the rest of the lathe. Adjust as
necessary, then check it again with the quill extended to get
straightness. Go back and forth until you get it acceptable at both
ends. Your tailstock is now aligned.

I hope this is of some help. If something seems to be confusing, I
find it's best pictured mentally if you think about it in the
extremes. Somehow it seems more obvious that way.

Good luck,

-Paul Moir