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I also was thinking of getting one of these machines. I am currently trying
to figure out if I want one of the 9x20 lathes or 7xX. Wonder if anyone in
this group has purchased one yet. I would love to hear a compairison
between it and the 7x12. I love the idea of true inch lead screws. I would
like to have the 9x20 in true inch. Any thoughts on this will be much
appreciated.

Ben

I bought one a couple of months ago. It works very well. The digital
readout has been very handy and their cam-lock tailstock is great.
I certainly would recommend one.

There's some comparisons here:

Some of the confusion about bed length may come from the tailstock
not being able to seat a standard dead center unless the ram is
extended an inch or so. Also, the headstock taper is a bit
undersize, causing the center to stick out farther than it really
should.
IIRC, there's a 9x20 group.

Roy
--- In 7x12minilathe@..., haplesstechnoweenie
<haplesstechnoweenie@c...> wrote:

I also was thinking of getting one of these machines. I am

currently trying

to figure out if I want one of the 9x20 lathes or 7xX. Wonder if

anyone in

this group has purchased one yet. I would love to hear a

compairison

between it and the 7x12. I love the idea of true inch lead

screws. I would

like to have the 9x20 in true inch. Any thoughts on this will be

much

appreciated.

Ben

Don't be overly concerned about true inch leadscrews.
The main (threading) leadscrew on the 7x lathes is
true inch. The cross feed and compound are 1mm pitch
with the calibrated wheels having 40 divisions. The
margin of error is very small (each rotation of the
handwheel is actually .03937 inches instead of .04000
inches and a single division is thus .000984 inches
rather than .00100 inches). Since you will no doubt
measure your work with "inch" measuring tools, the
error becomes negligible.

Frank Hoose



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

There's some comparisons here:

Some of the confusion about bed length may come
from the tailstock
not being able to seat a standard dead center unless
the ram is
extended an inch or so. Also, the headstock taper
is a bit
undersize, causing the center to stick out farther
than it really
should.
IIRC, there's a 9x20 group.

Roy
--- In 7x12minilathe@...,
haplesstechnoweenie
<haplesstechnoweenie@c...> wrote:

I also was thinking of getting one of these

machines. I am
currently trying

to figure out if I want one of the 9x20 lathes or

7xX. Wonder if
anyone in

this group has purchased one yet. I would love to

hear a
compairison

between it and the 7x12. I love the idea of true

inch lead
screws. I would

like to have the 9x20 in true inch. Any thoughts

on this will be
much

appreciated.

Ben

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Here's an example, which will hopefully make it more clear why the
small error of the dials is usually insignificant:

Suppose you want to turn a 1/2" diameter rod to .475" in dia. You
start by making a shallow turning pass to get a reference surface.
Let's say you measure it with your dial caliper and it is
now .497" dia. so you need to remove .497-.475" or
.022. So you will need to advance the cross feed by
11 divisions (reducing the radius by .011 will reduce
the dia by .022). To be safe, you advance by 9
divisions, then stop and check the diameter again.
Let's say it is now .477. For your final finishing
pass you advance the cross feed by 1 division reducing the diamer
by .002 to .475. The error of the dial for this small adjustment is
negligible - less, in fact, than the inherent
precision of the lathe.

The only time the error would be significant is if you advance the
dials by a full turn or more without rechecking the diameter by
measuring.

Suppose you needed to remove, say .240 and counted off 3 full
turns of the dial (.120) without taking another
measurement. Since the error for each full turn of the
dial is .040 - .03937 = .00063, the total error would
be .00189 or nearly 2 thousandths. In
practice, as you approach your desired diameter, you
would stop the lathe and measure the actual diameter,
then turn the dial by just a few divisions as needed to
reach the final diameter. With careful technique you should be able
to get the final diameter accurate to .001".

Also, the error is in the direction of removing less metal - it's
easy to take another pass with a small advance to final diameter. If
the early cut was too big, no amount of cutting will replace removed
metal.
These lathes have some flex; taking multiple passes without
changing the tool position will take another small cut or 2. If you
carefully measure, you'll probably find the flex, even on light cuts,
is bigger than the theoretical error of the pseudo-inch dials.

Roy

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

Here's an example, which will hopefully make it more clear why the
small error of the dials is usually insignificant:

Suppose you want to turn a 1/2" diameter rod to .475" in dia. You
start by making a shallow turning pass to get a reference surface.
Let's say you measure it with your dial caliper and it is
now .497" dia. so you need to remove .497-.475" or
.022. So you will need to advance the cross feed by
11 divisions (reducing the radius by .011 will reduce
the dia by .022). To be safe, you advance by 9
divisions, then stop and check the diameter again.
Let's say it is now .477. For your final finishing
pass you advance the cross feed by 1 division reducing the diamer
by .002 to .475. The error of the dial for this small adjustment is
negligible - less, in fact, than the inherent
precision of the lathe.

The only time the error would be significant is if you advance the
dials by a full turn or more without rechecking the diameter by
measuring.

Suppose you needed to remove, say .240 and counted off 3 full
turns of the dial (.120) without taking another
measurement. Since the error for each full turn of the
dial is .040 - .03937 = .00063, the total error would
be .00189 or nearly 2 thousandths. In
practice, as you approach your desired diameter, you
would stop the lathe and measure the actual diameter,
then turn the dial by just a few divisions as needed to
reach the final diameter. With careful technique you should be able
to get the final diameter accurate to .001".


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

wrote:

Don't be overly concerned about true inch leadscrews.
The main (threading) leadscrew on the 7x lathes is
true inch. The cross feed and compound are 1mm pitch
with the calibrated wheels having 40 divisions. The
margin of error is very small (each rotation of the
handwheel is actually .03937 inches instead of .04000
inches and a single division is thus .000984 inches
rather than .00100 inches). Since you will no doubt
measure your work with "inch" measuring tools, the
error becomes negligible.

Frank Hoose



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

There's some comparisons here:

Some of the confusion about bed length may come
from the tailstock
not being able to seat a standard dead center unless
the ram is
extended an inch or so. Also, the headstock taper
is a bit
undersize, causing the center to stick out farther
than it really
should.
IIRC, there's a 9x20 group.

Roy
--- In 7x12minilathe@...,
haplesstechnoweenie
<haplesstechnoweenie@c...> wrote:

I also was thinking of getting one of these

machines. I am
currently trying

to figure out if I want one of the 9x20 lathes or

7xX. Wonder if
anyone in

this group has purchased one yet. I would love to

hear a
compairison

between it and the 7x12. I love the idea of true

inch lead
screws. I would

like to have the 9x20 in true inch. Any thoughts

on this will be
much

appreciated.

Ben

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