THE ASIAN 7 X 10 MINI LATHE
ANOTHER LOW COST CHOICE FOR THE SCALE MODEL
MAKER
By Jose Rodriguez
Part One
For years, there was the original miniature Unimat metalworking
lathe which became a household word to just about every scale model
builder. Though one can still find some good used examples of the
legendary Unimat, sadly it is no longer made. Lucky for us, there are some
very good little machines presently available that seem to have been
specifically designed with the model engineer in mind. The Taig and Sherline
are without question the most popular and versatile of the 4" swing and
smaller category of lathes and as such, they are both excellent machines
for the money. Specially the Taig with its overall greater workpiece capacity
and spindle speed range.
I recently had a great need for a slightly larger capacity lathe,
one that would allow me to machine materials like 5-6" diameter flywheels
in stainless steel and yet, be small enough to move to other shop locations if
I had to. The 4" swing and smaller machines will accept riser blocks in an
effort to increase their turning capacities but in all truth, they really have to work rather hard to be able to take a .050" cut on a stainless steel flywheel
larger than 3-4". Chatter becomes a big problem with work of that type with
the smaller light weight tools. I had seen, as I'm sure many of you readers
have, a small Asian make bench style lathe sold through several mail order
companies that I'm sure most are very familiar with. The tool is being
described as a 7"x10" bench mini lathe with electronic variable speed
control. Although I have seen several short comments on the metalworking
FAQ about it, no one has gone into any great detail about the lathe itself.
Often chastising it rather than giving it a fair chance to prove itself. The
weight of 89 pounds from all the cast iron, immediately got my interest and
it seemed like I had found exactly what I needed for my medium size
steam engine projects. Here was a small machine that not only outweighed
my loaded Taig nearly 7 fold but could cut the type of materials that would
cause my smaller and lighter weight machines to growl like a bear. I
decided to take the plunge even after reading some of the rather
"negative" reports volunteered by some of the more "experienced " home
shop machinists out in the Internet world. Some didn't even own one but
somehwo seemed to "know" all about it! I obtained the machine on sale for
around $399 and that included shipping by truck. You all know from whom.
The tool arrived in good physical condition even though the packaging
showed all the sings of wear from its long original trip from Asia. In about 30
minutes I had the tool set up and running although I still had a lot of packing
grease to rub off of the milled surfaces. A set of little rubber anti skid feet
had to be screwed to the under side of the bottom pan and the gibs on both
the cross and compound slides were adjusted to a snug but not tight
condition. That wasn't any more difficult than on any other tool I've owned.
It's just that I was a bit shocked at how loose they were. The lathe is made in
China but the three jaw chuck provided with it is Japanese and of very good
quality. Right off the box it could repeatedly center unsupported work to
within .002" which is pretty darn good for most low to middle of ball park
three jaw chucks. With a little work on the jaw faces I'm quite sure you can
get it down to a lot less than a couple of thousands. It also came with a set
of numbered inside and outside hardened steel jaws. The twb basic speed
ranges are obtained via a two position gear lever that gives infinitely
variable range in a low range from 200 - 1800 rpm and a high one of 440 to
2900 rpm. The lever must never be shifted unless the spindle is completely
stopped or you will instantly strip the gear box. But then again, that would
make perfect sense on any machine. I find that the lathe will allow me to
easily cut even the toughest grade of stainless steel and 1018 CRS specially
when the speed lever is set for the low range. More torque to the spindle
that way. The tool holder is of the four tool type and can be rotated 360
degrees. It takes 5/16 square bits and I use HSS bits which I mail order in
bulk for as little as 70 cents each and grind them to fit my machining needs
with perfectly fine results on the majority of metals. With the most basic of
care I can produce very intricate parts, that is those with bores, steps,
shoulders, grooves, tapers, chamfers and the like that are within .0005" or
better. The lathe has auto carriage advance that can be run in both left or
right handed feed directions. The spindle rotation can be also reversed by
flipping a reverse switch. Again, don't try this on the fly! Why care about the
fact that the spindle can made to run backwards? Well, for one, you can cut
short tapers or chamfers on the edges of work without having to rotate the
compound beyond center toward the rear of the bed. You could just leave
the compound set at the customary 29.5 degrees used for threading and
just cut on the back of the work turning backwards. Very handy little trick.
Reversing a tailstock held tap out of a hole is made easy with a flip of the
reverse switch. With the carriage moving from left to right, you are able to
cut left handed threads as those found on cross slide lead screws. A nice
feature when you need to make one of those babies from scratch.
Threading can be done to any tpi from 12 to 52 by rearranging the included
change gears that connect the spindle to carriage feed screw. A chart is
provided with the lathe along with the set of change gears. The gears are
indeed made out of plastic but not just any kind of plastic. Whatever this
stuff is, it's a very tough slippery material. They also run very quietly when
they are meshed and running. I tried the metal set that the lathe used to
come with and it produced a lot more noise. So far in more than a year of
almost constant work, I have not detected any wear on them whatsoever.
Threading anything coarser than 16 tpi can be a problem as even with the
lowest available factory spindle speed of 200 rpm, it can still get away from
you pretty quickly specially when cutting a thread against a shoulder. There
is a way to further slow down the electronic speed controller but it does
require a bit of now how and maybe a bit or nerve. I have slowed mine down
to 30 rpm ( low lever setting ) with enough torque so as to make it extremely
hard to even slow the chuck down with my hand. How well aligned was the
spindle, cross slide, tail stock spindle ram, etc? I have to admit that I had to spend some time fiddling with the tail stock to get it aligned to the spindle
axis so it would give a parallel cylinder on work supported by the live center.
Once I was able to produce a 8" long, between centers held cylinder that
was within .0005", I called it quits and left the shop well satisfied. The adjustments for the tail stock were not very well designed. Not at all like that on a Southbend but you get what you pay for. The spindle axis is indeed
perfectly aligned to the lathe bed and the cross slide, as far as I can detect.
Maybe I got a good one! I turned 3" long unsupported steam engine
cylinder that was parallel to less than a couple of tenths along its entire
length straight out of the box. The chuck can be removed via three nuts
from behind the spindle backplate which is all in one piece. The back of the
chuck has a machined tapered recess that self aligns it to the matching
back plate and stud holes. Three threaded studs in back of the chuck lock it
to the plate. Once the chuck has been removed, you can insert a #3 mt
dead center or any other #3 mt size tooling. The overall spindle diameter is
about 1-1/4" in diameter with a 3/4" through hole. Much heftier than those
found on other so called miniature lathes.
Although this lathe in definitely not a beauty contest winner,
with its typical ugly green paint job, it's not so ugly that it would cause me to reject it as a very good low cost medium capacity machine tool capable of
just about anything I have asked it to perform.
In the next installment I will discuss the many adaptations,
modifications and special tooling I have made with it, for it. Many or these
modifications were done on the smaller Taig lathe. Which by the way, once
the second and final segment of this article is finished, several Taig article
will follow describing modifications, tooling projects specific for it as well as many other goodies for the miniature machine tool fan.
Click Here to Read Part Two
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Jose Rodriguez
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