ADAPTING A FOUR JAW CHUCK TO A HARBOR FREIGHT
"MINI LATHE" SPINDLE
By Jose F. Rodriguez
The Asian built 7x10 inch electronic variable
speed bench top lathe known as a the "Mini lathe" is
presently being sold through several tool houses at
prices ranging from as low as $349 including shipping,
and up although not so long ago it was being offered
at a whooping $1000 by a large discount tool mail
order company and just a few days ago I read that
somewhere in Canada it was being sold for over $1,200.
Though typically not very refined cosmetically, as
many Asian tools tend to be, it is however a very good
small, basic portable ( 89 pounds, shipping weight )
versatile little machine that can perform just about
anything asked of it.
The standard issue chuck is a three inch three
jaw chuck of unknown Japanese lineage and seems very
good in quality as well as being pretty accurate. It
is offered with both inside and outside set of steel
jaws. But what about when you need to hold square, odd
shaped stock or those instances when you need to
either center something close to perfection or
purposely shift a workpiece off center a certain
amount. You need a four jaw independent chuck for that
kind of work. Well, one is not available for this
lathe and any queries to any of the importers will be
returned to you with the same negative answer. After
carefully examining the chuck mount of the lathe, I
realized that there was nothing really exotic about it
and being fairly naive myself, I thought I should be
able to very easily adapt another company's chuck to
the mini lathe's somewhat strange spindle backplate.
The lathe spindle has a solid 1/4" thick ( there about
) plate that fits into a matching recess in the back
of the chuck. Three equidistant threaded studs on the
back of the chuck slide through the back plate's holes
and are secured with nuts behind the back plate. This
is a little tricky to do without constantly dropping
the nuts. Not enough clearance back there for normal
human size fingers.
For this particular conversion I chose the Taig
brand four jaw chuck because it is very good and the
price is ridiculously low at only around $50-$60
direct from Taig tools. It is about 3-1/2" in
diameter, about 1-1/2" thick and it is solid steel. I
removed all of the jaws and the screws and reversed
chucked it on another lathe so I could machine a snug
fitting recess on the back face of the chuck that was
a perfect match for the back plate of the mini lathe
spindle chuck mount. You could also machine the recess
on your Minilathe if you use the outside steps on the
jaws to hold the four jaw body and you first make a
matching flange to use as a fitting gauge. Check out
our video on just that very subject. You see, you
can't otherwise tell when you have reached the correct
dimensions on the recess as you would have to
constantly remove the three jaw just to check for fit.
I made sure that the chuck back face was perfectly
square to the rotation axis before I began removing
any metal. As I neared the correct diameter I began to
use the gauge so I could check the progress of the
recess on the chuck. I stopped when the gauge had to
be wiggled, but not forced into place. The fit was so
good the friction alone held it in place even without
the studs or nuts to hold it in. Now the three 1/4-20
mounting holes needed to be transferred, drilled and
tapped. That was a relatively simple job that I did on
my drill press and small rotary table. The holes only
need to roughly line up with the ones on the back
plate since their job is only to hold the chuck, not
actually center or locate it to the spindle axis.
After drilling and tapping the holes I screwed and
epoxied three equal length threaded studs of the same
length as those on the original chuck and gave
everything a good coating of oil to preserve the newly
machined surfaces. I also made three brass nuts out of
½ hex bar by drilling and tapping about an inch of
stock and parting off each nut. By making the nuts a
little bit thinner in cross section, they are easier
to screw on the studs in the limited room behind the
spindle backplate. During use, you can hold a test
dial indicator on the tool holder to center work using
a wiggler.
A second mounting possibility is the use of a #3
morse sleeve with a #1 morse center hole. These are
available from any tool supplier. Into this sleeve you
insert a #1 morse with 3/4-16 end adapter, available
from American Tool Co for about $19.95. You can coat
the inner surfaces of the adapter with low viscosity
CA glue and allow to cure. This whole set up then
inserts into the #3 morse spindle on the
Minilathe and cinched up with a draw bar (
construction of which to be described in a later
installment ). The registration flange of the adapter
is faced off to true it up perfectly square to the
lathe spindle. The Taig chuck or any other 3/4-16
threaded chuck can now be screwed to the spindle. I
have also made a flanged and threaded adapter to
accept threaded tooling. I have also made a lot of 3
MT tooling to fit the spindle with a draw bar. All of
these projects were prompted by the multitude of
statements made by many about the lack of four jaw
chucks and other tooling for this lathe. Yes, it was
true that a ready to use factory chuck or other
accessories are not readily available but I would have
thought that this rather minor hurdle would have been
an easy one to conquer. It turned out that it was!
E-mail Jose about this article
Jose
Rodriguez
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