Having had the mill for some time I can now
report on some of the changes I have made which, in my opinion improve it. In
all cases the changes needing to be made are relatively trivial.All of the feed handles have been bushed with brass inserts and a new spindle made so that the black handle will revolve with no perceptible shake plus the nut is now fixed by Loctite to the spindle so that the handle movement is independent of the nut.
The hinges on the belt cover were replaced by stronger hinges and the retaining arm reworked - the original was bound to have failed with dire consequences.
The 'drop leaf' bolts that lock the table and knee were replaced by homemade ratchet type.
A set of four pads were made to enable the simple levelling. These consist of a mild steel pad 2.5 inches in diameter with a 3/8" BSF stud and adjustment nuts.
An annoying rattle when taking a heavy cut was found to be due to the safety switch in the belt cover. The switch plunger was a sloppy fit and rattled, easily remedied with a bush.
A 4" vertical digital slide is now incorporated to
provide an accurate readout of the quill down feed. Above the caliper can be
seen the speed chart which shows the three belt positions giving best
performance (torque). To hide the top part of the slide I made a cosmetic
alteration to the pully cover. This consisted of adding a thickness piece to
the front of the cover and base with a channel for the slide. After filling in
the joins and repainting it is impossible to tell that the casing has been
altered. The alteration not only looks better but also prevents dirt and damage
to the digital slide.
A tachometer has been incorporated into a
control box to display the actual spindle RPM.The inverter power on off switch, coolant pump switch and 'X' axis Feed switch has been relocated and incorporated into the tachometer display box (all low voltage <14v). A flashing LED indicates that the Feed mechanism is engaged even if the feed power is off as a safety feature.
A new Power Feed mechanism has been made for the 'X'
axis based on bits in the scrap box. (see
article on making this unit) The unit shown in the photo is driven by a
telescopic arm with universal joints and this is in turn is driven by an
electric motor and gear reduction. The gear reduction is at the moment using
Myford change wheels. A variable speed 12 volt DC motor (ex car radiator
cooling fan) is used to drive the gear train and an ex wheel chair control used
to vary the speed. The feed motor is turned on and off using a 12 volt relay
and a central limit micro switch stops overrun or position.For a rapid traverse of the table I have added a very simple idea which uses a drill. See article on this idea
Update In order to adequately tighten the drawbar it is
necessary to lock the spindle. Unfortunately, the mill as supplied has no
locking mechanism. After seeing the same problem elegantly solved by Bill Pace
I decided to copy his approach. Because there are eight holes in the locking
rim it takes no time to find a locking location. My version is slightly
different in that the plunger pin once pushed into the locking position stays
there and both hands are free. It is withdrawn by pulling outwards and held
withdrawn by a detent, as seen in the picture. The making of the rim for
fitting under pulley wheel turned out to be a bit of a mission due to my lathe
being too small! Another problem was the fastening of the plunger block. Like
Bill, I located mine on the corner flat but found it was not at the correct
diametrical angle! A wedge spacer could have been made, but I decided instead
to use two cap screws from the underside. This locking arrangement saves having
to first insert a pin and subsequently remove it and inevitably loose or drop
it!. Now, in this new arrangement, the plunger pin is fixed and ready for use.
The pin is spring loaded and when not in use a detent holds it securely in the
withdrawn position. As seen in the picture, an angle post is fitted to the stem
of the knurled handle. This arrangement stops any accidental starting of the
mill by preventing the pulley cover from closing when the plunger pin is in the
lock position. To unlock, the pin (including the attached angle post) is pulled
out and rotated clockwise latching on the detent slot thus preventing the
pulley cover closing.
.