The Machine Shop
Power Cross-Slide Digital Read-Out
Reverse Tumbler Phase II QCTP Mount & Rear Toolpost
DC Motor Hand Crank Tap HolderPhase II Flange Nut Lever Revolving Tailstock Drive Coolant Pump Hand Wheels Tailstock Lock
Harbor Freight 9x20 Lathe Mods
.
Reverse Tumbler
The lever works quite smoothly. Nylon
washers are used on both sides, with the 1/8" nylon washer on the
inside serving also as a spacer. This avoids any side-to-side
movement of the gear plate. I cut the gear plate a little wider than
normal since I am still thinking about implementing a cam design to
change gear positions and leaving the lever in a fixed position on the
outside. For now, this solution works fine.
Back
After using the
above set up for over a year, I finally did put in the reverse tumbler
mod as outlined on Steve Bedair's site. The only difference was
in the way I implemented the gear shift lever. I really wanted
something that looked like it was a part of the original lathe. This is a simple
clamp lever which can be tightened and untightened to allow the gear
plate to slide upwards and downwards. It has female threads with
the bolt running through from the gear plate. The mid position of
the lever shown is the neutral position.
The Gage
Holder
The Micro-Switch Dog Clutch
Small Chuck Adapter
If you are looking for a
bellows-type way protector, you can fashion one from the bellows used
on the Mini-Mill. Little Machine Shop has a 9"x12" size listed.
Just search on "bellows". The ends can be wedged and held in
place on the headstock and apron using a few strips of thin stainless
steel cut to length.
The Cross Slide Bearing and
Compound Plate
At the same time, I placed a small compound lock lever
on top to prevent any movement during turning.
Tailstock Lever Lock
Saddle Lock Lever
A rear-mounted toolpost for parting operations has
several advantages over a traditional front mounted blade. In my
case, its addition enabled me to turn and bore from the front mount,
and cut-off from the back without needing to remove tools. This
increases speed considerably and is well appreciated when hundreds of
parts are being made. Since the cost of additional tool holders for
the Phase II tool post are fairly high, it was far cheaper in the end
just to acquire another complete Phase II Quick Change Toolpost and be
done with it. Since the Phase II base was there, I decided to
mount it to the rear of the cross-slide using a plinth I already had.
When necessary, the front-mounted compound slide can be removed, and
the rear mounted tool post simply repositioned on the front without
having to remove it altogether. The working distance between the
rear cut-off blade and the front turning tool is over 3" which is fine
since the majority of my parts are between 1-2" in diameter. And yes,
there is enough room for the handle on the rear tool post to open
properly to change tool holders there if wanted. I unscrewed the
rear handle since the main purpose is for parting off. At the same
time I made this addition, I also installed two slot covers to prevent
swarf from hiding in the slots to make it easier to clean..
Phase II QCTP Flange Nut Lever
Digital Read-Out
Since I do this type of work
regularly, my choices were to either buy a turret lathe or try to
modify the 9x20 to do what I wanted. First, be aware that this
modification is not for the light-hearted. You will need to use
a milling machine, band-saw, lathe, and likely give up
everything else in your life for a couple of days. The main task is taking a
3.5x3.5x2 block of mild 1018 steel or cast iron and turning it into a
yoke to hold the gears. This is what the piece will look like
after band-sawing and rough milling .
Here is a sequence of photos showing the module after
assembly: After this step is completed, you must take the
existing tailstock clamp and mill off its taper. The track I used measures 2 feet long. It is
.75" wide and .5" high. A half inch is the maximum height permissible
or else the tailstock clamp will hit the rack. The spur rack is 12 pitch and
purchased from Reed Tool Supply. The gears are 12-pitch, 1.5 OD., .75"
wide, with a 5/8" ID. 5/8' drill rod was used throughout along with
5/8" sleeve bearings. The turning rod can be retained with either
e-clips, or by 5/8" collars.
There are many ways to add a hand crank to the
9x20 for occasions when threading by hand is necessary. The
approach I took requires no drilling of the spindle at all.
Since I had an old arbor on hand, I simply machined it down to fit the
rear of the spindle. The splined end of the arbor acts as an
expanding collet to hold the hand wheel in place. This works
extremely well with no slippage. If you have a 1" diameter piece
of iron or mild steel available, you can make your own splined shaft
with a series of simple cuts. After cutting the slits, drill the
arbor all the way through to accommodate a threaded rod. I used
a 3/8" rod since that is what I had on hand, but you can use whatever
you like as long as you have the nuts to fit the rod.
The easiest way to form a cone on the nut is to
attach it to the rod and then turn it on the lathe. The cone
shape does not need to have a perfect taper and can be done while
simultaneously adjusting the x-y positions while turning it. This is
not as difficult as it may first seem. The hand wheel end of the arbor is machined to
fit the mounting hole on the hand wheel you choose. Make sure
you leave enough clearance so that the inside of the handle does not
rub against the gear door. I used a
Grizzly 6" wheel with a safety handle. The safety handle is a
nice feature in this application since it can simply be tucked out of
the way when the wheel is not in use to prevent inadvertent
knuckle-busting. The wheel may be held permanently in place on the
arbor shaft with a set screw or socket head screw. A nut (and washer) on the wheel end is
simply tightened to compress the entire assembly and keep the hand
wheel in place. To remove the handle,unloosen the nut and
give this end a small tap. This is an easy and gratifying project, and
looks and works great!
For flood cooling, a regular on/off switch could also be installed.
The pump motor is able to run continuously for over an hour
although not designed for this. For an even cheaper solution,
check out the used auto parts suppliers in your area, although it is
difficult to find a high capacity reservoir with a suitable shape.
Although I used a flexible
gooseneck connector to direct the flow and mounted it on my rear
cutoff block, the small windshield sprayers that come with the unit
could also be easily adapted. This is one of those satisfying, cheap
weekend projects that provides real convenience to those doing
multiple parting operations. Instead, the current
design uses a stepper motor combined with a cogged belt pulley
assembly which does not increase the handwheel shaft length at all. The main
larger pulley is attached around and directly to the existing
small cross-slide handwheel which serves as the hub.
To provide enough torque,
the motor I chose was a bipolar 6V/ 500 ma unit from Jameco
(#237577CJ). The bipolar drive controller came from Interinar
Electronics. The offset current on this controller was set at 3v.
The controller is driven by a 30v/1 amp external power supply
from RadioShack. The controller can handle up to 30v at 1.5 amps -
more than enough for this application. Since the detent torque on this
motor is low, no clutch assembly is needed and there is little or no
resistance when using the handwheel manually.
I boxed and mounted the
entire unit directly to the apron in a position that does not
interfere with leadscrew or half-nut lever access. As shown, the
unit was configured with an on/off switch, speed potentiometer
(10Kwith a 1k trimmer resistor added in series) a switch to
drive the motor in either 1/4 or 1/8th step operation, and a
forward/reverse 3-position switch with neutral center. The
cross-slide feed rate range is adjustable from a minimum rate of .288 inches/minute to a
maximum of about 7.6 inches/ minute and is limited by the setting of
the trimmer resistor in series with the main pot. The angle bracket which
attaches the motor and controller assembly was channeled to provide
horizontal and The double-flanged pulleys came from SDP-SI
(6J 3-26DF03708 and 6T 3-H48DF3720) and are 3.25 " and 1.5"
in diameter. This pulley ratio provides additional torque. The cogged belt is an XL type - the same as used on the
9x20 - but has a length of 23 inches. This pulley ratio is
critical and will work fine with the above stepper motor. If a
different stepper motor is used, you may need to experiment with
different pulley ratios. The larger 3.25" pulley was
bored out to fit a bushing that fits over the outside of the cross-slide hand wheel. for attaching the pulley This was machined from Delrin.
This bushing was simply cemented in place. I intentionally left a 2mm
thick flange on the Delrin bushing face so that it could be either
attached with small machine screws or cemented in place to the front
of the hand wheel surface. If you don't like plastic, another
option is to use
metal pulleys from Brown and machine them accordingly.
In use, the mechanism
works wonderfully and is a real time saver. My main goal was to
eliminate all of the hand wheel turning necessary between the
facing/boring
operation performed by the main toolholder and parting done with the
dedicated rear tool block. Normally, this
would require about 30 turns from one position to another for each
part. When doing hundreds of parts, this is a lot wasted time
and motion. With the power cross-slide, it takes only a few
seconds to change positions with no wear on the wrist. For facing operations, the
power cross-slide also works fine since the stepper feed-rate can be
adjusted from a real crawl to very fast. As usual, just be careful of your
depth of cut, speed, etc..
As for the controller box,
keep in mind that the electronics can be kept in a completely remote
unit and placed at any convenient location. Only the
stepper motor and pulleys need to be mounted in the front of the lathe.
I chose to integrate the motor and controller to keep the switches
conveniently in the front. The controls could have easily been
placed inside of my main DC motor control unit above the lathe also. The total cost of this
project came out to about $125 and a couple of evenings in the shop.
(Update)
Back
Before I added digital scales,
I had an older digital depth gage available, I made
a simple holder to attach it to the lathe. Two aluminum L-brackets were
machined and bolted to the 9x20 base to secure the ends of the gage. A third
bracket was fitted to secure the base of the micrometer to the lathe. This was
attached using the existing screws that secure the half-nut cover. The depth gauge can be easily removed at any time.
Above and to the left
are pictures of the 2" chuck normally used on the 7x12 mini-lathe.
Since this chuck comes with a MT2 taper, a MT3 to MT2 adapter was
used. The adapter was drilled and tapped to accomodate the
drawbar.
It goes without saying that the compound slide
plate
mod is mandatory, as I discovered only two days into turning.
The cross slide bearing mod is also interesting, especially when
critical threading is needed. I use the compound slide in
a 90 degree orientation just to get the extra .001" resolution it
provides.
The saddle on the 9x20
is normally locked by tightening a hex head bolt which is recessed.
The bolt head was perpetually getting filled with swarf which made it
a pain to insert a hex key. The easy solution was just to
replace the bolt with an adjustable lever. The normal bolt was
removed and the saddle was bored out to accept the lever bolt.
The locking plate was then drilled and tapped to accomodate it.
The lever has a low profile to easily swing under the compound slide.
Various adjustable levers are available. This one came from
Reid
Tool Supply, a great source for levers, knobs, and other
not-so-easy-to-find goodies.
Rear Tool Post
I had been wanting
to add a digital read-out for a while, but was turned back because
of the high price of full-featured units. I was finally
fortunate enough to find an older unit with glass scales at
auction. Unfortunately, the scales were 24" (which was OK)
for the x-axis, and 12" for the y-axis (which was not OK).
The 12" scales measured 14" overall which was far too long for the
7-8" travel of the 9x20. Although these are glass scales, I
found that they are easily shortened using a Dremel and cutting
disks. I carefully cut the aluminum frame of the scale
first, and then gently cut the glass itself. Since this is
flint glass (a Sargon scale), it cuts easily and does not shatter.
If this had been what has held you back from buying a longer unit,
you need have no fear. The remainder of the installation was
straightforward. I was fortunate in that the dimensions of
the encoder allowed it to fit precisely inbetween the ways,
thereby avoiding mounting it on the rear of the table. The x-axis
scale was mounted directly to the front of the apron for easily
access for maintenance and tweaking.
This is an older Ramtek 3000 DRO unit with Sargon glass scales.
It works wonderfully and I couldn't recommend this type of project
more highly for those that need repeatability in their operations
and for those as confused as I was trying to read the normal dial
calibration marks on the 9x20.
The
revolving tailstock drive mod came about mainly because I was getting tired
of carpal tunnel wrist caused by constantly twirling the regular
tailstock wheel on the 9x20 in and out all day long. This
modification leaves the original drive
function in tact, but adds a power track which allows much more rapid
movement of the tailstock by use of a hand-wheel, similar to those used
on larger turret lathes. The tailstock travels smoothly and
rapidly back and forth, and provides leverage to drill
and ream parts very rapidly without losing precision
Note
the small channel cut in the piece. This yoke
will be attached to the back of the existing tailstock. The small
channel will ride on top of the rear way. Measurements are all
critical since there is very little room to work with in this area of
the lathe. Measure twice, cut once!
T
he
guides must be milled absolutely flat so that the tailstock
glides smoothly along the rack without binding. Removing the
taper, by the way, does not prevent the user from tightening the
tailstock normally. I was quite surprised that there was no
slippage at all with the taper removed when clamped down. Also,
if you have not done so already, you do need to add a strong spring to
the underside around the bolt that attaches the clamp to the
tailstock. This will afford a fine adjustment mechanism later to
control drag and mainly prevents lateral x-movement of the clamp.
Adjusted carefully, the tailstock will glide smoothly along the ways
with no sideways movement. Originally I thought that this clamp
would need to be completely replaced with bearings. However,
this is not necessary if the taper is properly removed and the
underside of the ways where the clamp rides is clean and smooth.
As I found out, the underside of the ways guiding the tailstock are
perfectly milled, but covered with paint. Kudos to the Chinese
on the milling, and boo on the painting..
I
used collars in the final design since they allow for more fiddling down the
line with perhaps a separate power drive, etc. (See below to use the
lead-screw for a power drive.)
Hand Crank
The
splined end is expanded by a nut whose tip forms a cone. When
compressed, the tip presses against the inside of the wedges formed by
the slits and presses these, in turn, against the inside wall of the
spindle. This nut is permanently fixed to the end of the rod to
prevent it from turning. If you make your own arbor, you may
also need to drill this end of the arbor out enough to allow the cone to enter.
O
ne
of the quicker and cheaper ways to put more functionality into your
9x20 is to simply add different hand wheels. Here, the original
cross-slide hand wheel was replaced with a 4" cast iron hand wheel
from Grizzly. The short handle on the original hand wheel was
unscrewed. The new wheel was machined and fitted right inside the original
wheel, and
attached with set screws. At the same time, I replaced the
3-spoke wheel on the revolving tailstock drive with an 8" cast
iron wheel to match. The new wheel on the cross-slide adds a better
feel and seems to allow for faster and more precise positioning.
Also, note the use of a solid plinth under the QCTP toolpost replaces
the compound slide for more rigidity.
I
finally got tired of using a spray bottle and oil can to apply a few
drops of coolant during parting operations. When you do a
thousand parts, the motion itself becomes pretty tedious. The
cheap and easy solution came by installing a generic windshield
washer pump from AutoZone for $17. This kit is a bargain and comes with a decent-shaped
1 gallon reservoir, switches, sprayers, connectors, brackets, etc . I use
WD-40 for coolant, but there is no reason other coolants should not
function properly. A momentary contact switch was mounted on the
splashguard and allows for applying only a couple of drops at a time.
A one-way check valve for aquarium use was installed in the tubing to
prevent backflow so coolant is always primed at the tip. I modified a
simple Tetra check valve by inserting a ball bearing in the place of
the rubber assembly inside these. The pump can be powered by any
simple 9vdc or 12vdc wall adapter from Radio Shack.
I had been studying the problem of providing a power
cross-slide for the 9x20 for quite some time. The traditional
approach is to mount a stepper motor with extended shaft directly to
the hand wheel shaft such as in CNC conversions. Doing so,
however, results in increasing
the distance the hand wheel protrudes by about 5 inches - enough to
make its placement really inconvenient while
operating the lathe.
If
you have no intention of CNCing the 9x20 but want automation, this approach may be for
you.
vertical adjustment for proper belt tension. 
I do not use power for the actual parting operation itself since I
prefer to feel the progression of the cut of the piece and adjust
manually as necessary. 
I recently upgraded the cross slide leadscrew using
Sonny
Harrisson's screw kit.
This
is a ten-minute drop-in replacement for the original with a larger
diameter leadscrew and providing another inch or so of cross
slide travel.
Since the new leadscrew was longer, it was
necessary to modify the pulley assembly for the power cross slide.
While I was at it, I replaced the original stepper motor
described above with a small DC motor I scavenged from my old
Sherline lathe.
This provides for much better torque. The motor is controlled by the
original Sherline controller which was modified to reduce its
maximum speed, and also provide a reverse. The controller was
housed where the old 9x20 on/off switch and starter capacitor used
to be located. The controls for the power cross slide were
located on the headstock. The original front gearing chart was
relocated to the side, and a new front plate was installed which holds a motor
reversal switch (Part: CS-51210-G16-L22LbaB61) from
c3controls, the
speed potentiometer, and magnetic on/off switch.
Finally,
a power indicator was added.on top.
Legend
Thanks
If you have a specific question about any of the modifications of the 9x20 shown above, please feel free to drop me an email anytime. Most importantly, please join the 9x20 Lathe Group on Yahoo newgroups where you will meet many other 9x20 users a lot more knowledgable than I. |
Many
of the parts in the Series IV focuser are custom-made on our own machines.
This allows us excellent control over the quality of focuser components, and
the ability to manufacture one-of-a-kind items and accessories specially
ordered.
