I consider this to be one of the finest engineering designs ever produced for the home workshop.
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The last (RH) picture shows the Dividing Head set up on the Mill for cutting a 40 tooth,
40DP
bronze gear which is eventually to be the cam shaft gear in the 'Seal'
engine. The gear blank is bored for a taper fit and was then loctited
to
a mating taper on a turned mandrel held in the chuck. Later, a little
local
heat destroyed the loctite and the gear was separated. The single tool,
fly
cutter was made from silver steel using two buttons to form the gear
tooth
shape. This cam gear drives two steel 20 tooth gears which were also
made using
this setup.
I built the Four Way Toolpost designed by
George Thomas. This
toolpost is excellent in use and I have found it can repeat position
very
accurately. Although the current trend is for the drop on tool holders
I prefer
the indexing four way toolpost. After many years of using the lathe I
found
that I always seemed to use the same two or three tools to do most
jobs. Once
they are packed to height which takes little time they are instantly
available
on the index and it takes considerably less time to index the toolpost
than
unloading and loading a drop on tool. I have a rear toolpost (see
below) which
takes drop on tool holders so the unusual tools are pre-mounted ready
for use.
There are many designs around for rear tool posts and to be
honest most are
much the same. Being a simple, but very convenient tool, I have
attempted to
alter many established designs with convenience in mind. The main
changes are
the use of a fixed base unit, which comprises a base and pillar onto
which
fixes either tool block. The base unit can, of course be removed from
the
cross-slide, but even with the short slide it rarely gets in the way.
The tool
blocks can be removed in seconds and I have incorporated a socket to
the pillar
nut so that one only has to use the chuck key rather than find a
spanner - this
saves a lot of time. The tool holders for general square tools, all
mounted up
side down, are easily made and do not have to be a perfect fit to the
dovetail.
At present I have about ten of these all with tools that I only use
occasionally, such as a radius tool.
This
basic design has developed over the years and I now have two
types. One is used only for parting-off work whilst the other for a
variety of
turning and boring tools. The parting-off tool post is designed as a
solid
block and holds a single 1/8" wide x 3/4" cutter ground for
clearances and mounted upside down. The tool commercially produced so
it has
the correct form. This might seem a little thick for a Myford but as
the
parting-off cutter is inverted it provides extra rigidity and tool
strength.
Parting-off is now one of those tasks which is routine and easy. Rarely
do I
find it necessary to reduce speed but care has to be taken to maintain
a steady
cut but not too aggressive and no more chatter no problems! The use of
suds
helps enormously.
The
other rear tool post comprises of a block with a
dovetail tongue to take matching dovetailed tool holders similar to
conventional drop-on tools. The tool holder is adjusted for height
location by
a top screw and locked in position on the dovetail joint by two
pressure
screws. The main use for this tool holder is for a variety of turning
tools. I
have arranged for the tool block fastening bolt to be tightened using
the 3 jaw
chuck key which saves time looking for a spanner. When other tools are
required
the tool holder is swapped over. This is not a precision tool holder
where
positional repeatability is needed but it does the job I want - speed
and
convenience. In both cases the tool block is seated on a base pad plus
column (to protect
the slide table) and after use, rotated out of harms way but is always
available when needed. These tool blocks are easy to make out of stock
mild
steel and as the cutting tools are inverted they can withstand heavy
cutting
forces. My ML7 has the standard length cross-slide table but even so I
usually
leave the rear tool block attached. Removal in any event takes but a
few
seconds.
This mechanism is based on an article which
was in one of the
ME magazines. I think it was designed by Ken Metcalfe. I modified it so
that an
automatic release could be set and added a quick action lever placed to
the
right of the saddle. This is a much more convenient place for the
release lever
and requires just a slight tap to operate. On the opposite side is the
automatic release which is a small button. I find that this button is
very
convenient to operate by using my left hand to release engagement from
a screw
cutting task in conjunction with the release of the Screw Cutting Tool
(which
in my case requires my right hand to operate).
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Essentially a simple design which enables end mills to be sharpened in
minutes.
Seen in the photo is the double headed spindle with cup and normal
grinding
wheels. This is useful in that the two grinding wheels are available at
all
times. The main use for this tool is the sharpening of endmills and
small
drills. I have successfully sharpened a number 70 drill! The first
accessory is
a jig to hold end mill cutters for sharpening the end teeth. This was
designed
by Derek Brooks and was described in the MEW- No. 16 & 17. I
have made some
minor changes - the collets are pulled tight rather than using a front
ring.
The second accessory is a jig to sharpen the side flutes of endmills. This is to my own design and enables the cutting edge to be retracted away from the grinding wheel surface on completion of each forward stroke. Without this facility it is impossible to turn the tool to the next flute without damage to the cutting edge
see article
describing the design
of this Tool Rest
see article
describing the use of
these jigs to re-grind end mills
Designed by Don Unwin. This was
described in detail
including all drawings in the 1991 Aug/Sep edition of MEW pages 8-15.
Excellent
design and a very interesting tool to make with the added advantage
that it
will be used frequently. This tool has the advantage that the feed can
be added
whilst the tool is in motion. By lightly gripping a feed ring the feed
is
advanced by audible clicks each representing 0.00125". The photo shows
the
tool with a 5/8" dia. shank for fitting on the milling machine. A
Myford
spindle shank (to the right of tool) is used in the lathe.
Update! As happens the boring tool cutter jammed whilst boring a large hole and the inevitable jam caused the main body to crack! In truth I should not have allowed the extended slide to be over-stretched and the result was my punishment. Thanks to my ever-obliging friend 'Jack' some more bar material was found only this time in mild steel rather than the original cast iron. Another job waiting to be done and this is one that climbs up the priority list as this tool is one that is very difficult to live without when it comes to applying small feed cuts without constantly having to stop the mill when an adjustment is needed.
This is such a
simple attachment (can be made
in about an hour) and yet provides exactly the same control as the
Myford coned
clutch. The design principle utilizes the belt tension lever to operate
engagement. When the lever is relaxed the belt is "held" so that it
is lifted away from the driving pulley and so no wear occurs. Some
minor
adjustment can be made to 'hold' the belt by altering the diameter of
the front
belt guide. If you inspect the enlarged image it can just be seen that
the belt
is lifted out of the pulley 'V' thus even though the countershaft is
rotating
no motion is imparted to the belt drive. A small spring is fitted in a
pocket
recess at the back of the guide rail which eliminates any vibration
noises. I
have operated with the same belt for 20 years!
It is important to switch off the motor before attempting to change the belt pulley diameters or touch the belt. Although a limited amount of 'slip' control can be achieved by the tension lever it is not recommended as this will cause belt wear and friction heat.
Additional close up details (large files)
This
gearbox is supplied from Hemmingway (designed by D Machin) as a set of
castings
and drawings. Very good design and have used mine constantly for screw
cutting
and fine feeds for 15 years. As part of the kit and along with drawings
come a
detailed set of construction notes. These are very good and the use of
special
jigs (drawings and castings optionally provided) which enabled me to
appreciate
a different way of tackling this project. A great deal was learned from
this
project.
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I designed this attachment based on the standard Myford version but instead of the pivot point being centered it is from either end. The basic principle is following a Sine Bar and a spacer is used at one end to set the angle of taper. The register points on the table are 10in. apart so the spacers can provide very accurate tapers if made to 0.0001" accuracy.
The lathe must be correctly levelled and true. The attachment is initially set to turn parallel and then the spacer is placed at either end (depending on taper direction) and the main slide then clamped. The significant advantage of this approach is the simplicity of setting known angles with no dials or witness marks to judge.
First test using a spacer for a Morse 2 taper proved to be spot on when tested in the lathe. A basic set of 7 spacers provides for angles from 1 to 7 degrees in quarter steps, Morse 2, and standard taper pin.
I have changed the design for clamping the Cross-slide extension to the jig. Originally, as shown in the picture (right), the clamping method was by a cap screw. This method works OK but requires an accurate spacer washer below to ensure the clamped are is not distorted. The new design does away with the single large cap screw and spacer washer. A post is now permanently fixed to the slide and a recess in the top of it provides space for a washer which is clamped to the arm with 2 small cap screws. This method automatically adjusts for height and ensures the Arm remains un-distorted. In addition, the Arm is now attached using an angle piece which fastens to the cross slide table rather than the back end of the cross slide. This modification enables the Arm to be secured more easily.
I made this based on the George Thomas version. The chuck takes up to 5/32" diameter drills but these are really too big. It is perfect for drilling very small holes (<3/32" dia.) and allows a sensitive 'feel' to the drilling operation. The drill head is easily removed to enable the tapping arm to swing round from the back. This feature ensures tapped holes are perfectly square to the tapping surface and hopefully reduce tap breakage.
Knurling Tool to fit on ML7 Cross Slide
Shaper Tool to fit on Myford ML7
Retractable Screw Cutting Tool
