Cut a piece of 60mm diameter, 20.5mm long, place in the three jaw chuck and face
the first end, reverse, face the second end and produce holes A and B. If you would
like the outer diameter to have a machined surface, produce a mandrel with a short
spigot to fit the counterbore and tapped M6. With the workpiece on this, skim the
Mount the body on an angle plate, if possible with its outer diameter level with
the bottom and right hand edges as this will avoid any calculation, see rear left
of photograph 2. With that done scribe machine-to lines for the 12 and 14mm dimensions
then turn the angle plate on its end and similarly for the 15 and 21mm values. As
none of these are critical it will avoid any need for measurement during the machining
If you do not have a few tee nuts with smaller than normal tapped holes now is the
time to make just a few, say two off M6 and two off M5. Loosely mount the body on
the milling machine table with an M6 screw into an M6 tee nut. Place a 300mm rule
on top of the body aligning it with one of the scribed lines and rotate until the
rule appears to be in line with the table's axis, visually should be adequate as
precision is not required. With that done tighten the central screw, do not rely
solely on this though adding two bar clamps as seen in Photograph 21.
The Photograph shows that the bulk of the material is being removed with a normal
end mill prior to producing the dovetails with a dovetail cutter. As I have added
X axis (back/front) stops to my milling machine I was able to carry out the initial
metal removal by machining along the back edge, down the right hand side and returning
along the front edge, all without reference to leadscrew dials.
If you do not have X axis stops perhaps this is the time to consider adding them.
Following that, mount a 10mm end mill and machine the recesses shown, also the step
that creates the 21mm dimension, take note that this is deeper than the recess.
The dovetails must though be produced one side at a time, so start on the rear edge
gradually increasing the depth until the upright surface produced by the end mill
is just removed. Next produce the front dovetail but this time to avoid the cutter
grabbing the workpiece (down milling) the dovetail should be started at the right
hand end moving towards the left of the workpiece. When a full dovetail approaches
check with the Bearing Carrier gradually increasing the depth until the carrier just
enters freely, a close fit is not necessary. If you are using a large diameter dovetail
cutter you will have to permit it to machine into the end wall of the recess.
Finally, having removed the part from the machine table, fit the Bearing Carrier
near to the web at the end and clamp in position using the screw and ball clamping
mechanism, then with a drill that just passes through the M6 tapped hole, spot through
so as to set the position for the 4.5mm diameter hole. Remove the carrier and drill
the 4.5mm diameter hole to take the Feed Screw.
The Turned Parts 53- 55
These, parts are simple parts and need no explanation.
The table assembly starts on the next page.