Model Engineers’ Workshop – August 2019

10 http://www.model-engineer.co.uk Model Engineers’ Workshop

a few taken by Paul whilst making his own
saddle stop.
The dimensions shown relate to my
own machine and hopefully to other
Super 7’s made at around the same
time as mine (c.1971). I cannot vouch for
consistency with earlier or later machines,
particularly those with power cross-
feed where I believe that a different bed
design was used. Having said that, any
changes required to the saddle stop are
likely to be limited to the position of the
mounting bar in relation to rear overhang
of the bed. There is limited clearance here
between the bed and the turret, with the
minimum distance between the turret
assembly and the bed being around 1/16”.
The check is that if the overhang of the
bed from the rear mounting face is 0.375”
then all should be well.
As always, please check your own
machine and take any diff erences into
account. Importantly, where there is

an * next to a dimension this needs to
be checked against your machine or
components made and will be covered in
the text.
I have positioned the device at the
tailstock end of the bed. This avoids any
confl ict with the taper turning attachment
and also allows for full carriage travel
towards the tailstock end of the bed. It does
mean, however that there is a degree of
‘overhang’ when the saddle is at the very
right-hand end of the bed.
A couple of very simple pieces of tooling
are shown towards the end of this article,
although their use will be described when
needed.
A note regarding fasteners and threads
specifi ed. These are predominately imperial,
but metric where there is no readily
available alternative fastener, such as the
M4 button head screws holding the guide
pegs into the stop body. There is no reason
why metric threads could not be used
throughout, with 5/16” BSF being replaced
by M8, 2BA being replaced by M5, etc. The
choice is entirely yours. In fact, I tapped the

holes for the length screws in the turret

body as M8, fully intending to make the

screws from commercial M8 studding.

When I purchased and then tried the

studding, I found it to be an unacceptably

loose fi t, so I then had to thread the length

screws using a die.

Please note that all drawings have been

produced using third angle projection.

General arrangement (fi g. 1)

So, how does it work? The layout is shown

in the general arrangement drawing fi g. 1,

and the assembled unit is shown as photo

1 , where it is set-up on the bench as it

would be seen if looking at the back of the

lathe. Photograph 2 shows the turret as

fi tted in relation to the bed.

There is an attachment block (7.0) which

is held onto the saddle by means of single

1/4” BSF screw fi tted into a tapped hole

provided by Myford for mounting a coolant

pipe. The attachment block has a horizontal

hole in it for the stop rod (8.1) to be fi tted,

photo 3, and it is this stop rod that passes

through the stop body (5.1). An indexing

turret assembly (3.0) is then fi tted to the

other end of the stop rod to provide the six

stop positions. The stop rod may need to

be shortened if you work at the tailstock

end of the bed, rather than towards the

headstock end, however in twenty years of

use I personally have not had a job that has

required me to work that far away from the

spindle.

I’ll now have a few words about the

turret and stop units. The turret itself has

been designed to provide very positive

indexing of the six positions, giving reliable

alignment between the length screws (3.1)

on the turret and the end of the adjustable

stop attached to the stop unit (6.6 and 6.7).

Indexing of the turret is by means of spring

loaded balls which seat into a series of holes

in the indexing hub (3.4). These holes in the

indexing hub are spaced at 60 degrees to

each other. The indexing hub is keyed to

the stop rod.

The stop block is clamped to a tee-

slotted mounting bar (4.0) which means

that it can be moved in relation to the lathe

bed. It has a fl oating guide bush (6.1) to

2

3 4

Attachment to the lathe saddle (using an existing tapped hole)
(Paul Clark)

Turret body and parts (bronze bush has already been assembled into

the body)

The assembled unit on the lathe