Model Engineers’ Workshop – July 2019

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

component down to the local paint store
and got them to mix some matching satin
fi nish paint, which has worked very well.
There is a small shelf at the back of the
splashback, so I took this opportunity
to punch some holes in it using a small
punch tool normally used for making
holes in electrical enclosures, so that it
could be used for storing 3MT drill chucks,
revolving centre and my home-made
tailstock die holder. 6 more smaller holes
served for holding chuck keys. I also tidied
up the wiring to and from the inverter,
enclosing it rectangular plastic trunking
with clip on lids. I then used my engine
hoist to reunite the lathe and the cabinet
stand, before gently easing the whole
thing into the garage through the side
door, photo 4.
The headstock, gearbox and apron are
all oil fi lled, so I took this opportunity to
drain them and refi ll with ISO32 hydraulic
oil. The headstock has both plastic and
steel gears in the back-gear train which
ensures quiet running, but the plastic ones
are susceptible to damage if previous users
have made a habit of changing gear before
the spindle has come to rest. Fortunately,
the teeth on mine are virtually unmarked.
The D1-3 camlock spindle nose means that
the back gears are not subject to shock
loadings when trying to get a tight-fi tting
chuck to unscrew.
The time had come to actually try the
thing, so I plugged it in and switched it
on. The controls consisted of an on/off
switch, forward and reverse switch, and
suds pump switch. Everything seemed to
work, and I gently ran it up and down the
speed range (more about the speed range
later) and tried out the apron controls for
sliding, surfacing and screw cutting. All
good so far.
I then put a piece of 1” steel bar
in the chuck and tried a cut. A little
disappointing, as there was a tendency to
chatter. I consulted the handbook, which

I had got from Tony Griffi ths, and read

the section on adjusting the taper roller

bearing. Off with the headstock cover,

slacken the large castellated locknut,

tighten the inner castellated nut (both

threaded left hand) and retighten the

locknut. The handbook merely says that

the bearing adjustment is correct when

the bearing is hand hot after an hour

of running. I seemed to have achieved

this and have had no more trouble from

chatter since.

Screw cutting Gearbox

The screw cutting gearbox, photo 5, is

quite complex compared to Norton type

boxes, and to use it needs the operation

of three levers and one knob, in strict

sequence, some with the lathe switched

off and some with it running. I studied the

handbook very carefully before I used it

for the fi rst time, but I’ve got the hang of

it now. Simply going in there and playing

with the levers/knob is a sure recipe

for problems. It does 72 metric pitches.

covering all standard metric pitches from

0.20 to 7.00 and a lot of others, plus

longitudinal feeds of 0.03mm to 2.14mm

per rev or cross feeds of 0.012 to 0.84mm

per rev. Direction of travel is controlled by a

tumbler gear cluster accessible by opening

the sheet metal door over the screw cutting

train at the end of the headstock. Once

upon a time there was a micro switch on

The Denford 280 Synchro lathe as installed in my workshop.

Spare screw cutting gears stored inside
gear cover.

4

5

6

Screw cutting gearbox and its controls.