QUORN

TOOL AND CUTTER GRINDER

by D. H. Chaddock, C.B.E.
Part 111 From page 71

I F THERE is an error a square centre or, a centre

scraper will very quickly pull the hole a few
thous in the right direction. This tip may be
useful too to crankshaft and eccentric turners
who would like to have their throw plates the Fig. 14. Wheelhead bracket set up on the cross-slide
same both ends. Only a detail perhaps but it all for boring the I 3/8 in. hole.
counts.
The wheelhead bracket, Fig. 13, is too large
to swing on the faceplate of a 3-1/2 in. lathe but
it can be quite easily set up on the saddle for
boring the 1-3/8 in. hole for the grinding spindle
quill as in Fig. 14. There is sufficient metal in the
casting to accommodate a range of sizes, say from
1-1/4 in. to 1-1/2 in. dia. but as the writer has two
other spindles with 1-3/8 in. bodies this is the size he
adopted. The second major operation is to face
the flat surface for the motor mounting. A very
similar setting to that used for the boring can
be used again for this operation, but of course
with the casting slewed around at right angles to
face a fly cutter held in the four-jaw chuck. Put
a true 1-3/8 in mandrel (the body of the quill which
you have not yet turned does very nicely for this
so wait for it ! ) in the appropriate hole and with
DRILL 7/32" DIA BY 1-1/8" DEEP
C’BORE 1/4" DlA BY 3/4” DEEP 1-3/8" DIA
SPOT FACE 1/2" DIA OR TO SUIT WILL
- II TAP 1/4" B.S.W. .. DRILL AND TAP

CUT

i.+.---+I
W H E E L H E A D B R A C K E T 1 OFF CI.
FIG. 13

MODEL ENGINEER 1 February 1974 121

a D.T.I. held in the lathe chuck make sure it is before finally parting the screw from the bar
parallel to the lathe across slide-ways. Not strictly while you have plenty of stock to hold it by.
necessary in this job, but one day it may be, so Chamfer after knurling to remove the ragged
gain the experience now. In Fig. 15 the lathe is overhanging edges. The pivot screws are kiddies
in middle speed back gear, about 72 r.p.m. which practice jobs because, believe it or not, it is better
with a fly cutter set at about 2in. radius gives a that the 60 deg. conical points should not be too
cutting speed of about 38 feet/min. The change truly concentric with the screw threads. In the
wheels are giving a feed of about 1/2 thou per rev, final assembly slight eccentricity here will be used
as I find that the best way to reap off cast iron to take out any residual error in the rest. of the
with a light and somewhat elderly lathe is with a machining. ‘So if you make them too accurately
slow speed, a fairly deep cut, say l/10 in. deep you may have to make one again deliberately
and a steady feed. Not to worry if, as in Mr. eccentric !
Beck’s case, the cutter takes off more metal at the If you have opted for a screwed vertical
back of its cut than at the front. Most lathes do column, now is the time to make the adjusting
this anyway if, as they should be, they are set nut with its peg and friction pad shown in Fig.
to face concave and not convex. Just let the back 16. The peg finds its own angle to match the
cut right across the face and it will be as flat as spiral lead on the vertical column. On the
makes no difference. Using this face as a datum writer’s milling machine and grinder, both of
the 1-3/16 in. x ll/16 in. slots for clearing the which have this feature, the peg stays in place
wheelhead collar locking bolt can be put in either without any other fastening. If you have any
by packing up on the saddle or by bolting to doubt a dab of Loctite will fix it - after it has
a vertical-slide, set parallel of course to the lathe aligned itself with the thread of course. The idea
axis. Owing to the draft on the casting some of the friction pad is to prevent the nut backing
cleaning up of the inner faces of these bosses may off after the wheelhead is locked and the machine
be necessary before the wheelhead collar casting is running. As drawn it seems to give about the
can be interposed between them. The other right friction, but this can easily be adjusted
operations, including cleaning up the bosses upon by altering the depth of the saw cuts. So make
which the micrometer adjustment screws will them rather less deep at first and deepen them
bear, are conventional. until you have got the feel that you like best.
As in the case of the wheelhead collar, and for The workhead assembly shown in Fig. 17 com-
the same reason, particular care needs to be paid prises four main castings. The base casting shown
to the positioning of the 5/16 in. tapped holes in detail in Fig. 18 can either be clamped to or
which take the centre screws and upon which the slide along the front bar of the machine. In the
assembly rocks, So first drill them undersize to clamped mode the angular position of the work-
fit any convenient piece of silver steel. With this head is controlled by the rocking lever which is in
in place, the 1-3/8 in. mandrel in the quill hole and turn clamped to it. In the sliding mode the rock-
the job on a surface plate check with a D.T.I. ing lever also slides along the rear bar which
that both bars are free from “warp and wind” becomes, in effect, the rear shear of the machine.
(more cheers from Derek Beck). Unless you are A vertical extension on the base casting carries the
extraordinarily lucky they won’t be, so draw tilting bracket, detailed in Fig. 20 which, as its
them in the required direction with a round file, name implies, is the means by which front and
redrill to fit the next larger size of silver steel side rake is given to the tools being ground. It in
and try again. Before you reach 5/16 in. BSW turn provides the bearing for the rotating base, to
tapping size you will realise just how inaccurate be shown in detail in Fig. 24, which controls the
a drilled hole can be ! If you can get them to front and side clearance angles and, when free to
say 0.001 in. in 6 in. you are doing very well rotate between stops, provides the axis about
indeed. which radii are generated in tool and cutter grind-
The other details to complete the wheelhead ing. A boss on the head of the rotating base carries
assembly are the adjusting and pivot screws in optional long and short bar beds upon which
Fig. 16. One of the former will also be required interchangeable tool and cutter holders and a tail
for adjusting the rocking lever so make all centre may be mounted.
three while you are about it. Only the tips of the Commencing therefore with the workhead base,
screws need be case-hardened but unless you fear which is an iron casting, the first and most critical
distortion it is no bad thing to case-harden the operation is to bore the long lin. dia. hole a
threads as well to combat the inevitable wear to really close sliding fit for the front bar. If your
which all grinding machines are subject. Knurling lathe is above suspicion for this kind of work,
will be a test of your skill as a turner. Do it and mine is not, the procedure indicated in Fig. 19

122 M O l E L ENGINEER 1 February 1974

 3H6”

NUT 1 OFF C.I.

ADJUSTING SCREW
3 O F F CHMS

PEG I OFF FRICTION PAD

3/16" DIA. S.S. 1 OFF NYLON PIVOT 2 OFF CHMS.

FIG, 16
can be adopted. The casting is held at the boss end lathe and the hole bored with a boring bar be-
in a four-jaw chuck and the far end, after dressing tween centres, as was done for the base casting
up the edges of the cored hole, supported on a shown in Fig. 5. In this case you have assurance
large tail centre, preferably a running one. Suffi- that even if the lathe is not in the pink of condi-
cient support is then given for the 1.250in. dia. tion the hole will be the same size both ends. If
spigot to be turned to the finished length and dia- boring the long hole is the first operation the
meter. The spigot then serves as a truly turned second should be to cross drill and split the clamp-
bearing for the fixed steady and in this way the ing boss after which, with a jury bolt through the
casting is firmly supported front and rear for the hole it can be readily clamped to one of the lin.
long hole boring operation. Here it is essential that dia. bars as a mandrel for turning the 1.250in. dia.
the fixed steady is absolutely truly adjusted be- spigot and facing the ends.
cause if it pulls the casting in the slightest towards The second critical operation is to bore and
or away from the lathe centre line the hole will face the 5/16in. dia. hole which carries the pivot
not be parallel, even if the lathe in normal chuck bolt for the tilting bracket as accurately as pos-
work has been adjusted to bore parallel. sible truly at right angles to the long lin. dia.
If you do not fancy this method, the casting hole. Although the casting has at its back a
can be quite easily clamped to the saddle of the chucking piece it cannot, because of the mould-

-_-_-__y_-‘-.

’
I I fi
k
SECTION Y-Y SECTlON X - X

FIG. 17. WORKHEAD ASSEMBLY

MODEL ENGINEER 1 February 1974 123

ing draft, be held securely in a chuck. So first
file three or preferably four parallel flats on it so
that it can be held, without shake or wobble in
either a three- or four-jaw chuck. Put one of the SPOT

lin. dia. ground bars in the already bored hole

and in a “turn around test” with a dial test
indicator held in the toolpost or on the saddle
check that the reading is the same both ends. It
won’t be, so you will have to draw the flats on the
chucking piece until the error is reduced to rea-
sonable proportions, say .001in. at either end. This
is a very sensitive test and will serve to demon- Fig. 18.
WORKHEAD BASE , O F F C.I.
strate that just grabbing a casting by the chuck-
ing piece and hoping for the best is not conducive
to precision work. It is there for convenience in
holding, not a jig to ensure accuracy. That you
have to put in yourself.
Once truly chucked, the 5/16in. dia. hole can
be rough drilled, trued with a small boring tool
and reamed to size. Take particular care that the
face against which the tilting bracket seats is
faced as truly as possible, slightly concave but
never convex. The clearing cut for the pointer and
facing the surface on which the protractor scale
will eventually be engraved involve interrupted
cuts so take it steadily, middle back gear, pre-
ferably with autofeed. Before breaking down this ROCKING LEVER I OFF CI.
setting and while the surfaces are still running true
it is very convenient to engrave the protractor scale and stamp the numbers. This will be dealt
with in detail in connection with the rotating base
Fig. 19. Boring the long I in. hole in the workhead and is the same for all the scales with which this
base. (Photograph: N. Hemingway.) machine is equipped. After it is complete the
chucking piece will be machined away in the pro-
cess of milling the seating for the locking bolt.
Continued on page 128

1 OFF G.M.

12 RAD CLEARING
CUT 5 / 8 " DEEP

124 MODEL ENGINEER 1 February 1974

CLASS MB - GROUP OF MINIATURE Commended :
FIGURES R. Turner (Devizes)
Bronze Medal :
D. M. Catley (Reigate) CLASS MF - 54 MM FIGURES
Commended : Commended :
D. M. Catley (Reigate) A. Proctor (Barnet)
CLASS MC - CONVERTED SINGLE CRAFT SECTION
FIGURES
Silver Medal :
K. S. Frampton (Portsmouth) CLASS WA - MODERN FURNITURE
Bronze Medals: Highly Commended :
K. S. Frampton (Portsmouth) D. G. Keen (Harpenden)
K. S. Frampton (Portsmouth)
Commended : CLASS WB - WORK IN GLASS-FIBRE
K. Jardine (Basford) Very Highly Commended :
D. M. Catley (Reigate) H. Wilson (St. Albans)
CLASS MD - GREAT WARS CLASS CLASS WD - GENERAL CRAFT WORK
No Awards Bronze Medal :
E. H. Ives (Ipswich)
CLASS ME - ARTILLERY Very Highly Commended :
Silver Medal : E. E. Penn (Acton)
J. Dorman (Edmonton)

QUORN TOOL GRINDER

Continued from page 124

The slitting is best done with a circular saw

about 4 in. dia. and care must be taken to stop
the cut before the saw cuts into either the 1 in.
dia. bore or the tilting bracket boss.
Thanks to a small nib on the inner side of the
curved arm, suggested by Mr. A. Throp, the
rocking lever detailed in Fig. 18 can now be con-
veniently and securely held in a four-jaw chuck
for machining the 1.250in. dia. bore a close fit on
the already turned spigot of the base. At the same
setting one side can be faced but the other is
faced after cross drilling, slitting and clamping
to any convenient piece of 1-1/4in. bar set to run
true in the four-jaw chuck. The nib may be filed
away or left where it is.
The tilting bracket detailed in Fig. 20 is, in the
prototype machine, a steel casting, but owing to
foundry difficulties in running, the long pointer is
now replaced by a gunmetal casting. It is an Fig. 21. Machining the tilting bracket. (Photograph:
interesting piece to machine and in spite of its A. Throp.)
complexity not difficult if the right sequence of
operations is followed. The first is undoubtedly to For the second operation, to be shown in Fig.
hold it in the four-jaw chuck, as in Fig. 21, with 22, the casting is clamped by its tail with this face
a bridge piece of bright drawn mild steel across in contact with an angle plate secured to the face-
the boss and the stop face to spread the load. In plate of the lathe. It must, however, be set rather
this setting the 5/16in. dia. hole can be rough far forward so that the 1-1/2in. radius clearing cut
drilled, bored true and reamed to size and the can be taken to full depth without the tool strik-
index finger faced flat to serve as a datum face ing the edge of the angle plate.
for all subsequent operations. To be continued

128 MODEL ENGINEER 1 February 1974