310 
HORO 
nefs of the pivots; the next ftep will be to attach them to 
their arbors. The great wheel, however, notwithflancling 
what we have iaid about riveting, fcrewing, and foldering, 
is not fixed b}' any of thefe operations, but is attached to 
its arbor by a method which admits of its being-taken off 
at pleafure, thus :—a hole is opened by a broach in the 
centre of this wheel, large enough to take the arbor of 
the fufee without play, and, when it is prefled clofe againfl: 
the end of the fufee, or, in our prefent inflance, againff 
the plane of the fecorid large ratchet, two marks are 
made, with a fine file, at opposite fides of the arbor, clofe 
to the plane of the wheel; it is then taken off the arbor, 
and two fquare-fided notches are filed carefully in the faid 
marks or the arbor, but not deep enough to injure its 
ftrength ; a collet with a circular hole, like that at the 
centre of the wheel, made at one fide of its centre, and 
with a flraight-edged flit acrofs the centre from the faid 
hole, is then put on the'arbor, after the wheel has been 
firft put on,, and is puflied forcibly along the notches of 
the arbor, till, by means of the oblong apefture, it is con¬ 
centric with the wheel, againfl the plane of which it 
juefles, when in the notches, and keeps it clofe in its 
place, and at the fame time allows it to turn on its centre 
without the arbor. The auxiliary fpring is ferewed or 
pinned, in the next place, atone end to the great ratchet, 
and at the other to the great whe.el, as before noticed. 
When the wheel is thus frjrnly attached to the fufee ar¬ 
bor, with a power to recede but not to proceed, on ac¬ 
count of the click, without carrying the arbor with it, 
it muft be put into the turning-frame and examined, as 
to its being truly centred, and alfo as to its being in a 
plane perpendicular to the arbor; which trial may detect 
fome flight alterations, neceffary to be made, ,to fulfil 
-thefe two conditions: after which, its pivots may be 
turned to their exaft fize, hardened, and poliflied. 
The practice of fome workmen is, to folder their collets 
on the arbors with hard folder, but we difapprove this 
practice, and recommend loft folder, particularly if the 
arbors have been before hardened; it is fcarcely neceffary 
to add, that, if the ends of the Collets are opened a little 
within, the folder will there have beds to contain a quan¬ 
tity fufficient to keep the wheel firm on its arbor. What 
we have here faid will not be equally applicable to the 
hour or centre wheel, becaufe it is ufually riveted on the 
end of its pinion, which will require a riveting punch 
and clamp, on purpofe to prevent any injury being done to 
the pinion. Before the wheels are all firmly attached to 
their arbors, they mufl be tried in the turning-frame, or 
.callipers with a ftraight edge for that purpofe, to fee if 
they are concentric, and that their planes are perpendi¬ 
cular to their arbors, which conditions the workmen call 
being “ in the round,” and being “ in the flat;” and, 
.when properly adjlifted in thefe refpects, they may be 
finally fixed as above deferibed, and their arbor-pivots 
finifhed. Should a wheel, that has had its teeth rounded 
in the engine, be at any time fo.und a little eccentric in 
the trial, before it is fixed on its collet, which will not 
happen if the central hole be enlarged with a good broach 
and with due care, the remedy in this cafe would be, to 
mark the fide of the wheel which has the longeft radius, 
and enlarge the central hole carefully on that fide moft, 
and then to make a new collet for it, after the hole is 
again made perfectly round, and found to be concentric 
on an arbor that fits it; but, when the teeth have been 
rounded by hand, the wheel may have the eccentricity 
rectified on its own arbor, and be again rounded where the 
,teeth have been touched by the graver, which is the com¬ 
mon praftice, and which conftitutes the only or the greateft 
recommendation of manual rounding of the teeth. 
The fiies ufed in rounding the ends of the teeth of a 
wheel are fmooth, and curved on one fide, and have each 
a projecting pivot at the remote end, which a dexterous 
workman holds againfl one finger of the left hand as a 
reft behind the wheel, while the right hand guides the 
LOGY. 
file from one fide of the tooth to the other, alternately, 
with a degree of rapidity which furprifes the. fpeffator. 
We have hitherto fuppofed our piece not to be jewel¬ 
led, nor bufhed with bell-metal, which addition enhances 
the price, but greatly diminifhes the friftion in the pivot- 
holes. If the holes are carefully enlarged with agood broach, 
finall pieces of metal holding ruby, agate, or bell-metal, 
may be made to fit them exactly, the holes in which may 
be refpeCrively equal to the original pivot-holes, and then 
the good aftion of the wheel-work will not be altered. 
The friClion in the pivot-holes is greatly diminiflied too 
by the application of fine nut-oil; they are, therefore, 
generally chamfered, or counter-funk, at the exterior fur- 
faces of the plates, in order that the oil may be retained; 
but what fhould be the exaft depth "of the bearing part 
of the pivot-hole, is a matter not abfoiuteiy decided. 
As the pallet-wheel makes many more revolutions than 
any other in the movement, it is neceffary that the metal, 
of which it is made, fhould not be very deftruClible, par¬ 
ticularly when pallets are ufed which rub againfl its teeth ; 
we therefore recommend a tempered fleel wheel to be ufed, 
which ought to be alfo divided and cut*with extraordinary 
care, becaufe any irregularity in the fhape of the tooth, 
or diflance between the teeth, would injure the fcape- 
ment, and produce befides fu.ch irregularity in the motion 
of the feconds-hand, placed on this wheel’s arbor, as 
would offend the eye. 
There is no part of a clock which requires _ greater 
nicety in the execution th<m the fcapement, or part which 
limits the intenfity and duration of the impulfe given 
to the pendulum by the maintaining power, and which 
keeps up the due quantity of motion, that would other- 
wife be gradually diminifhed to a Hate of quiefcence, by 
reafon of the unavoidable friClion at the point of fufpen- 
lion, and of the refifiance which the air affords to the fo- 
lid parts of the moving-pendulum. It has been faid that 
the breadth of each pallet mull be fomewhat lefs than 
half of a fpace meafured from tooth-end to tooth-end of 
the pallet-wheelj; but the quantity of diminution muft not 
depend on conjecture; therefore the breadth is left at firft 
equal to one half as nearly as can be afeertained, lb that 
the diminution of breadth may be effected by tentative 
adjuflment, firft partially when the wheel has its teeth 
finifhed, and when both it and the anchor of the pallets 
are inferted on pins urged into the pivot-holes of the 
frame, or trial-plate; and again more minutely when 
they are fixed on arbors, and mounted in the frame. To 
enfure the perfeCt portion of a circle at the extremities of 
the anchor, we recommend that it be put on a motion- 
arbor that juft fits the central hole, and that it be turned 
in a frame or lathe, like a whefel, before it is cut; for then 
it is certain there will be no recoil in the pallet-wheel 
and feconds-hand, when thole parts prefs againfl the ends 
of the teeth, during an excurfion of the pendulum; and, 
if the inner circles could be turned alfo after the efcape 
is nearly adjufled, it would be defireable ; however, the 
point of a graver may trace in the turning-frame this in¬ 
ner circle, and then a proper curvilinear file, made and 
kept on purpofe, may take off the interior fuperfluity of 
metal. In adjusting the Hopes and breadth of the pallets, 
it will be ferviceable to iniert an index on the pallet’s ar¬ 
bor, after it is finifhed and the pivots turned, and to 
mark on the frame-plate the quantity of the fcapement 
angle, in this inftance z° at each fide of the perpendicular 
demitted from the pivot-hole, which will be a good guide 
for the true final adjuflment of the efcape. Particular 
care muft now be taken that there be as little drop as pof- 
fible, i. e. that, as foon as one tooth has completely efcaped 
the face of its pallet, the next acting tooth fhall be clofe 
to the back of the following pallet, fo as not to ftrike it 
with a jerk; the place where the firft contact takes place 
between the end of the tooth and interior or exterior cir¬ 
cle of the pallet, accordingly as it is the leading or fol¬ 
lowing pallet, muft be very near the commencement of 
