THE AMOUNT OF LOCK.
If we study the large drawing, where we delineate the escape wheel ten
inches in diameter, it will readily be seen that although we claim one
and a half degrees lock, we really have only about one degree, inasmuch
as the curve of the peripheral line _m_ diverges from the line _B f_,
and, as a consequence, the absolute lock of the tooth _C_ on the locking
face of the entrance pallet _E_ is but about one degree. Under these
conditions, if we did not extend the outer angle of the exit pallet at
_t_ down to the peripheral line _m_, we would scarcely secure one-half a
degree of lock. This is true of both pallets. We must carry the pallet
angles at _r s n t_ down on the circles _c'' d'_ if we would secure the
lock and impulse we claim; that is, one and a half degrees lock and
eight and a half degrees impulse.
Now, while the writer is willing to admit that a one-degree lock in a
sound, well-made escapement is ample, still he is not willing to allow
of a looseness of drawing to incorporate to the extent of one degree in
any mechanical matter demanding such extreme accuracy as the parts of a
watch.
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