VOL. I.END‑ADJUSTMENT AND LOCKING DEVICES.PLATE IV.
Fig. 418.Fig. 419.Fig. 420.
Fig. 421.Fig. 422.Fig. 423.
Fig. 424.Fig. 425.Fig. 426.
Fig. 427.Fig. 428.

To cause a single nut to lock itself and dispense with the second or jamb nut, various expedients have been employed. Thus in [Fig. 418] is shown a nut split on one side; after being threaded the split is closed by hammer blows, appearing as shown in the detached nut. Upon screwing the nut upon the bolt the latter forces the split nut open again by thread pressure, and this pressure locks the nut. Now there will be considerable elasticity in the nut, so that if the thread compresses on its bearing area, this elasticity will take up the wear or compression and still cause the threads to bind. Sometimes a set screw is added to the split, as in [Fig. 419], in which case the split need not be closed with the hammer.

Another method is to split the nut across the end as shown in [Fig. 420], tapping the nut with the split open, then closing the split by hammer blows. Here as before the nut would pass easily upon the bolt until the bolt reached the split, when the subsequent threads would bind. In yet another design, shown in [Fig. 421], four splits are made across the end, while the face of the nut is hollowed, so that a flat place near each corner meets the work surface. The pressure induced on these corners by screwing the nut home is relied on in this case to spring the nut, causing the thread at the split end to close upon and grip the bolt thread.

Check nuts are sometimes employed to lock in position a screw that is screwed into the work, thus screws that require to be operated to effect an adjustment of length (as in the case of eccentric rods and eccentric straps) are supplied with a check nut, the object being to firmly lock the screw in its adjusted position.

The following are forms of nuts employed to effect end adjustments of length, or to prevent end motion in spindles or shafts that rotate in bearings.

[Fig. 422] shows two cylindrical check nuts, the inner one forming a flange for the bearing. The objection to this is that in screwing up the check nut the adjustment of the first nut is liable to become altered in screwing up the second one, notwithstanding that the first be held by a lever or wrench while the second is screwed home.

Another method is to insert a threaded feather in the adjustment nut and having at its back a set screw to hold the nut in its adjusted position, as in [Fig. 423]. In this case the protruding head of the set screw is objectionable. In place of the feather the thread of the spindle may be turned off and a simple set screw employed, as in [Fig. 424]; here again, however, the projecting set screw head is objectionable. The grip of an adjustment nut may be increased by splitting it and using a pinching or binding screw, as in [Fig. 425], in which case the bore of the thread is closed by the screw, and the nut may be countersunk to obviate the objection of a projecting head. For adjusting the length of rods or spindles a split nut with binding screws, such as shown in [Fig. 426], is an excellent and substantial device. The bore is threaded with a right-hand thread at one end and a left-hand one at the other, so that by rotating the nut the rod is lengthened or shortened according to the direction of rod rotation. Obviously a clamp nut of this class, but intended to take up lost motion or effect end adjustment, may be formed as in [Fig. 427], but the projecting ears or screw are objectionable.

Where there is sufficient length to admit it an adjustment nut, such as in [Fig. 428], is a substantial arrangement. The nut a is threaded on the spindle and has a taper threaded split nut to receive the nut b. Nut a effects the end adjustment by screwing upon the spindle, and is additionally locked thereon by screwing b up the taper split nut, causing it to close upon and grip the spindle.