A means of locating and locking two flat surfaces together. These are usually a fixture plate and a subplate.
It locates in the same manner as locating pins. In other words, there are two precision bores (receiver bushings) located on two precision pins (shanks).
Two shanks are the maximum needed to locate. Anything more is a hindrance rather than a help. (This also applies to locating pins.)
The Ball Lock® system achieves its holding force by a combination of force generators. A threaded screw exerts force onto a center ball which, in turn, directs this force onto three balls that register on a taper seat.
This would depend on the particular application, but in most cases, we would recommend that at least four shanks be used (two shanks to locate and lock, and two shanks to lock only).
This is accomplished by only using liner bushings for the locating shanks and drilling a clearance hole (shank diameter plus approximately .030") for the remaining shanks.
It is recommended that the use of the Ball Lock® Mounting System for locating and clamping of fixture plates be incorporated in a systematic process. All fixture plates should have two locating points positioned as far apart as possible. There is no advantage to having more than two locating points. If more than two flanged shanks are required to provide additional hold down force, omit liner bushings in the additional holes in the fixture plate and allow 0.030” (0.76mm) over the nominal size. The additional clearance will ensure that these holes have no influence on the locating holes.
The center distance of the receiver bushings in the machine table, tombstone, or subplate should be as accurate as possible (±0.0002” or ±0.005mm is recommended). Accurate location will assure interchangeability of numerous fixture plates. For accurate repeatability within ±0.0005” (±0.013mm) of true position, both liner bushings in the fixture plate should be primary liners and the center distance tolerance should be ±0.0002” (±0.005mm). For a slightly looser fit, repeatability within ±0.0015” (±0.04mm) of true position, use (1) primary and (1) secondary liner with a center distance tolerance of ±0.001” (±0.003mm).
If the center distance between the two locating holes (receiver bushings) is held to ±.0002" tolerance, and two primary liner bushings are used, then repeatability of ±.0005" can be maintained.
The only difference between the primary and the secondary liner bushings is that the secondary liner bushing has an oversized I.D. to accommodate the wider center distance tolerance on your fixture.
The location of the liner bushing is not critical, but in order to be consistent, we recommend that wherever possible, locate the liner bushings at bottom left and at top right.
Both locating and locking are accomplished in the same motion. Two and one half turns are the maximum needed to lock (whereas a 1/2–13 cap screw with one and a half diameters of thread engagement would need ten turns to lock). On C.N.C. machines, the repeatability of fixture locations makes indicating of the fixture unnecessary.
Counterbore the fixture plate to a diameter large enough to allow easy removal of the shank. Note: The thickness of the plate section under the head of the shank is critical! It must conform to plate thickness recommended in the catalog.
It is possible that by adjusting the depth of the counterbore for the receiver bushing, you can still use the Ball Lock® System. If there are any questions on this type of application, please call 1-877-426-2504.
The shank is made of alloy steel; heat treated to 40-45Rc and should stand temperatures up to 400°F. However, the “O” Ring that retains the balls could disintegrate. Note! Be aware that thermal expansion of your plate could affect the center distance tolerance and repeatability.
