Adjustable Kinematic Couplings

Adjustable Kinematic Coupling, three views
Adjustable Kinematic Coupling, three views

It is often desirable to be able to adjust the elevation and the level of the “Z”-axis of a kinematic system.

Adjustable Kinematic Coupling, exploded view
Adjustable Kinematic Coupling, exploded view

The simple, inexpensive way to achieve this is to use two or three balls, attached to threaded-posts, that can be moved discretely in or out of threaded holes in one of the kinematic platforms. The final adjustment of these simple devices can be locked in position with simple jam nuts. We build a family of these high quality, off-the-shelf devices, in a fairly broad range of sizes. All of these devices are very economically priced.

Custom devices that are smaller or larger than these off-the-shelf standards can be economically produced on special order. Components with metric dimensions or custom threads are common variations. These adjustable kinematic components can also be custom constructed in nonmagnetic or electrically insulating materials, as well as in long-wearing, abrasive-resistant, tungsten-carbide versions. Versions of the designs with ceramic spherical contact surfaces are a common requirement. The balls used on the standard devices are very spherical, with a one microinch (25 nanometer) Ra surface quality.

The spherical contacts on the standard components are made from a micro-grained martensitic stainless steel, hardened to 58 HRC minimum. This material has the extraordinarly high tensile strength of 285,000 PSI. Typically a flat surface is ground on a stainless-steel ball at approximately one-third of its diameter. A blind hole is E.D.M.’ed into this flattened surface on the ball. The truncated and drilled ball is glued over a pin to the top surface of the threaded post. The elevation of the ball can be adjusted with a standard hex-wrench to tighten or loosen the bronze-screw. A smaller hex-wrench can then tighten the set-screw inside that sets the position of the bronze-screw via an expanding mechanism. A custom-made hollow hex-wrench can be purchased allowing the set-screw to be tightened without removing the larger hex-wrench.

  • The smallest standard, adjustable kinematic sphere is our part number AJ-10-HX. It has a #10-32 U.S. – N.F. threaded post. The thread is one inch – 1.00” (25.4 mm) long. The ball diameter is a XXX (XXX) inches [XXX mm].
  • The next larger size is AJ-250-HX. It has a one-quarter (0.250 inch) [6.35 mm] diameter threaded post, with 28 threads per inch U.S. – N.F. The thread is one inch – 1.00” [25.4 mm] long. The ball diameter is XXX (XXX) inches [XXX mm].
  • The next larger size is AJ-312-HX. It has a five sixteenth (0.312 inch) [7.9 mm] diameter, threaded post with XXX threads per inch U.S. N.F. The thread is one inch 1.00” [25.4 mm] long.
  • The next size up in this standard configuration is our part number AJ-375-HX. It has a three-eighths (0.375) inch [9.53 mm] diameter post with XX threads per inch U.S. –N.F. The thread is one (1.00) inch [25.4 mm] long. The ball diameter is XXX (XXX) inches [XXX mm].
  • The largest of our standard off the shelf design is part number AJ-500-HX. It uses a slightly different design. It uses a straight one half inch 0.500” (12.7mm) diameter body that has 20 threads per inch. The threaded body is one inch 1.00” (25.4mm) long. The xxx inch xxx mm diameter ball has a drilled hole in it. The ball is glued over a pin that extends down into the 1/2” diameter body.There is a hexagonal hole in the bottom of the body of this part. This hexagonal hole will accept a standard hex key to facilitate adjustment. This part is supplied with a stainless steel jam nut and washer to facilitate rigidly locking the final position.
Part Number Diameter of Ball Diameter of Thread Number of Threads Per Inch Length of the Thread Price
AJ-10-HX #10 32 T.P.I. 1.00 inch long
(25.4 mm)
$
AJ-250-HX 0.250”
(6.35 MM)
28 T.P.I. 1.00 inch long
(25.4 mm)
$
AJ-312-HX 0.312”
(7.94MM)
XX T.P.I. 1.00 inch long
(25.4 mm)
$
AJ-375-HX 0.375”
(9.53 MM)
XX T.P.I. 1.0 Inch long
(25.4 mm)
$
AH-500-HX 0.500” (12.7MM) 20 T.P.I. 1 inch long
(25.4 mm)
$
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