Building a teeny tiny vee block for Kinematic applications presents some unusual challenges.

The design chosen uses the well-proven cylindrical post-mounted vee block. The post is used to both locate and clamp the vee block in position.

The cylindrical post is precision ground to .250 inches (6.35 mm) plus nothing minus .0005 inches (.0127 mm).

The flange adjacent to the post is ground flat and square to the post. The post is drilled and tapped for a 4-40 hold down screw.

After precision grinding the flat prismatic faces of the tiny vee block, these faces are precision lapped.

The vee block is constructed from a high chrome, high carbon, Martensitic stainless steel that is hardened to 58 HRC minimum. This ultra fine-grained material provides excellent repeatability with good fret resistance.

This very small size component will match balls from just under three sixteenth's (3/16" ) of an inch ( 4.8 mm ) to just over one quarter inch ( 1/4" ) ( 6.4 mm ) diameter. Our part number on this item is VB-187-CPM.

This device is designed to accept spheres from five sixteenths of an inch 5/16", 0.3125" ( 7.9 mm ), three eighths, 3/8", 0.375" of an inch ( 9.5 mm) is nominal, to one half of an inch, 1/2", 0.50"
(12.7 mm) in diameter. It is our part number, VB-375-CPM.

The cylindrical mounting post is precision ground to three eighths (3/8") of an inch ( 0.375", 9.5 mm ) diameter plus zero minus 0.0005 inches (.0127 mm). This post is one quarter of an inch ( 1/4" ), 0.250" ( 6.35 mm ) long.

The flat flange adjacent to the post is precision ground flat and square to the post.

The included angle of this vee block is 90 degrees.

This device is designed for universal mounting from either the front or from behind.

The major diameter of this Vee Block is three quarters (3/4") of an inch (19 mm).

This component, also known as a Standard V Block, ( Part No. VB-75-SM, made from Hardened Stainless Steel ) is designed primarily for high load carrying kinematic couplings and precision tooling applications. The contact area between a sphere and the precision ground flat surfaces of the Vee block is greater that that between a sphere and two cylinders. This gives the Vee block a much higher load carrying capacity than the two cylinders.

This Vee block component is designed for flat surface mounting to the kinematic or tooling platform.

The precision flat lapped base of this component is held in solid contact with the top surface of the platform by two cap screws. It can be clamped down from either the front or from the rear.

Two through holes are provided, one at each end of the Vee. They are tapped for #10 x 32 screws. Using these tapped holes, the Vee block can be pulled down solidly against the platform from behind. If front mounting is desired the Vee block can be held solidly against the platform by two #6 round head screws. These screws will pass through the center of the same tapped holes but from the front surface.

There is a 1/2 inch diameter shallow counterbore in the flat base of this component. The remaining annular ring provides a very stable locating surface. This counterbore provides a recess that will hold adhesive if the component is glued down.

These Vee blocks are made of very fine grained, high chrome, high carbon, stainless steel that is hardened to 58 Rc and ultra cold cycled for long term dimensional stability.

The 90 degree ground faces of the Vee block are tangent to any ball diameter from 5/8" (.625 inch, 15.875 mm) to 1.00 inch (25.4 mm), with the ideal size being 3/4" (.750", 19.05 mm).

This kinematic Vee Block component (also known as Cylindrical Boss Mounted Vee Block ) is designed for both high load carrying capacity and easy installation. Because the contact area between a sphere and the precision ground flat surfaces of the Vee block is greater than that between a sphere and two cylinders, this Vee block has a much higher load carrying capacity.

Precise location of this component is achieved through a precision ground cylindrical post. The flange adjacent to the cylinder is also ground flat.

This design facilitates the accurate installation of this component without the use of precision machine tools. The desired mounting is simply scribed on the surface of one of the kinematic or tooling platforms with a compass. This circle is then divided into three equal cords and the intersections are center punched. The top and bottom platforms are clamped together. Three holes are then drilled and reamed, through both of the platforms. This can be done on a drill press or even with a hand drill. With the three .500 inch ( 12.7mm ) diameter holes now drilled through both platforms three of the cylindrical post mounted Vee blocks can be mounted on one platform, and three of the part number 75 B-T balls can be mounted on the other to form a perfect kinematic system.

These Vee blocks are made of very fine grained high chrome, high carbon, stainless steel that is hardened to 58 Rc and ultra cold cycled for long term dimensional stability.

The 90 degree precision ground faces of the Vee block are tangent to any ball diameter from 5/8"(0.625 inch, 15.87mm) to 1.00 inch (25.4 mm), with the ideal size being 3/4" (0.750 inch, 19.05mm).

To orient the Vee and to prevent any rotation, there is one 0.093 inch (2.3622 mm) diameter dowel pin hole machined through the outside edge of the flange.

These Vee blocks can be held in place from either the front or the rear. They can be solidly bolted down from the front surface by a #10 hexagon socket head cap screw. The head of this capscrew is recessed in a counterbore to avoid contact with the ball. For back surface installation, use a #1/4-20 hexagon socket head cap screw. The Vee can also be pulled down from behind by a 1/4 inch-20 bolt screwed into the threaded hole in the center of the cylindrical post.

In kinematic applications, plane flat surfaces have a higher load carrying capacity than cylindrical or spherical ones.

Flat surfaces with very fine surface texture are quite slippery, so they provide excellent alignment of the mating spheres.

Producing high quality flat planes on prismatic devices requires a unique approach. Lapping the inside flat faces of a Vee Block or even worse the inside faces of a Trihedral Cup is not at all a practical task.

An approach that can produce the highest quality internal prismatic devices is the split design. Instead of constructing the device as a monolith, which is conventional wisdom, each facet of the prism is produced as a separate but symmetrical unit.

A very high quality flat facet can be easily produced on the truncated surface of a cylindrical post. Rigidity is not lost by splitting the faces of the prism, because the cylindrical design provides a simple method for extremely rigid mounting. By machining a trench in the Kinematic Platform with an end mill that has the same radius as the cylindrical post itself, and gluing the assembly together under load, an extremely rigid assembly results.

The reason that this design can so far outstrip the rigidity of a monolithic component is not so obvious; but it is due to the inherent weakness in the joint connecting the monolith to the Kinematic Platform.

For light loads, there is seldom any reason to use this more complicated flat facet design, when three spheres will form an excellent trihedral cup and two cylinders a fine Vee Block.

A universal component that will fill a broad array of high load kinematic applications is a three quarter inch (19mm) diameter cylindrical post that is truncated at a 45 degree angle. This one component will function well with any ball size from one half inch (13mm) to over one inch (25.4mm). Better repeatability can be achieved by using a steeper angle but this will reduce the load carrying capacity.

These components can be produced for surface mounting by drilling and threading a hole in the flat base but in doing so much of the systems rigidity is lost.

Because the relative cost of raw material is rather small, in relation to the overall cost of this component, tungsten carbide with its tremendous stiffness or Young's Modulus of Elasticity of 98,000,000 P.S.I. and high hardness of 91-HRA has been chosen as the standard material.

There is wide latitude of design options of both size and materials to cope with different loads, corrosive environments, temperature, as well as magnetic and electrical qualities. We will custom build just about any design to fill specific customer needs.

The average price for a steel Prismatic Post is $45.00 ea.

How can four points be good Kinematics? For anyone who has tried to level a four-legged table their answer will probably be that it is impossible.

The subtle principals behind the excellent performance of all kinematic couplings is the fundamental nature of spherical geometry and the self aligning nature of three contacts.

The simple fact is that every point on the periphery of a sphere has a common point axis. When balanced vector forces are applied to the surface of a sphere the resultant of those forces manifests itself at this point axis.

When working with Kinematic couplings you can toy with the surfaces that transfer the forces to the spheres almost at will, but if you expect predictable results you dare not mess with the spheres themselves.

The question then is how can we split the Kinematic system to steady a clumsy platform that is unstable? If we believe that we can cheat almost at will with the force drivers then we can take a simple element like a Vee Block or Parallel Cylinders, saw it down the middle, spread the pieces and we are in.

The problem, of course, is how can we do our thing on the spherical part of the coupling? Using two small spheres or cutting a sphere in half and spreading the parts out until they contact the separated walls of the Vee Block will leave us with alignment and positioning problems that would make you wish that you had opted for a plain prismatic design in the first place. The answer is to simply go back to the principles.

If the target surfaces of the split Vee Block are four inches apart, then we need a single sphere that will be tangent to these surfaces. But a four-inch or larger ball is far too big, too heavy and too expensive to be practical. From the discussion so far, a viable solution is deducible. All that is needed is two small spherical segments with the proper spherical radius rigidly mounted tangent to the faces of the split Vee Block.

The method of attachment will dictate the actual design perimeters of these spherical segments with the only constraints being their radius of curvature and that their tangent contacts bisect at the appropriate spherical radius.

This is presented for basic design information of how to do it as the component, for each design must be custom manufactured.

Our large array of spherical lapping tools assures fast delivery of these custom components.