In the precision mechanical workshop of Bonanomi we manufacture two reference tools that are essential for dimensional inspection. The first is the control block, also known as V-block, vee block or V-prism, used both for inspection and for positioning on machine tools. The second is the control cylinder, or cylindrical square, used to check the squareness and flatness of vertical walls.

Control Block for Machine Tools

The control block is a precision mechanics industry product designed to hold a cylindrical element between its V-shaped walls. In this way the workpiece stays perfectly centred in its housing. It is precisely this shape that gives control blocks their common name of prismatic blocks.

The blocks are mainly used in pairs and are available in two types: 1V and 4V.

Cast Iron Control Block

1V control blocks have two side slots for clamping and a central V to house the workpiece. The 4V control block, on the other hand, has 4 Vs of different widths, one on each external face.

V-blocks are normally used on dressing plates and surface plates for marking out, alignment and inspection of cylindrical workpieces. They are also used to position and clamp cylinders on machine tools.

The material used is G30 grey cast iron with a lamellar structure and a surface hardness of 200-220 HB, highly resistant to wear.

The control block can be machined in two precision classes:

• precision ± 0.01 ground
• precision ± 0.05 milled

Control Cylinders

The control cylinder is a machined cylinder used as a reference for checking the squareness and flatness of vertical walls. Its key characteristics are cylindricity and squareness. Because of this function, it is also known as a cylindrical square or cylinder square.

Placed on a dressing plate, the control cylinder provides a surface that is perfectly perpendicular to the base. This surface can be used as a reference to check workpieces, fixtures and measuring instruments. It is an ideal complement to control rules for geometric inspections.

In the Bonanomi precision mechanical workshop it is manufactured in both steel and cast iron, and it is used in both metrology and production environments.

Custom V-Blocks and Control Cylinders

As an alternative to the standard precision mechanics products shown in the catalogue, Bonanomi can manufacture any size, using any material, to best meet the needs and requirements of the end customer. Contact us to request custom control blocks and custom control cylinders.

Control Blocks and Control Cylinders Available in the Express Shop

Looking for our V-blocks? You'll find them in the Express Shop: select the size you are interested in and wait for our formal quotation.

The following 4V control blocks are currently available:

• 4V Control Block 175x175x75
• 4V Control Block 150x120x65
• 4V Control Block 150x100x67
• 4V Control Block 130x100x65
• 4V Control Block 120x90x60
• 4V Control Block 90x90x50
• 4V Control Block 75x75x50
• 4V Control Block 60x60x50

Not Just Control Blocks and Control Cylinders: Other Bonanomi Products

In addition to control blocks and control cylinders, at the Bonanomi workshop you can request our third-party machining services or the manufacture of the following products: clamping planks, clamping squares, clamping cubes and towers, clamping plates, surface plates, control rules, parallel boxes, test benches and support and levelling columns, in any material or size.

Frequently Asked Questions

What is a V-block and what is it used for?

A V-block, also called vee block, V-prism or control block, is a precision cast iron tool with one or more V-shaped grooves. It holds and centres cylindrical workpieces. It is used on dressing plates for marking out, alignment and dimensional inspection, or on machine tools to position and clamp shafts and cylinders during machining.

Why are V-blocks used in pairs?

A cylindrical workpiece, especially a long one, must be supported at two points to remain parallel to the reference surface. For this reason V-blocks are used in pairs: the two Vs act as two identical supports and keep the workpiece perfectly aligned during inspection.

What is the difference between a 1V and a 4V V-block?

The 1V block has a single central V to house the workpiece and two side slots for clamping: it is ideal when the block needs to be fixed to a machine tool. The 4V block has one V on each external face, each with a different width: a single tool covers several workpiece diameters, simply by turning it onto the right face.

What is a control cylinder used for?

The control cylinder, also known as a cylindrical square, is a precision reference for checking the squareness and flatness of vertical walls. Placed on a dressing plate, it provides a surface perfectly perpendicular to the base, against which workpieces and instruments can be compared. It is used both in metrology rooms and in production.

Control Cylinders: All Sizes