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LINEAR BEARINGS AND GUIDES

Most CNC machines whether home-brewed or commercial may use linear bearings and guides to smoothly move assemblies in linear directions.

There are many manufacturers of these guides and bearings such as THK, IKO, Thomson/Danaher, NSK, INA and others. Each manufacturer has its own design and thus, bearings and guides are not interchangeable between manufacturers.

In addition, each manufacturer has not only size and material options, but perhaps most important, the type of bearing guide block to use.

There are also those with retained ball bearings, caged or uncaged - the latter being more noisy than the former - and those where the ball bearings simply fall out when removed from the guide.

We are writing this since we're planning on developing a bench-top mini-mill utilizing these components and those readily available from certain machine manufacturers to create a machine that is rigid, easy to assemble, and has the increased work envelope that exceeds the X2 and even X3 mills.

In our initial stage, we're simply gathering information on the components that will be used. Since precision and off-the-shelf availability (not to mention proven in many shops!) are some of the top criteria, these linear bearings and guides will be used.

One of the important block choices to make is that of rigidity in all directions. Thus, we will require bearings that have a "4-way" load capability. In addition, we've opted to find a manufacturer that is well-known, hence our decision to use THK's line of products. THK has two series of blocks suitable for our needs: SHS and HSR. The SHS series is their top-of-the-line, with caged balls and the 45 degree contact with the rails allowing for 4-way equal load (radial and lateral directions).

As for size, metric is the unit used and 15mm to 25mm sizes are ideal for the type of machine we want to build. Luckily for us, they are commonly found on places like eBay and local auction houses new and used.

We've provided a pricing chart below to give you a sense of the cost of such hardware - they're not cheap!

What exactly are the differences between the SHS/HSR (in other words, those with two rows of 45 degree contact bearings) versus the "standard" style with a single row of 90 degree contact bearings? Click here to see some examples.