The importance of replacing a bit block retainer

By: Ian Cheshuk

Something of great importance in the maintenance departments of underground mines is how to prolong the life of equipment. It is crucial to maximize the service life so they can avoid having to replace equipment prematurely. This can be a balancing act for some. Although it can be tempting to keep items until they break, sometimes it’s more financially valuable to replace items before they completely fall apart so that other items aren’t damaged, and time isn’t lost. One item that needs to be checked and replaced regularly is bit block retainers.

What is a bit block retainer? 

If you’re not familiar with this tool, we will start with some background. A bit block, or bit holder, is the primary structure securing the cutting bit in place on the mining machine. The bit block retainer is a part of the holder mechanism and ensures the bit is kept firmly in place. It stays with the bit block and allows for a bit to be replaced without the retainer being removed. Once you understand its job, it becomes clear why it’s so important. For high-impact work, it’s key that this doesn’t break down or take on significant wear, as this will impact its ability to properly retain and locate the cutting bit.

Why is replacing the bit retainer important? 

After a certain number of bits have been removed and installed, it’s important to replace the retainer to maintain the ideal bit retention. If a retainer is left in a block for too long without a replacement, you might see how it affects the work being done. Over time the materials can fatigue due to the loading and thermal stress, which will eventually reduce its ability to securely retain the bit. It can cause the bit to move too freely in the block, which will then subject the bit block to excess wear. Due to this, it makes more sense to replace the bit retainer on time rather than wait until it damages your bit block.

On top of this, ensuring you have a well-functioning retainer will help to maintain bit retention. As mentioned, the retainer loses strength over time for a variety of reasons, including damage from heat, from loading or from frequency of changing bits. So how do you know when it’s time to replace the bit retainer? The first and most noticeable indicator is a loss of positive bit retention, which provides axial movement of the bit in it’s block. Experience over time as well can provide insight as to the frequency of required replacement, such as the number of productive shifts, tons cut, or mining panels. It may be a good idea to periodically remove the retainer at time of bit change in order to inspect the retainer for visible damage or deformation.

How can Bit Service help? 

At Bit Service, we manufacture many different types of retainers for radial bit block applications. In some cases the mining operation prefers to replace the retainer with every new bit, ensuring constant positive retention. Our B710 insert fits this application and provides a cost effective single or limited use application. In the longer term applications, we have our standard B670 retainer and our B1016 retainer. If you’re working at higher temperatures, you might want to consider the B1016, because it has increased resistance to heat as well as higher retention forces. This is balanced by slight increases in effort at time of installation which will become a preference in operator feel to balance ease of use with service life and retention stability.

With all that in mind, it just makes sense to properly replace a bit block retainer regularly and reduces wear on the bit block – both for safer and more precise work and to save money on replacing bit blocks from retainer wear.