Article by: Fred Hoekstra
This month I am talking to you about the tools that we use when we trim, with particular focus on knives.
These are the most important tool that you will use and it is important that they are used correctly which means they need to be kept clean and sharp.
We get a lot of knives of varying quality sent to us from all over New Zealand to be sharpened. The main thing that determines quality is the hardness of the steel used. The harder the steel the longer it will stay sharp. Most knives are made of stainless steel. Stainless steel is relatively hard and therefore will keep its edge reasonably well. However, some of the cheaper stainless steel knives are very soft and will go blunt quite quickly. Often farmers will buy these cheaper knives because they tend to be used for many things other than hoof trimming and it becomes quite expensive if you have to keep replacing them. The better quality hoof knives are made of hardened steel. These knives will stay sharper for much longer than stainless steel knives, but they will rust if they are not kept dry. Because they are so hard they can break easier than stainless steel knives so it is important to use the right trimming technique. The horny tissue needs to be sliced off not broken off. What I mean by this is that many people tend to start a cut and then part way through twist the knife so as to cause the hoof to break off rather than making the slice clean. Generally people are not even aware that this is what they are doing, but it is something I encounter frequently when running training courses.
When we trim cows it is important that our knives are sharp. We wouldn’t like it if a surgeon performed an operation on us using blunt knives. Not so much because it is harder work for the surgeon but more because the end result is not the same. This is the same for cows. If we use blunt knives we are more likely to cut ourselves and the trimming job is not going to be very successful. By using sharp knives you can be much more precise with less effort.
Sharpening knives is, however, not the easiest thing to do. It takes a lot of practise and patience. We use a bench grinder with a linishing belt. This will sharpen the blade and create a nice bevel. The angle that you put the knife onto the belt will determine the angle of the bevel. As a rule of thumb, this bevel needs to be a minimum of 10mm. Many of the knives you can buy have a much steeper bevel than that which makes the knife much more difficult to use, giving you less control with your cutting. We sharpen the hook of the knife on a rubber disc attachment on our grinder. You can sharpen the hook on the outside if you wish, but you should NEVER sharpen the back of the blade. If you do, you end up having to tilt the knife when trimming and it is much more likely to cut into the hoof rather than taking a slice off. I know it is very tempting to touch up that side of the knife because it is easier to get a sharp edge but you will ruin the functionality of the knife. (To be continued..!)