How to Install the Knife, Top Strap & Nut Bar
September 23, 2021 | Ag Parts
At Kooima Ag, we pride ourselves in offering the best replacement parts money can buy. Our commitment to our customers doesn’t stop there. We want to make sure you have all the tools and knowledge you need to help you get back in the field quicker. Follow along with us as we walk through how to install the knife, top strap, and nut bar on a JD® 7000 series machine.
For starters, you will need to open the machine in order to install the new knife, top strap, and nut bar (Corn Knife K63136KIT & Grass Knife K69500KIT). Once the machine is open, you will want to remove the old knives. The bolts get torqued which will cause them to stretch, so it is also a good idea to change them when you get new knives. Inspect your top straps and nut bars before installing new ones. Sometimes these are ok to be reused.
When removing the knife, use your impact to take out the bolts. After removing the knife, you will see a lot of debris and rust on the face of the cutter drum. It is very important to scrape this off and get it clean. To clean it even better, pop out the bottom nut bar. You can use the old knife to scrape the debris and rust off of the cutter drum. Be sure you clean out the middle also.
Once the area is clean, start by installing the nut bar on the bottom. Then, move on to the top strap. It is very important that the beveled edge it towards the front and not upside down. If it is upside down, it will just collect stuff. There is a small bend in it like a lock nut. So, keep the beveled edge up and the bend down. Now that it is lined up, you can twist in the new bolts.
After the top strap is installed, we are going to work on inserting the knife. So, you will slide it under the top strap and snug it up. Use the shearbar edge as a locator to where it has to go. Based on where the other knives are located, you can determine the new position of the knives. Hold the knife in place for now by hand tightening the center bolt.
Keep in mind if you replace one knife, you should replace the knife directly opposite of it on the cutter drum. This will help ensure the balance of the drum. Try to get the knife as close as possible to the edge of the shearbar. You can move the knife up or down to be closer or farther away. Once the knife is in the right place, tighten the bolts. Double check to be sure the knife didn’t move while tightening. Next, you will want to get your torque wrench. We set ours to 195 to be on the stronger side. The manual does say 150-200 so set your wrench in that range. Be careful when torquing the bolts not to slip and hit any of the knives. After torquing, you will want to run a sharpening cycle and get all of the knives trued up. Torque the middle bolt first then move to the outside. Check one last time to be sure you clear the shearbar.