 Welcome to Cutting Slots and Key Seats. Cutting slots and key seats is a common job on the Bridgeport milling machine. A key seat is a groove of any size that's cut along the axis of a shaft or spindle. It's designed to fit the bottom half of a key. The top half of the key fits into a keyway in the corresponding part. When the shaft, key and part fit together, it's called a keyed joint and it prevents relative rotation between both parts. A keyed joint connects a variety of gears, pulleys, couplings, washers and blades to the shaft. In this video, we'll explore how to cut a key seat. Placement of the key seat is very important. It must be in the center of the shaft and at the correct depth. In addition, you also need to make sure it's the correct width. Typically, there is a two-thousandth width tolerance for any key seat. There are different ways that you can secure the workpiece. You can clamp it in a vice, clamp it to the table or by using V-blocks. It's important that your workpiece is secure for the remainder of the steps. Next, select your end mill. Remember it's better to select one that's smaller than the key seat you need to cut. If you pick an end mill that's the same size, you run the risk of over-cutting and creating a slot that's too wide. In addition, select the shortest mill you can. Longer flutes mean the end mill deflects more as you're cutting. Finally, if you're cutting in the middle of a shaft, make sure the end mill is center-cutting. This means you can plunge with the end mill. Once you've selected and installed your end mill, find the center of the shaft. Move to Holder in the bridge port spindle before mounting the edge finder into the holder. Turn the spindle on and set the RPM for using the edge finder. Lower it down to the side of the shaft. Move the Y-axis until the edge finder kicks out and zero it on the digital readout. Raise the edge finder and move the Y-axis until it's on the other side of the shaft. Lower the edge finder down to the side of the shaft again and move the Y-axis until it kicks out. Raise the quill until the edge finder is above the part. Turn off the spindle. Record the number from the digital readout and divide it by two. Move the Y-axis until the digital readout displays this number. Zero out the digital readout in the Y-axis. This is the center of your shaft. Now use the edge finder to establish zero in the X-axis on the end of your shaft. Mount your end mill into the correctly sized holder. You should always use an end mill holder and not a collet. Lock the spindle to keep it from moving as you cut the key seat. With the spindle off, raise the knee until the end mill is close to the top of the shaft. Place a piece of paper between the top of the shaft and the end mill. Continue raising the knee until you can't move the paper. Set the collar on the knee to zero, remembering to compensate for the paper's thickness. Cover the knee and move the cutter until it's clear of the shaft. Turn on the spindle and set the RPM based on the end mill you're using. Raise the knee to the depth of the key seat. Depending on its size and depth, you may need to take multiple depth cuts. It's also important to remember that the key seat depth also includes the crown. Use the chart in the machinery's handbook to tell you how much deeper to cut the key seat for its width compared to the shaft diameter you're cutting. Handfeed the table so the key seat is cut to the specified length. Then, handfeed in the opposite direction to move the cutter out. Measure the width of the key seat. Make sure you're using proper measuring equipment, including gauge blocks or precision pins. It's not enough to measure it using only a caliper. Once you have this measurement, subtract it from the key seat's size and divide by two to determine how much material needs to be removed from both sides. Use a depth micrometer to measure the key seat depth. This gives you the chance to make sure you're still accurate to the print specifications. Because the key seat needs a precise measurement, don't remove all of the material in one pass. Adjust your Y-axis to remove half of what you've calculated and cut one side. Then, take the same amount off the other side. Measure again and repeat this procedure until the key seat is the correct width and depth. Your last step is to deburr your work. You've completed cutting slots and key seats.