The Riving Knife Upgrade for Non-Through Cuts Prevents Dangerous Kickbacks on your Table Saw (556223) \n \nShopsmith Riving Knives on upper saw guard systems are positioned at the back side of the saw blade and are designed to prevent the saw kerf from closing onto the teeth of the rotating blade once the cut has been made. When this kerf closing occurs, the potential for a dangerous kickback is increased significantly. \n \nIf Your MARK V 520, 510, 505 was manufactured after November of 1985, your upper saw guard mechanism includes a riving knife that's designed to prevent this kerf-closing when making through cuts. The MARK 7 / MARK 4's also include this system. For your own safety and protection, we advise you to always use this system when making through cuts on your Shopsmith table saw setup. \n \nThis Non-Through-Cut Riving Knife will provide that same level of anti-kickback protection when making cuts where the blade does not pass all the way through the workpiece. Although the remaining wood that is not cut away from the stock during these non-through cuts may keep the kerf from closing on the blade, the workpiece could still rock or tilt slightly, permitting a wedging effect that could initiate a kickback. A wide metal Riving Knife at the outfeed side of the sawblade will prevent this wedging effect from occurring. \n \nThe Riving Knife is slotted to slip quickly and easily into the clamp for the upper guard in your lower guard on Your MARK 7 / MARK V 520 / MARK 4. Just drop it into position behind the lock plate on your machine's lower saw guard and tighten the plastic wing knob. A few seconds and you're ready to safely make your cut(s). Works equally well when making straight or bevel cuts at any depth. \nImportant Safety Information \n \nThis Non-Through Cut Riving Knife will not accept your upper saw guard and is therefore this Riving knife is designed for use when making non-through cuts such as narrow single or multiple-pass saw blade cuts in any direction for grooves, rabbets, half-laps, etc. where the saw blade is covered by the workpiece. It is NOT intended to be used when making through saw cuts. Never make through-cuts without the upper saw guard installed. ALWAYS use your upper saw guard with its standard riving knife when making through cuts. Not to be used with a dado head of any kind. \n \nNote: For MARK 7 / MARK V 520, 510, 505 / MARK 4 Only. It does NOT work with the MARK V 500.