When you get into machining, the first tool often used is an end mill. It’s simple, it’s fairly straightforward on purpose, and it’s the universal standard tool for machining. But, we all know that that is just the beginning – tool boxes fill up because there are an endless number of options for tooling. One tool that is often misunderstood, or even disregarded, is the slitting saw. While these saws are often relegated to very specific operations, they can be an invaluable addition to your shop.
The Mill’s Parting Tool
Sometimes you might be dealing with a thin part or something that has a challenging feature to hold on one side, making that part a challenge to finish on the back side. A slitting saw gives you the unique opportunity (at least on a 3-axis mill) to get to the underside of a part. This means that you can use a slitting saw to cut off a part and finish it by hand. While the surface finish might not be as nice as a TTS Superfly Cutter, this process can save the day with those thin or hard-to-hold parts. 
Relief Slots
Relief slots are features in a part that allow it to clamp around something. Adding a relief slot give a part the ability to move slightly without compromising the integrity of the part too much. While you can use a tiny end mill, over a massive number of passes to create a relief slot, a slitting saw can often do so in just one or two passes. This is exactly what slitting saws were designed to do – create wide, deep, thin slots in parts quickly and without destroying your cutting tool. 
Slotting Around a Part
When you need to cut a slot around a part, you have two options; either use a fourth axis and an end mill, or use a slitting saw. The fourth axis option works, but requires extra workholding considerations and most likely moving a part from a vise to the fourth axis in the middle of the cutting process. A slitting saw can make that slot in the same setup with only a tool change. While they are often forgotten about, slitting saws make a valuable addition to a quickly-filling toolbox.
