Parting Tool Feed Rate Calculator

The feed rates for this parting off tool are important because any miscalculation during cutoff operations will typicaly either blow out the insert, throw the part through the shop or ruin surface. Once that blade meets up with that whirling bar, heat builds up and chips does not clear out. Its narrow profile also doesn’t forgive like a turning tool does.

Get your feed and speed dialed in correctly, however, and parting will become one of the most consistant operations on the lathe. There is a balance between control and aggression; the trick is to let the insert do its thing without rubbing but not slam it in as hard than you would face.

How to Cut Parts Safely and Well

Overhang is important. People don’t give it enough credit. An extra quarter inch will cause clean cut to chatter because it acts like a tuning fork and makes blade flex. That’s why the calculator considers how much overhang there is compared to your cutoff depth. It then penalizes it to match what happens when holder flexes.

Also it considers your coolant selection because if you go with flood coolant, that stuff carries heat and chips away, whereas going dry mean slowing down so you don’t weld. Most of this has to do with material behavior. Titanium demands conservative numbers; stainless work-hardens the instant you hesitate, while mild steel forgive a fair amount. Aluminum loves speed (but throws stringy chips that jam up in the groove unless you retract often enough).

That’s why we see peck rhythm in the results. Retracting at just the right time will prevent packing, but each pull-out add time. The tool calculates total cycle time including retracts. This lets you decide for yourself whether a slightly slower continuous feed or faster pecks actualy save minutes on the clock.

Rigidity of set up is one thing that quietly hides in the background but dominates results. If it were a long stickout on a light manual lathe, depth would of tear it apart. But it’s a heavy CNC turret capable of handling it. The calculator folds all of that into a modified feed and a set-up rating that indicates to you if you’re livig dangerously or playing it safe. It does not replace judgment, but it gives you a clear margin number indicating when to trust the math and when to back off.

Blade sharpness and center height are most common errors. If the tool is run just a few thousandths too high, it will push instead of cutting which causes a lot of deflection right at the center. Maintain a keen edge. Running a dull parting blade cause enough heat that the insert substrate softens long before you realize your finish has gone south.

The other element is blade width. A narrower blade limits how hard you can push and let you part closer to the shoulder. A wider blade handles heavier feeds on big stock, but it must have serious rigidity or it will twist. Use page’s reference tables to find your match between width and depth for the material you’re working with so that you stop guessing.

The secret of successful parting is delivering confidence at just the right rate. Rub if you hesitate. Break if you push too hard. Find that sweet spot between those extremes. The cut clears the groove cleanly without gouging, chips neatly curl out and a clean face is left behind. Get your rhythm right there and you’ll find the cutoff almost boring, on a lathe, that’s exactly what you want.