Peck drilling and cycle time: G83 vs G73

G83 and G73, briefly

Both are peck-drilling canned cycles: instead of plunging a deep hole in one shot, they break it into a series of pecks so chips can clear and the drill doesn’t pack and snap. The difference is what happens between pecks.

G83 (deep-hole peck) retracts the drill all the way back to the R-plane after every peck. The flutes come fully clear of the hole, chips fall away, then the tool rapids back down for the next bite. It gives maximum chip evacuation, and maximum air travel.

G73 (high-speed peck) only backs the drill off a small amount, just enough to snap the chip, then keeps drilling. The chip isn’t fully evacuated, but the tool barely moves between pecks.

Why the difference is a time question

Every one of those retracts is non-cutting time. The drill is moving, the clock is running, but no metal is coming off. G83 makes a full retract and a rapid re-approach on every peck. G73 makes a tiny hop. On a single shallow hole that’s noise. On a deep hole pecked a dozen times, it’s the difference between the two cycles, and it’s all overhead.

The peck count multiplies it

Peck count is roughly hole depth divided by the peck increment Q. Drop Q to take smaller bites, often done for chip control or in hard material, and the number of pecks climbs, and with G83 so does the count of full retracts. A 30 mm hole at a 2 mm peck is fifteen retracts per hole on G83. Halve the peck to 1 mm and it’s thirty. The cutting time barely changes. The air time doubles.

Then multiply by every hole

One hole’s retract overhead is small. A bolt-circle, a cooling plate or a mould base with dozens or hundreds of deep holes is where it lands: the per-hole overhead times the hole count, all of it non-cutting. This is exactly the kind of motion a cutting time estimate quietly skips, which is why a drilling heavy job so often runs longer than the quote.

Putting a number on it

UltraNC expands every peck into real moves. It feeds each bite at your drilling feed, and rapids each retract and re-approach at your machine’s rapid rate and acceleration. So when you load a G83 program it counts every full retract, and a G73 program counts only the hops. The difference shows up in the estimated cycle time instead of being assumed away. Switch a deep-hole program between the two cycles, or change the peck increment, and watch the number move. Nothing is uploaded and there’s no sign up.

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Common questions

What is the difference between G83 and G73?

Both peck a deep hole in stages, but they clear chips differently. G83 (deep-hole peck) retracts the drill all the way back to the R-plane after every peck, fully evacuating the flutes. G73 (high-speed peck) only backs off a small amount to snap the chip, then keeps drilling. Same hole, same depth. The difference is how far the tool pulls back between pecks.

When should I use G83 instead of G73?

Reach for G83 when clearing chips matters more than raw speed: deep holes (a common rule of thumb is roughly four drill diameters or deeper) and materials that throw long, stringy swarf such as aluminium, copper or stainless. Fully lifting the drill out on every peck evacuates those chips and takes load off the tool, which is worth the extra seconds. G73's short chip-break hops suit shallower holes and shorter-chipping materials like cast iron, where full retracts would only cost time you don't need to spend.

Which is faster, G83 or G73?

G73, usually by a clear margin. Its short chip-break hops skip the full retract-and-re-approach that G83 performs on every peck, so it spends far less time travelling in air. The deeper the hole and the more pecks, the wider the gap. G83 trades that time for better chip evacuation, which still matters in deep holes or stringy material where G73 would pack chips.

How much time does peck drilling add to a cycle?

It depends on hole depth, the peck increment (Q) and which cycle. Every peck adds non-cutting motion, at minimum a retract, and for G83 a full retract plus a rapid re-approach. A deep hole can be a dozen or more pecks. None of that removes metal, and across a plate of holes it becomes a real slice of the cycle that cutting-only estimates miss entirely.

Can the drilling cycle change cycle time more than the feed rate?

On a part dominated by deep holes, often yes. Halving the peck increment or switching G73 to G83 multiplies retract moves across every hole, which can move the clock more than a feed rate tweak does. The retract overhead scales with the number of pecks and the number of holes, so it compounds fast. The only way to know for your program is to simulate the posted code.

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