Quick Guide to the G04 CNC G Code [Tips and Tricks]

a graphic of a cnc machine with text that says learn g code today G04 dwell






The machine will stop moving for a set amount of time

A G04 code makes the cutting tool stop moving for specified amount of time. Following that amount of time the machine will proceed to the next line of code.

When to use a G04 code?

G04 codes are used for multiple reasons. They are used on lathes specifically, to break the chips. This way you don’t end up with one super long, razor-sharp chip.

They are also used to improve surface finishes on both lathes and mills.

What to think about when using a G04 code?

There is some variation to how G04 codes are called out. The difference is how the dwell times are listed.

Depending on what brand/controller your machine is, the following can change:

  • Letter used in callout to list time. Common letters are F, P, U, and X.
  • Seconds vs milliseconds. 1 second = 1000 milliseconds. Some machines work in seconds, others work in milliseconds.
  • Decimal or no decimal. Some controllers require a decimal. Some don’t allow a decimal. Some allow either way, but treat the number different based on whether you use the decimal or not.

Real standardized stuff ain’t it?

Still, these differences should help you troubleshoot any program issues you have related to a G04 dwell code. Check out the examples below to get a better understanding of how you might see dwell codes on your machine.

I am not experienced enough with all brands of CNC machines. I would like to add a list here that tells the most common ways to callout a G04 command based on the CNC manufacturer.  If anyone has experience with a variety of machines, please leave a comment below and I will make sure to add the info to the post.

4 G04 code examples and descriptions of what they do

Example #1

N005 G04 P3

This is line number 5 of the program.

G04 sets the movement mode as dwell

P3 is the amount of dwell time = 3 seconds.

Example #2

N040 G04 F5.0

This is line number 40 of the program.

G04 sets the movement mode as dwell

F5.0 is the amount of dwell time = 5 seconds.

Example #3

N040 G04 F5

This is the same line as above, on the same controller. The decimal changes how the machine reads the code.

This is line number 040 of the program.

G04 sets the movement mode as dwell

F5 is the amount of dwell time. In this case, 5 milliseconds = .005 seconds.

A big difference. Watch those decimals.

Example #4

N100 G04 U5

This is line number 100 of the program.

G04 sets the movement mode as dwell

U5 is the amount of dwell time = 5 second.

CNC codes that are similar to G04

The table below lists all of the other G codes that control movement like a G04 code does.

Want to learn more about G Code for your CNC?

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