See how address values change the actual toolpath through synthetic NC and verified figures, not by memorizing command definitions alone.
There are many G-code explanations online, but few show how the path changes when a single address is changed. Every article here is built around a short NC example written specifically for the explanation, together with the path drawing produced by interpreting that example with the CNC Path Analyzer engine. The drawings are not hand-drawn illustrations: the engine recalculates them every time the pages are built, so if a number in the text and the drawing disagree, it is caught by the checks before publication.
Rather than just listing what each command means, each article covers the points that actually cause confusion on the shop floor (G71, where the same letter U means different things on different lines; lathe X, where diameter and radius get mixed; tapping cycles, where F is tied to the pitch) together with calculations you can try yourself.
The examples are synthetic programs unrelated to any specific part or customer drawing, and they do not define workholding, tool lengths or offsets. Paste them into the tool to run the path yourself and check the concept, but on a real machine follow that machine's manual and dry-run procedure. If you find an error in the content, let us know through the contact page; we will check it and reflect the fix together with the change history.
Explains the difference between G00 and G01 in terms of speed, path shape, modal behavior and safe height, and shows how to read the approach, plunge, cut and retract sequence of a milling example together with its path drawing.
Explains how to tell G02 (clockwise) from G03 (counterclockwise) together with plane selection, the 180-degree problem of R commands, I/J/K center commands and full circles, using a milling example and its path drawing.
Explains why the X value in a CNC lathe program means a diameter rather than a radius, why it appears as a radius in the screen drawing, and U/W incremental commands and the G18 ZX plane, using a chamfering example.
Explains the difference between G90 absolute and G91 incremental commands, repetitive machining where incremental mode is useful, and accidents caused by not switching the mode back, using a rectangle example and a coordinate-tracking table.
Explains the G71 OD roughing cycle of FANUC-family lathes in its two-block format: depth of cut, retract amount, finishing allowance, the rules for writing profile blocks and common alarm causes, together with the actual path drawing.
Explains, with an example containing an arc, how the G70 finishing cycle re-reads the P–Q profile blocks of G71, G72 and G73, when F and S inside the profile are applied, and the practical order with a tool change in between.
Compares the G72 face roughing cycle with G71 to show when to use it, why W in the first block is the Z depth of cut, how to write the profile blocks from the face inward, and how to choose the tool, using a flange example.
Explains the two-block format of the G76 multiple threading cycle with an M24×2 metric thread example: calculating the minor diameter and thread depth, the relationship between first depth of cut and number of passes, and start-position clearance, together with the path drawing.
Explains the G83 peck drilling cycle of machining centers with a three-hole example: Q infeed and chip evacuation, the difference between the R point and the initial point, choosing G98 or G99 return, the difference from G73, and how the meaning of R changes in lathe G83.
Explains with a three-hole M8×1.25 example why the relationship F = S × pitch must always hold in the machining center G84 tapping cycle, the difference between floating and rigid tapping (M29), and how to set tap hole depth and the R point.
Explains with a rectangular contour example how to tell G41 (left) from G42 (right) cutter radius compensation on a machining center by the direction of travel, D numbers and offset values, and the overcutting and alarms that occur in start-up and cancel blocks.
Explains with an example the relationship between machine and work coordinates, what selecting a G54–G59 work coordinate system means, how to repeat the same program on several vises, and the accidents that happen when the wrong offset is chosen.
Explains with a facing example how lathe G96 constant surface speed control changes the spindle speed according to the X diameter, why a G50 maximum spindle speed limit is needed, and when to return to G97 for threading and drilling.
Explains with an example the difference between lathe G99 feed per revolution (mm/rev) and G98 feed per minute (mm/min), how to convert between them, how they correspond to machining center G94/G95, and accidents caused by mixing up units.
Explains with an example the structure of calling a subprogram with M98 and returning with M99, the P number and repeat count L, how to machine the same slot at several positions with an incremental subprogram, and the types of call errors.
Uses a two-pass lathe OD example to explain the calculation cutting time = distance ÷ feed per minute, conversion from feed per revolution, non-cutting time such as rapids and tool changes, and why simulated time differs from the actual cycle time.