Machinery's Handbook, 31st Edition
1368 CNC FIXED CYCLE CODES the bottom of the hole. The dwell period should be a minimum of two spindle revolutions to allow for a full clean-up in case 50 percent spindle speed override is in effect. To calculate minimum dwell, divide 60 by the spindle revolutions (r/min): ( ) ⁄ r min 60 Minimum Dwell seconds = To convert to milliseconds, multiply the result by 1000. Example: For 750 r/min, the minimum dwell will be 60 / 750 × 1000 = 80 ms. Deep Hole Drilling (G83): The G83 fixed cycle is used mainly for deep hole drilling using the following format: N__ G99 (G98) G83 X__ Y__ R__ Z__ Q__ F__ From the R-level, the drill will cut by the amount of Q__, which specifies the depth of each peck. When the peck depth Q__ is completed, the drill retract to R-level, than rapids back to cut another depth—there is small non-programmable clearance between the cuts, that is part of the cycle (See Fig. 17). A general rule of peck drilling is that the greater the Q__ amount is, the fewer pecks will be generated and vice versa. Some controls allow programming of the actual number of pecks required. No peck motion will ever exceed the final Z__ depth.
G98
G99
Z0
Q
d
Q
d
Q
Z-depth
Fig. 17. G83 Fixed Cycle. Chip Breaking (G73): The G73 fixed cycle is used mainly for chip breaking and has the following format N__ G99 (G98) G73 X__ Y__ R__ Z__ Q__ F__ Its basic function is the same as for G83, but the drill does not retract after each peck, only after the last peck. In both cases, the G98 or G99 retract method will be applied for the last peck only (see Fig. 18).
G98
G99
Q
Z0
d
Q
d
Q
Z-depth
Fig. 18. G73 Fixed Cycle. Right Hand Thread (G84): The G84 fixed cycle is used for cutting a right hand thread and has the following format N__ G99 (G98) G84 X__ Y__ R__ Z__ F__
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