THREAD/AUTO[,LEFT-RIGHT][,IN-OUT],START,s,LENGTH,l,DIAMTR,d1,d2,INCR,s1[,s2]
[,ATANGL,a][,PULBAC,d,a][,BOTH],[PITCH,p][,REPEAT,r][,OPSTOP][,OPSTOP]
[,SELECT,s][,CLEARP,x,y] [,FEDRAT,f1,f2,f3,f4,f5] [,START,s,n][,TAPER,x,y,a
The THREAD/AUTO command allows you to program an entire threading operation by means of a single statement.
You can specify a variable number of data items, according to the options you desire, and you can specify them in any order. Each item consist of either a vocabulary word only or a vocabulary word followed by one or more entities in a fixed order.
You must always specify the following data items:
START LENGTH DIAMTR INCR
The THREAD/AUTO command assumes a point tip cutter and hence ignores the CUTTER statement in effect.
The THREAD/AUTO process generates a series of passes, cutting into the part a specified amount on each pass until the specified total depth has been reached.
Each pass is composed of four moves:
5. The Step-in move, which moves the cutter into the part an amount specified by INCR. This move is perpendicular to the centerline unless specified otherwise by ATANGL.
6. The actual threading move, which is parallel to the centerline unless specified otherwise by TAPER.
7. The Pull-Back move, which moves the cutter away from the part. This move is perpendicular to the centerline unless otherwise specified by PULBAC.
8. The Return move, which moves the cutter back to a position from which the step-in move for the next pass can be made. This move is always parallel to the centerline.
Following are descriptions of the various THREAD/AUTO data items:
RIGHT or LEFT
RIGHT Specifies a right hand thread. Threading moves are made in the direction of decreasing centerline dimension, from tailstock towards the headstock. RIGHT is the default condition.
LEFT Specifies a left hand thread. Threading moves are made in the direction of increasing centerline dimension, from headstock towards the tailstock.
OUT Specifies an external thread. The stepover from one pass to the next is made in the direction toward the centerline. OUT is the default condition.
IN Specifies an internal thread. The stepover from one pass to the next is made in the direction away from the centerline.
START,s Specifies the centerline dimension of the point where the thread move is to start.
LENGTH,l Specifies the length of the thread move, measured parallel to the centerline. The length is measured from the centerline dimension specified by START,s in the threading
direction specified by RIGHT or LEFT.
DIAMTR,d1,d2 Specifies the major and minor diameters of the thread. The order in which the two diameters are given is immaterial; the larger is used as the major diameter and the smaller as the minor. External threads are cut from major diameter to minor; internal threads from minor to the major.
INCR,s1 Specifies a constant incremental distance to cut into the part on each pass. The distance is measured perpendicular to the centerline.
INCR,s1,s2 When you specify two values following INCR, the larger is used as the depth of cut for the first pass and the smaller as the depth of cut for the final pass. Intermediate passes are made at proportionately smaller depths to provide a smooth transition from the starting depth to the final depth. If you specify two equal depth values, the result is the same as if you specified a single value.
ATANGL,a Specifies the angle between the step-in move and a line perpendicular to the centerline. It is positive if the step-in move is in the same general direction as the thread move;
negative if opposite. The angle must be less than 90 degrees in absolute value.
ATANGL,0 is assumed.
PULBAC,d,a Specifies the distance and angle of the pull-back move. The distance is measured from the end of the threading move in a direction perpendicular to the centerline. The angle is measured between the pull-back line and a line perpendicular to the centerline. It is positive if the pull-back move is in the same general direction as the threading move;
negative if opposite. The angle must be less than 90 degrees in absolute value.
PULBAC,.5,0 is assumed.
BOTH Specifies that both the treading move and the pull-back move are to be made in threading mode. By default the pull-back move is NOT made in threading mode.
PITCH,p Specifies the number of threads per inch. For multiple start threading you must specify PITCH in the THREAD/AUTO command. Otherwise, you may specify PITCH either in the THREAD/AUTO statement or as a regular post processor statement preceding the THREAD/AUTO statement.
REPEAT,r Specifies the number of time the final pass should be repeated. The final pass is made at least once; the REPEAT count specifies the number of additional times it should be made. If you do not specify the REPEAT, REPEAT,0 is assumed; that is the final pass is made only once.
The THREAD/AUTO Clearance Point
The THREAD/AUTO data items SELECT, CLEARP, OPSTOP, and OPSKIP provide various options relative to a move to a clearance point that is made on each repetition of the final pass except the last.
These words are ignored if REPEAT,O is given or implied since the final pass is made only once in this case.
SELECT,s Designates the point at which the optional operations are to be performed. SELECT,1 selects the intersection of the pull-back move and the return move and is assumed if SELECT is not specified. SELECT,2 selects the intersection of the return move and the step-in move.
CLEARP,x,y Designates the x and y coordinate of the clearance point. After the cutter reaches the selected point, it then moves to the clearance point, an OPSTOP command is output, and the cutter then moves back to the selected point, after which the regular path is resumed.
If you do not specify CLEARP, no clearance move is generated.
OPSTOP Is not necessary and is ignored if you specify CLEARP since an OPSTOP command is automatically output at the clearance point. If you specify OPSTOP without CLEARP, an OPTSOP command is output at the SELECT point.
OPSKIP generates a post processor OPSKIP/ON command preceding the move to the clearance point and an OPSKIP/OFF following the move from the clearance point back to the SELECT point. This causes block delete codes to be output with the moves to and from the clearance point. OPSKIP is ignored if you do not also specify CLEARP.
FEDRAT,f1,f2,f3,f4,f5
The FEDRAT data item can be used to specify the feed rate for each of the four moves of a regular pass as well as the move to and from the clearance point.
Each feed rate may be specified in one of these ways:
1. A non-zero scalar f causes the postprocessor command FEDRAT/f to be output preceding the move.
2. The word RAPID causes the postprocessor command RAPID to be output preceding the move.
3. A scalar zero causes no feed rate command, neither FEDRAT nor RAPID to be output preceding the move with the result that the previous established FEDRAT command remains in effect.
If no FEDRAT command is specified the following is assumed:
FEDRAT,RAPID,0,RAPID,RAPID,RAPID
Multiple Start Threading
START,s,n You can program a multiple start thread by using this alternate form of the START data item. The entry s specifies the centerline dimension of the point where the thread move is to start. The entry n specifies the number of threads to be cut. The first thread is started at the dimension s and each additional thread is offset in the direction opposite the threading direction a distance equal to the lead divided by n, where the lead is the reciprocal of the pitch. You must specify PITCH in the THREAD/AUTO statement when you program multiple start threading. If n is not specified it is assumed to be 1, with the result that only one thread is cut.
Tapered Threading
TAPER,x,y,a You should specify TAPER only if the thread is not parallel to the centerline. The entries x and y are the centerline and cross slide dimensions, respectively, of any point on the major diameter of the thread, if external or minor diameter, if internal. The angle of taper, a, is measured between the tapered line and the centerline and is positive if movement along the taper is in the general direction opposite the stepover direction; negative if in the same general direction.
The thread move is started at the point where the tapered line intersects the line perpendicular to the centerline at the START dimension.
With a non-tapered thread, the position of the thread relative to the centerline is established by the DIAMTR information, but with a tapered thread, the position is established by the tapered line. The only purpose of the DIAMTR information is for specifying the thread depth. In the expression DIAMTR,d1,d2 the values of d1 and d2 individually are not important – only their difference. The thread depth is calculated as follows:
depth = (major diameter – minor diameter) / 2