Have a look at 5axiskins.c in the linuxcnc/src/emc/kinematics folder. That kinematic is used in the simulation configuration found at /configs/sim/axis/vismach/5axis/bridgemill/5axis.ini
Inside '5axiskins.c' you will find some commentary and the definition of the DEFAULT_PIVOT_LENGTH that you will probably want to change to 160:
/********************************************************************
* Description: 5axiskins.c
* kinematics for XYZBC 5 axis bridge mill
*
* Derived from a work by Fred Proctor & Will Shackleford
*
* Author:
* License: GPL Version 2
* System: Linux
*
* Copyright (c) 2007 Chris Radek
*
* Notes:
* 1) pivot_length hal pin must agree with mechanical
* design (including vismach simulation) and augmented
* with current tool z offset
* (typ: mechanical_pivot_length + motion.tooloffset.z)
* 2) C axis: spherical coordinates aziumthal angle (t or theta)
* projection of radius to xy plane
* 3) B axis: spherical coordinates polar angle (p or phi)
* wrt z axis
* 4) W axis: tool motion. Negative values increase tool radial
* motion example: drilling into body at b,c angles
* 5) W axis motion is incorporated into the motion of the
* joints used for X,Y,Z positioning and no motor or
* hal pin connections are required for the joint specified
* as JW. However, a joint must be configured for W to
* support display of the W axis letter value for
* complicated reasons. (motion/control.c computes joint
* positions only for the number of configured kinematic
* joints (NO_OF_KINS_JOINTS) and the joint positions
* are needed to display axis letters via inverse
* kinematics.
* 6) If no coordinates module parameter is supplied, kins
* will use the required coordinates XYZBCW mapped
* to joints 0..5 in sequence.
* 7) Multiple joints may be assigned to an axis letter
* with the module coordinates parameter
*
If a coordinates module parameter is supplied,
* the kins will map coordinate letters in sequence
* to joint numbers beginning with joint 0.
* 9) Coordinates XYZBCW are required, AUV may be used
* if specified with the coordinates parameter and will
* be mapped one-to-one with the assigned joint.
********************************************************************/
// non-required coordinates (A,U,V) can be set by using
// the module coordinates parameter
#define REQUIRED_COORDINATES "XYZBCW"
#define DEFAULT_PIVOT_LENGTH 250
Note that this kinematic creates a hal-pin called 'pivot_length':
struct haldata {
hal_float_t *pivot_length;
Make sure you provide the required value (ie your 160mm plus any tool-length offset) in your hal. As in the file '5axisgui.hal' in the 'bridgemill' simulation configuration. You will probably want to remove the stuff for the vismach script so you will end up with something like this:
# compute pivot-length needed for 5axiskins
loadrt sum2 names=pivotsum
addf pivotsum servo-thread
setp pivotsum.in0 160
net :tool-len <= motion.tooloffset.z
net :tool-len => pivotsum.in1
net :pivot-len <= pivotsum.out
net :pivot-len => 5axiskins.pivot-length
