Table of Contents
IntroductionManual Operation & Start-up Procedures
Programming in the ISO (EIA-274-d or G-code) Format
Canned Cycles
Subroutines (Macros) and Loops
Console Editing
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Definitition of TLOs:  Please look up ( ^ )  and to the right
Procedure for setting TLOs
Running Programs
Data Transfer PC<---> CNC
Demonstration Program
Credits and Copyright Information

Bridgeport Heidenhain CNC Mill
Programming & Operating Instructions

Chapter 7
Setting Tool Length Offsets (TLOs)


Tool length offsets (TLOs) amount to nothing more than the jog distance the Z-axis must travel from its fully retracted position to the position where the cutter makes contact with a Z-zero reference surface (usually the top surface of the workpiece). This is accomplished by "touching off" each cutter on the reference surface (using a feeler gage) and loading the jog distance into the appropriate TLO register. When each tool is "called," the appropriate TLO is accessed and used to offset the Z-axis origin.

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Procedures for Setting TLOs

  1. Make sure the quill is fully retracted and the Z-axis register reads zero at that position. If necessary, zero out the Z-axis register (in Chapter 2).
  2. Load each cutter into a toolholder, making sure it is securely held so it won't slip in use.
  3. Adjust the height of the table so that the longest cutter/toolholder assembly can be installed in the spindle without interfering with anything.
  4. Press the HAND WHEEL OPERATION h-hndwhl.gif (1094 bytes) key and press Z and h-ent.gif (1095 bytes)  keys to make the Z-axis active.
  5. Hand wheel the cutter to the Z-reference plane, using a feeler gage such as a 0.100" gage block.
  6. Press the EDIT program h-edit.gif (1076 bytes) key and move the cursor to highlight the "L" parameter in the appropriate Tool Definition block.
  7. Press the DATA TRANSFER dataxfer.gif (1095 bytes) key to transfer the jog distance displayed in the Z-axis counter into the Tool Definition block. Then press the EOB h-eob.gif (1062 bytes) key.
  8. Retract the quill back to Z = zero.
  9. Repeat the process for each cutter.

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Last updated on Friday, January 14, 2005 by Bill Hemphill