Tool Length Offsets - OLd Spindle

This tutorial will teach you how to measure and set your tool length offset(TLO).  For each different tool used in a program, the machine needs to know the length of the tool to compensate for.  Use the equation below to calculate the TLO.  For example, if you measure your tool length to be 0.9 inches, the corresponding TLO will be -(3.6-0.9)=-2.7.

TLO = - (3.6 - Tool Length in Inches)

The Pocket NC does not have an electronic system for measuring tool length.  This means that the user will have to predetermine the length of each tool before its first use and have a means for repeating the position at which the spindle clamps each tool.  We recommend two options, using a shaft collar or using a tool with 1.5”+ of shank so that it is stopped against the back of the spindle.ome of these were included with your Pocket NC, but you can also order more if you need to here(Size 4, ID 0.115").

Once you know the TLO values for all of your tools, you can set them in AXIS.

Method 1(Preferred method)

1.  This is done in AXIS by clicking File>Edit tool table as shown in the image below.  If the window pops up for you, go on to step 4.  If it doesn't, go to step 2 for a Mac or step 3 for a PC 

2.  The Mac my be having issues with the SSH connection. Two situations likely have occurred at this point.

2a. You have had your Machine interface open for more than about 10 minutes and you need to restart the machine by powering it down and then restarting it to get this edit tool table option to work this way. You can also try option 2b directly below or go to the second method found below after the Windows explanation.

2b.  You may have opened the tool table properly and due to where it is on the Linux screen you need to open it by going down to the Dock and right click on the Xming Icon and select “Show All Windows” This will likely bring up the tool table and you can select it from there. If this does not work go to the second method found below after the Windows explanation.




3.  With a PC you are likely having an issue where the Tool Table is off the screen and you need to bring the window up onto the screen. This can be done by hovering over the Xming icon until the two window comes up. Then right click on the tool table window and select “Maximize”. 

4. To set the tool table to reflect our earlier example, we will change the value of Z to -2.7 and the tool diameter to 0.125".  It is important to remember that this value is the diameter of the tool, not the diameter of the shank.  After updating the values for your tools, press "Save File" and then "ReRead".  Once you are done with your updates, quit to the main AXIS window.  Once in the main AXIS window, click File>Reload Tool Table to update the offsets.

After you have reloaded the tool table, you can check that the offset took by typing G43 H1 and pressing enter (that is if you changed tool 1, type H2 if you changed tool 2).  Once you have entered G43 H#, you will see TLO Z changes to the number you input in the tool offset page.  Most tools will fall between -2" and -3".

If you are consistently using the same tooling throughout your programs, you can bypass having to change the tool offsets by making sure you use the same tool numbers when generating toolpaths in you CAM software.

METHOD 2(If Method 1 did not work)

1.   If you have a Mac Open up a secondary Terminal window by right clicking on terminal and selecting “New Window”.   If you have a PC right click on “Putty” and select your desired boot option to open a second window.

2.  In the second terminal window, sign into your Pocket NC.  Then type in the command “scite” (Command sensitive) to open the text editor.

3.  Once Scite opens, go to File>Open.

4. Select “pocketnc” (red arrow) → “linuxcnc” → “configs” → “ARM.BeagleBone.PocketNC” → Change to “All File” (Blue arrow) →  “tool.tbl”

5.  With “tool.tbl” open, edit the tool table as needed. In this format you must use the notation defined below.

Example -       T10 P10 Z-3.21 D0.123; Tool Ten
Description -    Tool# _ Program# _ Zoffset _ Diameter of tool _ ; Tool notes

When in doubt follow the notation of the other tools. 

6.  If the asterix (*) is by the file name (see blue arrow above) the file is not saved. To save the File go to “File” → “Save”.

7.  Once the Tool table file has been edited go back to the Machine interface window.  Two windows can be open at the same time if you follow step 1 of this method.

8.   In the machine interface window go to “file” → “reload tool table…”. 

Important - Without doing this step you will not be able to use the new tool offset values in machine kit, unless you restart the machine.