By: Jeff Davis

The main problem with using a Drill-Mill for CNC work is the fact that the Z-axis has only 5" of travel. You must keep this in mind when choosing your jobs for this machine. I found that if I was only using end mills and I was not going any deeper than 5" everything is fine. The real problem happens when you have to use a drill. Standard jobber drills are very long and the drill chuck is long too. I decieded to purchase a full set of "Screw Machine" length drills as seen below. I have three sets, Number, Letter and fraction sizes. The longest drill is the 1/2" drill and it is 4" long. This has helped to keep my working Z area usable.

You might think that all you have to do is raise the head if you need to have a long tool, then lower it back again after your done. Well not so easy when you don't want to loose your X-Y (0,0) location that you set at the begining of the job. There are others who have setup a way to locate the head back where it was before you moved it, but it would be nice to not have to do this at all.

To the left you can see the three sets of screw machine length drills I have. Click on the picture for a larger image.

What I want to do is have standard tooling that will all be the exact same length, this way I will not need to change my head height and risk loosing my 0,0 location. If I can design a tooling jig that will allow me to set all the tools to the same length, then two things will happen.

1) I can work my job without moving the head. 2) I will only need to set the Z-axis zero once, all the tools will be the exact length so changing them will not change the Z zero setting. See below, I am not there yet but I'm getting close to the longest tool, the drill.

The tooling to the left from left to right. (1/8"EM, 1/4"EM, 3/8"EM, 1/2"EM and the drill chuck with a screw machine length drill.) Using end mill holders I was able to get close to the length of the longest tool, the drill. (The 1/8" & 1/4" EM have extensions I made.) Click on the picture for a larger image.

I'm going to need to make extensions for all the end mills in order to get them longer. As you can see the drill and chuck is about 9" long.