Tools - Tool holder for QCTP

Although this is a pretty simple build, I have created measured drawings as a time save for anyone else who would like to make these:

Note: Drawings updated Oct. 22, 2013 to add dimensions for the OXA QCTP.

Drawings in PDF format: https://docs.google.com/file/d/0Bykt5WZ092aWTTJ0WTRjZ2UyZnM/edit?usp=sharing

Drawings in LibreOffice Draw format: https://docs.google.com/file/d/0Bykt5WZ092aWTDFsOXJnZER1dnM/edit?usp=sharing

The Dovetail

The dovetail cut (which attaches the tool holder to the QCTP) is the most critical cut, and precision of both depth and width is required.

Start the dovetail cut using a 3/4" end mill cutting in the center of the workpiece. Them, using a 60° dovetail cutter cut out the two side to the required width. I determined the required width using my setup by trail and error, and then recording the final positions of the dovetail cutter for each side. By repeating these measurements on subsequent pieces I was able to make the cuts fairly quickly.

Note in the picture to the left (the initial cut with 3/4" end mill), I have also constructed a work stop so I can quickly position (or re-position) a series of workpieces very quickly. Using the method for my initial run, I was able to make the initial 3/4" cut in each of three workpieces, and then put them each back in place to complete the dovetail cuts. This greatly reduces the number of tool changes required, and eliminates having to do setup measurements for every single piece (except the first one).

In this photo (left), the final dovetail cuts have been made.

Cutting the tool groove is quite simple. A 1/2" end mill is positioned in the center of the final groove position (the final groove will be 0.520" width), and cut to the required depth. The cut is then widened to the final required size by climb milling each side an addition 0.010" (climb milling gives a smoother finish).

I have not shown drilling the screw holes for the various set screws, as this is quite straight-forward. The required screw hole positions are given in the drawings listed above.

I have also not shown (either here, or in the drawings), directions for other tool types such as boring bars. However, the plans given can be readily adapted to other tool types.

Here again is the completed tool holder (left) shown with a purchased tool holder on the right. Note that the purchased tool holder has been anodized black; in addition to being cosmetic, anodizing give the tool a harder surface. For this particular application, however, I do not believe that lack of anodizing will impair the functionality of the tool holder, so I will be using them as shown.

Update - Mass Production

Finally got around to using the aluminum cut-offs I bought, and made a whole bunch of tool posts - as you can see in the photo to the left. On the far left of the photo, you can see that I also made a bunch of dovetailed "blanks" for future use, in case I want to make boring bar holders or some other special kind of toolholder. You may also notice, in the back of the middle row of completed holders, a not quite finished toolholder - that's because I accidentally drilled the wrong size hole for the depth stop screw on that one - fortunately I checked before I messed up all of the others. I rescued the bad one by epoxying the screw into the hole - I'll see how it holds up in actual use.

I'll note here that it was faster to make 14 toolholders than to make one or two, in the sense that the time per holder was much less do to reduced set up time. BY using stops and other techniques, I was able to set up a small production line and run every blank through each step of the process in series, along these lines:

1. Rough out cut for dovetail with 1/2" end mill
2. Complete dovetail using dovetail cutter (with stops on the mill table to facilitate positioning)
3. Mill tool groove
4. Drill hole for depth stop
5. Tap hole for depth stop
6. Drill 1st hole for tool holding screw
7. Tap first hole for tool holding screw
8. Repeat 6. and 7. for other three holes

In the photo to the left you can see the basic set up for the "production line." You can also see that I got a new vise for my mill (and made a vise clamp for it), and this greatly speeded up the process as it was faster to use the new vise than my old screwless vise. In the picture I am roughing out the dovetail slot with a 1/2" end mill - using the vise and vise clamp, I was able to quickly position each blank in succession and mill to depth (with the help of the depth stop on the mill).

The mill table stops I made came in handy for completing the dovetail with the dovetail cutter (in fact, I had this job in mind when I made the stops).

Another time saving procedure I used was to de-burr the pieces after milling using a "scotch-brite" type abrasive wheel - this not only removed the burrs efficiently, it also improved the general appearance of the pieces by giving them a more polished finish. The photo to the left show the before (right) and after (left) appearance after deburring.

Finally, the photo to the left shows an improvement I am trying out. In the left of the photo, you can see the thumb nut as it is used in the "factory configuration." In this configuration, the thumb nut is used upside down (to provide a broader surface to contact the tool post), and locked in place with an ordinary hex nut. This works, but it's a bit fussy to adjust, and the hex nut is not convenient to use.

In my improved configuration, I made a flat knurled nut (9/16" diam., 1/8" thick) to provide the height adjustment, and used the other knurled nut to lock it in place. The bigger flat nut is easier to adjust, and can be locked in place without the use of a tool - quick and easy. Now I just have to make 15 or 20 more of the flat nuts!

Improved tool height stop

[Added Jan. 30, 2014]

This photo shows the improved tool height adjustment from another angle. After using this new configuration for a while, I have found it to be a big improvement over the simple hex nut, and I have converted all of my tool holders to this.

Ideally, I would have been able to purchase the knurled flat nuts, but I have been unable to find a source of these at a reasonable price. Instead, I made them myslef using the method shown below.

The first steps in making the knurled flat nut are as follows:

1. Drill a centered hole in a length of 9/16" brass rod, and tap for 10-32
2. Knurl a section of the brass rod, and chamfer the end
3. Using a parting tool, cut partway through the brass rod (see photo to the left) 1/8" from the end.

4. Chamfer both sides of the partial cut (see photo to the left)

5. Continue parting to part off the nut

6. Chamfer the rough edges (left by the parting tool) of the threaded hole

I used a countersink bit on my mill to do this, tightening the vise just enough to hold the knurled nut without marring it.

The completed knurled nut. One down, 23 to go!

I was able to get five or six nuts out of each section of knurled rod. I would then drill, tap, and knurl another section of rod and so on.

As an early experiment, I tried tapping the nuts after I sectioned them off, but found it was much more difficult to get a straight tap.

To repeat the measurements, each nut is made from 9/16" brass rod and is 1/8" thick. I estimate the cost of each nut at about $0.25 each (material only, not including labor). Unfortunately, this method of making the nuts results in a lot of wastage (using a thinner parting tool, would reduce the cost slightly).