An easier possibility for the home machinist is to use a more sophisticated insert. Dorian makes some nice dovetail cutters that lay down the insert. If we lay the insert down, we had better be prepared to twist it a bit or we are going to lose the 60 degree geometry. Make matters worse, we are forcing the whole edge to cut, and not just the tip radius (hence the nasty steel needle chips). I’m using a very simple insert mounted flat (neutral rake). An error of 0.0067″ and one cutter is doing all of the work.Īnother thought is to find a way to introduce positive rake. Once could assume that an error in positioning one insert versus the other of 0.001″ would therefore use up about 1/7 of the advantage of having a second cutter. So, in the 1/2 revolution before one of the two cutters moves into position to take a cut, the workpiece
The trial cuts I made above were done at 900 rpm spindle speed and probably 3 inches per minute feed rate– 1/2 handwheel turns per second and 1/10″ per turn. The tolerances involved are pretty tight. One could contemplate building a 2 insert cutter, but it would be important to position the each insert to take very precisely the same depth of cut. Thoughts and Tidbits for Future Cutters and Other Would-be Cutter Makers… The difference in vibration and surface finish was very noticeable. If we move the workpiece right to left, we are performing conventional milling. This yields a better surface finish as it is supposed to, because it requires less cutting pressure. As the piece moves from left to right, the cutter rotates clockwise, and the cutterĪnd workpiece are moving in the same direction.
In the picture above, if I am cutting left to right, I am climb milling. That little 4-40 tap might break off in the hole! I used a piloted tap and some Tap Magic: worried To position it I laidĪn insert in place and then used the X and Y handwheels to get the bit Successive passes with the end mill are all it takes… While milling and used a 30 degree angle block clamped to the table to I placed the cutter in a V-Block to hold it securely This is my first “real” work on the mill, so it should be interesting. We have to hold a piece of round stock at exactly the right angle to the X-axis in order to make the cut.
The mill so that I can take an endmill and cut the pocket that the insert sits in until it’s deep enough that the insert’s cutting edge is on the centerline of the cutter. Basically, I need to set up the dovetail cutter on There’s not a tremendous amount to do on the mill, but it would be hard to make this cutter without one. Not bad, eh? Ready for the mill work next. I alsoĪpplied a little file and sandpaper to it while it was spinning there…
You’ll be free soon my pretty!įlipped it around and faced off the base. Once the shank is turned down, turn your compoundĪround so you can cut the 60 degree taper that is the head of the cutter…īuck Chuck! Note that I cut the same taper as a chamfer to finishĬarbide insert parting off tool. Whew doggies: she’s so hot she’s smoking! Start turning the shank down to 1/2″ diameter… It cuts very accurately, and I can hold a thousandth without really trying to hard, so the 2 hours didn’t require much focus just enough to stay out of trouble. The work shown below in the photos took me about 2 hours to do on my Lathemaster 9×30 lathe. Given the piece I had wasĪ bit long, I also center drilled so I could use a live center to support it for greater rigidity. Face and turn it for squareness before starting. The first thing to do is put some 1″ or so round steel stock into the lathe. I wanted something compact, with a 1/2″ shank, and easy for me to machine. This was not hard to do as the shape is very simple and the key dimensions are readily available on the Internet: The first thing I had to do was make a 3D model of a TPGB insert. It seemed like a good size for the toolholder dovetails, and I try to keep reusing the same insert types so restocking isn’t so painful to manage. The TPGB 21’s are right in the middle of the insert sizes my boring bars use. The TPGB insert style I chose was based on some boring bars I had. Indexable Tooling is very economical in that respect. I wanted an indexable dovetail cutter to make it easy to swap in new cutting edges as needed.
So, I made this cutter as my first “practical” mill project. To do that I have to be able to cut the dovetails. I wanted to make Aloris-style QCTP holders for my lathe. Indexable Dovetail Cutter for CNC Joineryĭovetail joints are both strong and aesthetically pleasing, but they require a special dovetail cutter.