This process does not actually twist the tubing it nearly swages flats on the tubing while the user advances and rotates the tube. Unlike a power hammer the nibbler has a definite stroke, this creates a uniform deformation on the surface of the tube.
After each pass the lower tool is raised a small amount to gradually create the finished form. On the first pass a shallow pattern is impressed into the tube. Once this initial pattern has been impressed the work will naturally follow the lower die as the grooves in a screw follows the lands in a nut; this maintains a consist ant pattern.
 |
 |
Fig 1 |
Fig 2 |
fig1 and fig 2 are simplified functional views of a Pullmax type nibbler with punch up and the punch down.
 |
 |
Savage 3/8 plate nibbler |
This was my first machine a Savage nibbler. It will nibble 3/8 plate!. I had big plans to restore it then a Pullmax P5 became available and I have not really looked at since. Restored and modified, this machine could be sweet.
 |
 |
Pullmax P5 Side View |
Front View |
My second machine a Pullmax P5. The P5 runs much faster than I want it to so I added a VFD (seen on the right) to control the speed. The handle seen in the front view controls the length of the stroke (three strokes 0.040" - .125" ). Although not easily seen the steel bamboos were also partially made with the nibbler .
 |
Bowl |
This bowl was made in about 20 minutes. Most of the time is spent changing tools. The edge stretching tool can be seen in the tool holder of the front view. Excuse the rust I dug this out of the scrap pile.
 |
Spindle Detail |
Incising on square section and between the lands of the twist were make with a chisel in the upper tool holder. The swaged section uses the same fuller dies used to make the twist.
Here is my newest machine:
 |
CN900 Co-ordinate copy nibbler |
Greater capacity and more features than my P5 plus it has a variable speed pulley soI can elimintate the VFD.
For additional information visit the US Patent office website. USPTO Pullmax Patent