I have made dozens of these, and they are pretty good kits. There are just a few tricks to making them work well. I always turn the tenon, or if I use the short blank method, then I face the edge a bit. This way, I know I don't have an angle.
I check and double check the blank length. If you get too excited with the trimmer, the pen won't work.
The big trick is to make sure the tube being pressed into the centerband is clean. A small bit of glue or junk here will deform the inside of the tube, and things will get sticky. Sometimes, the CB, or the tube will need a few passes with a file to get a perfect fit. The inside of this assembly must accept the transmission with no binding.
The inside of the end ofthe centerband that faces the nib must fit over the lower blank without binding. This in my experience, is where most of the failures are. If the lower blank is even the slightest bit oversized, the pen won't work. On some platings, a light touch with the file is necessary to open up the inside of this part just the slightest bit.
On a few batches of chrome ones, the nib opening is just a bit tight. A couple of touches with a very small file will allow the refill to extend and retract without binding.
This seems like a long list, but it's not really too bad. Most of it is just good penmaking practice. The final result is a smooth, reliable pen.
The flat top double twist American pens are always among my best sellers, and I always get requests for them. I try to steer people to fancier pens, but these seem to be favorites. They are a nice, medium size for both man and women. They have a fairly classic design, and they look nice with both wood and acrylic.
Dave