There are 2 way to approach this. I am going to go with the one that I think will best help out in this case.
this is what the cut should look like when you are finished.
You will need a skew and a parting tool. Technically you can do it with each of those by themselves but often times I find the parting tool does not yield a good clean 90 degree corner so enters the skew. You can use other types as well, i.e. side scraper with a pointed tip, flat nose scraper among others.
First you need to take the width of the band and get a good idea of how many chisel width cuts you will have to make. For my parting tool it is 3 times the width, your number will be unique to the chisel and how it is ground.
You want to cut no more than HALF the width of the parting tool on each cut, I like to use 1/4 of the width. The reason for this is the first cut will have the majority of the parting tools width on the bushings. from there you branch over to the next cut and the position will change but your ending point will not.
You do not want to make it to the end but super super close reason for this is to true up the corner and that will require another cut or 2.
In this photo I have 2 cuts to clean up greatly. the one to the left of the X you see a ring about half way down the cut, that has to come out as that is the #1 cause of failures on this cut.
If you don't this is how it will look.
the band will likely have a gap that prevents it seating properly.
If you take your skew and hold it at an angle you will quickly see that very tip is close to a 45 degree angle and can easily get into that corner and make you a true 90 degree cut, the direction of the cut will be left to right, or right to left. You are ONLY cutting from the tip of the skew. If you over cut slightly that will not hurt as that is where the glue will pool up at plus you will not see it from the outside.
In this photo the white crusty areas is where I used the skew, this skew was not terribly sharp either but it serves the purpose here. My skew is also slightly rounded and not true flat so I can cut at any part along the width of the edge. From knife making rough areas make excellent glue surfaces, more surface material to bond with, the best surface is bead blasted, second best is sanded surfaced on BOTH items.
this is a side shot. it *IS* sloped in slightly but not to great. One big problem that I have seen is you add glue, push the band on and the glue squeezes out all over the place and pushes the ring off. the relief cut in the back helps this greatly.
Here it is again with the band in place, not glued. As we can see there is a ring on the very edge, technically I could use the skew and touch up that high ridge to make it flush but you really have to get a magnifying glass out to see this ridge. Also this is just a test section I was using and not a full pen.
The other thing to note is on the inside of the band is a sloped ridge which allows for a higher rounded corner. I am not sure if they are on all the kits but there is on this one, it is not much at all.
Also worth noting this is the same cut that you make on the foot of a bowl to hold it in the chuck jaws, but on bowls you want them to have more of a slant.
Hope this helps.
