There is one other element to peening bolsters that is often the nemesis of newbies. The tang hole needs to be at least 5-10% larger than the pin. If the tang hole is a snug fit, like the bolster hole, the pin will start to bulge a tad there, and raise the bolster a tiny bit off the tang. It takes all sorts of serious whacking to get it to lay flat....if it ever does. I can look at the bolsters on many new makers knives and see that gap caused by too tight tang holes. I also put a small chamfer on the bolsters and the tang where they meet ( on the inside...not the outside) just to be on the safe size..
As said, the bolster hole should be reamed....preferably with 5 degree taper carbide reamer ( or similar) .....to give it a slight taper. The pin will then expand to seal this extra space, and lock the assembly solid and tight forever. If you just do a small chamfer on the hole rim, you may well grind that whole area off in the finishing and shaping...and the bolster will pop right off.
As Stan pointed out - NEVER put glue in the rivet hole ,or it will show up as a circle around the river - maybe now, maybe later. The pina and the hole need to be free of polish, grit, and any oil/dirt/glue, etc.
What I do with folks who want help riveting a bolster on is suggest they take a piece of flat stock and cut two one inch pieces and a six inch piece. These will be the tang and the bolsters. Don't worry about grinding them flat, this is just practice. Drill one bolster pin hole through the assembly, slide in a pin, and drill the second hole ( Don't even think about drilling both at one time). Then enlarge the tang holes with a drill bit a few numbers larger. Cut the pins one to one-and-a-half diameters longer than the stack's thickness.For a 3/8" stack and 1/8" rivet pins, the pin should be .500" to .550" long, with flat filed ends.You can file a tiny chamfer on one end of the pins...the key word is tiny. Place a piece of thin shirt cardboard ( about 1/16" thick) on the anvil or other hard, smooth, and flat metal surface. The cardboard is to allow the pin to move a bit out of the other bolster when first starting the peening. Place the assembly on the cardboard/anvil, hold it down snug with two fingers, and lightly peen the rivets with the round end of a ball peen hammer. Just five or ten light taps to start mushrooming the heads. Turn the assembly over, and remove the cardboard. Peen the other side. Flip over again and work the heads with medium taps...flip and tap, repeat until the rivets are fully mushrooms and larger than the holes. If there is too much sticking out still ( because you left too much to start with) file it down until there is just about 1/16" sticking out. Now you can use the planishing side of the ball peen hammer to really set the rivets solid. Polishing the hammer face is a good idea for a smooth finish.
From there you just file and sand the pins flush and finish the bolsters. I don't shape or smooth the bolster beyond basic shape until the handle is on the knife.
Once the procedure is fully understood on practice metal, go and do your knife and bolsters.
Those who do a lot of bolster riveting on a larger scale, use a hydraulic rivet press to do the job....but it requires learning the skill before you take that on.
