The bolster is not only stylish, but it adds weight to the middle of the knife and protects the end grain of wooden handle scales. The thickness of the bolster will usually be the same as your scale thickness. I like 1/4" thick stainless stock and find 1/4" or 5/16" scales a good match. 416 or 304 stainless makes a nice bolster, but bolsters can be G10, bone or whatever tickles your fancy.
Although you could make bolsters entirely with hand tools, files, hacksaw and so on, a drill press would be considered an asset when making the pin holes. Start with the most powerful tool in your shop, the permanent marker.
Be sure to leave enough space between the pieces for your hacksaw or band saw blade to get through when you separate L & R later on.
With the left bolster piece positioned exactly where you want it, clamp with vise-grips and drill the pin holes.
If you want to make a block like I use for the drill press see my page on Drill Press Block #3 for instructions.
Here I like to put a temporary pin to hold the L bolster piece to the tang. Insert it into one of the holes. When the L and R pieces are perfectly lined up, clamp with vise-grips and remove the temporary pin. Drill through the L piece, and tang all the way through the R piece.
Unclamp the pieces and finish the fronts.
After drilling (if your drill press is nice and square) you can put some temporary pins and finish the fronts. I use plain old 1/8" rod from Home Depot.
Remember that the bolster fronts will be nearly impossible to finish once pinned to the knife.
Finishing means, shaping, sanding and buffing. Here are the two pieces after some work on the buffing wheel.
Although there are no rules about what pins to use, generally the same material is used for pinning. E.g. brass pins on brass bolster pieces. There is nothing to say that you cannot use pins to contrast or use mosaic pins.
With the pins cut about 3/16" longer than required for a flush finish, clean them with fine sandpaper so they shine. Clean the pin holes on the bolster with acetone so that no cutting oil or debris is in the holes. Clean the tang with sandpaper and sand the mating bolster pieces. The aim here is nothing remains which may be visible.
No flecks, filings, dirt, fibers or hair is allowed between the metal pieces...period. Brush, blow, clean 100%.
You will want to scuff the interior surfaces with coarse sand paper, (I use 60 grit) and clean all surfaces with acetone or high-test rubbing alcohol.
This is where I like to use a small amount of Acraglas to seal the bolster pieces to the tang. This prevents moisture migration and ensures the joint is easy to keep clean. Be careful not to use too much epoxy. Also be careful not to allow the epoxy up into the pin holes. Epoxy in the holes can appear as a ring around the pin when finished.
A hydraulic press the your friend when it comes to squeezing the bolster pieces on to the tang. But how do we squeeze them and press the pins at the same time? The trick is to provide some precise spacers. Two pieces of 1/8" steel with a 3/16" slot cut into them for allowing the pins to stick through. This type of plate will let us squeeze the bolster pieces tightly to the tang, and squash the pins a tiny bit. See my picture, as a small stack of flat washers will work for this as well. If you can figure out a way to do this with a hammer, please let me know.
Once we have the bolster pieces pressed firmly to the tang and the pins squashed just enough to hold everything together, it's time to put the big squeeze on. A hammer on the anvil works at this point too. We need to squash the pins and leave zero space in the pin holes.
Shaping the bolster from here is academic. I use the files, small wheels, drums on the drill press or whatever is needed to shape and clean up.
Be careful about heat. Too much grinding will burn the Acraglas. If you are using regular 50/50 epoxy you'll smell it burning and it's not pretty.
Well there you have it. One way to attach a front bolster. Again, not the only way to do it, but one that I can say that produces great results. Please let me know if you have tried this and if you have any suggestions on how to improve the process.