How to Make Better Bolsters

by John Lewis Jensen

First Steps Toward a Beauty of a Bolster

Because my work is so complicated, my first step is to draw and refine everything on paper, working out all of the issues in terms of design and proportions. Once this is done, I make about six Xerox copies of the drawing that will be cut and pasted to material as needed.

In the case of these bolsters, I had Timascus on hand already. It came precision-milled from the supplier in a 1/8-inch thickness. However, as you can see in the accompanying photo, there are some rough tooling marks that should be eliminated. The smoother the contact surfaces are to other contact surfaces, the tighter the overall fit of the knife parts. It is important and critical, to me anyway, that components be “air tight,” and that there are absolutely no visual gaps between materials.

I hand sand the flats. Even though I am technically using the 4-inch-by-36-inch belt sander, I am not turning it on, as that would be a bit too aggressive in this case. The piece is small and would be hard to hold against a moving belt. It could easily get away from me, which could damage the piece and/or my hands! I simply hand sand it with even pressure on a 320-grit sanding belt.

I’m not trying, in particular, to remove thickness, only to eliminate the slightly irregular tool marks. This takes a bit of elbow grease, especially with the material being titanium. I just want to smooth out the surface. I have carefully cut out the bolster section from my overall drawing and double-stick taped this shape down to the topside of the raw material that I want to be my front bolster.

As you can see in the accompanying photo, I have smoothed the surface. You can see the grit marks of the sanding belt, but the bolster material is certainly smooth and flat to the touch and sight. The process is repeated for both bolsters.

I use permanent double-stick tape to stack and adjoin the top and bottom bolsters together. I sand until all surfaces that will come into contact with other surfaces are completely flat. In this case, I remove the tool marks off the bottom of the top bolster (I don’t have to worry about the topside of the top bolster right now), and both sides of the bottom bolster. The latter will be coming into contact with not only the bottom side of the top bolster, but also with the knife body, as well as with table surfaces in sawing, grinding and drilling applications.

I do not overlap the strips of tape. Instead, I lay them down carefully, side by side, so that they lie on the same plane. Otherwise they could be off of square by a few thousandths of an inch.

Be careful to get the proper double-stick tape. 3M makes a permanent version (color coded red) and a not-so-sticky version (color coded blue). This can be confusing because the overall color of both packages is yellow plaid. Make sure you use the red version. The blue version will not hold up through the bolster-making process and is likely to fail to hold the pieces together in their proper places.

Layered Bolsters

In the accompanying photo, you can see the two Timascus pieces stacked and taped. Underneath this you’ll discern two more rectangles of material. These additional pieces are .0035-inch-thick rectangles of titanium that I have pre-cut. They are also going to be a part of the bolsters, as a sort of an under-liner of the Timascus. I felt the Timascus thickness was a bit too thin in regards to the proportions of the rest of the knife.

The additional bolster layer will thicken things up a bit, as well as give another visual element to the overall design of the knife. Another layer underneath the bolster will give the knife a dynamic and dimensional appearance. It is also one more layer to work with a file and/or anodize. I have been using this idea for a while; it’s more work, but adds a nice touch, something you don’t otherwise see on knives.

I have carefully double-stick taped all four bolster layers together and am now giving the assembly a good squeeze in a vise to secure everything in place.
I trim the excess tape from the sides with an X-Acto blade. This excess tape will get in the way otherwise, catch on work surfaces and clog up with grit when I start cutting. I suggest getting in the habit of working cleanly and orderly. It will save unforeseen headaches.

I also run a bead of Crazy Glue along the edges of the assembly to help secure everything in place and keep parts from moving and shifting as I start the initial work. It is important not to overstress or overheat the stacked layers during this critical stage of construction. Be careful not to melt the glue and tape. Until we get screws in place, it is important that the layers stay aligned.

After making sure the band saw and worktable are square, I carefully cut the bolster to rough shape, just outside of the design line. I try to cut as close as I can to the line, but still leave myself a little room for cleanup. The band saw makes some rather rough marks along the newly cut edges.

You want to give yourself enough room to grind out those marks without grinding into your profile. If you cut too close to the line, by the time you’re done finish-grinding the saw marks, the bolster could be undersize. The band saw does not cut curves. You can tweak the blade a bit, but you’ll have to take off large chunks of material at a time from in the curvy areas. Yes, lots of material and money end up on the floor!

On the grinder, using the back platen with table accessory, clean up the convex areas of the material stack only. Before doing this, you should knock off any rough burs created by the band saw on the bottom side of the material stack, using either a fine file or by running the stack across 320-grit sandpaper on a flat surface. The material stack should rest flat on the table, thus assuring square grinding.

There are two areas along the profile to stay away from for the moment, still leaving them rough, and therefore a bit oversized. These are the areas—shown with arrows in the accompanying photo—that share the outside profile with the rest of the knife. Blend those later after you know proper placement of the bolsters on the knife.

Now it’s time to clean up the concave areas with an oscillating spindle sander. This is traditionally a woodworking tool, but it works great for knifemaking and keeps all parts at precise 90-degree angles in relation to each other. I recommend finding an oscillating spindle sander with a laminate top, as opposed to a metal top. The laminate top will cause fewer scratches on your material as you’re moving it around and into the sanding drum.

The Aggressive Grit

You can also get several different grits of sanding sleeves. Start with the most aggressive grit sleeve to quickly erase the band-saw-blade marks. Again, this is a woodworking machine, so it does not have a lot of natural aggression. Compensate for this by using the most aggressive grit sleeves. As you get closer to a finished profile, change incrementally to the smoother grit sanding sleeves.

In the accompanying photo, you can see the difference between the now-smooth areas that were finished up using the sanding machine, and the still-rough, band-saw-cut areas. The small, hooked area of the bolster, as well as the tip in front, will be cleaned up later with a different tool ideal for tighter areas.

Apply Dykem steel bluing layout fluid to the general area on the frame of the knife where the bolsters will meet it.

Using the calipers, measure and lightly mark where (according to your full drawing of the bolster area of your own knife) you want the rear, bottom edge of the bolster to rest against the handle.

In the related photo, it’s easy to see, in the slight, rough overhang of the bottom-rear-most concave area of the bolsters (now lying in place on the knife), why I suggested leaving that part unfinished after the band saw cut. It is the area that will be blended once the bolster is secured in place.

Use a small, preferably copper-jawed, clamp to hold the bolster stack to the knife body. Copper-jawed clamps lock up precisely and don’t mar surfaces, as do steel C-clamps. Get in the practice of wiping off the contact faces of the clamp, even if just with your fingers. This will prevent any dust or grit from getting on your work, potentially scratching surfaces or preventing proper lock-up of the clamps to your work.

In the accompanying photo, taken from the rear side of the stack, you can see the area that has been left rough and overhanging on the top side of the bolster. Further on in the bolster-making process, it will be necessary to blend the outside profile of the knife with the areas that overhang.

Use a sharp-tipped scribe to trace the profiles of the finished bolster areas onto the handle where they will eventually be secured. You now have two placement marks showing where the bolsters will permanently reside on the handle. Until securing the bolsters to the frame, the registration marks consistently show you where the bolsters are supposed to touch the handle each time they are moved in the building process, whether intentionally or unintentionally.

Remove the drawing and tape from the top of the stack, and remove the stack from the clamp (it would be in the way now). Paint a layer of Dykem on the top surface. Lay the bolster stack in the proper position on the frame of the knife by lining the stack up with the previously scribed profile marks.

Between eyeballing the proper position according to my design, and then refining by measuring, I’m going to mark out the placement of holes to drill by scribing an “X” at the center point.

I’m now going to line up a center punch on the crosshairs, knock the top of the punch lightly with a rawhide or plastic mallet, and therefore register a mark for drilling my holes.

A Bit Closer to the Bit

I like to work as close to the drill bit as possible. My table only rises to a certain level, so I raise my work up closer to the tip of the drill bit by placing the bolster on a precision 1-inch-by-2-inch-by-3-inch block.

Make certain the table is square and level and that all work surfaces are clean, assuring a perfect hole.

Drilling into any material, and especially titanium, requires even pressure, and above all, patience. Proper drilling is done by penetrating the material in small increments, backing the drill bit out, then burrowing a little deeper into the material; in and out, in and out. Do not drill all the way through the material in one motion; you are sure to wear out your tools, as well as potentially break the drill bit off in your material.

The holes will eventually be tapped for 2-56 screws, so the drill bit to use here is a number 50. Drill bits come in regular, long and short lengths. I prefer the short bits because they are more than adequate as far as flute length goes. Rarely in knifemaking is any one hole drilled over an inch deep. The shorter the drill bit, the sturdier it is, which also helps eliminate wobble.

After drilling the first two holes, it is time to separate and clean up the four layers of the bolster stack. I use an X-Acto knife to wedge apart and separate the pieces.

Even though the stack was held tightly together, some small burs formed from the cutting, grinding and drilling of the material. The burs can start to push the layers apart and knock the stack “off square.” Visually, you may not see the unevenness, but you will later see and feel the difference when you try to screw things together that are supposed to be at perfect 90-degree angles in relation to each other. Take the time to catch it before it happens.

I use another type of scribe to scrape off the residual tape from all the surfaces of the bolster pieces. A little nail polish remover also helps with this. I prefer nail polish remover to straight acetone. The ingredients in nail polish remover make it work better than acetone alone.

I use a small riffling file to go over the drill holes on both sides of each piece, carefully removing burs. The curve of the riffling file ensures that I’m only hitting the area of material that I want to, isolating the cleanup to where specifically needed.

Take care to stay away from the edges. With a regular file, you’d be dragging it across the entire expanse of surface, causing unnecessary scratches, and you’d also run the risk of slipping and nicking the nice, square edges of your material. If you nicked them deep enough, they could be visible, which is unsightly and a mark of bad craftsmanship.

Marks of a Good Maker

I mark the underside of all four pieces using a number set to punch-mark the pieces for identification: #1 for the front side; #2 for the backside. From here on out, most operations on the bolsters will be as separate front and backside steps. It is important to marry the front and back bolsters with their corresponding under-liners for each operation. Because you will be constantly taking everything apart and putting it back together again, it is essential to keep the correct pieces paired.

Place the front bolster pieces on the front side of the knife, again using the previously scribed lines to indicate proper positioning. Use two clamps to ensure no movement during the next critical stage of passing the drill bit through the predrilled holes in the bolster and through the handle core.

Position the clamped assembly on two precision 1-inch-by-2-inch-by-3-inch blocks to assure flatness and stability, and to make clearance room for the clamps. Make sure the blocks are on the same plane! Using a new, sharp #50 drill bit, position the bit in perfect alignment with the previously drilled bolster holes, raising and lowering the bit while the drill press is in the “off” position.

It is important to properly position the material to assure a clear continuation of the bolster hole into your knife frame. From here, turn on the drill press and carefully lower the bit through the bolster hole and into the material underneath, again slow and easy, in and out, in small movements. Repeat this process for the second hole.

As you can see in the accompanying photo, there is quite a large bur on the exit side of the previously drilled hole. Not all burs are this noticeable, but they are always there after machining operations. You may not even notice most burs by sight, only by touch. This is why it is so important to clean your material after each machining operation.

In the accompanying photo, notice the efficient function of a riffling file; there is just a small concentrated area of the file in contact with the surface of the material.

Imagine all the burs that were created as the drill bit passed through from one material layer into the next. The burs can and will actually cause separation of material, even under the pressure of the clamps. The material has to go somewhere! So from here on out, get used to this mantra: Disassemble, de-bur and reassemble!

In the related photo, you can see all of the layers and parts fully disassembled, including the internal structure of the knife: damascus blade, titanium tang wrap/handle core, two titanium liners, and the front-top and bottom bolsters with their under-liners.

At this juncture, it’s a good idea to carefully de-bur the bolster holes in all layers, as well as to give all parts a light, flat rub on 320-grit sandpaper. The sandpaper will ensure that dirt and other particles are removed, and that the parts are clean before reassembly. The next step is to tap (thread) the two bolster holes drilled thus far in all layers of the knife.

Use a 2-56 hand tap to thread the previously drilled holes. Tapping involves patience, above all things, and in order to cut threads into the sides of drilled holes, taps have to be extremely hard. As such, they are brittle and prone to breakage. Use new, sharp taps with cutting fluid.

The Tip of the Tap

Carefully and constantly check for straightness. Gently insert the tip of the tap into the hole, and with a little pressure, give it a clockwise twist to get it started. This is the only time you should use pressure. Once you feel it bite, let the tap do the rest of the work. Using small one-eighth and one-quarter turns, twist the tap further into the hole, back it out, then repeat just a little past where it reached the first time.

You will be able to feel when you are biting into fresh material. If you hear a loud squeak, immediately stop and reverse the tap! It’s better to take a half an hour per hole, if necessary going through several taps per hole, rather than break a tap, especially in titanium.

Use a fresh tap per bolster, particularly when tapping titanium. It may even take two taps per bolster. It has taken me up to eight hours to remove a broken tap. It’s not fun! I have recently discovered that an EDM shop close to my house can effectively blast out broken taps for about $60 a pop.

After all the bolster screw holes have been tapped in all parts, de-bur once again. Reassemble the blade, tang wrap/ handle core and liners, and again run a 2-56 tap through the holes to blend the threads. Disassemble, de-bur and reassemble.

The next step is to permanently mate the front-top and bottom bolsters to the handle core using screws. It is essential that the surfaces where the bolsters meet the frame are clean and flat. Double check for burs from the tapping process, and gently sand both sides of the assembled knife core until they are flat. Repeat the process for both sides of the bolster liners and the bottom side of the Timascus bolster.

Assemble one bolster, the bottom in this case, onto the frame using two clamps. Use two #50 drill bits in the holes to align the parts. It’s handy to have extra drill bits on hand in this case, so keep you’re worn-out drill bits. Use the shank of the drill bit, not the fluted end. The non-fluted end will fit nice and tight into a tapped hole. You may even have to gently push the drill bit into the hole with a few taps of a rawhide or plastic mallet.

“Tapping” cuts threads into the wall of the hole, creating ridges that are wider than the initial drilled hole. The ridges of the threaded hole that face inside are still the same diameter as the initial pre-tapped hole. Get the alignment drill bits all the way through all components, and then clamp everything together. Now you know everything is square.

You have to remove the drill bits, which might take some help from a pair of pliers. Remember that in drilling, the bit will go into the hole easily because the bit is spinning. Flutes allow for air, pressure and debris to escape. This is not the case with the shank being hand forced into the hole; that is why it seems so much tighter.

Now that the holes are all re-aligned, run the tap through the already tapped components one more time to blend the threads. Blending the threads will help the screw smoothly transition from one layer to the next. Repeat the process for the second hole. Disassemble, de-Bur and reassemble.

After re-tapping the holes, and with a clamp in place to hold the alignment, insert a few 2-56 screws. Now that the screws are in place, you won’t be quite as reliant on the clamps for assistance as you were previously, and you will be adding more screws.