Intro: Making an X-acto Knife Handle With Lignum Vitae
A while ago, I was meandering the aisles of my local wood supply store and noticed, in their collection of pen blanks, a stash labeled as Lignum Vitae. Now, having previously explored the world of wooden bearing surfaces, I understood the wood to be one of the more absurdly dense and resinous species known to man. Such properties made it a prized material for below water propeller bearings on ships. I'll proudly acknowledge that I'm a sucker for an exotic hardwood, so I bought one of those pen blanks and resolved to do something interesting with it.
I decided to try making a holder for X-acto blades.
The basic steps are:
1. form the handle
2. cut a slot for the blade
3. fit the blade and make some metal shims
4. lash the handle together
The tools I used are:
- a lathe and associated chisels
- a bandsaw
- a drill press
- metal snips
Some alternative tools
- a pocket knife. The handle can be formed without a lathe. the machine just makes it easier.
- any saw with a kerf around 1 mm
- a hand drill
Step 1: Preparing the Blank
Before you can start turning, the pen blank has to be prepared to go on your lathe.
This procedure will vary slightly between lathes, but it boils down cutting a slot or two for the drive spur and drilling a small hole for the tailstock.
For my lathe, I use a 1/4 inch slot with a 1/16 inch hole centered in it in one end, and use a 2/16 inch hole in the other.
Step 2: Turning the Blank
To turn the pen, you'll use standard turning techniques: riding the bevel to engage the cut when using traditional tools, and aiming at the axis of rotation when using carbide tools.
It will depend on what wood you're using, but sanding from 180 up to 1000 grit should achieve a good surface.
Some notes on design.
1. the two ends should be about the same length, though both can be slightly longer than the middle section
2. the section which holds the blade should be about an eighth inch wider than the tang of the blade is
3. the section which holds the blades should either have a straight taper or be very close to cylindrical
4. the bulges seem to look better when they are equal in maximum radius
notes 1 and 4 are just stylistic recommendations, but 2 and 3 have bearing on the functionality of the end product.
I added grooves on my first attempt. They add texture and interest to the piece, though I didn't think they fit well on the second attempt.
Step 3: Fitting the Blade
The key in this step is developing a snug fit when the blade is slipped into the socket. This interface will never be as firm as the grip developed when a production handle is tightened, but it is certainly serviceable.
The scary part of this step is cutting the slot for the blade to fit in. You will want the blade to take just enough kerf for the blade to slip into the slot and be held lightly by the sides. You can use a bandsaw for this operation, but thin bladed bow or jewelers saws will work as well. A 1/16 inch hole drilled at the base of the slot can reduce stress concentrations and allow the lashing to be more effective.
The angle of the blade is maintained by a bit of metal on each side. I used a piece of light gauge aluminum for the second knife, but something thinner would be better. I would recommend using a piece of soda can folded into a "T" shape instead. The tang of the blade will contact the lower part of the T with the upper part resting on the surface of the handle. When you make a set of metal bits, hold them in their position in the slot, and test that the blade can just slide between them with no room to wiggle side-to-side.
Step 4: Finish the Handle
Now that you are done with test fits, it is a good time to finish the wood. Sand and buff any scratches out, and decide on a finish.
I frequently immerse my small turnings in melted hard candlewax, though much more orthodox finishing solutions would be a hardening oil such as walnut or boiled linseed oil. Pen finish would serve well also.
None of these are film-forming finishes. I can't add much to a conversation on film forming finishes, but I do know that they can encounter issues when applied to especially dense and resinous woods.
I'd love to hear your thoughts on this topic in the comments section
Step 5: Lash the Blade In
The lashing serves to tighten the grip that the slot has on the blade. It also provides a bit of textured grip, and holds the metal bits securely in their place.
For this step, I used a heavy duty waxed nylon thread which is produced for leather stitching work.
position the blade so that its heel is just beyond the front of the handle, and the metal bits prevent it from sliding any further back.
Begin the lashing by poking the end of your thread through the slot just below the metal. It is still attached to the spool at this point. wrap the long end around to where the short end protrudes, give the two ends a half twist, and begin wrapping the tread tightly up the handle. Each wrap should be tight, stack snugly against its neighbor with no overlap, and pin the tail end on each pass. Take care that the first few wraps when you encounter the metal bits don't shift them or leave any gaps.
Make wraps up the handle untill 2-3 wraps after the metal bits are covered, then reverse to wrap tightly back down the handle. To finish the lashing, add two or three half hitches and tuck the end of the line back through the slot.
Step 6: Notes on Working Lignum Vitae
this was my first time working Lignum Vitae and it was quite an experience.
On the wood itself...
- it is freaky hard
- it tears out fibers a bit more easily than you'd expect
- I ended up just scraping for the last half of the turning to keep my tool from catching and damaging the piece
- This may have had to do with the fact that my tool rest couldn't get quite close enough
- sanding didn't raise any dust. all of the wood removed stuck on the sandpaper
- sanding up to 1000 grit and then buffing with a cloth produced an adequate surface
- straight off the lathe, it felt like there was a coat of wax on the piece
- the boiled linseed oil that I applied didn't really soak in
At any rate, working with this piece of wood was very interesting. The color and texture don't really excite the imagination, but are still quite pleasing. The most special thing about it is the density. To the touch, it just doesn't feel like wood. It's just far too cold and hard.
Thanks for coming along for this project.
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