Removable Onlay Scales

[Bolster]

Removable onlay scales are not as popular as full-height scales, but they are sometimes seen on lightweight outdoor knives where the user may want to remove them and go with a “naked” skeletonized knife. The slim G-10 Halpern scales are undersized onlay scales; I happen to like them, and they allow my precious jimping to stand proud. So if you are a weirdo like me, you may be interested in the path a pair of onlay scales took me. This how-to comes with a caveat: I’ve not done this before. So perhaps you can read this as a step-by-step list of things NOT to do when making a pair of removable onlay scales.

Step one: Retrieve that sheet of 1/4” particle board that your wife always asks you, “Why do you keep that ratty sheet propped in the garage where I trip over it?” Yes, that one. Sketch the naked handle onto a corner of the particle board, drink 4 beers, then bandsaw it into rough shape and you’ll probably obtain the same fine workmanship that I did below. Then attach it to the mule handle with some countersunk flathead screws. 10x32s, if I remember correctly.

[Bolster]

Step two: After another beer, prepare to operate one of the most dangerous machines in the shop, your router. That unprotected chunka carbide spinning at 20,000 RPM is kinda like playing with a jet engine. Choose a bottom-bearing guided bit (upside down here) and set the bearing so it touches the handle. A little lower, please. Better to cut a little low (into the particle board) than a little high (into the steel) in this case. I’ve tried it the other way and believe me, this way is better, and nobody calls the paramedics this way.

[Bolster]

Three: Now you have the shape of the handle as a pattern, and you don’t need to expose your precious to what comes next.

[Bolster]

Four: Choose a way to terminate the leading edge. For me, a Proto 1” socket was right. Draw and erase lines until you get impatient, and then go with the last line you drew. Cut and sand to the line. I don’t like handles that crowd the blade, so my terminating line is well back, but enough to cover that front hole.

[Bolster]

Five: Attach your particle board handle to the blade and admire it! OK, you’re done. Easy, wasn’t it! (What, you don’t like particle board handles on one side of the tang with bolts and nuts sticking through on the other? OK, whatever. Keep reading.)

[Bolster]

Six: Dig out that undersized bearing for your flush cut bit and put it on. It’s easier if your router is turned OFF during this procedure. Notice how the carbide hangs out beyond the smaller bearing. You may be tempted to tighten that nut fast by holding a wrench on it and then turning on the router, but that approach doesn’t work very well. I still haven’t been able to pry loose the last wrench this procedure embedded into the wall. In the background notice the particle board pattern on top and a chunka 1/4” walnut on the bottom. Those two have been double-sided taped together. The top pattern will run against the bearing, and the walunt will be cut undersized by the bit. At this point, stop and notice, for the first time, that your router table is constructed of G-10. Wow. I could cut that up and make handles of it…if I had a router table…

[Bolster]

Seven: Here is the undersized onlay handle cut to size, flipped upside down from its cutting orientation. It’s not a super-fun procedure because the handle and cut is hidden beneath the pattern and you have to go on faith. Note to self: Find a way to hold the setup with some sort of clamp. Spinning bit is a little too close to fingers for a care-free experience. Also, find a bit that allows the cut handle to be seen during the process. I tried a flush cut bit that had the bearing at the top, not bottom, but it was a different size, and none of my bearings fit it.

[Bolster]

Eight: Router a radius onto the handles with a bearing-guided roundover bit. Frown at the burned marks. Time for a new, sharp bit? This one is only 30 years old, practically new. Later, decide that 1/8 is not enough roundover, too blocky, and switch to a 3/16 roundover instead. In order to get the handle “tall enough” to rout with a bearing-guided round-over bit, I had to double-sided tape "stack" the two handles together. That made the roundover routing relatively easy.

[Bolster]

Nine: [Edit: See post of June 18th for an easier way of doing this. This post is now outdated!]

Now the fun begins. Clamp the scale JUST SO onto the tang, viewing the perimeter of the tang all around the scale for evenness. Now, using a 3/16” milling bit which will slide through the small holes in the tang, cut .066 deep into the wood to create a recess for the threaded barrel. That .066 comes from complex math calculations called “subtraction.” My kid did them for me, as said kid is good at math. Now counterbore those holes for the threaded barrel. Swear when you accidentally go .010 deeper, and compensate by making the matching cut in the other scale .010 shallower. These recessed barrels will help lock-in your handle for a tight slip-free (but removable, no epoxy here, folks!) fit.

[Bolster]

Ten: These ^ measurements are for a 4-40 x 3/16” x 1/4” threaded barrel and 4-40 x 1/4 button head screws, as seen here. Certain un-named people in my shop have been known to make really stupid errors, so mark the targeted holes with arrows so the dunderhead doesn’t make another idiot mistake. I noticed that no hex wrench would quite fit these buttonhead screws. Turns out, they're torx. Oh, it says that on the package.

[Bolster]

[Edit: See following post of June 18th for an easier/better way of doing this. This post is now outdated!]

Eleven: This step causes sweat to bead on the forehead, and should have been done along with step Nine. But somebody wanted to test the fit, so the setup was unclamped. Now we have to re-clamp precisely. Place the clamped scale in your drill press or mill, and with the machine turned off, use that 3/16” mill bit to re-locate your holes. This entails a lot of twiddling so the hole is in the exact same position it was when you drilled it. Mutter under your breath that you now understand why the smart people use specialty guided counterbore bits for this. Once your 3/16 hole is re-located, remove that bit and insert a center finding ("countersink") bit. Do NOT jump to a drill bit at this point, it will wander. Peck a little divot into your scale with your center finding countersink bit for the drill bit to follow. Then change out to a drill bit the size of your screw body (I think mine was a #35 bit?) and drill through. Once again, that valuable piece of particle board that your wife hates comes in handy, and keeps the back side of the scale hole from blowing out as you drill through. And…don’t drill so far! Dang it. Another hole in the mill table. Well, if I want to mount my knife scales to my mill table, that will be easy to do now.

[Bolster]

Twelve: How mentally imbalanced are you? If you are at the babbling-and-drooling stage, then you may want to put lightening cuts into the backside of your scales, to save precious fractions of an ounce. I’m using walnut here because it’s a reasonably-lightweight, reasonably strong wood, and this is for a backpacking knife where every tenth of an ounce counts. I’m unaware of any man-made scale material that matches wood for lightness AND strength combined; most resin-ated products are considerably heavier. These scales weighed 0.6 oz before I made the various lightening cuts. I scooped out another tenth of an inch, while keeping the area around the screws full depth. After considerable work and with all the lightening cuts made, they weighed 0.6 ounces. Now that’s progress.

[Bolster]

Thirteen: Linseed oil. I’m looking for a finish akin to case-hardening. I don’t want a heavy resin penetrating the wood and adding back fractions of ounces. Wipe on (and then wipe off) the first coat of boiled linseed oil. For sure, do both sides of each scale; finishes on one side only lead to warpage.

(Xplorer might have notified me a little earlier that boiled linseed oil is already boiled, and that fireball I made in the back yard on a camp stove was unnecessary. Well, who needs eyebrows, anyway. I guess the wife was right, not to let me try it in our kitchen.)

Important point: As linseed oil dries on rags, it heats up and can spontaneously combust, so find a safe place to stash your used oil rags. For safety, I’ve placed my pile of crumpled-up linseed oil rags in the garage atop an old, smelly, mostly-empty gas can that was just the right size.

Huh, those holes look oval. I've inspected them up close and they're not oval. Why do they look oval in the photo? Dunno.

That’s it for now. You might consider, and then reject, the idea of checkering the scale handles so they match your neighbor’s nice shotgun stock. Unless your neighbor is leaving for a European vacation, that is, and has asked you to keep an eye on his house while he’s gone. Then, maybe checkering to match would make sense. More to come, but there’s a week of linseeding between now and the next photos…

[Xplorer]

AWESOME!! I love this!

With some hard work and less than a case of beer...Mule is handled!

Thank you for the tutorial.

[Sevenco]

Great tutorial, tempted to try this, thanks!

[AlexRus]

Great work and awesome tutorial!
Thank you!

[TomAiello]

Awesome scales, and nice tutorial. Thanks Bolster!

I think I need to buy a router table now. :)

[Bolster]

Thanks guys. There are several shameless lies embedded in my writeup, and one of them is that I'll wait an entire week before posting a photo of the knife. Who am I kidding, I don't have that kind of willpower. Here, with only three applications of linseed oil. It doesn't have the deep shine yet, but can give you an idea of where it's going.

There is some parallax in the photo. Rest assured that the amount of tang visible is more uniform than it appears...the small-bearing-on-flush-cut bit makes a consistent tang exposure relatively accurate.

I have several criticisms of my work but will save those for a follow-up post.

[Alexander135]

Very nice work Bolster-beautiful handle.
I see you are still on your quest for the lightest handle scales for your mule.
Do those scales weigh 0.6oz combined?
Also, by how much did you undersize the scales in comparison to the tang? Looks about 1/16th of an inch

[Bolster]

With a bit of additional Foredom work, it's also a Stash Knife. Given their relative worth, a $5 bill will fit in with room to spare, a $20 is tight, but $100 is really a squeeze. With Ben in there, this knife is worth almost a hundred dollars, but old Ben was happy to get out after the photo was taken.

Yes, Alex, about 1/16 all around...and that was due to the bearings I had on hand, not intelligent design. After this exercise I would like to purchase a bit that allows multiple different sized bearings, somethign like the Freud 32-504, only preferably with the bearing shaft-side. Oddly, that Freud set does not allow 1/16" inset. Yes, the scales are 0.6 oz combined before finishing. We'll see what the oil adds.