Hack-It-Yerself, Make it Sharp

Replacing a Knife Handle

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Figure 1 – A beloved old knife with a broken handle. Click any picture to enlarge.

Good morning everyone.

One of our favourite kitchen knives is an old Sabatier 4” paring knife that we bought around 30 years ago. It’s the first knife I reach for (when it happens to be clean) when I need a small knife for food preparation, and over the years it has been used, abused, and run through the dishwasher a zillion times. A couple of years ago, the plastic handle finally cracked badly enough to where a big chunk of it fell off, and we had to set the knife aside until I got around to replacing the handle, a job that I just completed rather successfully, in fact.

I would think that this is a fairly common problem for beloved old knives, so I’m going to take you through the steps that I went through in replacing the handle (scales is the proper term) in case some of you might want to try it. A word of warning though: this was my first time at replacing a full length tang type of handle and I didn’t look up any instructions. I just did what I could see that needed to be done to get what I wanted, and it pretty much came out how I wanted. It would have been nicer if I hadn’t tried to saw off one of my fingers with a hacksaw, but you can’t have everything.

This is going to be a rather long article, so if you’re not interested in the knife repair, now is the time to bail. The handle repair starts after the jump.

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Figure 2 – Safety third

Preparation

The first thing I did was decide what kind of wood I was going to replace the old knife scales with. A good hard, dense material always makes the best (to me) knife handles, and since it’s a kitchen knife it needs to be impervious to water as possible. I decided on a wood called cocobolo, a type of rosewood that grows in Central America. It’s a very dense wood with lots of resin in it, a bit oily, plus it’s gorgeous and one of my favourite woods. I also happen to have some on hand which is another big plus.

The next step is to tape up the blade of the knife (figure 2) so that I don’t cut the crap out of myself while working on the handle. I also tape a small piece of emery cloth over the point of the blade so that I don’t stab myself either. Safety third.

Removing the Old Handle

Now I needed to remove what was left of the old scales from the knife. The normal procedure for doing this is to take a hacksaw and saw diagonally through the rivets on one scale, then both scales can be removed with a little persuasion. In my case however, if you look at figure 1 you’ll notice that I have an exposed rivet on one side, plus the plastic scales are cracked from top to bottom at every rivet. It looks like I can saw along the tang to cut the exposed rivet, then the adjacent piece of scale could be worked loose, and so on.

I clamp the blade of the knife at the bolster in a soft-jawed vise with the handle vertical. The bolster is the pot metal-looking thing between the blade and handle that looks kind of like a guard. The blade doesn’t offer much support, so I steady the handle with my left hand and start carefully sawing the rivet with a hacksaw. I start to slow down when I’m nearly through, then when I cut through, the handle below the rivet pops out sideways and goes flying off and the hacksaw drops onto my left index finger and, because I’m still sawing, cuts a big gash in it. Stupid, stupid, stupid.

The first rule of fingers: if you don’t want to lose any, don’t put them where a working saw blade can get them.

Time for a short break to staunch the bleeding while cursing my endless stupidity.

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Figure 3 – Knife with one scale removed. And the blood cleaned up.

Once I’m repaired, I reposition the knife in the vise to grip the tang instead of the blade and I finish removing the scales without further mishaps. One thing I found interesting after I had the old scales removed was to discover extra holes in the tang that had plastic connecting the two scales together, meaning that the handle had been injected-molded onto the tang and that the rivets were added for durability.

Prepping the Tang and Bolster

The tang had 30 years of accumulated rust and crud on it so I cleaned it up with a detail sander and 80x sandpaper.

Fitting the new scales to the bolster was going to be a problem. If you look at figure 2 where the scales meet the bolster, the junction is not square but curved. Taking a closer look, the surface is not only curved but has a compound angle to it, and the curve is parabolic meaning it is curvier on one end than the other. Trying to carve the new scales to fit that thing would be a huge pain in the ass, plus I had nicked the bolster with the hacksaw when I cut through the last rivet. Not wanting to spend days trying to fit the new scales to that mess I did the only reasonable thing: I took a smoothing file and cut the bolster flat and square to the tang, making for a much simpler joint.

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Figure 4 – Knife with clean tang and blanks for the new scales

Making the New Scales

The cocobolo that I decided to use was a plank about an inch thick. The old scales were ~¼” thick and ~3 ⅜” long and I needed to make the scale blanks large enough to be sanded down flush all around. I sawed off a portion that was about ¼” wider than the widest section of the tang and about ¾” longer. I resawed two panels ⅜” thick and ran them through the drum sander to remove the saw marks and make the surfaces parallel, with the panels ending up 1/32” thicker than the final dimension.

At this point I discovered a couple of hidden voids from insect damage in the scale panels. Normally, cocobolo doesn’t have any voids like that because the wood is poisonous and not many bugs attack it, but something got into this. Lucky me. Rather than start all over, I elected to repair the damage using cyanoacrylate (superglue). I’ve developed my own twist on this method of repair over the years (by making lots of mistakes that needed to be fixed) and I use a special type of glue, Loctite 410, on repairs to dark wood. It’s black, slightly flexible when cured, and will take a high polish. When I’m lucky the repairs are invisible, and when I’m not, the repairs appear to be another random dark spot in the wood. It’s a real butt-saver.

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Figure 5 – Traced outlines on the scale blanks

After fixing and leveling the repair, I covered what would be the inside of the scales with masking tape and traced the outline of the tang onto the tape using a dull pencil and marked the rivet holes with an awl. The tape makes it easier to see the pencil lines, and using a dull pencil makes wider lines and makes it a bit easier to cut the shapes oversized. One of my main concerns was getting the scales to fit tightly to the bolster, so I tried to mark the rivet holes slightly closer to the bolster, thinking that would help to draw the joint together.

Next I cut out the rough scales using a scroll saw, sawing along the outside of the big pencil lines.

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Figure 6 – Scales have been sawn from blanks. The bolster has been filed square to the tang.

Drilling the rivet holes was going to be a tricky affair. The rivets needed a recess on the outside of the scales for the rivet head to fit into so that it will be flush with the final surface of the scale, but it can’t be too deep or too shallow. The hole for the rivet shank has to be drilled exactly in the center of the rivet head recess, otherwise the rivet head won’t go into the recess. All of these holes have to be lined up exactly over the rivet holes in the tang, else the scales won’t fit square to the bolster or the tang.

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Figure 7 – Scales with completed rivet holes.

First, I drilled 1/16” holes from back to front on both scales at the locations I marked with an awl. These small holes would serve as a guide for the center point of the lipped brad-point drill bit that I would use for the rivet head recess, and for the drill bit for the rivet shank. The rule for drilling a holes with a counterbore is to drill the counterbore first, in this case the recess for the rivet head, and the through hole (for the rivet shank) second. Using calipers, I measured the thickness of the rivet head, and taking into account the extra thickness of the wood I set up the drill press for making the counterbores, making several test bores and measuring them, then making the counterbores in both scales.

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Figure 8 – Knife rivets. Image from Lee Valley

The holes for the rivet shanks need to be over sized slightly because the way knife rivets [figure 8] work. A knife rivet consists of two halves, one half has a hollow shank and the other has a solid shank that is hammered into the hollow half to hold the riveted items together. Doing this causes the hollow shank to swell out, and it you don’t account for this you can split the scales that you so tediously crafted when you set the rivets. I measured the hollow rivet shank and determined the drill size, and very carefully drilled the shank holes. Popped in rivets to check for fit and everything looked just f&&king ducky. Whew.

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Figure 9 – Scales have been riveted to the tang.

Attaching the Scales to the Tang

Knife rivets come in general sizes and lengths, and I needed to see if the rivets I had needed to be shortened for the handle assembly. I placed the hollow half of the rivets into one scale on top of a small anvil, positioned the tang over the rivets and placed the other scale on top of the tang. I wanted the top of the hollow shanks to be at the top surface of the tang when they were threaded through the scale, but the rivet shanks were quite a bit too long. I marked the shanks with a scribe and took them over to the disk sander and shortened them.

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Figure 10 – Pin punches. Image from Starrett Co.

I reassembled the bottom scale and hollow rivets, tang, and top scale on the anvil. I took a solid rivet half and placed it in the center hole of the scale, and using a pin punch (figure 10) and a small ball-peen hammer I set the rivet tightly enough to stay together. Everything still looked good so I did the same on the other two rivets.

Due to the extra thickness of the scales, the rivet heads needed to be recessed when they were set, and I couldn’t do that on the anvil. I took a pin punch that had just the right size to fit into the rivet head recess (lucky!) and clamped it into a mechanic’s vise. I located the pin punch into the first lower rivet recess, and using a slightly smaller pin punch, I tapped the rivet halves together to where they were slightly loose, then did the same on the second and third rivets. I tried maneuvering the scales and tang to get the best fit at the bolster, then set all of the rivets, but taking care not to over-drive them lest I split the scales. You can see the result in figure 9.

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Figure 11 – Handle replacement complete.

Shaping the Handle

Checking for the fit at the bolster, I could see that the scales weren’t flush. Dang. I had an idea on how to fix the problem, but first I needed to get rid of all the excess wood and shape the handle.

I started out by using the disc sander to sand the back of the handle nearly flush with the tang, then sanding the face of both scales flush with the rivet heads, then I sanded off most of the excess from the round butt of the handle.

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Figure 12 – Sanding drums. Image from Lee Valley

I couldn’t get at the bottom of the handle with the disc sander, so I chucked up a sanding drum in the drill press and sanded off the excess wood from the bottom of the handle, not quite flush with the tang, and shaped the area around the point on the bottom of the knife butt.

Next I need to make a taper in the handle to blend it in with the bolster. Using a detail sander and 80x paper, I worked the wood down nearly flush with the bolster, rotating the knife constantly to keep things symmetrical.

At this point it was time to deal with the gaps between the scales and the bolster, and for this I turned to my magical fix-all, Loctite 410. With a small piece of blue tape, I taped off the gaps at the back (spine) of the handle, and worked the glue into the gaps using a fine pointed dentist’s probe, a thing kind of like a needle with a handle. After I had worked in as much glue as I could, I wipe off the excess and applied accelerator to set the glue quickly and keep it from running out of the gaps. I let the glue set for a couple of hours, because Loctite 410 sets very slowly, then removed the tape, and added a bit more glue to the low areas in the gaps and hit it with the accelerator again, and let everything set overnight to get good and hard.

The next day, I used the detail sander and 120x paper to sand the handle and my repairs flush to the mating surfaces. At this point I noticed something odd – the rivet heads were rotating from the vibration of the detail sander and the sanded surface of the rivets didn’t line up with the surface of the wood anymore. Damn. Trying to rotate the rivets with my fingers didn’t work, for now they pretended to be seated solidly, the lying bastards. Working with the detail sander, I got them as close as I could to the proper positions, then reset the rivets again, and re-sanded the scales flush with the rivet heads again. They were close but not perfect, dang dang dang.

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Figure 13 – Finished handle replacement showing opposite scale.

I hand sanded the handle down to 400x, slapped a coat of wax on it and declared it finished, and you can see the end product in figure 11 and figure 13. I could have polished and waxed it to a high gloss, but after a couple of hand washings in the kitchen that finish would be gone, and besides I generally prefer the appearance of a semi-gloss finish anyway.

All in all, I think I did a pretty fair job for a first attempt. My fix for the gap between the scales and the bolster worked extremely well, the join is now invisible and you can’t tell that I fixed it with black glue. You can spot the repairs I made for the insect damage if you look closely, but they don’t look too nasty.

The knife feels marvelous in your hand too. The original handle was much more boxy in shape, which served a purpose of being a general handle for anyone to grasp securely. My handle is more customized to what I like and what feels good in my hand, but still retains enough flat surfaces and edges to grip securely. I’m quite pleased with the results, all things considered.

So, what do you readers think? Was my effort worthwhile or did I blow the repair? Was this account of the repair of any use to you? Let me know what you think.

 

All pictures by the author except where noted.

Other Image Sources

Lee Valley

The L.S. Starrett Company

 

  • But my Henkles paring knife broke just past the bolster lip. I think something might have fallen on it in the knife block. I didn't bother to try to weld it back together and will just get a replacement.

    • The Professor

      The blade broke off from the tang? Wow, that was some impact.
      Yeah, in that sort of situation you're better off replacing the knife if you can. That would be a very complicated repair, if it could be done at all, because of the bolster.

      • I have no idea how it happened. I just found the handle laying on the counter. Neither my wife or mother-in-law, who had been baby sitting, claims to have any knowledge of how it happened.

  • pj134

    If only I knew how to sharpen it after repairing the handle…

  • OA5599

    A poisonous handle on a food prep knife that also happens to get washed in the dishwasher. Dear Professor, I must regrettably decline that dinner invitation.

    • The Professor

      Bah, coward!

      /actually, now that it has a wooden handle, the dishwasher is verboten.

  • Well done! That looks fantastic!
    Even your tools look pretty (admiring the wood block). The Mrs. has two wood blocks but they weren't cut straight so they're more like wood rhombuses. Also quick question: do you actually have an anvil or an ASO (anvil shaped object)? The Mrs. just picked up a 150lb anvil for $200 from a former employer. He even threw in a free Kitchen-Aid Mixer (long story).

    • OA5599

      Your wife picked up a 150 lb anvil? Lucky you. She won't need to bother you to bring the 50 lb sack of dog food in from the car.

    • The Professor

      Thank you very much.
      I actually have two ASOs – a very small jewelers anvil that weighs about a pound, and one a bit bigger that weighs about 10 pounds and is the one I was referring to. I would absolutely love to have a full sized anvil, but new 150 lb anvils sell for over $1000, and used ones that aren't junk are nearly that expensive. Tell your wife that I'm horribly jealous and that I lust after her anvil.
      That wooden block is something I made from the scraps left over from my youngest boy's senior HS project, a large butcher block table. Here's a picture:

      <img src="
      http://i1144.photobucket.com/albums/o491/dmilligan666/Woodworking/Butcher%20Block%20Table/table13_resize.jpg&quot; style="border:2px solid black;" alt=" " border="2" width="400">

      • pj134

        That… is awesome…

        Although the plugs not lining up hurt my OCD…

        I mean everything else is so perfect, but the plugs aren't straight… I bet there is good reason for it… but still…

        • The Professor

          Yes, the plugs are laid out like that for a reason. The top line of plugs covers the screw holes that hold the table aprons in place for gluing, and the lower ones hold the table legs in place. They're staggered because there are two more screws holding the legs from the adjacent side and it keeps them from interfering with each other.
          That table is easily one of the most difficult things that I've ever made, and one of the handiest. It sees constant use in the kitchen.

          • pj134

            Hah! You act as if you don't have five foot long clamps!

          • The Professor

            Oh I do, but only 5, not the 16 or 20 that were needed at times to clamp that thing together. On top of that, you had to hold everything in register while you were setting the clamps, and then the glue on the wood made parts want to slide around in every direction when you applied pressure….
            It was a f&&king nightmare, over and over.

  • disqus_RYocsHn9pl

    Funny, I did a search for “kitchen knife repair handle” and came across your posting, in which you replaced the handle on the exact same Sabatier knife I have to repair, with an identical break in the handle! If only I had the tools at my disposal to do what you did.

  • Robin Goldberg

    Great job! Gives me an idea of what I might be in for if I attempt the repair I have in mind. Thanks for posting.

  • BKF

    I’m in the process of taking 12 unfinished forgings of the same knife from the Sabatier factory from about 100 years ago from rough to finished knife, including all of the grinding and heat treating.

    I like your solution of grinding the bolster’s compound curves flat. Will definitely do that.

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