# Mounting Handles with Reversible Glue - Experimental Process....for those curious or interested



## CPD

Several months back in an unrelated post on burn-in's http://www.kitchenknifeforums.com/archive/index.php/t-19997.html had the idea to try animal hide glue for mounting handles. No one who chimed in had tried it as of then and it seemed worth some experiments... I've finally had a chance to test the theory and the results were successful in my limited tests. Wanted to share the whole process for anyone who is interested. 

First, a little background: I like building things. I like to cook and do it professionally, occasionally. I appreciate great knives. Making sayas and handles was a natural progression. What's never felt natural, or easy, is the process of mounting a custom WA handle. 

The traditional method of burning-in a handle is great, in theory. It's reversible, it's straightforward...and who doesn't occasional enjoy playing with fire. The problem is, custom handles usually have a bunch of parts that don't like high heat. Glue joints melding spacers and mixed materials -even when assembled with a through-dowel- are not always welcoming to a red hot tang that might melt or weaken the glue. And similarly, dense and oily exotic woods aren't terribly welcoming to the idea of expansion and contraction that heat introduces. They have a bad habit of cracking if not handled with care. And even when you're careful, they'll occasional remind you - luck isn't always on your side.

With the many hours and, or, dollars, that go into a custom handle - it's an unpleasant moment when you break one before even putting it to use. Been there, done that.... and no joy.

The alternative - glue the beast on with epoxy - has its own pitfalls. most obvious beyond messy - it's pretty much permanent. If the handle shifted while the epoxy was curing (maybe because an oversized tang hole left room for movement?) Or the handle otherwise ended up out of alignment? Oh well. And if you love the handle, but maybe not love the marriage of it and one particular blade after giving it a spin for a while...Too bad there too. Removing an epoxied handle brings high odds the handle won't survive the surgery and will have to be amputated. 

Hide glue, long used in instrument making and other woodworking projects, has the dual benefits of being both a rigid and reversible glue. Unlike wood glues or epoxy, it doesn't flex...."no creep" to use the technical phrase. When it dries, it can usually be fractured along the glue line and the glue joint will not move. And as for reversible - get it wet and hot...it'll liquefy. Or again, just give it some force in the right place to get it to shear against itself. Antique restorers and luthiers use it for exactly these reasons.

I make sayas with hide glue so I can open them and refit them in the future if needed...and it works like a charm. Mounting handles was a random 'what if' idea.

Now, of course, reversible from wet and hot conditions doesn't sound ideal for a kitchen or kitchen knife...but waterproofing is easy enough and hot means over 160-180 degrees. That's not likely going to be an issue . If you've heated your expensive carbon knife to an internal temp inside the handle at that range, something's wrong. Then again, if it does happen...with hide glue, you can always re-glue it with fresh glue.

Over the past month I've experimented with the idea a few times and come up with a recipe that seems to work. For test purposes I've had two handles glued on this way all month long..a wa-converted Forgecraft and a mini blue #2 yanagabi. Both have custom handles but neither are so rare or valuable to outweigh the risks. On the forgie, I mounted the handle (and removed it) a couple times over a several days before leaving it on to see if it held up. It did. After a month, I felt comfortable enough to apply the same technique to my favorite knives, a pair of Heiji's. (I'll post a picture of the forgie and yanagiba at the end of this post)

The recipe is relatively simply. I used "Old Brown Glue" a brand of liquid hide glue that's easy to work with (as opposed to traditional hide glues that have to be melted in glue pots). Old Brown Glue can be bought from bunch of woodworking suppliers or even Amazon. The process worked on tightly seated handles, and where there was an oversized tang hole.

Hide glue prefers to be warm, so step one is to let the bottle sit in some hot water while I get things ready. 

Tang Prep - I clean any slag or residue off the last inch of the tang and coat the rest of it (all but the last inch) with a thin coating of shellac. I use an alcohol based high grade shellac, not a water-based product like bullseye. Traditional de-waxed shellac in alcohol is an amazing sealant. It may or may not be necessary, but it's an easy way to protect the tang against any chance of rust or surface damage.

The exposed last inch of the ting is rubbed with a little bit of garlic. Borrowed from a website that borrowed from an old book....the garlic is a historic technique to apparently micro-etch the metal and make the hide glue bond to it. (there are other additives that can make hide glue suitable for other materials or even waterproof it). May or may not be needed but I went with the approach from the first try and it worked.

Gluing - make a paste out of the glue and very fine saw dust that has the consistency of very thick honey. You want it to be able to fill the tang hole but still displace when the tang is seated. If it's too thin, it will take longer to dry (potentially a couple days) and be weaker but would still likely work. Also, too thin, if not a tightly fit pair, the knife may move around while the glue is drying. Conversely, if it's too thick, you will have a hard time filling the hole or seating the knife. "Just Right" is when the knife goes in with some resistance, maybe even needs a few mallet taps on the butt of the handle....

Once seated, the glue needs to dry. It took a few hours to begin to set up but as much as a day to fully harden depending on the mix. I like to set the knife vertically - blade up - during this period so gravity makes any liquid glue settle to the bottom of the tang hole.

Any spillover during the gluing process is easily cleaned up with a damp rag before setting it aside to dry.

While drying, the glue may shrink and settle some leaving you with a recess at the top of the tang hole. You can fill this with an added mix of the glue paste a day later, then let that dry..or let it be pending the final step.

To test dryness, I test the glue with a toothpick or small pick of some sort to see if it gives. If it's still got any give, it needs more drying time. Once dry, it'll be hard and not move.

For the final step, I put a thin layer of epoxy (CA glue would also work) over the top of the tang hole and on the ferrule to act as a "barrier coat." It's thin enough that I can scrape it off with a chisel or sand it off in the event that i want to do a removal, but thick enough to insure no accidental moisture access to the hole. If you left a recess in the tang hole, the epoxy will fill it...but this will take more effort to clean out later in the event you want to remove it.

For removal, in my experiment (done without an epoxy coat I'd later have to scrape off), I took a hot, wet cloth and wrapped it around the ferrule/tang. that began to soften the glue near the opening....then let a little water soak on it...hit it with a hair dryer....and I was able to remove it similarly to removing a burned-in handle (A push block and a wooden mallet). I did crack a ferrule on one removal attempt - tried to force it with too much hammer persuasion before it was ready - but I was successful on other tries. 

Remounting was easy because hide glue will bond to itself so full removal of old glue was not needed. 

Here's a picture of the two practice knifes I tried the process on. Both are more than a month in with use, cleanings and zero movement that I can see or feel. (the sayas in the picture are assembled with hide glue too)


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## Geo87

I was wondering if anyone was going to follow up on this. Thanks for doing it and thanks for the write up. Great work! 
Removable handles is a brilliant idea if you have an expensive handle you love on a knife you want to sell.


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## marc4pt0

Thanks for your time and write up on this. Great info here, much appreciated.


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## toddnmd

This is very interesting info! Clearly, you have a lot of knowledge, and many of us appreciate you taking the time for such a thorough explanation!


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## Castalia

Thanks for the post; great info! I have been considering trying a WA handle one of these days. How do you heat the glue to remove the handle when you want to reverse the process?


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## CPD

Castalia said:


> Thanks for the post; great info! I have been considering trying a WA handle one of these days. How do you heat the glue to remove the handle when you want to reverse the process?



Thanks all for the feedback and replies. Hope some others will try and experiment further. Removable handles, in my opinion, are ideal.

Castalia -- Hide glue softens from moist heat so steam is a good option. In my test I took a hot, wet dish rag and wrapped it around the tang/ferrule area for a while. That began to soften the glue closest to the tang... I refreshed the towel a few times. Then I blew a hair dryer on the tang tang/hole area to heat it further. You could probably use a steam iron, a tea kettle...even hold it over a steaming pot to get the steam to start to soften the glue. I wasn't too scientific in trying different methods to figure out what might work best... I was more focused on seeing if the idea would work at all. It can definitely be refined and improved.

Once softened, you put a block of scrap wood against the top of the handle running the length of the blade. The wood scrap should be long enough to extend safely past the blade by at least a few inches. hit the end of the wood with a mallet a few times so the force is transferred down to the handle and pushes it off .... the handle will slide off similarly to a burned in handle (it's the same method). It takes a few hits and some patience....but it worked for me. 

The thing about hide glue, that is an added help is that when it breaks, it usually shears from itself along the glue-line. That means unlike other glues that tend to take a lot of wood fibers or material with them...even if not fully softened, under enough force, the glue should break apart from the mallet strikes anyway. The cautionary note is - if you hit too hard you could end up cracking the ferrule depending on the material it's made from.

Once the handle is removed, scrape out some of the dried glue residue as needed to insure you'll get a good fit when remounting it...but you don't have to be too precise. hide glue bonds to itself so any residual dried glue in the handle is not likely to cause any problems provided you have room to seat a new tang.


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## Framingchisel

Great. Thanks for the info.


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## rick_english

I've been able to reverse epoxy, but it takes a LOT of heat---no fun. This idea sounds like a plan. I also like to apply cold bluing to the tang before setting it. Really helps to prevent rusting.


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## CPD

rick_english said:


> I've been able to reverse epoxy, but it takes a LOT of heat---no fun. This idea sounds like a plan. I also like to apply cold bluing to the tang before setting it. Really helps to prevent rusting.



Cold bluing ..cool idea!

On reversing epoxy - think that was a discussion in a prior thread - part of the problem was multi-component handles that have been assembled with epoxy to begin with. If you try and reverse the epoxy holding the knife in place, and are successful , odds are high you will also reverse the assembly of all the handle components. Maybe they go back together after and are reglued...but that presumes the wood, or resin stabilized wood if any, didn''t warp or otherwise move from the heat too. Kind of a cascading series of potential problems.


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## apicius9

Ok, now we need a WIP on cold bluing 

Stefan


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## CPD

apicius9 said:


> Ok, now we need a WIP on cold bluing



+1


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## zackerty

I am following this thread with interest...

A violin making friend uses the horse hide and horse hoof glue, so that his and other violins that he repairs, have reversible repairs...

I have always trusted epoxy for whatever I make or repair, so a natural tried and tested method, adapted for knives is something that I am keen to see how others cope...

BTW, most 24 hours epoxies can be softened by placing the glued object in a pre-warmed container just filled with boiling water...you might have to do it a few times with freshly boiled water, but it will let go eventually... 

Acetone will work, but might damage the scales enough that they need to be replaced...


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## mlau

I re-read the post.

Genius! i like your use of old brown glue instead of fresh hot hide glue, as getting the right mixture has been hard for me.
With your permission, I'd like to send this to my sushi-making friend...with the caveat that my work will NOT look as nice as yours.


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## mlau

One quick question:

How much of a gap do you want between the tang and the wood?
Are you simply drilling an oversized hole and filling it with the hide glue, or are you mortising out a precise pocket for the blade to be friction fitted in?

I'm asking because my hide/fish glue tends to have a fairly thick viscosity.
Not sure how much of a gap that I'll need.


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## CPD

Matt - thanks for the complement and feel free to share it with anyone.

To your question - generally speaking, and ideally, you want the tang to be as precise a fit as possible before there's any glue involved. That's true whether it's my hide glue technique, or in general. In practicality, though, there's two different areas where fit comes into play: 1. where the tang enters the knife at the ferrule (the visible joint), and then 2. internally, inside the handle. Often (on handles not designed to be installed with a burn-in method), custom handle makers will try for a tight fit at the ferrule and leave a larger recess inside the handle. There are a lot of reasons for this ranging from: minimizing the amount of work necessary to custom fit the handle to different knives (it's easier to predrill a larger hole in the handle body during construction and then have a tang hole that fits a wide range of knives than it is to have to fit both the ferrule opening and the internal body)... to reducing handle weight to retain a balance point on the knife....to practical matters of how the handle was constructed (when dowels are often used to reinforce structure with different materials).

With my method for hide glue, how big the opening shouldn't matter much. The glue and sawdust paste fills in any space/pocket around the tang. Excess squeezes out when the tang is inserted and what remains locks the pieces together. The important thing is just making sure the viscosity is as thick as possible while still able to flow/be displaced

I suspect you could achieve similar results with traditional hot hide glue/fish glue but I chose the liquid hide glue because I could be sure of consistency and viscosity every time. hot hide glue, depending on temperature and batch, will have different consistency, curing times and different bond strengths. For me, there was no upside to that added complexity. Also, as far as viscosity goes, you want to get a gel like paste. The saw dust (in my view) is important. hide glue will dry as resin by itself but it's an evaporative/curing drying process. Trapped inside a handle, that process can be slow...and the longer it takes, if you don't have a really precise fit, the more chance there is you get out of alignment. The saw dust helps wick and absorb moisture and it also (in my theory) adds structural rigidity (like rebar in concrete or fiberglass mat in epoxy).


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## apicius9

That's on my list for this weekend. I have a few of my own knives to rehandle, good time to play with that. Got some old brown glue, And there is an abundance of saw dust all over my shop :O Got some syringes and hope it will be liquid enough to squeeze it into the handle after I mix it up. Just need to find a way to temper the glue, maybe I need to take my sous vide set-up to the wood shop. Heat the glue and cook a few steaks while I am at it 

Stefan


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## CPD

apicius9 said:


> That's on my list for this weekend. I have a few of my own knives to rehandle, good time to play with that. Got some old brown glue, And there is an abundance of saw dust all over my shop :O Got some syringes and hope it will be liquid enough to squeeze it into the handle after I mix it up. Just need to find a way to temper the glue, maybe I need to take my sous vide set-up to the wood shop. Heat the glue and cook a few steaks while I am at it
> 
> Stefan



Stefan - don't worry too much about the glue temp with the old brown (unless the sous vide steaks is the real goal  . I had the same thoughts before I started...was going to go set up sous vide...debated how hot etc.... then, reality: once I got going, a tiny bit of impatience crept in and I did my first test run with the hottest water my tap put out. Just said "screw it" and dove in. I did that one on and old forgecraft knife ....it was a tester I wasn't afraid to risk...and it held up well. I was able to reverse the process as described and then remounted the forgie a second time. Warming the glue is more about getting a thinner viscosity and longer open time with the liquid hide glue. Different story with true hot hide glue...but I digress.

Two side notes not sure if I mentioned in my original post: using a syringe with the sawdust in the mix can be a little messy. I had some clogging issues when trying to get the right consistency. The process worked best when I used the ultra fine sawdust from my dust collector... Second, I found it helped to use a wooden skewer to push around inside the tang hole a few times when filling to help get any air bubbles out...that or a few taps of the handle on the heal. I tape off the ferrule and handle to keep things clean but beauty of the hide glue - water clean up. So mess doesn't matter much....

look forward to seeing and hearing how it turns out. Any questions feel free to shoot me a PM if needed.


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## mlau

Dear CPD, 

I just tried PMing.
You must be popular, as your mailbox is full.


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## sharptools

I have been thinking about trying rehandling and have been doing some research on what people have done in mounting. Here is the one question I have. Is it possible to completely mount with just beeswax? I've seen more than one person suggest beeswax for filling near the opening. Is it too soft for holding the knife in place? The melting point seems to be ok. 62C/143F.


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## JBroida

sous vide knife?


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## sharptools

Yum?


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## sharptools

gentle heating to loosen glue I assume?


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## JBroida

yeah... very good heat control so you can evenly and consistently heat up the glue without having any potential damage to any other part. Wrap the blade, vacuum seal, and circulate until glue softens. At least that is how it would work in my mind... but i might be totally crazy.


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## sharptools

Any takers on the beeswax question as an alternative to reversible glue.


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## oldcookie

Isn't the shear strength for beeswax too low to use as a glue for knife handles?


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## JBroida

not near strong enough to hold in by itself. For a burnt in handle, it could seal the inside from water, but its not effective as an adhesive.


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## rick alen

As far as using wax for gluing, there are readily available very hard waxes used for a variety of machining operations that might very well work great. They can also be had with differing melting points, from <150F to 375F and possibly higher.

You would likely need a well roughened or otherwise pitted/scalloped surface to insure things don't break loose.


Rick


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## mark76

I've used Sugru to mount a handle. I don't think it's a good glue if you want the handle to be removable. But it handles a lot better than epoxy: not messy at all and a very clean fit.


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## Dan P.

Cutlers' pitch; Wax (bees'), resin (pine) or pitch (pine, birch, other tree or plant or mineral pitch) and binder (charcoal dust, brick dust, saw dust, etc.). I add a little boiled linseed to give a gummy quality that wax does not give. The ratios you use will be dictated by how hard (more resin) or flexible (more wax or oil). The filler is to give it colour and because dust is cheaper than the other ingredients.
Heat to apply and remove, it's non toxic and cheap. BUT... sadly it does not have 2 tonne shear strength (or whatever).


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## CPD

wow, surprised to see this thread back around. Had forgotten it. 
As an update - 

Jon, the sous vide circulator as heat source was a great idea! I tried it with the knife I first started the hide glue experiment with (forgecraft wa conversion pictured). Afraid I didn't keep notes on time and temp but the process did work. Bagged knife in the circulator for a bit, a little "persuasion" similar to removing a burned in handle...and it came off cleanly. I remounted same way as my original thread and now, months later...still going strong.

As for durability - two favorite knives I mounted with this method after I was done experimenting are still sturdy after more than six months use, occasionally pro kitchen and very frequently home kitchen. No shift in the mounting at all.


Mark76 - how has the sugru held up? Sugru, as I understand it, is just a version of silicon rubber once it's cured...so it is somewhat flexible/elastic and it can be cut or torn. wedged in to the handle cavity, I can see how it would be a great and waterproof gap filler... but is it really strong enough for regular use?

Happy Thanksgiving, all.


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## mark76

I used the Sugru on my daily use petty and a gyuto. Thus far (half a year) it has held great. It is elastic before drying, but after drying it is quite hard. Besides, but you use only such a small amount you won't notice any elasticity in practice. And it's very stong.


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