My Knives Scales are Falling Off...

CDHumiston

CDHumiston

KNIFE MAKER
The last 3 knives I have made have had problems with the scales falling off under minor pressures.

Knife 1: 440C Stainless Madrone wood scales and Devcon 10 minute epoxy

Knife 2: D2 Tool steel Yellowheart wood scales and JB Weld epoxy

Knife 3: A2 Tool steel Green G11 scales and Tracy's 30 minute epoxy

I think I must be prepping the metal wrong or something. I may be polishing it too much on the tang. All three blades are fixed full tang knives.

Do I need to really rough up the surface of the metal before attaching scales?

Any help will be appreciated.

Thanks,
 
Chris, What I have done is to leave the Tang Rough. If it is going to be covered by scales I leave it rough. I also drill a couple of extra holes and fill those with Epoxy as well. Roughening up the pins also gives something for the epoxy to Grab, I think. But then I'm the new guy and really don't know as much as I'd like to. The only metal I Polish is exposed or immediately adjacent to the exposed metal,under the scales.
 
CDHumiston said:
I may be polishing it too much on the tang. All three blades are fixed full tang knives.
Click to expand...

If you are buffing the blade with a buffing wheel and compound, then that may be it.

The abrasive polishing compounds are wax, or grease based and if not cleaned off perfectly with good solvents like acetone and hot soapy water, will act as a release agent for the epoxy.

Roughing up the tangs will help.
The Loveless video demonstrates him using a sandblaster to abrade the tang for a better epoxy fit in addition to his hollowed out tang.

Avoid too much pressure that squeezes out all the epoxy and creates what is called a glue starved joint.
 
Chris Ive had one knife fail from glue and material . The handle is snakewood and has now cracked 5 times seriously on 3 seperate occasions . The glue im using acriglass sup pose to be the best out there . The knife got left in the sink the other day and the handle pretty much popped off . I havent had any trouble since I switched to gorrila super glue. I have another epoxy thats better than anyother type on the market as well its from LEE VALLEY called G2 epoxy . ALot of the canadian makers have switched to this . I prep all my tangs l like this . I take a diamond bit and scour the area then wipe clean with acetone then glue the handles on. It does help to have a few extra holes for glue to stick to . I also take the scale and with a sharp scribe or leather tool deeply scratch the wood that will give more for the glue to stick to and soak into . ALso wipe off the handle material some times it can be oily like ironwood cocobolo and rosewoods have lots of natural oils .Hope this helps chris . kellyw
 
If you go to say six pins , could be 1/8 diameter and any good epoxy with a rough tang all should be good unless you install a fiber liner in between and it gets wet. The liner will swell and pop the scales. Of course Corby or Loveless type bolts will always work. Frank
 
Frank Niro said:
If you go to say six pins , could be 1/8 diameter and any good epoxy with a rough tang all should be good unless you install a fiber liner in between and it gets wet. The liner will swell and pop the scales. Of course Corby or Loveless type bolts will always work. Frank
Click to expand...

Sound advice
I've read somewhere that there shouldn't be any need to key the surfaces but I always do. I drill a few extra holes and 'dimple' the surface with the drill and often use a dremmel to grind a few lines in the surface.
I try and get surfaces as clean as possible, using acetone or similar and I use Devcon 2 Ton which I warm slighty (gets it nice and thin) before using.
Here's a couple of 'before and after' pics

JethroKnife001.jpg


JethroKnife2006-1.jpg


Chris:)
 
surface preparation is far more important than the adhesive used. a slick metal surface will slough off adhesive every time. So will an oil or other residue. Steve S in our Glue Wars tests had every bond pre-maturely fail after he used Green soap to clean the surfaces.
Glue companies test their adhesives using sandblasted parts for a reason. It is the best surface for a good purchase of the adhesive.
does some one have a link to the Glue Wars thread on CKD?
 
Everything said about surface prep +1

And don't over clamp. Just a little pressure to hold it all together. Spring clamps, rubber bands, etc.
 
Two words: Corby bolts. They're now available in several sizes from our friends at USAKnifemaker. Like clamping scales, they don't need to be super-torqued down either. I bet a little loc-tite would go a long way, but haven't tried that yet.

Last year I rehandled a big Becker Brute for a fellow that wanted to keep the original scales/bolts and replace them if he ever sold the knife. So I used no adhesive at all, just Corby's, and cut the slots deeper so he could take it apart. The client reported that he tested it extensively by chopping wood and brush, and the scales didn't loosen up. That was my first time using Corby's and it made a believer out of me.

I have come to think of epoxy as mainly a sealant to keep moisture off the tang, and try to use at least one mechanical fastener. Of course the other fellows are correct that you can very good results from proper surface prep, etc. Guess I'm just a "belt and suspenders" kind of guy ;)
 
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Thanks for all the advice.

I am pretty sure after reading this and looking at the tang that I'm not prepping right. My tang is ground to smooth and slick. I'm going to rough it up and try again.

I do use pins and have some corbys on order. But I still want the glue to hold tight. The scales that came off last night pulled loose when I was doing final drilling for the Mosaic Pins.
 
Just a thought... I let my epoxy cure for at least 12 hours at room temp before doing any more work on the scales. Not saying you don't, but I didn't wait long enough once and ended up starting over :eek:
 
Thanks James, this last set had been on the knife for a week. I'm fairly convinced the tang is just ground to smooth and shiny...I'm going to work on it tonight.
 
Three words Gorilla Super Glue. I let My Glue set at least 3 Full minutes sometimes 5 minutes before I work the handles.
 
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Hey Chris,
I have a WIP I did in my forum about handles. Heres a couple pics of what I do to "dimple" the backs of my scales, and then I rough up the tang with about 60 grit or so, then long set golfsmith epoxy, overnight lightly clamped. In my WIP its step by step if you wanna check it out. Anyways, heres the pics of the scale backs.

dimples.jpg

eopxyready.jpg
 
Shaughnessy said:
Hey Chris,
I have a WIP I did in my forum about handles. Heres a couple pics of what I do to "dimple" the backs of my scales, and then I rough up the tang with about 60 grit or so, then long set golfsmith epoxy, overnight lightly clamped. In my WIP its step by step if you wanna check it out.
Click to expand...

OK, I ground the tang with a 60 Grit belt tonight. I'll dimple the backs of the scales before I try gluing them up. I'll also take a look at your WIP before I start gluing up.

Thanks,
 
Also hollowing out the center of tang a bit has been recommended to me by a few people to help adhesion. Corbys are probably one of the best things to use though. They'll hold the scales on without glue, the glue can basically act more as a sealant when you use them.
 
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I use corby bolts or pins with tapered holes peened in and super glue after the handle scales are installed. The only time I use epoxy at all in for hidden tang handles.
 
This might not be a popular suggestion, but my recommendation is to get rid of the 5 minute epoxy. The reason I tout using acraglass so much is because it is simply a better all around product.

Early in my knifemaking career I used Devcon 5 minute epoxy....and about 5-6 years later I had people calling me saying that the handles on their knives were coming loose. This prompted me to do some "epoxy research"....

I dug for a long time and finally got to know a fella who was a chemical engineer at one of the companies that makes epoxy (name and company intentionally left out). What I found out shocked me. Most 2-part epoxies that you commonly find in stores is chemically engineered to start breaking down in 4-5 years. When I asked "Why!?" the individual chuckled and told me... "We are in the business to SELL epoxy, if we made something that lasted forever, you'd never have to buy any more of our product!"

After trying a number of different adhesives, I found and settled on acraglass....mainly because it has a 10 year shelf life, and a guaranteed 50 year hold life. The closest thing I have found to those numbers is one of the West System marine epoxies that has a 5 year shelf life, and a guaranteed 25 year hold life. Both are great "glues", but I chose the Acraglass because it has a thinner consistency when mixed, and since I build a lot of hidden tang knives, it better suits my application.
Acraglass is certainly not cheap....I spend about $60 for a 28oz bottle of resin, and a 7oz bottle of hardener, but that's enough glue to last me for approx. a year. But if you add up the cost of all the double tubes and/or bottles of Devcon you use, I think you'd find that not only is the acraglass a much better product, but it's also more economical.

The tang prep does play a major role too.....roughed up and completely clean are two MUSTS.
 
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