Jump to content

What are the limits of glued handles?


JohnCenter
 Share

Recommended Posts

Another beginner question brought up by my other thread.

 

I am curious what is the general consensus on the use and limits of handles being glued on? No pins or any other mechanical bonding.

 

I have seen the method used for small hidden tang knives but also to my surprise big choppers (leukus and seaxs). As a beginner what do I need to know to make sure I use this method correctly so that knives do not fail in use?

 

 

Link to comment
Share on other sites

The short answer is: it depends...

 

The handle on a properly surfaced and cleaned hidden tang using a good epoxy will often hold to extreme abuse.  

 

Many factors will influence the strength of the bond though, like the surface roughness, cleanliness and quality of the epoxy...

Link to comment
Share on other sites

Well if the handle material was micarta with a good epoxy, I would bet my life on it.

I would still put notches in the tang and make sure they're filled with epoxy, that counts as a mechanical bond I guess.

Link to comment
Share on other sites

I have tested this idea quite a bit.  The last formal test I did I took a hardwood handle (ash or hickory) and did a 7 inch blade with a stick tang (about 3/16 x 3/8 x 4) epoxied into the handle.  I used Gflex epoxy and let it set 24 hours.  I then used pipe clamps to attach the handle to a 3 foot long pipe.  I then used a 2 handed whanging process into the end grain of a For stump.  After about 6 blows ( or "whangs") the wood failed as the tang started to bend.  The epoxy required a hammer and anvil to remove.

I did not break the tang juncture, even though I used pretty square transitions.  The tang was soft and it started to bend about 3/4" behind the ricasso.  There were no mechanical connections at all, just epoxy in a hole in the wood.

Geoff

"The worst day smithing is better than the best day working for someone else."

 

I said that.

 

If a thing is worth doing, it is worth doing badly.

- - -G. K. Chesterton

 

So, just for the record: the fact that it does work still should not be taken as definitive proof that you are not crazy.

 

Grant Sarver

Link to comment
Share on other sites

IMNSHO, the concern for adding something other than the epoxy is much ado over nothing. 

I think that most problems with epoxies come from improper mixing and poor surface preparation. If the directions say to mix for 60 seconds, don't stir it up and call it good. Mix it for the 60 seconds. Prep the surfaces correctly and most importantly, leave a small amount on the bench to check and make sure the glue has set in the directions listed set up time. If you come back and the stuff on the bench is still runny, you screwed something up and you need to take it apart, clean the pieces and do it again.

 

This blade (and two others almost exactly like it) measures 10 inches long, 1.75 inches wide, with a 4.75 inch long handle. It survived the ABS JS performance test (as did the other two) with nothing other than a stick tang stuck in a piece of ash with West Systems epoxy.

Performance blade V2.jpg

 

This knife has been my personal carry for 16 years at work, camping, hunting, you name it, and I have taken this knife into the field and done what needed to be done.

Same handle design, except the wood is cocobolo, a notoriously waxy wood that some folks say is tough to glue and the epoxy is generic 30-minute stuff purchased at the local hardware store. The blade is 4.5inches long by 1.25 inches wide. 

 

My Hunter (4) V2.jpg

 

So, it seems that the presence of a pin, or other mechanical fastener is not really necessary.

Especially when you consider that this knife is several hundred years old and the handle is probably stuck on with a mixture of pine tar, beeswax, and sand.

 

Pic 1.jpg

  • Like 3

“So I'm lightin' out for the territory, ahead of the scared and the weak and the mean spirited, because Aunt Sally is fixin’ to adopt me and civilize me, and I can't stand it. I've been there before.”

The only bad experience is the one from which you learn nothing.  

 

Josh

http://www.dosgatosdesignsllc.com/#!

https://www.youtube.com/channel/UCdJMFMqnbLYqv965xd64vYg

J.States Bladesmith | Facebook

https://www.facebook.com/dos.gatos.71

https://www.etsy.com/shop/JStatesBladesmith

Link to comment
Share on other sites

I add shalow notches to my tangs and have started sand blasting tangs and the under side of guards before glue up before i did the blasting i didnt have any issues it just made sense to me as i have the blaster for other uses to add it to the prosses 

  • Like 1

Brandon Sawisch bladesmith

 

eagles may soar but weasels don't get sucked in to jet engines

Link to comment
Share on other sites

16 hours ago, dragoncutlery said:

... and have started sand blasting tangs and the under side of guards before glue up before i did the blasting i didnt have any issues it just made sense to me as i have the blaster for other uses to add it to the prosses 

 

This is a thing I have had to study some in my real job.  What we found is that bead blasting a glue surface is a good thing. (Shocking, I know)  However, it doesn't actually make the joint much stronger.  What it does is reduce the variability of the glue joint.

 

For example, a particular joint might have an average breaking point for 17 pounds over 30 test samples.  However, the test samples may range from 10 to 20 pounds.  The exact same parts bead blasted might have an average breaking strength of only 18 ponds, but 30 test samples may only vary from 16 to 20 pounds.

 

What Josh said is probably the most important thing about epoxy.  Proper mixing and surface prep are key.  If you don't get that right, you may only get a fraction of the published strength of the joint.

  • Like 2

-Brian

Link to comment
Share on other sites

I would add that if you have a fit that can develop a significant amount of pressure and therefore friction, like with a shallowly tapered tang, a significant amount of the loading can be taken my the tang-handle interface with the glue serving primarily as a bedding material. This is likely how knives like the one Joshua posted can still be incredibly durable. It’s often surprising how much force you can transmit with friction interfaces. Try hammering a foot or two of steel rod into the ground and then try to pull it out. With nails, you can hold together a whole structure with just metal-in-wood friction (also, it’s a slightly different idea, but the Washington Monument doesn’t have any mortar etc, it’s all gravity and friction). 

  • Like 1
Link to comment
Share on other sites

On 3/14/2022 at 9:23 PM, dragoncutlery said:

and have started sand blasting tangs and the under side of guards before glue up

My industrial experience was with epoxy-bonded aluminum bicycle frames. The prescribed bond prep was to blast with aluminum oxide grit followed by rinsing with isopropyl alcohol, no exceptions, no substitutes.

Link to comment
Share on other sites

  • 2 weeks later...

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

×
×
  • Create New...