Epoxy for loose (bad) tenons ?

[Steve1]

I am working on a sapele dresser, and I missed on cutting a bunch of tenons, so anyways I have a bunch of tenon joints where one side of the tenon makes good contact with the mortise and the other side has maybe .015" to .020" clearance.

Should I glue veneer to one side of the tenon and try again, or could I use epoxy in these joints ?

 

[ChuckM]

I'd do the veneer approach.

 

[Cheese]

I'd go the epoxy route...easier to deal with and probably a stronger connection. I've done aluminum dominoes with epoxy and they're a "done deal" as far as being a permanent connection goes.

 

[luvmytoolz]

I'd second the epoxy, it soaks into the timber reasonably well and creates a super strong bond.

 

[PaulMarcel]

I'd use epoxy with a filler like West System's 404 high-density filler (or your brand's equivalent).

Wipe the epoxy on the tenon, add a tiny bit of filler to the pot, then apply the epoxy-filler mix to the side with clearance. Doesn't have to completely fill that side. When it cures, it'll be a rock.

If you don't have any similar filler, you can use sawdust. I have 404 on the shelf so that's what I'd grab.

Another alternative is to put glue in the mortise and on the side properly cut. On the other, put some of that PC Lumber epoxy putty (looks like a Tootsie roll). Smash a blob of it so it is a hair thicker than the clearance and it will fill the void and harden in a similar way to the 404 method.

 

[mcfal12]

I'd use epoxy with a filler like West System's 404 high-density filler (or your brand's equivalent).

Wipe the epoxy on the tenon, add a tiny bit of filler to the pot, then apply the epoxy-filler mix to the side with clearance. Doesn't have to completely fill that side. When it cures, it'll be a rock.

If you don't have any similar filler, you can use sawdust. I have 404 on the shelf so that's what I'd grab.

Another alternative is to put glue in the mortise and on the side properly cut. On the other, put some of that PC Lumber epoxy putty (looks like a Tootsie roll). Smash a blob of it so it is a hair thicker than the clearance and it will fill the void and harden in a similar way to the 404 method.

Another option could be a combination of patching the tenons with a combination of a domino and wood glue/epoxy. Cut them off after it dries and recut the tenions. That’s obviously a lot more work but if you’re uncomfortable with the above choices it is a viable route.

 

[squall_line]

Can you clarify if the looseness/lack of contact is on the flat part of the tenon or the short sides of the tenon?  I'm assuming on the flat, since you mentioned veneer, but it would make sure that the recommendations are proper/adequate for the actual issue.

 

[Packard]

I agree with others who suggest epoxy.  I used to be able to find 30 minute epoxy.  I was not able to find it recently.

Buy the longest cure time epoxy you can find to allow for an extended glue up assembly.

I am of the opinion that a very slow cure time enhances the bond to wood.  It allows the glue time to flow into the pores in the wood before it sets up.  If I could find 2-hour epoxy, I would definitely use it.

I find that epoxy will fill rather large voids, and a looser fit will allow for faster assembly.

Note that there will be some hydraulic action while assembling with epoxy. Be prepared use greater clamping pressure and be ready for squeeze-out. I assembled 1” diameter shafts into 1” holes with epoxy.  The hydraulic pressure tried to push the shaft out of the hole.  I drilled a couple of tiny holes to allow the epoxy to flow into the holes rather than push the shafts out of the holes.

Addendum:  I did a search for 2-hour epoxy, and Amazon carries one version. There are probably others:

Blue-Label General Purpose Slow-Setting Epoxy (2 hours) 10 Packs (#04005)

 

[Steve1]

Can you clarify if the looseness/lack of contact is on the flat part of the tenon or the short sides of the tenon?  I'm assuming on the flat, since you mentioned veneer, but it would make sure that the recommendations are proper/adequate for the actual issue.

Yes, the issue is on the long side of the tenon.

 

[kevinculle]

On cure time, I routinely use West Systems G-Flex 650 epoxy in woodworking applications where its characteristics provide advantages.  It has a pot life of 45 minutes and working time of 75 minutes with full cure time of 24 hours at 72F.  Once I have the assembly made up and clamped, I then use a 75W grow light for smaller assemblies or an old 300W halogen work light for larger assemblies to raise the temperature and accelerate the cure.  I use a thermocouple and setup the light to get the joint area to 140F-160F (60C-71C) which will bring the joint to full cure in 2 to 4 hours without sacrificing strength.

 

[Packard]

On cure time, I routinely use West Systems G-Flex 650 epoxy in woodworking applications where its characteristics provide advantages.  It has a pot life of 45 minutes and working time of 75 minutes with full cure time of 24 hours at 72F.  Once I have the assembly made up and clamped, I then use a 75W grow light for smaller assemblies or an old 300W halogen work light for larger assemblies to raise the temperature and accelerate the cure.  I use a thermocouple and setup the light to get the joint area to 140F-160F (60C-71C) which will bring the joint to full cure in 2 to 4 hours without sacrificing strength.

I did not know you could accelerate cure times with heat.  Will that work for any rated cure time?

I’ve been told that using more or less than the recommended hardener will change cure times.  I am reluctant to do that, fearing that it will compromise the strength of the joint. 

I have had good luck screwing wood screws into the edge of MDF by first drilling an oversized pilot hole that is just small enough to allow the screw to barely bite into the MDF.  I apply the epoxy to the screw threads with generous amounts of glue.  I then screw into the edge.  Because the pilot hole is oversized, I never got any splitting.  And the strength into the edge was excellent.  I suspect it results in a stronger hold than the glue-a-dowel-into-the-edge-first and then use the screw. It is faster and easier too.

 

[Michael Kellough]

[member=74278]Packard[/member] that is a superior approach to securing screws in the edge grain of MDF but sometimes you can get away with simply putting a clamp where the screw will enter. Prevent the wood from spreading and it will compress around the screw. Or the head will snap off…

 

[Koamolly]

Lots of good info at West Systems.
https://www.westsystem.com/instruction/epoxy-basics/dispensing-and-mixing/

FYI…. ”DO NOT attempt to adjust the epoxy cure time by altering the mix ratio. An accurate ratio is essential for a proper cure and full development of physical properties.”

I've used a lot of West Systems Epoxy. Really like the GFlex. It was previously mentioned but you want to mix the liquids and wet each piece, then add whatever additive, mixed in really well, then apply the additive to joint and assemble.  I usually will warm up  the joint and the epoxy a bit with a heat gun.  It will allow the epoxy to flow better for wetting.  Epoxy works better without high clamping pressure causing squeezing out most the glue so your loose joints will be really strong filled with epoxy. 

West has really good additives.  You can use them for fillers and to mix to consistency you want.  Also, their cups and stirrers are really worth getting.  They last a long time and epoxy snaps off after curing. Can be reused many times. 

 

[PaulMarcel]

I hit update and Koamolly put the right update: don't adjust the amount of hardener to change the cure time. Long ago, I did that intentionally with the 205 Fast hardener and found that the pot started smoking and the epoxy was bubbling (although slowly). Smeared it on some scrap just to see what would happen and the result looked like cracked glass after curing. I'm pretty certain the strength was greatly compromised (I didn't glue together any joints with it).

 

[smorgasbord]

I'd just add that the pumps are worth whatever they charge.

 

[Packard]

I'd just add that the pumps are worth whatever they charge.

I must have missed the reference to “pumps”.  What pumps?

 

[luvmytoolz]

I'd just add that the pumps are worth whatever they charge.

I must have missed the reference to “pumps”.  What pumps?

West sell pumps that screw into their resin containers so you don't have to pour it. Just pump out the amount you need.

 

[PaulMarcel]

West sell pumps that screw into their resin containers so you don't have to pour it. Just pump out the amount you need.

Plus you can move them to new hardeners when you finish one (same to same, duh). I'm on at least my third 405 on the same pump. One thing is curious: the 405 and 406 have different mixing ratios with the 105 resin, yet the pump for it works for either one.

 

[Koamolly]

Pretty sure the 205 and 206 hardeners are the same ratio at 1:5.  The 207 is 1:3.  They make a different pump for 207.
https://www.westsystem.com/products/300-mini-pumps/

 

[Packard]

I'd just add that the pumps are worth whatever they charge.

I must have missed the reference to “pumps”.  What pumps?

West sell pumps that screw into their resin containers so you don't have to pour it. Just pump out the amount you need.

Ah!  Thanks for that info.  Sort of like shot pours at a bar.  The epoxy I’ve used has you squeeze out a line of the glue and another same-length line of hardener.  No pumps.  Plus the stuff I’ve used is too viscous to run through a pump.