Epoxy for joinery question

[VizslaDad]

Hi folks - I am building a Stickley-inspired entry bench for some family friends. I have not finished tuning the joinery for my quadralinear legs, but I anticipate some minor gaps here and there. Epoxy was already in my plans for gluing up the legs, and I think I have enough J-B Weld ClearWeld Pro on hand to glue the legs and their cores together. However, I worry that the 5 min set time on the material I have could be unforgiving. I could let me shop get colder than 40 degrees F and that could give me a little more (and less pleasant) working time. All of this is to say I believe I should spend the money to get a quart or two of one of the commonly available two part epoxies. If anyone has a recommendation for/against a specific product I would love to hear it. 

I am currently looking at buying System 3 resin and their #2 (medium/30 min pot life/55 degree application temp) hardener. Their #1 can handle temps as low as 35 deg F but only has a 15 minute pot life. The #3 requires 75 degrees(!) but has an hour long pot life. I know so little about these adhesives that I don't know where to start to compare System 3 to West Systems or the other ones.

Thanks for any advice anyone can give.

p.s Here are some snapshots from Bob Lang's Shop Drawings for Craftsman Furniture in which I found the joinery technique I'm using for the legs. My leg pieces are a hair shy of 2 inches wide so this technique has made for some exciting work with pushblocks. 

 

 

[Mick S]

I think you're the best one to make that determination. Here's what i would recommend:

Once the leg pieces are milled and prepped for assembly, practice the glue up dry two or three times so that you can get the hang of it. Then use mineral spirits in the place of the epoxy, applying it just as you would the epoxy and time the whole process. 

Once you're comfortable that it will take 8 minutes or 14 minutes or whatever, add about 5 minutes to that to give you the actual glue up time. Epoxy is slickery stuff and your pieces may want to creep on you, so be prepared for that in your practice runs.

 

[wtnhighlander]

My experience with epoxy is that the longer work time formulas (West, in my case), stay runny for a long time, and can escape the joint easily. I prefer wood glue for joinery, and epoxy to fix defects. The 5 minute stuff is great for small gap filling.

[Coop]

I have used West System for several years with no complaints. With having no severe temp constraints in Houston, I would guess working time to be 20 minutes or so. That could probably be extended but I tend to get a pucker when it starts to thicken, although adjustable. 

[drzaius]

DO NOT, I repeat, DO NOT attempt any but the smallest, simplest glue up with 5 minute epoxy. 5 minutes is about all you get but if mixed in larger batches, the stuff can go off in only a couple of minutes.

You're welcome.

[Chet]

2 hours ago, drzaius said:

DO NOT, I repeat, DO NOT attempt any but the smallest, simplest glue up with 5 minute epoxy. 5 minutes is about all you get but if mixed in larger batches, the stuff can go off in only a couple of minutes.

You're welcome.

This sounds like there may be some experience behind this post. 

[drzaius]

2 hours ago, Chet said:

This sounds like there may be some experience behind this post. 

Maybe...

[Don Z.]

I've used a lot of epoxy.  Here's what I can tell you.

 

WEST is very flexible, because you can use different hardeners, and you can add the appropriate thickeners.  It's a little expensive, but you're paying for their R&D, and their customer service.  By the way, by "flexible", I don't mean the epoxy itself flexes, I mean you can adapt it to different uses: Colloidal silica for strength, micro balloons for fairing, etc.

I like System Three.  System Three has their "SilverTip" epoxies, which are pre-loaded with colloidal silica, so you don't have to add it.  

I was going to add: "Whatever you do, remember that epoxy is exothermic.  That is, it makes its own heat as it cures.  What this means in practice is that you don't want to mix it in a styrofoam cup, it will cure even faster, perhaps even melting the cup.  You can slow down the reaction by mixing it in a flat pan... spreading it out keeps the heat from "consolidating", speeding its own cure."

 

Then I got to thinking about what you're using it for, and how you need to clamp things together once you've applied the epoxy.  If I were in your shoes, I'd use Thixo (WEST), or System Three's equivalent, or even score the equivalent from Jamestown Distributors.  These are basically a mix that comes in a caulking tube, with mixing tubes on the end so that you simply lay a bead down, and you have plenty of time to clamp up.  Let the mix harden in the mixing tube, toss it, and then screw on a new tube the next time you need some.  For the amount you're gluing, you'll have some from one tube left over.  Also, remember, contact pressure is enough, you don't need to clamp too tightly.  I'd consider taping the joints, adding the epoxy, then "rolling" the legs together and clamping.  Should work.  People glue 40 foot birds mouth masts together with this stuff, yours should be easy in comparison.

Oh, and do a search for an eBook by Russell Brown.  Everything you ever wanted to know about working with epoxy, but were afraid to ask.  But for this job, I'd use Thixo.  

[Don Z.]

I wanted to add a link.  In looking up the link, I realized I've used this stuff so much, I confuse myself.

Thixo is the Jamestown Distributors house product (sold as "Totalboat").

https://www.jamestowndistributors.com/product/product-detail/64347

 

The WEST system stuff is called SIXten.  Same idea (also on the Jamestown site).

SystemThree calls their's "Gel Magic".  

https://www.systemthree.com/products/silvertip-gelmagic-non-sagging-epoxy-adhesive

Any of the above will do what you need it to do.  I just glanced at the specs for SystemThree, because I had the page open.  Minimum cure temp is 50 degrees, gel time at 77 degrees is 30 minutes, and tack free at 77 degrees is 3 hours.  Because it's not sitting in the cup, the exothermic reaction is not working against you.  Also, you're only mixing that one thing you're working on... If you really want to take the time, you can put the glue on half the joint, clamp it all together, wait for the cure, then take it apart and glue up the remaining side.  Twice as much work, but you'll get comfortable with the epoxy.  Once you understand the Chemistry, you can get really creative with the stuff.  It really is better life through chemistry.

[VizslaDad]

Wow, thank you everyone. This thread shows a wealth of information and experience.

My first leg's worth of pieces were only fair to middling off the tablesaw, and are now approaching okay after an hour's work fiddling by hand. We'll be putting that leg against the wall. I cut the profiles for this particular leg the other day and my setup wasn't great, I think. It looks like my riving knife needs to be tweaked.

That said, I just finished cutting the rest of the profiles into my leg pieces and they are pretty good. The legs go together squarely and the miters aren't very gappy along any corner, but there are some gaps. I think I can improve them with a little shoulder plane work. This is all to say that structural gap filling is a necessity in this glue-up. I will probably also burnish the corners with my card scraper burnisher, too. This is my first furniture project in a couple years so I'm trying to avoid digging new holes for myself while chasing perfection.

@drzaius I felt silly about considering the 5-minute stuff after I posted my original question. I'd probably be more likely to adhere the workpieces to my bench than get the joints together properly. 

@wtnhighlander I would prefer to use wood glue here, but this is a special situation for me. The legs have four miters and  an interior core. Despite my best efforts I'm going to need to rely on the epoxy to make up for my shoddy joinery  

@Coop what you say makes sense. I think I am going to try @Don Z.'s suggestion of one of the thicker products. 

@Don Z. I've seen people use Thixo and similar on youtube etc. but I didn't know where to place it in my consideration set. Your description sold me! I had originally thought to use the tape-and-roll to keep the pieces in position during glue up. I think I am going to use the tape-and-roll + a thick epoxy product like Thixo a shot. 

[Chestnut]

15 hours ago, VizslaDad said:

I would prefer to use wood glue here, but this is a special situation for me. The legs have four miters and  an interior core. Despite my best efforts I'm going to need to rely on the epoxy to make up for my shoddy joinery

With the huge surface area of long rain glue joint you could get away with wood glue here. These joints will see minimal stress so you don't really need to have 100% of the surface area covered in glue.

That said if you are buying an epoxy there is a significant cost involved (~$200) and the volume a bulk buy can save you is tremendous. My West system gallon of resin has lasted me MANY years and per volume is FAR FAR cheaper than the 5 min stuff from box stores with a MUCH higher quality. Consider not the epoxy for this specific case but the best epoxy for all you current and possible future needs. For reference West system gallon kit is 168.8 oz of epoxy for $190 ($1.125/oz) a 5 min at $5 for 0.85 oz is $5.88/oz.

I use epoxy for

• complicated long open time glue ups
• crack filling, knot filling, defect filling
• fixing kitchen utensils
• attaching knife scales to blanks
• casting applications
• sealing the end grain of furniture legs (which can act as furniture slides for chairs or protect outdoor furniture)

With that list in mind i decided on West System with the 207 Hardner. It has equal strength to all the other high quality epoxies but has the benefit of being used for applications where it's clarity is appreciated. There are other clear options from other manufactures so I'm not exactly suggesting West System I'm suggesting getting the system that focus on a clear result. This allows the flexibility for doing castings and fillings. Leaves tinting open but also allows for the addition of fillers like Don mentioned above.

The 207 has a good 45 min open time. The down side is the temperature requirements. That said if you  find yourself needing low temp grab a different hardener in a small size that works with lower temperatures.

[Wimayo]

This is not relevant to your question, but I just can't help but comment on the joinery. The only reason for the little corners is to hold the 4  pieces in alignment as the glue is drying. You can do the same thing with a spline (or biscuits, but wold be a lot of them). And, the spline is a whole lot easier to cut. I made 9 legs recently for a corner desk. Worked great.

[VizslaDad]

On 1/27/2021 at 7:07 PM, Wimayo said:

This is not relevant to your question, but I just can't help but comment on the joinery. The only reason for the little corners is to hold the 4  pieces in alignment as the glue is drying. You can do the same thing with a spline (or biscuits, but wold be a lot of them). And, the spline is a whole lot easier to cut. I made 9 legs recently for a corner desk. Worked great.

Oh I hear you. To be honest, I wanted to test myself and my tool setups a bit since I have been away from furniture projects for a couple years. I have some of Bob Lang's Craftsman furniture books and enjoy all the joinery drawings in them. When I saw the Stickley joinery with the little corners it looked like something to try to gauge where I am at the moment.

Hindsight being what it is, I should have just used my domino or splines! 

 

[VizslaDad]

On 1/27/2021 at 10:50 AM, Chestnut said:

With the huge surface area of long rain glue joint you could get away with wood glue here. These joints will see minimal stress so you don't really need to have 100% of the surface area covered in glue.

[...]

I use epoxy for

• complicated long open time glue ups
• crack filling, knot filling, defect filling
• fixing kitchen utensils
• attaching knife scales to blanks
• casting applications
• sealing the end grain of furniture legs (which can act as furniture slides for chairs or protect outdoor furniture)

[...]

I read you loud and clear. I do agree wood glue would probably be fine. I bolded your items that I am applying to my situation (I hadn't thought of the last one, but that is a great idea!). I am thinking that the imperfect interface between the "leg box" pieces and interior core will require actual structural filling. Plus, the long open time will give me more time to fiddle with the fit/fix clamp induced slippage vs racing against the clock. I will still practice my glue up routine multiple times before showtime of course.

[Wimayo]

18 hours ago, VizslaDad said:

I read you loud and clear. I do agree wood glue would probably be fine. I bolded your items that I am applying to my situation (I hadn't thought of the last one, but that is a great idea!). I am thinking that the imperfect interface between the "leg box" pieces and interior core will require actual structural filling. Plus, the long open time will give me more time to fiddle with the fit/fix clamp induced slippage vs racing against the clock. I will still practice my glue up routine multiple times before showtime of course.

I'm with you on the use of long set time epoxy. Gluing, aligning. and clamping multiple pieces takes time and epoxy provides it. Also, I found when doing a similar project, long miters don't always fully cooperate and the epoxy provides some gap filling capacity and reinforces the very fragile corners. Good luck.