CA vs. epoxy/

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Woodchipper

Woodchipper

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I was looking at some YT videos and one mentioned epoxy to avoid blowouts of acrylic blanks. Now...there was mention of 5 minute epoxy. That might work for mixing a small batch for one pen but I would look at doing a few pens at a time. Not necessarily an assembly line but to mix a batch and allow the epoxy to set up at about the same time and then turn. In the past, I have use Devcon Two Ton epoxy. Fellow told me about it years when I built golf clubs. Your experience and expertise are welcome. TIA.
 
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If you have followed me on this forum through the years, you would know whenever this conversation comes up I am a huge proponent in using System3 T88 epoxy for gluing in tubes and also my segments when making my own blanks. It has never failed me and is very strong. It is gap filling despite what some say here. Will say this the longer open time and this does not cure for 24 hours, they stronger the adhesive is. 5 minute as well as 15 minute work just fine but as you say you need more open time to do muliples of projects at once. I stand behind this adhesive. It does have a yellow color when cured so if you are looking for a clear epoxy this is not it but System 3 does have that too. Less open time.

https://www.systemthree.com/products/t-88-structural-epoxy-adhesive
 
I have used JB Weld and System3 T88 a good deal now. The T88 is amazing stuff, so I second what John says. Can't really go wrong with it!

Something I learned about epoxy is that its curing strength and curing time is dependent on temperature. At room temp, most epoxy's will require a 24 hour cure. However, and this is actually well documented in the T88 data sheets, at a higher temperature, you actually get a much stronger bond, and it cures faster as well. The higher temperature increases the flow of the glue, which maximizes cross-linking, maximizing the bond strength. From the data sheet:

https://cdn.shopify.com/s/files/1/1...-78af-4eba-8466-27b2898ee639.pdf?v=1589919304
"At 77°F, T-88 will harden in 6-8 hours and will reach functional strength in 24 hours. T-88 has been specifically formulated to cure as low as 35°F without reduction in strength; this cure will require approximately one week. At 150°F, T-88 will set within 30 minutes and develop maximum bond strength and impact resistance after 2 hours. If excessive flow-out occurs, allow 2-4 hours at room temperature before heat cure."
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The "standard" open time with T88 is 25 minutes (IIRC 77 degrees), although this is also temperature dependent and you can get more open time at cooler temps. If you work at room temp, then you'll have that 25+ minutes regardless. Once you have glued all your tubes in, then place them somewhere warmer, ideally at 150 degrees, and you'll have a fully cured set of tubed blanks within a couple of hours.

A note about the JB Weld stuff. I have been using the two larger bottles of the 5 minute two part. The info on the back says 5 minute set and 1 hour cure. In my experience, the 1 hours bit is way off. You can feel a lot of flex in the bond at 1 hour, even with a perfect 1:1 mix. I find it can take even longer than 24 hours for a really good, solid, hard set. I have experimented with higher temp curing. I think it helps, but I still find its closer to 24 hours than the specified 1 hour. In the end, while JB Weld can and does indeed cure with a very strong bond, I find the T88 is just a better product, and with the ability to cure it at 150ºF within a couple of hours, it can definitely speed up the overall pen making process.
 
I used System3 T88 until somebody suggested I try DevCon "two ton" (the slow cure version). Since he made custom bows and arrows using it, I thought it would be worth trying some. Now I use DevCon when I can find it, if the local Ace Hardware is out of stock I'll use T88.
 
duncsuss said:
I used System3 T88 until somebody suggested I try DevCon "two ton" (the slow cure version). Since he made custom bows and arrows using it, I thought it would be worth trying some. Now I use DevCon when I can find it, if the local Ace Hardware is out of stock I'll use T88.
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I find the two Ton epoxy at Ace Hardware. They have ordered it for me on occasion. Will look into T88.
 
I've used the BSI (Bob Smith Industries) epoxy I get off Amazon for years now without any issues. Its the 5 minute cure and I can mix up enough for 3 cigar pens and get them all tubed before it starts to cure. I have also turned some within 30 minutes of glue-up with no problems. For me its pretty inexpensive, easy to get off Amazon, and has never had any blowouts so it definitely works for me...
 
Different companies make different "timeline" curing epoxies. 5, 15, 20 / 25, 30 minutes and 1 hour, and more. I have and use 5, 20 - 30 and 1 hour epoxies, depending on how many objects I am gluing and how much open time I need.

Blowouts: If one is willing to spend the time (several hours) doing a research here on IAP, there will probably be a 10 to 1 blowout on CA vs epoxy. The reason will probably be four fold.
1a. Just because it sticks doesn't mean that it has good adhesion - and the reason is due to air cavities between the tube and blank. The LACK of understanding this is the greatest cause. CA will stick at several points between the blank and tube, but when a blowout occurs, and looking at the tube and blowout piece - it has been common here for the pen maker to post a surprise at the lack of adhesion points. A blowout does show where the adhesion IS and IS NOT.
1b. Thin is more of a culprit than medium or thick CA, but medium and thick still can have considerable air cavities between the tube and blank.

2. CA is far more brittle than epoxy. Brittle adhesive does not stand "shock" as well as "hard but non-brittle" adhesives. A "catch" produces a shock/jolt/jarring and brittle will let go quicker. Some epoxies can become brittle enough that they will let go also, but In My Opinion, the "let go" during a catch is because the tube is not clean or has not been scored. (See 4 below.)

3. Since Epoxy is more like extra thick CA, and since it is not basically brittle, it is easier to add epoxy and it not drop or spill off the tube before inserting. There is another step in using medium/thick CA and also epoxy: adding clay/putty inside the tubes to prevent the epoxy from building up inside ahead of the insertion and going inside the tube as it is inserted further.

4. Score/sand or wipe/clean the tube before using. This should be done regardless of the kind of adhesive used.

I use epoxy about 75% of the time and polyurethane expanding adhesive about 25% (give or take a little). The reason is that poly expands into areas in which there may be an air cavity inside and therefore give 100% adhesion coverage area-wise between the tube and blank. John T and some others have a special technique in which they get close to or full 100% coverage with epoxy, and have never had a blowout with epoxy (especially in using T88). Also I need to mention as John T has pointed out that expanding polyurethane can cause problems with its expansion and he is right. But, if one is aware of and experienced in this, there are ways around the expansion problem. Experience helps.
 
leehljp said:
2. CA is far more brittle than epoxy. Brittle adhesive does not stand "shock" as well as "hard but non-brittle" adhesives. A "catch" produces a shock/jolt/jarring and brittle will let go quicker. Some epoxies can become brittle enough that they will let go also, but In My Opinion, the "let go" during a catch is because the tube is not clean or has not been scored. (See 4 below.)
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This is a big one! There are flexible versions of CA, which might reduce this problem, but even fully cured, epoxy has a slight bit of flex. Its not rock hard, just enough flex to give you a strong bond and just a tiny amount of give to prevent say a catch from ripping everything apart.

The amount of flex in epoxy can be problematic too, but it shouldn't be a problem with proper mix ratio. Improper mix ratio, or potentially too-little cure time, and the flex in epoxy can also potentially let go at adhesion points. Had this happen once with some solid color acrylic blanks that I'd been segmenting together (in fact, a project I haven't even finished, was last working on it in late winter or spring before my year...eh, imploded...) I think I'd mixed the wrong ratio, and the bond had too much flex, both on the tube and between the segments. All of it ended up peeling apart during turning! I tried CA, and ran into the brittleness issue. That was when I started using T88, and it worked like a charm.
 
Jon brings up a great point about flexing of adhesives. Now with what we do and the thinness of materials we use flexing is not the holy grail of our failures but it can be when using adhesives such as CA, Glues such as epoxy and somewhat polyurethane glues will have enough flex to help avoid those mishaps in our journey to finish turning a pen and also keep the parts or segments together. Could also help if dropped. Hank brings up the point about CA glues being a contact glue and it is. It will dry and mostly disappear when gluing in tubes unless tube is touching the inside of the blank. Not much gap filling abilities from CA. When brittle it snaps easily and thus the many blowouts you see are for this very reason. Many books and many teachers still preach the use of CA as an adhesive for tube installing. This mainly is because it is quick and dries quickly to be able to move onto next step quickly of the pen turning journey. I just was never a fan of this for above reasons. Also Hank brings my name up when it comes to the use of Polyurethane adhesives, and I am not a fan of this either but do realize they are a step above CA. Nothing wrong to use them if done right. With that said I ran into this article that explains polyurethane glues and the methods to use, the pros and cons and leave it up to you to decide if it is an adhesive you want to use. I do not even use in my woodworking for I think there are better alternatives but again to each their own. Knowledge is a powerful thing and maybe this article will help add some knowledge to your tool belt. Good luck and happy turning.

https://sawsonskates.com/polyurethane-glue/
 
Interesting replies and thanks. Lee, I was watching a video yesterday. Can't remember the guy but he put the CA on a piece of cardboard and rolled the tube over it to get an even coating.
 
Woodchipper said:
Interesting replies and thanks. Lee, I was watching a video yesterday. Can't remember the guy but he put the CA on a piece of cardboard and rolled the tube over it to get an even coating.
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But it does not matter because CA is not gap filling. Unless that tube fits snugly in the drilled hole and there is no play then it has a good chance of being OK. But if there is any room between blank and tube the glue dries and shrinks and only where the contact points are with blank and tube is what is glued. Even thick CA shrinks when dried.
 
I am pondering mixing a batch of Two Ton Epoxy which is 30 minutes set time. Use a cheap hobby paint brush to apply it and insert tubes into several prepared blanks. Your thoughts? BTW, not looking to be a production pen maker.
 
You can buy those acid brushes for peanuts and they can work. What I use is popsicle sticks. Use the same one that I mix with. I have a small block of wood that I cover with wide packing tape. I mix what I need and then wipe down with acetone to clean the block ready for next time. After a few mixtures you really get a feel of how much you need to mix. You can always mix more without it being a problem. I use an old screwdriver o put epoxy in the blank hole. Plug tubes with playdoe and any squeeze out use screwdriver to put back on block. This is so second nature to me because I do it so often and use epoxy adhesive for so many things.
 
I get 100 hobby brushes from Oriental Trading, just a few cents each. I used them for applying epoxy to custom fishing rods...use and toss. Still have a bunch on the shelf.
 
JohnT., these are the kind of paint brushes they use in daycare.

Adding: Got down to the last part of an acrylic blank and got a chip/blow out. Trying the cheap brushes to spread the CA more evenly.
 
jttheclockman said:
But it does not matter because CA is not gap filling. Unless that tube fits snugly in the drilled hole and there is no play then it has a good chance of being OK. But if there is any room between blank and tube the glue dries and shrinks and only where the contact points are with blank and tube is what is glued. Even thick CA shrinks when dried.
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I think to a degree, CA can also seep into the wood. This is probably more true with open grained woods, but CA doesn't just shrink, I think it will also soak in in some cases. I mean, this is one of the reasons we will often use thin CA on a blank before applying a CA finish...it can soak in and "seal" the wood or for softer and more brittle woods, "stabilize" it.

Between shrinkage and this soaking, I've found CA is just not an optimal glue to use for tubes in blanks. I guess it might be a bit better with resins, but still, epoxy seems to do a better job filling the space.
 
FWIW, I'm now going to epoxy, Devcon 5 Minute Gel Epoxy. Only done a couple of pens so it is a "wait and see" situation.
This is a good video on gluing.
 
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