Some data for the great Gorilla Glue/polyurethane glue debate

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AllanS

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Just as an experiment on a 'learnin' pen'* I played around with Gorilla glue due to see if it will help with the number of blow outs I'm getting ala the Loctite GO2 failure thread, here's a couple of data points that i just found out

Gorilla glue foaming out through gaps in the segmenting. That was actually a pretty snug fit for the segmenting too, needing a few seconds on the belt sander to thin the segment down enough to just fit. This was with the end clamped closed to keep the tube from potentially being pushed out. That expanding foam had to go somewhere.
But the CA that glued the segment in held it in place.

Gorilla on segments 2.jpg
The shine line dampens the impact, but there is a very visual hiccup at that point in the pen. The same issue can be seen at the other side of the segment.
Gorilla on segments 4.jpg
On the scallops side the gorilla glue got in there and pressed open the segment. Segment was glued down with epoxy (either Mercury or T88, I can't remember which line of effort this happened on). I was able to get in there in time and clamp down the segment before the glue set.
Gorilla on segments 5.jpg


For me I think I'm going to avoid Gorilla glue etc for any segmented pens I'm working on. That being said, the foaming/expanding aspect appeals to me on non segmented pens as I too tend to see large 'dry' spots where there is no glue on those times when I have a blank blow out.





* Ala Fred Bruche's "Sometimes you win, sometimes you learn"
 
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monophoto

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Very interesting. My experience with using polyurethane to glue in tubes has all been positive, but I don't do a lot of segmenting.

One could arrive at the conclusion that this experience demonstrates that polyurethane should not be used to glue tubes in segmented blanks. In my mind, that generalization is entirely too broad.

Or, one could conclude that the segmenting glue-up needs to be done better if polyurethane is to be used to glue in the tube. Perhaps that's a good thing - if you see foaming between segments when you glue in the tube, you should revisit the process used to glue up the segmented blank to prevent that problem in the future.

Or, one could conclude that the use of polyurethane glue when inserting the tube is a quality check on the segmenting - foam between segments indicates that the segmenting glue-up was defective, and the blank should not be used. Again, probably a bit harsh, but it really depends on how severe the foaming is and the impact of the finished blank.

I'm somewhere between the second two interpretations. But I will note that it would be incorrect to assume that using polyurethane glue on the tube compensates for sloppy segment glue-ups because the foam will penetrate any gaps between segments - yes, the foam will penetrate gaps if they are present, but that foam has little or no structural strength. It may fill the gaps cosmetically, but it doesn't strengthen gaps that are weak.
 

leehljp

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Thanks Louie! Spot on!

To me, any gap in a segment in which tube-blank glue-in can escape - the builder needs to revisit his techniques and gain more experience. For any gap that can be seen by the naked eye or for glue to escape - more practice is needed.

Unwanted holes and spaces in segments are learning moments or events.

Kinda reminds me of a construction worker I knew who was finishing the baseboard in a house and cut one board too short: "No Problem, Enough Caulking can fix that!" 😊
 
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AllanS

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more practice is needed.
Now I don't have a dog in this fight and there is _no_ doubt about needing more skill here. Like I said this was a learning pen - I mostly wanted to see what I can do with scallops and start getting familiar with my new Byrnes.
(BTW the final pen is uuuugly but the ones that come after it will appreciate it's noble sacrifice to the cause.)

I can see that the problem with the lower segment on pics 1 & 2 is structural as the dimple or mar is on both sides at the same edge. As I said, I had to sand them down to get them to fit into the cut and I would guess that segment was sanded at a very slight angle. The flaw is however only around 1/32nd of an inch / sub 1 millimeter in size. There are similar flaws with the upper and middle segments that are even smaller than that.

As for the 3rd pic where the glue was pushing open the scallop - I'm showing that simply to show that there is indeed outward pressure. Now if that pressure could have been mitigated by giving the epoxy more time to cure (I may have to give it 48 hours because 20-24 wasn't cutting it) and/or brass that thick is just a general pita to work with at that angle.

I can and will be looking at ways to get a more even sanding as well as adjusting my curing times (and about 10 other improvements - like I said... this pen is uuuuuugly) but for _me_ the chance that an unseen flaw of that size can end up ruining the final product just isn't worth the risk.
 

AllanS

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yes, the foam will penetrate gaps if they are present, but that foam has little or no structural strength. It may fill the gaps cosmetically, but it doesn't strengthen gaps that are weak.

On this we certainly agree. And, from my so far singular experiment, those weak gaps let the glue come up to the surface and left a problem with the end result - finish was 3 coats of thin CA and 4-5 coats of medium and there is still a feelable divot at the weak spots mentioned above.
 

mark james

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Just a thought from my small rabbit brain, and past experience:

If you have blow-outs and see areas with inadequate glue/epoxy/CA coverage - the greater problem is the application of the glue/epoxy/CA, not the adhesive.

I prefer 2-part epoxy for all segmentation on the blank, then also epoxy for the blank on the tube, and let dry overnight. And I agree with the above; if you are depending on the 'swelling' factor of Gorilla glue to fill gaps, you need to tweak your cutting skills.

BUT, as you said, this was a 'Learning Pen,' so in that regard it is very valuable. Cheers!
 

howsitwork

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Thanks for the information by the way, I tend to use epoxy but have used gorilla glue for celtic knot pens and it worked but i prefer the epoxy , cos I can colour it
 

Woodchipper

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Interesting and observations on using Gorilla glue or other poly urethane glue. I never used it as the gorilla wouldn't fit in my small shop. ;) Background here: I built custom fishing rods for seven years. I used Titebond III for gluing cork rings for grips. When Gorilla Glue came on the scene, rod builders hated it as the foaming was a #$%& to clean up. For me, I would compress the rings in a press, wipe excess TBIII with a wet paper towel and let the grip dry overnight. Next day, it was turned with no glue line...only the segments were visible.
 

AllanS

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If you have blow-outs and see areas with inadequate glue/epoxy/CA coverage - the greater problem is the application of the glue/epoxy/CA, not the adhesive.

Oh no doubt. But so far I've tried both CA and epoxy, up to and including smothering the blank with glue, swirling the tube around in the blank, pulling it half way out and seating it in the other end, and a few other things. I haven't been able to get a good pattern analysis on why I have the occasional blowout. So I just happened to have some gorilla glue sitting around and gave it a shot and I might still use it for non-segmented pens.
Actually, I'll probably continue on with learning things for myself and sacrifice that learnin' pen and tear it down to the brass tubes to see how the glue holds there.

I prefer 2-part epoxy for all segmentation on the blank, then also epoxy for the blank on the tube, and let dry overnight. And I agree with the above; if you are depending on the 'swelling' factor of Gorilla glue to fill gaps, you need to tweak your cutting skills.

BUT, as you said, this was a 'Learning Pen,' so in that regard it is very valuable. Cheers!

For clarification - I'm looking at 'filling the gaps' only in terms of unsegmented/whole blanks. Having the gorilla glue seep through the cracks actually caught me by surprise - though it's obvious in hindsight.

I've seen a couple of blowouts there a whole chunk of the blank flew off of the tube, making me think that it never got glued in the first place.
 

AllanS

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Thanks for the information by the way, I tend to use epoxy but have used gorilla glue for celtic knot pens and it worked but i prefer the epoxy , cos I can colour it

Just curious - did you also have the glue foam through the lines or was the fit tight enough to keep that from happening?
 

leehljp

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Thanks for the information by the way, I tend to use epoxy but have used gorilla glue for celtic knot pens and it worked but i prefer the epoxy , cos I can colour it
I personally use epoxy for celtic knots and segments. The poly glue for me is only for blank to tube.

AlanS:"I've seen a couple of blowouts there a whole chunk of the blank flew off of the tube, making me think that it never got glued in the first place."
THAT is the problem with CA and Epoxy for most people that have blowouts. That is why Poly is so good at this one specific point. But the other way around it is to perfect the Epoxy, which I and many others have not yet done, however many of those think they have.

I have filled and wiped the insides of a blank with thick layers of epoxy, and thickly coated a tube on the outside (with the ends of the tube plugged to keep epoxy out of the inside of the tube) then push and twirl slowly the tube into the blank. It still gets a lot of air pockets in it which weakens the blank.

Again, this is where Poly glue shines, no air pockets and weak spots in segmented blanks between the tube and pen blank.
 
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jttheclockman

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I just want to clear some information I am picking up here. Now there are some that can make CA work and that is great but think that is the one adhesive that your detail to perfection is really needed. It is an adhesive that is brittle and any type catch can add so much strain and snap the blank from the tube. But again if the turner is proficient with their turning they probably get away with this. Gorilla glue is another possible choice if used properly and again I stand behind the fact that it is not a good glue for segments even if your segments are super super tight. Again I will explain my reasoning. You are more than likely gluing end grain to end grain which is your weakest of all wood joints if you do not reinforce and with pen segmenting that is just about impossible. Why would you want to add an expanding gluing to stress from the inside the joints you painstakingly tried to secure. To me just not the adhesive of choice. Now you want to use it on solid wood or acrylic blanks have at it.

But here is where I am having trouble when people say that epoxy leaves gaps and can fail. Then you are not doing the glue up correctly. I am not pushing epoxy because like mentioned there are other options. But here is how you glue a tube in a blank using epoxy. Or to those who like to jump down my throat, here is how I learned and still to this day use this method. Forget the fact that epoxy is messy and there is left over for throw away. Glue is one of those tangibles that is just inherited into pen making. After awhile and doing many pens you have a feel for how much of each part you need for gluing your blank or blanks. Now I have said many times here my go to epoxy glue is System3 T88. There are many other epoxy glues that can be used so that is a matter of choice. But after mixing both parts, I take a thin tool of some sort ( I have an old thin screwdriver I have been using) And I coat both ends inside the blank. So now the blank has plenty of adhesive. I then take the tube and I coat one half with epoxy and stick in one end and twist it. I then take this out and now add some more epoxy and do the same on the other end of the blank but this time leaving in and pushing in to the point that I now coat the second half of the tube and push this in as far as needed. Epoxy will be pushed out the back end. I take my tool and catch this and wipe off. I should mention I plug the ends of tube using Playdough. Works well. Now I will wipe the blank with acetone to clean any drips and set aside laying flat on a object of some sort that the ends hang over so if there is any residue on the ends it does not adhere to the object I am resting the blank on. After 24 hours or so I knock the playdough out and clean any residual inside tubes and get ready for turning. Now I spelled this out the best I can here but never ever ever will I have a failure of tube not holding. Just can not happen.

Just wanted to put some info into this topic of my way of gluing tubes in a blank. If it helps just one person than it was worth the typing. Happy turning.
 

howsitwork

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I use a similar application technique to JT but even so when I have a blow off where the wood leaves the tube I have found areas not completely visibly filled with glue. Now it maybe that the glue is attached to the now departed fragment (s) or it maybe that there was somehow some air swirled up inside during insertion . I can’t prove it either way but it works for me unless my skew technique isn’t up to scratch or I’ve now honed it ( tribute to Hank here ) enough. Expanding glue and segments just seems to me to be risky and my jointing is not upto the standards displayed by many on this site. Thats my reality and I’m practicing to improve.

when I say not completely filled I mean there is NO part of the tube which hasn’t got glue film on but some parts it’s got grain imprint, some parts it hasn’t.
 

leehljp

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I use a similar application technique to JT but even so when I have a blow off where the wood leaves the tube I have found areas not completely visibly filled with glue. Now it maybe that the glue is attached to the now departed fragment (s) or it maybe that there was somehow some air swirled up inside during insertion . I can’t prove it either way but it works for me unless my skew technique isn’t up to scratch or I’ve now honed it ( tribute to Hank here ) enough. Expanding glue and segments just seems to me to be risky and my jointing is not upto the standards displayed by many on this site. Thats my reality and I’m practicing to improve.

when I say not completely filled I mean there is NO part of the tube which hasn’t got glue film on but some parts it’s got grain imprint, some parts it hasn’t.
Thank you for your reply. I appreciate that.

There is one part that seems to be misunderstood: Expanding glue proponents DO NOT recommend poly glue for segmenting joints together.

Expanding Glue, if used, should only be used when/for gluing the tube into the blank.

BTW, Yes, I do the same basic with epoxy as you do, and as you noted find areas not completely filled or see a few bubbles. For every spot we can see, there will be at least that much more that will be unseen.
 

penicillin

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There are some esteemed and highly experienced pen turners here. I am not one of them. I have made lots of pens, but never tried a segmented pen. Someday perhaps.

I use polyurethane to glue tubes in solid pen blanks. I buy the smallest bottle of original Gorilla Glue and it lasts a very long time. I rarely use polyurethane glue for anything else. Here is a pile of random thoughts related to using polyurethane glue for pen tubes:
  • I have tried many glues for gluing pen tubes inside pen blanks:
    • I prefer polyurethane.
    • I use epoxy or (rarely) Gorilla Clear (silane) glue if the blank is translucent or transparent.
      • I may also paint the tube or the inside wall of the pen blank.
    • I use CA glue for pen tubes, but only for demos and classes where there is not time for anything else.
      • I tried "5 minute epoxy" but it takes longer than 5 minutes to cure. CA is "instant."
  • I assume that the gap between the tube and the pen blank is very small, within "polyurethane tolerance" (my term). I can feel the friction and snug fit along the walls of the pen tube as I slide it in and out of the pen blank before gluing. In other words, I do a reasonable job of drilling my pen blank accurately to match the tube.
    • Some people here seem to think that there are large gaps and spaces for air pockets. Not so, in my opinion.
    • I wonder whether this is the key point that other people are missing about why polyurethane works well for those who prefer it.
  • I like polyurethane because the foaming action eliminates whatever gaps and air pockets may remain.
    • True, the foamed glue is not strong, but there should not be much. In my opinion, we are not facing a situation with large bubbly gaps everywhere between the tube and the pen blank. The "gaps" are more like the diameter of a wood fiber.
    • I believe that the foaming action helps distribute the glue better.
  • I like polyurethane because it dispenses directly on the pen tube from the container. No mixing, trays, or special brush required.
    • ... and no waste.
  • I like polyurethane because it works with my Rockler silicone mats.
    • Some people say it doesn't work, but it works for me.
    • I let the pen blanks and tubes cure overnight on the mat. The polyurethane glue foams out slightly on the mat, but it sticks to the blank when I pick it up the next morning. A chisel quickly slices off the foam-out before milling.
  • I dislike epoxy because:
    • It requires mixing.
    • It is messy.
    • ... and stinky.
    • It requires a tray or some other disposable object (piece of cardboard, whatever) for mixing it.
    • You need another disposable object (stick, flux brush, whatever) to apply the epoxy to the tube or pen blank.
    • You can't use those nice reusable silicone brushes, trays, mats, etc. with epoxy.
      • Actually you can, but only once. :-(
    • Whatever epoxy is leftover is wasted, and epoxy is expensive compared with polyurethane.
When I choose a glue, one thing that I think about is its texture when cured. Some glues cure hard and rigid. Other glues cure with some flexibility or rubberiness (aka elasticity). It matters. The following is my personal opinion based on my experience with using these products:

Hard and Rigid after Curing
  • Polyurethane Glues
  • Some epoxies cure hard, others cure flexible.
  • CA Glues
    • The only exception is "Flexible" CA glue
  • Titebond Original (Titebond I) wood glue
  • Most "old" wood glues (e.g., Elmers)
  • Hide glues (another kind of wood glue)
Flexible and/or Rubbery after Curing
  • Gorilla Clear
  • Some epoxies cure flexible, others cure hard.
    • I use West Systems G-Flex, which I call "flexible".
  • Flexible CA Glue (special type of CA)
    • NOTE: Most CA glues cure hard and rigid.
  • Titebond II and Titebond III wood glue
  • Rubber cement, contact cement, etc.
 
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AllanS

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So I just put the learnin' pen back on the lathe (goodbye JR Gent, you were sacrificed for a noble cause) and have to say that in stripping it down to the tube it didn't put up much of a fight. One data point doesn't make a solid trend but it certainly seemed to give way easier than and CA or epoxy held blanks I've had to strip down.

As much as I'd hoped it would solve my blowout issues, Gorilla glue - segmented or not - does not seem to work for me.

There is one part that seems to be misunderstood: Expanding glue proponents DO NOT recommend poly glue for segmenting joints together.
...

Sorry, not buying it. Was this not you and Monophoto who made clear comments about my lack of skill (which I'm not denying) with segmenting being the problem with why the gorilla glue foaming out?


....One could arrive at the conclusion that this experience demonstrates that polyurethane should not be used to glue tubes in segmented blanks. In my mind, that generalization is entirely too broad.

Or, one could conclude that the segmenting glue-up needs to be done better if polyurethane is to be used to glue in the tube. Perhaps that's a good thing - if you see foaming between segments when you glue in the tube, you should revisit the process used to glue up the segmented blank to prevent that problem in the future.
...
Thanks Louie! Spot on!

To me, any gap in a segment in which tube-blank glue-in can escape - the builder needs to revisit his techniques and gain more experience. For any gap that can be seen by the naked eye or for glue to escape - more practice is needed.
 
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AllanS

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If you have blow-outs and see areas with inadequate glue/epoxy/CA coverage - the greater problem is the application of the glue/epoxy/CA, not the adhesive.

I prefer 2-part epoxy for all segmentation on the blank, then also epoxy for the blank on the tube, and let dry overnight. And I agree with the above; if you are depending on the 'swelling' factor of Gorilla glue to fill gaps, you need to tweak your cutting skills.

Yep. Now that I've moved away from brad point drill bits (and thank you jttheclockman for the break down on those), I'm hoping that will help things, because I can't see what I might be doing wrong. If I can't figure it out, I'm just gonna have to drown the little brass suckers from here on out.
 

jttheclockman

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Alan, hang in there. You will figure things out and settle in on a process and adhesive that works for you. Just like all other steps in making a pen with the more you do the better you get at it and learn along the way. I must say here to set the record straight. I have never blown a blank up or had one come free of the tube. so I do not know if every single MM of the tube and blank are covered with adhesive but will say who cares and what the heck difference does it make?? If the blank blew up because there was no glue on it then no matter what, that was not the cause of the blowout. Learn to use the tools better and you will make those blowouts go away. Good luck to you and to all. Happy Turning. May your blowouts be far and few between.
 

AllanS

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I really don't know what I'm doing wrong - but I'll figure it out, even if I have to stop being lazy and actually apply some sciencey type rigor to minimize the variables. Part of it may have been tools too dull and/or bad technique and pushing too hard, but I think I've gotten past _that_ variable.

And for me, it's part of the fun. Not the blank blow itself out but the testing of different options. Right now I've got a large tray of different epoxies, CA, friction polish, etc that I'm all testing out.

Next up I'm going to do a some ad-hoc testing between Maguires and Hutt Plastic polish.
Anyone have a spare glossmeter hanging around? :)
 

jrista

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I really don't know what I'm doing wrong - but I'll figure it out, even if I have to stop being lazy and actually apply some sciencey type rigor to minimize the variables. Part of it may have been tools too dull and/or bad technique and pushing too hard, but I think I've gotten past _that_ variable.

And for me, it's part of the fun. Not the blank blow itself out but the testing of different options. Right now I've got a large tray of different epoxies, CA, friction polish, etc that I'm all testing out.

Next up I'm going to do a some ad-hoc testing between Maguires and Hutt Plastic polish.
Anyone have a spare glossmeter hanging around? :)

What are you using to sharpen your tools? Are you using CBN wheels on grinder? If not...you might want to look into CBN wheels. A 350 grit should do quite nicely. The CBN wheels sharpen much, much faster, and will usually get your tools much sharper, than a standard aluminum oxide wheel. I have been turning since 2020 (right when the pandemic hit, actually), and I think I had both my aluminum oxide wheels replaced with CBN within a couple of months. The difference in the sharpness and cutting capabilities of the tool between the two types of wheels is dramatic. Been using the same CBN wheels for a few years now, they are still working fine, still giving me super sharp edges and tools that don't catch, grab, or shred my pen blanks.
 

AllanS

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Currently using a norton 3x-k 80 and 46grit. That and a diamond hone work pretty well though the CBN will be an upgrade someday. I just decided that I needed the Byrnes table saw more right now and I need to let the discretionary budget recover from that hit. (Totally worth it though).
 

leehljp

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If Gorilla (POLY) glue lets go, then in the same exact situation, CA and Epoxy also will let go. There is only one scenario in which those two (CA & Epoxy) will hold in that situation and Gorilla won't: CA sets and cures in seconds to minutes; 5 minute Epoxy sets in 5 and reasonably cure in 1 hour to turn. But Poly requires overnight 14 to 18 hours. Anything less and it hasn't cured and it can let go. However one recommendation regularly written with Poly is to let it sit overnight.

So what can cause this - CA and Epoxy and Poly to let go - as written in the opening sentence in this post?
1. agressive and unsharp tool, but this is only likely if the next step is valid
2. microscopic film or oily hands. A film on the tube or some people have oily hands and it gets onto the tube before the adhesive is applied. I have never had problems with this, but if one does a search, numerous turners recommend wiping the tubes or sanding the tubes lightly before applying the adhesive.

With a clean tube and or sanded tube, for most people, poly will hold far better than CA or epoxy. All one has to do is read about blowouts going back 10 - 15 years to back that up, regardless if one likes one glue or other. It is not about ego trips or yours is better than mine. It is about getting the job done. BTW, I too use epoxy on most, but when I want HOLD (on segmented pens), I use Poly.
 
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