Epoxy Show Down (2019)

Is Bob Smith Epoxy (Either Mid or Slow)

  • Better than G/Flex

    Votes: 0 0.0%

  • Total voters
    6
Joined
Nov 15, 2005
Messages
1,194
Has this testing been done!? Can we say definitively that G/Flex is better than Bob Smith or is it just the gold standard that we don't question? I'm out of my depth with epoxies and was wondering where the knife-making community stands in 2019.

If it hasn't been tested, how would yall propose this test to look?

Cheers,
JKeeton

 
I did my own personal testing on some small wood blocks a year or so ago. Nothing definitive in regards to your poll question.

I’ve been using Bob Smith for the last three years, I have never had any problem. I have a box of G/flex but frankly I’ve never used it.

I also use golfworks two part 24 hour epoxy. I use this alot for hidden tang kitchen knives. I've done my own "destructive testing" on a handle and I'm confident with this epoxy. I’m a golfer and I used to make my own clubs so I know this epoxy from club assembling. It's also less costly than the other commercial epoxies.

If you are talking about gluing handle scales onto full tang knives, I rely on the mechanical pinning of pins.

If I really need something fastened with glue, I use Loctite 324 speed bonder (with activator)
 
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Google "glue wars" and have fun.

I've used Bob Smith slowest cure, BladeBond Ultra, and got some G-Flex when my favorite supplier was out of BladeBond. They feel slightly different when cured in the cups I mix them in, but I haven't had a failure yet. But I've only made kitchen knives which are different from hard use choppers.

The conventional wisdom here is that surface prep is actually more important than the specific brand of epoxy. I sand with 60 grit sandpaper, then clean with acetone first then isopropanol (rubbing alcohol) last. Some people have found that common acetone from the store leaves some type of residue that can interfere with gluing whereas isopropanol doesn't.
 
been using Gflex for so long now without problems that i won't ever be switching unless they switch it up and make it bad, or quit making it. plus you can buy it in pretty good bulk amounts!
 
When you are testing two quality products I do not know if the average home tester has the means to scientifically determine if one is superior to the other. I use Gflex but would use Bob Smith's if the Gflex were not available at the time of ordering.
 
I’m gonna stick with Gflex. I have done some refurbs where I have had to remove scales that were attached with Gflex, and if you prep/,mix correctly, it is REALLY a great epoxy!!!!!!
 
If doing tests, you have to compare apples to apples. Comparing a 24 hour epoxy to 1 15 minute or 30 minute epoxy isn't going to be an accurate test.

I have used a lot of epoxy over the years and never had a problem with a 24 hour cure resin … regardless of the name brand.

The other issue is how much "better" one brand is over the other, and how much "better" a 24 hour epoxy is over 15/30 minute epoxy. They will most all do what we need, it is more a factor of ease of clean-up, application ease, and cured color.
 
Good points from all. I totally understand the "if it's not broke don't fix it" mentality; and in this case the decision probably not going to result in a "failure" one way or the other.

I have an inclination to challenge industry standards and rule of thumbs. "That's the way we've always done it" generally #triggers me.

When you are testing two quality products I do not know if the average home tester has the means to scientifically determine if one is superior to the other. I use Gflex but would use Bob Smith's if the Gflex were not available at the time of ordering.

A proper test would be difficult to set up, like you're saying. Impact & shear strength would have to be tested under different temperatures and humidities, right?

If doing tests, you have to compare apples to apples. Comparing a 24 hour epoxy to 1 15 minute or 30 minute epoxy isn't going to be an accurate test.

If you were trying to figure out if one of the mentioned epoxies was a better fit for your application (say holding on knife scales) would it matter?

The other issue is how much "better" one brand is over the other, and how much "better" a 24 hour epoxy is over 15/30 minute epoxy. They will most all do what we need, it is more a factor of ease of clean-up, application ease, and cured color.

This would be hard to quantify!


One last thing; I've read that the mid cure Bob Smith is better for knife handles than the Bob Smith slow cure because it's a more flexible bond. Is there any validity to this?
 
Found this one a golfmakers forum

“...bit of research on sheer strength of epoxies, and found some testing done by Texas A&M. The test jig they used basically took two pieces of aluminum and overlapped them applying epoxy to the mating surface. They then pulled these two pieces of aluminum from each end and got their results. So I assume that is a definitive test for sheer strength.”

Name brand accepted golf epoxy is often rated at 3,000 psi lap shear strength. Some up to 4,000

I saw @kuraki posted a while back -
System 3 T-88 still has 1000 psi lap shear strength in an aluminum/aluminum bond at 180 F.

John, is it the same for g/flex?
 
Does g flex really take 24 hours to set?

BSI Slow Cure "sets" in about 30 minutes, and cures in about 8 hours.

I think we are comparing a 24 hour cure epoxy to an 8 hour cure epoxy, not a 30 min cure epoxy. Seems like a difference in marketing.
 
Hi Guys,

I started the "Glue Wars" back 2005 - Man do I feel old!

Over the years I've thought a lot about the issue and concluded that the ability for the adhesive to maintain its integrity over time, conditions and materials is more important than strength. The strength of the holding power comes from mechanical bonds (screws, pins, etc.) anyway.

As J. Keeton ponders: "is Bob Smith slow better because it's a more flexible bond?" An adhesive with a little give is going to be better, simply because different materials expand/contract differently (moisture and temp). It's all about maintaining a waterproof seal and keeping the parts in place.

Also, milkbaby, is right on the mark: surface prep is key. Can I add flatness and squeeze under the heading of surface prep?Over squeezing will hose up the best epoxy on the planet. If there's a little warp in the tang or slabs, it's soooo easy to tell yourself during gluing, "Hey there's a gap. I'll just crank the clamps down a little and make it go away." Every failure I've had is because I did that.

Back the question at hand, you need the test of time to determine which of those epoxies is the best choice. You can accelerate time by using torture. I think a dishwasher is a great way to run the test. Glue your favorite materials together without a mechanical bond. Leave it in the dishwasher for a month. Freeze it in a block of ice a few times for good measure.

If all the adhesives stay intact, choose the one you like working with best.

PS I still prefer Loctite Hysol. The dispenser is so convenient and the consistency is perfect for what we do. Not to mention dimensional stability and it's approved for aircraft construction.
 
Thanks for the thoughts Sando Sando . You're the Glue OG! I like your dishwasher stress test. And from what I understand the 15min (Medium) BSI is actually more flexible than the slow cure.

If anyone has any good ideas for testing (methods and procedure) let me know... I may take on this gauntlet.

We're talking about G/Flex model 6508 right?
 
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Another thing I just thought about, I prefer BladeBond over Bob Smith because it tends to be less viscous and the pot life is longer giving me more time to work with it. So even if two adhesives are close in holding power, there may be other factors that determine which you like best.
 
Bob Smith 30min slow cure actually cures in 8 hours as stated before.

It works exactly what it was made for and does a fine job.

With the use of mechanical fasteners the scales will never come off or loose if done correctly
 
I would love to see some testing! I use g/flex and have for years.
 
Bob Smith 30min slow cure actually cures in 8 hours as stated before.

It works exactly what it was made for and does a fine job.

With the use of mechanical fasteners the scales will never come off or loose if done correctly

What is BSI 30min designed for? Good to know... I use corbies or loveless in every knife. #paranoid

Edit: This is from the product page:

"MID-CURE 15 min. epoxy is used in larger areas where more working time is needed. It is more water resistant and can be used as a substitute for QUIK-CURE in most applications. MID-CURE is our most flexible epoxy and is ideal for gluing to fiberglass surfaces."

"SLOW-CURE 30 min. epoxy works best for forming reinforcing fillets on joints. It has the highest strength of our epoxies. It is waterproof and more heat resistant. SLOW-CURE can be used for bonding if you’re willing to wait overnight. Fillers such as micro balloons can be mixed with SLOW-CURE and FINISH-CURE to form a putty-like consistency. Such fillers will usually decrease the working time by about 25%. Bonded objects can be handled after 8 hours and the cured epoxy reaches full strength within 24 hours. "

I would love to see some testing! I use g/flex and have for years.

I just ordered some G/Flex. I'll put it head to head with BSI mid cure... Not exactly sure how yet, but I'll put something together. Walter Sorrells has some fun test he ran on some epoxies on his channel.
 
Bob Smith is huge in the Remote control hobby, it is also a big seller for knife making.

As stated before the prep is super important for all adhesives to get full strength.
 
Bob Smith is huge in the Remote control hobby, it is also a big seller for knife making.

As stated before the prep is super important for all adhesives to get full strength.
so true, I normally sandblast the underneath side of the scales and keep everything degreased w/ acetone. never had an issue.
 
Bob Smith is huge in the Remote control hobby, it is also a big seller for knife making.

As stated before the prep is super important for all adhesives to get full strength.

When using g10 liners, do you hand sand them? I could see belt grinder gouging them quite easily.
 
When using g10 liners, do you hand sand them? I could see belt grinder gouging them quite easily.

Hand sand liners or bead blast them
 
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