epoxy problems

kile

kile

Joined
Mar 19, 1999
Messages
620
In the last 3weeks, I have had the epoxy on two different knives, fail to harden. It was two differnt types of epoxy bought at two different places, and it was two different brands, I had this happend one other time, but I assumed it was bad epoxy. I am usually very careful when getting ready to attach the handle scales, I rough up all surfaces meant to be attached, wipe everything down with acetone, then mix the epoxy, and spread it on. I was using some 90 minute epoxy both times, and over a week later it was still gummy. I left the knives clamped up, and when I went to grind them, I was careful not to get anything to warm, I noticed the scales start to spread apart from the tang. I squished them back together and epoxy squished out, I then just pulled the scales off with my fingers, and the stuff was exactly the same as it was when I first mixed it. The stuff on the outside was hard, but the rest of it was runny. It was fairly cold in my garage, but It took over a week, I would guess the average temp in my garage was about 45 degrees, is that too cold for the epoxy to set? Or am I doing something else wrong?

ON a similar note, I am getting sick of working with epoxy, and would like to be able to screw handles on for fixed blades, I have no idea what tap size to buy for what kind of screws, so if someone could tell me some common tap sizes and the screws that go with them, and maybe where to get them, I would be very grateful.
Thanks
Kyle Fuglesten
 
The only thing I can figure is temperature. The only problems I can remember ever having with epoxies on a couple occasions I did not mix it properly. I don't remember curing epoxies at low temps. Epoxy will cure more quickly at higher temps. At ambient room temps of about 70 F. or so it takes epoxy about 5 days to completely cure even though it hardens to the touch much sooner.

You can clean the mess up with vinegar but vinegar will corrode steel very quickly.

I too am thinking of trying some screw-on scales. I suspect they should be of a rather fine pitch and I also suspect that the threads should be epoxied.

Roger
 
Kyle,
Its the temp. I did the same thing years ago. My garage was too cold and the glue didnt set. Also, I been using acorn bolts to put in handles. you dont need a tap for them. They really work well. I even put a little appoxy on the threads, so they wouldnt work thier way loose later on.
Good luck
Jack
 
Kyle, for the winter, do all your epoxy work in the house, store the epoxy there too. In the summer, it's still a good idea to store the epoxy in the house. More stable climate.
That stuff has to be at least 70 degrees to start working properly. There are exceptions, but 45 degrees is a bit much.;) :D
 
Thanks for the help guys, I epoxied a few more scales on today, and I did them all in the house. The last time my epoxy didn't harden was last spring, and it was very cold for about a week at the same time I was having the problem.
 
FWIW, I was researching epoxies from 3M. Lots of great data available on their stuff.

I came across something interesting. Did you know they make cyanoacrylate (super-glue) adhesives specially for steel? OK I didn't. The shear strengths are similar to epoxy! These are sold under "Pronto" label.


"CA-100 Toughened material that provides high peel impact strength, thermal shock resistance, excellent metal bonding capabilities, and improved heat resistance. Meets MIL-A-46050C Type II, Class 3."
Click to expand...


Overlay shear strength of 2000 on steel and 2900 on aluminum (comparable to epoxies) and a T-Peel average of 15.

The handling time is only 20-70 seconds so there's not fooling around. But it is slower than most cyano's. Full cure in 48 hours.

I was suprised to find strengths in the range of 2 part epoxies and "improved heat resistance". However the heat resistance wasn't qualified.

In any case MSCdirect sells it: http://www.mscdirect.com/PDF/PDF02/1706.pdf

Looks like it's worth some tests.

Steve
 
I work in a garage that gets pretty cold at times.After epoxying the handles on I put a lamp with a 100 watt bulb about 10 12 inches away from the handle. This helps the cure. I also use duro or devcon 5 min epoxy. It seems to adhere better. I have not had one fail.
Take Care
TJ Smith
 
When in a hurry or cold out side I put the assembled
knife in the oven set at 140 deg. for two hr using a
24hr expoy works good fully set up and ready to finish.
Gib
 
Hey Kyle... Temperature and age will affect the epoxy like the others have said. I have stopped using Devcon because the last four (4) batches I bought were bad. Expiry dates on them is far in the future yet when I got them in the mail each box had one of the bottles discoloured a urine yellow colour. I called the factory and the response I got was basically, yeah well that happens, thanks for calling ...have a nice day. Sometimes I'm a little slow on the uptake so I bought another box at a show in Detroit a few weeks back after opening several to find one that was "crystal clear" like they advertise. Three days later it had turned colour as well.
I've gone back to using marine epoxy mixed in a small dixie cup with a little talcum powder as a binder and epoxy dye. It takes longer to set up (overnight) but I've never had a problem with it holding.
I know the convienience of the 2 Ton rapid set up time will seduce me again in the future. I just can't seem to qiut banging my head against that wall.

Kraut
 
I am using a lot of screws on my handles. I use a 2-56 and can be used on 1/8". On 3/32", I ofset the holes for each set. I usually get mine from MSC or Fastenal usually around $8.00 per 100.
 
I use a epoxy called 220, it is used in jewelry making
and Rio Grande 800 545 6566 you can get it in 8oz size
I have used it for 8 or 10 years with no problems. Gib
 
you may not have mixed it well enough, or it may be the kind your using. I did buy a really cheap epoxy once that did not completely harden. If I use a slow drying epoxy I will put the knife
in an oven on low for about an hour to help it cure. The room temperature does have alot to do with curing, thehigher the heat, the faster the hardening, unless its not mixed well, or you have a bad batch. when I worked for Dassault aviation for three years In upholstery we used many epoxys on a daily basis. It can be possible to get a bad batch, but the temp, and the wa its mixed can also make a difference.

I usually use the plastic weld epoxy from duro and it works well, but it does harden quickly so I try to use it in lower room temperatures to buy time. I buy it and the waterproof 2 ton duro at walmart for about $2.29 and $1.99 respectfully. I havent had a problem with either of them.

hope this helps some. :)
 
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