Epoxy Problems Again

thanks dan. yeah its a weird problem i'm trying one set tonight with just the handle screws no extra pressure from clamps or anything. and of course probably the biggest factor using acraglass. the weird thing is i've had handles fail and use the same method (so it seems ) the next time and it worked out. or using materials like micarta that come pretty damn flat already and it fails then try it again with the same epoxy and same handle material and it works. weird. we'll see what the acraglass does doing a nice big recurve clip point. stabilized maple burl handles stainless pins and thong hole. god i hope i don't have to rip the handle off this one too.
 
Surface prep before glue up is the single most important part of sticking stuff together. Sandblasting the metal and scratching up the other material (micarta, wood, bone, etc) and using 'good' adhesive outperforms the best adhesive and just scratching the metal.
Acetone leaves an oily residue as does green soap and most everything else. Wipe it on a sheet of clean glass to see what I mean. Alcohol does a fairly decent job of leaving less residue than most cleaners. If you sandblast, you don't need to use the cleaner.
Do NOT use Devcon 2 part epoxy. K&G, Accraglass or golf shafting epoxy finished in the top of our tests. More exotic Loctite E-120hp and Loctite Speedbonder 324 also were very good choices -available from Mcmasters.com.
Gorrilla glue tested the best of them all for joining wood to metal.
 
well i guess its time to get the sandblasting cabinet. first i need my milling machine. does it ever end? :)
now if i could just sell some of these knives i could afford all the tools i want
 
No one seems to have pointed out that the bolts are not meant to be torqued down super tight.If yo do,you may warp the other areas of the scales.You only want it tight enough to bring the scales down to ALMOST contacting the tang.If you squeeze it too tight,you squeeze out all or most of the epoxy.The over tight bolts also apply uneven pressure to the scales and can lift the ends.The epoxy is a sealant and bedding compound more than a bonding agent.A good mechanical attachment with Corby rivets is one of the best securing systems around.Accra glass is superb for bedding knife scales.
 
I'll add just one more thing-Perhaps the most important thing in addition to cleanliness and proper adhesive selection. You need to add glass beads to your adhesive so you maintain an adequate bond line thickness. Epoxy requires a minimum of .005" as a bondline thickness.
.010" is better. In the helicopter biz, our spec was .010 to .030, but, bondlines thicker than .010 start to look unsightly. Without the beads, when you torque up on the fasteners, you squeeze almost all the epoxy out of the joint, and, it really screws things up.
And, no, it won't make your knife look ugly. You won't even notice it if you fit up your parts correctly.
Also, I abrade both the tang and the inner surface of the scale by grinding a trough down the center using a 60 grit belt. This is in addition to using a 60 grit belt to flatten these surfaces. In this way, I have a THICK bondline of .030 or more over perhaps 60 of the area, with the thinner bondline at the edges.
One last thing-Don't get too strong when you torque your handle bolts down, or, you'll cause the ends of your scales to lift up. If you use a new belt to flatten your scales, and apply pressure right in the center of the scale, you can create a SLIGHT concave surface that will pull flat when you tighten the bolts. This will assure a good fit at both ends of the scale, with no gaps.
 
sounds like some good info. i was going to try the acraglass last night but for some reason my 4X36 doesn't want to run it keeps blowing fuses. a good excuse to go out and get a disc grinder. any suggestions? probably in the cheaper range, too bad i can't get one of rob frink's machines right now :grumpy:
 
Michael J. Spangler said:
sounds like some good info. i was going to try the acraglass last night but for some reason my 4X36 doesn't want to run it keeps blowing fuses. a good excuse to go out and get a disc grinder. any suggestions? probably in the cheaper range, too bad i can't get one of rob frink's machines right now :grumpy:
Click to expand...

I got an old 220 volt 3-phase 12" grinder from Walt Fleming <wrfleming@snet.net> via eBay. He mailed me a while ago saying he had another one available. You might him a line if that would suite you. It was a bit rusty but really solid -- the bearings are good enough that it take about a minute after turning off the power before it starts to slow down noticably. I'm sure that OSHA wouldn't approve but I like it :D

He's in CT, not to far from RI.
 
I've seen a lot of discussion about the epoxy, but have you thought to address the issue of the wood? After you sand the tang side of the wood flat, let it set overnight and check it the next day to see if it is still flat and not twisted or curled slightly. With burl wood you can run into a lot of different problems. Is your handle material stabilized? If not, the next time try some pieces that are stabilized and see if your problem still exists. Before I assemble the handle material to the tang permanently, I preassemble the handle and hold it up toward a light source to see if the light shows through at any place on the handle. If it does, mark that area with a pencil so that when you take it apart you can examine that area to see what could be causing the problem. When sanding a piece of burl, I sand it on a flat plate and only sand in a push or pull stroke on the wood. If you push and pull when sanding you may end up with a high area in the center of the piece and lower areas on the outside edges of the wood. This is something you don't want.Hope some of this will help. Have a nice day.
 
gorilla glue, in my tests, does not work well joining two man made materials like micarta to metal. joining wood to metal, gorilla glue is amazing.
 
bladsmth said:
No one seems to have pointed out that the bolts are not meant to be torqued down super tight.If yo do,you may warp the other areas of the scales.You only want it tight enough to bring the scales down to ALMOST contacting the tang.If you squeeze it too tight,you squeeze out all or most of the epoxy.The over tight bolts also apply uneven pressure to the scales and can lift the ends.The epoxy is a sealant and bedding compound more than a bonding agent.A good mechanical attachment with Corby rivets is one of the best securing systems around.Accra glass is superb for bedding knife scales.
Click to expand...
I agree in most part :)

the right tool for the right job Mike ..
I use epoxy and nothing but, and I won't claim it the best to use either..
to many ways to mess up anything to call anything the best..IMHO
but I also use mechanical means to hold to be sure. I use it to seal and only lay claim to that.
Mike you know how the stuff works by the old scales you just took off right?

I just re handled a bowie I made for a guy well over a year ago, he decided to have a larger grip and both were from his
un-stabilized walnut, I used epoxy and 2 plain brass 1/8" pins.
I had to use the band-saw
to cut them off, I cut close to the tang and had to wedge a knife blade
between what was left to remove the rest..

I use a dremel cut off wheel to mare up the tang and the under part of the
slabs, this makes a place so you can't squeeze out to much epoxy and you can get the seams close then. but I use it as a sealant mainly,and the rest is a plus if done right..
I also grind with the dremel cut off wheel a slot to form an epoxy biscuit at the guard and the ends of the slabs/scales
this will help stop lifting from warping,, if the air is humid that could make a difference too..
and lot of rain lately..use at room temp.. as the others say too keep stuff flat..we can talk about it at the H/I if you want.. :)

edited to add
thinking about it after the facts..
Stacy I didn't quote you to target you , I hope you don't think that,, you just had some good points there.. :)
 
Dan,That is good advice on preparing the scales and tang.I grind a groove down the tang and scale to make an epoxy pocket,or drill LOTS of holes.I use epoxy most of the time,but used to use Acra Glass,too.With the proper preparations,and the materials being in the right condition,any good bonding system will make a tight joint.
No offense taken,Dan.
 
alright well i fit that bad larry up tonight. i made sure things were nice and flat, i scuffed everything up with 36 grit. everything was nice and clean and ready to go, proper measurements of the acraglas resin and hardener, fit it all together and used c clamps but parely put any presssure at all. basically just enough so the clamps were touching the handle material and not pushing on it
i think this might have been my main problem, that would explain it always hapening in the same spot, i think overtightening would probably be more of a problem near the ricasso than any other spot due to the lack of th pin towards the front of the handle material, unlike the butt end which i always have a thong hole in, could the front be more succeptable to pressure due to lack of a pin?
well we'll see how this one comes out, so i can get over my fear and get back to making knives. nothing sucks more than going through 5 sets of handles on a knife and still not getting it right

thanks to all of you for the info and suggestions i apprciate it.
p.s. how long should the acraglas set up for? thanks again

Mike
 
needs 2 hours to get set and 24 hours to be solid. That said, I haven't had any problems leaving stuff overnight and working on it in the morning.
 
Michael, et al.,

On the disc sander, yes, they can be very expensive! I used two different ways to save hundreds of dollars and still get great machines.

For the vertical I purchased TruGrit's model WITHOUT the motor and controller. I found the identical 0.5 horsepower Leeson motor and contoller on Ebay. I believe I saved near $400 here.

For the horizontal I also went to Ebay for yet another DC variable speed--though not reversible like the one above--half horse motor and controller. I then bought a disc from Rob Frink and a mounting bracket from Uncle Al. I have an awesome horizontal grinder (this is great for flattening small and non-magnetic stuff that is hard to hold vertically) for about half or less of what they are going for new.

Both these grinders are 9" so I can use standard sheets and save huge $$$. They are also practically aerospace quality.

Having visited Michael Vagnino's shop over the summer, I now feel like I need another vertical--one horse that overhangs the bench. The Trugrit is really great for precise work, but hard to flat grind an entire blade on.

John Frankl
 
alright no luck i give up. damn thing was fine. glued up nice. shaped out the whole handle, polished it up. cleaned it all up ready for an edge on it. brough it to work to show my boss.... picked it up later on my way out of work. scoping it out and bang there it is. damn slab lifted up, front of the right side. well i'll bring two messed up blades to the hammer-in on sturday and see if you guys can tell me what's wrong. untill then i'm sticking out of the shop :mad: :grumpy: :thumbdn:
 
rj martin said:
I'll add just one more thing-Perhaps the most important thing in addition to cleanliness and proper adhesive selection. You need to add glass beads to your adhesive so you maintain an adequate bond line thickness. Epoxy requires a minimum of .005" as a bondline thickness.
.010" is better. In the helicopter biz, our spec was .010 to .030, but, bondlines thicker than .010 start to look unsightly. Without the beads, when you torque up on the fasteners, you squeeze almost all the epoxy out of the joint, and, it really screws things up..
Click to expand...

RJ,

The "glass bead blasting media" is a nice trick. I always either pocket or relieve underneath any inlay or fixed blade handle to make the minimum on the bond requirement. Did anyone else "get" this trick?

I like blasting the surfaces with 60 grit AO in some cases also for added grip support.
 
Michael J. Spangler said:
alright no luck i give up. damn thing was fine. glued up nice. shaped out the whole handle, polished it up. cleaned it all up ready for an edge on it. brough it to work to show my boss.... picked it up later on my way out of work. scoping it out and bang there it is. damn slab lifted up, front of the right side. well i'll bring two messed up blades to the hammer-in on sturday and see if you guys can tell me what's wrong. untill then i'm sticking out of the shop :mad: :grumpy: :thumbdn:
Click to expand...

Mike what did you say you are using for scales?
they should not be curling up in the first place.. with or with out glues.

either they are wet and while you work it you are altering the water content causing stress in them or you are putting water in the material doing the same..or with the heat of working it you are warping them..
they are lifting with-in a short time on you right?
 
dan: i was using curly curly maple on this one, not stabilized. but i've had the problem with stabilized stuff i flattened myself, and i've had the same problem with micarta. which as we know comes in as flat as can be, and is pretty stable stuff. but the funnt thing is i've had the problem. removed the handle material and replaced it with micarta again and it was no problem. same epoxy, same pins, everything. J. Mulcahy brought up a good point today when i talked to him. could it have something to do with the humidity??
that might be one variable i overlooked. my shop is open, and very humid almost all year round. thats' where i do all the mixing and prep, then they set in my house. i noticed when i did some handles at IG's i dind't have that trouble. his inside shop is always bone dry too. could this be the problem?? either way dan i'll have 2 blades with the same problem for you to pick apart at the hammer-in and you can let me know what you think. thanks for all the help guys it's much appreciated
 
I don't think it would be humidity with the stabalised wood or micarta as they shouldn't be affected by humidity. I don't have alot of experience yet but all I can think of is over tightening or the parts are not all totally flat. Humidity could be a factor with the nonstabalised wood though.
 
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