Warped Scales

SS369

SS369

Well-Known Member
Good day all.

Needing some input on the why it happens and potential fixes.

I have well stabilized scales of various woods, burls, some dyed, some
not.
I flatten them on a flat plate, till I cannot see between them, using 60
grit paper finishing with figure eight motions.

I did not use powered sanding so no heat was introduced.

Against each other they were flat and almost "Stick" together.

I then glue G10 liners with a thin smear of GFlex epoxy, prepped and all
cleaned with denatured alcohol.

Clamping is done with small spring clamps, three per scale, on a flat
piece of angle iron.

After a 24 hour cure, I remove them and notice that they are bowed from
each other, sufficiently so that if I flatten to remove the bow, the
liners will look pretty sorry.

I am trying to straighten them by clamping and over shimming where
needed and placing the affair in front of a space heater, rotating every
so often.

So far no improvement.

This has happened before and I can't stomach wasting such beautiful,
unique materials.

Any ideas for salvaging these and possibly future work?

Thanks in advance,
Scott
 
SS369 said:
Good day all.

Needing some input on the why it happens and potential fixes.

I have well stabilized scales of various woods, burls, some dyed, some
not.
I flatten them on a flat plate, till I cannot see between them, using 60
grit paper finishing with figure eight motions.

I did not use powered sanding so no heat was introduced.

Against each other they were flat and almost "Stick" together.

I then glue G10 liners with a thin smear of GFlex epoxy, prepped and all
cleaned with denatured alcohol.

Clamping is done with small spring clamps, three per scale, on a flat
piece of angle iron.

After a 24 hour cure, I remove them and notice that they are bowed from
each other, sufficiently so that if I flatten to remove the bow, the
liners will look pretty sorry.

I am trying to straighten them by clamping and over shimming where
needed and placing the affair in front of a space heater, rotating every
so often.

So far no improvement.

This has happened before and I can't stomach wasting such beautiful,
unique materials.

Any ideas for salvaging these and possibly future work?

Thanks in advance,
Scott
Click to expand...
 
As a guess, the glueing of the scales to the spacer might be the problem. I would suggest that you glue the spacer to the handle, let it set up , then as a separate operation, glue on the scales.
 
I have had it do exactly the same thing. Keep in mind that stabilizing helps prevent *some* movement but if wood is going to move then it's going to move. Any time you cut a scale and it sits for a while you can expect some warp.

Here's a sneaky trick I learned from Ed Caffrey that I have used to great benefit: Black liners with black epoxy. IF you put some black dye in your epoxy and use a black liner, the two will be indistinguishable when cured. So if you have some minor gaps, a thick layer of epoxy will fill that gap and blend right in with the black liner. You will never see it.

Also, the amount of warp you see between two scales will only be visible by half, because only half the gap will be on one side of the knife.
 
I think what may be happening is when you glue the G10 to the scale and the epoxy sets up one of the two shrinks and you get your "bow". I would do what Bruce suggests and glue the g10 to the knife and then glue the scale.

Colored epoxy is also a great trick - Black, brown, etc. You can also use sawdust from your scale material to "somewhat" match and fix issues.
 
Both good suggestion to try in the future.
These scales have bright yellow G10 liners, so no colorant that I have will work.
When I purchased these scales they were already 5/16 thick and extremely flat, so they only needed roughing up.
Ideas to salvage them?
 
I don't think you'll have to remove as much as you think to flatten them. If you cut to shape before you flatten, you can effectively minimize the the amount you thin the liner to almost zero where it's visible at the edge.
The question is will they continue to shift after you attach them.
 
SS369 said:
Both good suggestion to try in the future.
These scales have bright yellow G10 liners, so no colorant that I have will work.
When I purchased these scales they were already 5/16 thick and extremely flat, so they only needed roughing up.
Ideas to salvage them?
Click to expand...
Pictures?
 
That makes sense.
And yes, that is a good question.

I feel pretty confident, when all is said and done, that the epoxy will adhere the scales/liners to the balde, but I would like to know the for sure reason for the warp...

Could it be that the GFlex is not the epoxy to use for this part of the process? Do I need to use less flexible epoxy for this, attaching liners and scales?
Will superglue cause the same thing?

It's just that you start out with all flat items, clamp on a flat surface, not over clamped, etc. and boom, they come out warped.
 
Pictures
One pic back to back shows the warp best.
Other liner to liner clamped on one end.
 

Attachments

  • IMG_5903.jpg
    IMG_5903.jpg
    1.7 MB · Views: 33
  • IMG_5904.jpg
    IMG_5904.jpg
    1.8 MB · Views: 34
SS369 said:
That makes sense.
And yes, that is a good question.

I feel pretty confident, when all is said and done, that the epoxy will adhere the scales/liners to the balde, but I would like to know the for sure reason for the warp...

Could it be that the GFlex is not the epoxy to use for this part of the process? Do I need to use less flexible epoxy for this, attaching liners and scales?
Will superglue cause the same thing?

It's just that you start out with all flat items, clamp on a flat surface, not over clamped, etc. and boom, they come out warped.
Click to expand...
Different rates of expansion? Different rates of epoxy absorption ? Magic?
 
At this point you have nothing to lose. I would try applying some gentle heat combined with a little clamping persuasion to see if you can't get that scale to relax.
 
Bruce McLeish said:
Different rates of expansion? Different rates of epoxy absorption ? Magic?
Click to expand...

I suspect chemical reaction (heat) between the G10 and the epoxy as it cured. I have had scales do this to me with G10, exactly like the picture shows but never with fiber liners.

As a general rule, I don't epoxy my liners to the scales ahead of time. The handle goes together like a sandwich all at once when I put it on the knife. (Scale, epoxy, liner, epoxy, next liner, epoxy, blade, epoxy......) then it gets clamped to cure. The only time I pre-epoxy the liners to the scales are when I'm combining different pieces of scale material and using the liner as a substrate to glue them to for support.
 
To you all. Thanks for all the input!

The different rates of expansion - magic!
Exothermic heat during cure !
Doing the clamping/heat/over-bending as I type. Continuing that is. I just don't want to crack them.

I believe I will do my glue ups at one time from here on out., as per Mr. Wilson said.

Scott
 
You know, Scott- if you can get the warped scale almost flat, you can always flatten the wood side and that becomes your new inside surface where you can add a new piece of G10. You'll need new pieces of G10, of course, but in the big picture you can salvage the scale. You'll end up with a handle that has your old G10 scales on the outside. Then just grind them off as you shape the handle.
 
True what you said John.
They're bookmatched, but I did pick the most awesome sides..
I'm going to work on the overbending for now and see if that helps. If not, then I will check out whether the Corbys will pull them flat enough (using clamps, not the actual rivets.).
I'm considering thinning the G10, as well, to see if that'll relieve some of the warp. Maybe get rid of it completely and start again.
If it weren't for the challenges this would be boring. ;-)
BTW, you guys are great.
 
Is the handle hardened? If it was mine and I wanted to save it I might try some hidden pins in the handle to help hold the scales.
Maybe even a small burr on the heads? < That's recycled information but I'm going to try net time I do hidden pins

edit: and I'm still a little green so I apologize if I'm overreaching.
 
I don't think I'll try any hidden pins - too fiddly for my hands. But, I reckon I could add another Corby in the center.
Not sure if I will like the looks on this particular knife though.
Drilling 61 HRC steel is not my favorite and with the lightening holes already done, I'm unsure that I'll have the place.
 
I suspect the problem you are having is not from gluing, it's from sanding. When you sand something it starts to heat up from friction. Since you are sanding only on one side it is expanding on one side and causing the material to warp as you sand. You are, in a sense grinding a hollow into your scales. When it cools, it returns to it's original un-warped self with the hollows in them. Next time you sand stuff flat, try this. Get them as flat as you always do, the same way you always do, set them aside until the next day, or at least a couple of hours. When they are totally cooled off blacken the "flat" side with a magic marker and touch them again on the sander and you will probably see only the ends touched. You can also look between them for light but the sanding method is more obvious.

I always flatten in stages and the last sanding is very lightly on completely cool material. This will happen on any phenolic and any natural material.

By the way, I always glue liners in while I am gluing the scales on.
 
Thank you Mark for your reply. I appreciate every little tidbit along this journey.
What you have written makes sense and I understand it. But, in this case I only hand sanded the materials to roughen them as they were acceptably flat.
In the past I have glued up sets to choose from, before completing the blades. This time I ran into a mystery.
I actually called West Systems and spoke with them to see what they could offer in the way of possible explanations.
They were great to talk with, very helpful and informative, but perplex as to the actual cause.
I went over my complete procedure with the chemical engineer and he pointed out a few things I could do differently. Shared some things about G10 I did not know. He also called me back later to tell me he had run it by some coworkers and got their input.
Long story short, he suggested to use isopropyl alcohol, not denatured, and use a caul to put between my clamps and the scales to spread the clamping force.
Now all I have to do is salvage these...
May choose to do liners to scales to blade in the future.
 
You must log in or register to reply here.
Back
Top