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Veteran Advisor
ericjoseph2001
Posts: 1,774
Registered: ‎11-07-2009
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soft metal inlays

I've tried 2 separtate blanks with aluminum inlays that have shattered on me.  I glued them with CA glue as have many before me so I just can't figure out what I'm doing wrong.  I have used several clamps to keep things flat and true while drying and usually cut at a 45 degree angle so I'm not gluing straight end grain. Left it clamped for about an hour which should be sufficient for CA glue by far.  Any tips?  Should I be using epoxy instead?

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johnclucas
Posts: 2,050
Registered: ‎10-26-2009
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Re: soft metal inlays

What are you inlaying the metal into.   CA is not my choice for anything I want to last.   I prefer epoxy and I try to scratch the back surface to give it more mechanical holding power.     You would have to describe or post a photo of what your trying to do .  Then we can help you more.

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Bill Boehme
Posts: 1,032
Registered: ‎10-27-2009
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Re: soft metal inlays


ericjoseph2001 wrote:

I've tried 2 separtate blanks with aluminum inlays that have shattered on me.  I glued them with CA glue as have many before me so I just can't figure out what I'm doing wrong.  I have used several clamps to keep things flat and true while drying and usually cut at a 45 degree angle so I'm not gluing straight end grain. Left it clamped for about an hour which should be sufficient for CA glue by far.  Any tips?  Should I be using epoxy instead?


If you are referring to layering metal sheets with layers of wood such as when creating a peppermill blank, I would not use CA.  While the end result of the finished product resembles an inlay, it needs to be treated differently because the glued joint is much weaker than the wood or even a glue-up wood joint.
Cyanoacrylate adhesive is brittle and also doesn't withstand shock loads very well.  Epoxy would be much better.  Wood glue does poorly on metal.  I think the ideal adhesive would be something that is very strong and slightly less brittle than either CA or epoxy, but I don't know what might fill that requirement.
Whatever you use, scuff up the metal with sandpaper and clean it thoroughly to remove any oily or waxy residues that could weaken the bond.
Use very sharp tools because even under the best of conditions the wood-metal glue joint could fail if you have an "oops".  Wearing eye and respiratory protection is always important, but the dangers are more significant when cutting and sanding metal.
One more thing is that some CA adhesives are more brittle than others and all CA gets more brittle over time.
Veteran Advisor
ericjoseph2001
Posts: 1,774
Registered: ‎11-07-2009
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Re: soft metal inlays

I roughed up the aluminum some hoping for a better bond, I was trying for a simple cross section, two inlays, opposing 45 degree angles to make an X.  I ended up gluing one up then cutting another 45 degree cut and inlayng the other piece of aluminum which of course didn't hit the "X" I was hoping for due to the waste I removed with the miter saw.  I did a celtic knot once and just stopped short of cutting all the way through the wood with my bandsaw and a stopblock set up.  I guess I need to try that route again and use epoxy.  I'm sorry I have no pictures, nothing in progress, and threw the other pieces out.  

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Bill Boehme
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Registered: ‎10-27-2009
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Re: soft metal inlays

[ Edited ]

One more thing about safety -- DO NOT "feel" the turning with your bare hand with the lathe running -- or with the lathe OFF until after the surface has been carefully sanded to remove any fine metal edges.  Even then I would be cautious about "feeling" the quality of the surface.

Honored Advisor
johnclucas
Posts: 2,050
Registered: ‎10-26-2009
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Re: soft metal inlays

You should also be aware that wood moves and metal moves differently.  I use 5 minute epoxies because they have more flex than the slow set epoxies.  At least the ones I use do, can't say that for all epoxies.   I'm assuming your inlays are relatively small so wood movement shouldn't be a problem.

Frequent Contributor
JTTHECLOCKMAN
Posts: 84
Registered: ‎10-21-2009
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Re: soft metal inlays

What are you making???  Is this a pen, bottlestopper or something else???  Will you be drilling it after the blank is made up???  Whenever I use metal to wood I always use epoxy for some of the reason mentioned. I use System3 epoxy. Roughing the pieces is key.

John T.
Veteran Advisor
Bill Boehme
Posts: 1,032
Registered: ‎10-27-2009
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Re: soft metal inlays

Even with an inlay where CA is used as a filler for a decorative medium, I have found it to be unacceptable due to its brittleness which leads to chipping along the edges of the inlayNever again will I use CA for that purposeEven the sharpest tools and very light cuts, I couldn't completely stop the chippingI now use either Devcon super clear epoxy or clear InlaceIn the long run Inlace is cheaper although the initial expense is somewhat high due to the quantity.

 

For your purpose where you are layering wood and metal (Celtic knot), a strong adhesive is what you needSince John mentioned that there is an epoxy that is slightly flexible, that might be the best choiceThe only glue that I have used for this purpose is regular epoxyJB Weld could be used if the color doesn't cause a problemWhatever adhesive you choose, make sure that all of the joints are very tightIf the adhesive is used to fill any gaps, it is almost guaranteed to failBesides that, glue gaps in a Celtic knot look terrible.

Veteran Advisor
Bill Boehme
Posts: 1,032
Registered: ‎10-27-2009
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Re: soft metal inlays


ericjoseph2001 wrote:
....... I have used several clamps to keep things flat .... Left it clamped for about an hour which should be sufficient .......

The word "clamps" reminded me of something else.  When gluing wood to something else with CA, clamping is usually not necessary and could even be counterproductive.  The reason is that CA begins to react with the wood very quickly, but not necessarily with the metal side of the joint.  Once the process begins things should not be moved or else the joint might fail.  The trouble with clamping is that things will move as pressure is applied.  One type of movement is from squeezing the excess glue out of the joint.  This produces a shearing force between the glue that has already started to set and the glue that is still fluid.  The other movement happens when the two parts slide as clamping pressure is applied.  This is especially a problem with a 45° joint where it is impractical to apply the clamping pressure perpendicular to the glued faces.

 

If accelerator is used, the joint will be further weakened.

Veteran Advisor
ericjoseph2001
Posts: 1,774
Registered: ‎11-07-2009
0

Re: soft metal inlays

Thanks again for all the tips.  I'll back up and punt, when I get a chance to play around I'll try again.  My turnings are small, about 1/2" x 1 1/2" at largest.  

 

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