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Bonding metal to poly-finished wood

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Forum topic by cjg225 posted 02-13-2017 02:09 PM 1082 views 0 times favorited 11 replies Add to Favorites Watch
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cjg225

7 posts in 303 days


02-13-2017 02:09 PM

Topic tags/keywords: walnut finishing

Hi all,

First-time poster here.

I am nearing completion of a project that has taken me a few months mostly because I haven’t been working on it as much as I could have. I have a bit of a conundrum right as I am about to be fully done.

I have a solid walnut plaque that I’ve stained and finished with Minwax fast-drying polyurethane (clear satin). It’s not quite as good as I hoped, but by no means is it bad. It’s definitely good for someone of my limited skillset.

The project is one to recreate a plaque my father received when he left Germany in the Army in the mid-70s. The plaque does not hang on a wall, but rather sits flat on a horizontal surface. The plaque had a brass plate on it with some words, 6 Distinctive Unit Insignia (DUI) pins glued to the wood, the Artillery branch lapel insignia glued to the wood, and a canon screwed to the wood. The plaque was water damaged many years ago and was severely torqued. My father and I long planned on re-doing the plaque, but he passed away back in October 2015, unfortunately, before we ever actually got around to doing this together. A master-woodworker family friend told me that the wood was probably too damaged to reuse, so I had a bare walnut plaque made to order and then I finished it.

The problem I am facing is this:

Is there a way to bond brass (I believe that’s what DUIs are usually made of) to poly-finished wood? I believe on the old plaque they were bonded with hot melt, but I am not 100% certain. I am playing around with my test board right now, where I tried all the various stains and finishing techniques. One of the 6 sections is finished basically the same exact way the actual project piece is finished.

I tried bonding the old DUIs (I bought a brand new set because the old ones weren’t in the best shape) with hot melt to my test board today. One of the DUIs pulled right off, but one seems to be firmly bonded to the wood. Not sure why the difference. Maybe it was a problem with the back of the DUI (which isn’t 100% clean, as I said, from the old plaque).

Does hot melt expire? I have no idea how old the hot melt sticks I have are. They’re probably very, very old. Maybe it was more of a problem that the hot melt isn’t fresh than anything else.

I randomly asked some people I know, and a person mentioned Loctite 5-minute-set epoxy. I intend to try that this afternoon. The packaging says it bonds with glass and ceramic, so it must have some ability to bond with a fairly smooth surface. The same person also mentioned roughing up the surface with some sand paper, but these brass items are very small, especially the Artillery branch lapel insignia (which is just two very, very small crossed canon barrels), so I worry about overdoing it… and accidentally ruining part of the finished surface that will be visible.

Rather than flail around, though, I am wondering if folks here have some better, alternate ideas or have some tactics I might try to ensure a good bond with epoxy or hot melt.

Thanks for any advice or insight folks have.


11 replies so far

View wuddoc's profile

wuddoc

231 posts in 3551 days


#1 posted 02-14-2017 05:01 AM

Alternate ideas.
Escutcheon Pins
Small Brass screws
Double sided Tape

-- Wuddoc

View howellusn's profile

howellusn

2 posts in 300 days


#2 posted 02-14-2017 02:48 PM

https://www.amazon.com/Hardman-Double-Bubble-Setting-minute/dp/B00C6SLAWQ/ref=pd_sim_60_2?_encoding=UTF8&psc=1&refRID=0E2H4C15FY575VE5VV3Z

This is what me and others at my old navy command have been using for years and it works like a charm. Nice small packets as well so you don’t waste much vs the bigger epoxy blends out there.

View Dave Polaschek's profile

Dave Polaschek

1182 posts in 415 days


#3 posted 02-14-2017 02:48 PM

Surface prep is important. I would rough the poly behind where the metal will go (make a q-tip with a toothpick or dowel and steel wool for the fine work), and clean the backs of the DUIs thoroughly. Super-fine steel wool, perhaps? Then either 5-minute epoxy or hot-melt should work. But the surfaces have to be clean. They may have been glued with PVA glue or something which new glue will not adhere to.

-- Dave - Minneapolis

View cjg225's profile

cjg225

7 posts in 303 days


#4 posted 02-15-2017 12:53 AM

Thanks a lot for the advice, all.

I’ll look into that epoxy. I have just Loctite 5-minute epoxy from Home Depot that I have to try.


Alternate ideas.
Escutcheon Pins
Small Brass screws
Double sided Tape

- wuddoc


Unfortunately, the pins or screws wouldn’t work. The insignia are actually usually worn as pins on a dress uniform, so their entire surface area is used for the image presented. There’s not negative space to go through with a win or screw.

Surface prep is important. I would rough the poly behind where the metal will go (make a q-tip with a toothpick or dowel and steel wool for the fine work), and clean the backs of the DUIs thoroughly. Super-fine steel wool, perhaps? Then either 5-minute epoxy or hot-melt should work. But the surfaces have to be clean. They may have been glued with PVA glue or something which new glue will not adhere to.

- Dave Polaschek


Yeah, I’m discovering I’ll need to do good surface prep. I’ve tried some hot melt on my test board already, and, oddly, experiment in which I did no surface prep is the one that has held the best. I mean, the board and insignia are clean as it is, but I didn’t rough up either for one experiment and it’s held well. I doubt that’ll be the general rule, though. I intend to rough up the poly side for sure when I move over to working on the project piece. The insignia I’ll be putting on are brand new, compared with the used, old ones I am using in my experiments. Might have an effect on how well it bonds.

View papadan's profile

papadan

3584 posts in 3202 days


#5 posted 02-15-2017 01:10 AM

How long has the poly been drying on the base? Give it at least a week indoors to be sure it is cured. Then just used small amounts of your epoxy to attach your Units. The chemical reaction of the epoxy could affect your poly if it is not cured.

View squazo's profile

squazo

51 posts in 1478 days


#6 posted 02-15-2017 02:45 AM

VHB tape from 3m

View papadan's profile

papadan

3584 posts in 3202 days


#7 posted 02-15-2017 03:25 AM

I believe the contact area of the units would be too small for mounting tape to hold

View cjg225's profile

cjg225

7 posts in 303 days


#8 posted 02-16-2017 01:51 AM



How long has the poly been drying on the base? Give it at least a week indoors to be sure it is cured. Then just used small amounts of your epoxy to attach your Units. The chemical reaction of the epoxy could affect your poly if it is not cured.

- papadan


Less than a week since the final coat was applied. I actually have posted this same topic on another woodworking forum to maximize the information I get. Someone there pointed out this issue, as well, and told me to let the poly cure for a few more weeks to be extra sure.


I believe the contact area of the units would be too small for mounting tape to hold

- papadan


I’d say that the insignia are each, very roughly speaking (since only two are square-shaped), 1 inch by 1 inch. Someone on the other forum recommended Fastcap Speedtape to me, which seems to come in 1/4-inch wide through 1-inch wide varieties, amongst others.

VHB tape from 3m

- squazo


Does 3M make it with a polyester back? I was looking at foam-backed VHB tape from 3M and thought that would provide a decent-sized gap behind the insignia because of the thickness of the tape. Unless I am misjudging the thickness of the foam based on Internet pictures…

View patcollins's profile

patcollins

1605 posts in 2698 days


#9 posted 02-16-2017 02:01 AM

Shoe-Goo

View Loren's profile (online now)

Loren

9605 posts in 3481 days


#10 posted 02-16-2017 03:54 AM

super glue. It bonds metal to glass and
I would expect it bonds brass to poly.

If the issue is pins on the back of the brass
pieces, dollop hot glue onto glass and
press the pin in, then pop off with a chisel.
Super glue the flat back of the cured
hot glue to the poly.

View cjg225's profile

cjg225

7 posts in 303 days


#11 posted 02-19-2017 06:22 PM



super glue. It bonds metal to glass and
I would expect it bonds brass to poly.

If the issue is pins on the back of the brass
pieces, dollop hot glue onto glass and
press the pin in, then pop off with a chisel.
Super glue the flat back of the cured
hot glue to the poly.

- Loren


Well, the pins aren’t the issue as much as I just need to ensure the insignias don’t pop off. I actually sort of want to keep the pins intact.

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