Fillers for metal&wood

ironbut · 1910

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Offline ironbut

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on: August 05, 2012, 06:47:51 PM
I noticed a thread today where a builder was worried about some scratches on the plate he planned to paint. In that particular thread, it sounded like the scratches were fine enough that the hammertone paint would almost certainly fill the voids.

After reading the thread, I did realize that some of the beginners might not know a good way to fill scratches/dings on the plate before painting (especially with paint with any gloss since it'll show pretty fine scratches).
The best filler for scratches in metal that's generally available is Bondo Spot Glazing Putty. You can buy small tubes of it at most auto parts stores and is made to fill scratches and dings in auto bodies in preparation for painting.
It's a lacquer based filler and it's main advantage over most any other type of filler is it's ability to fill very shallow voids and not come out as you sand it flush. Just be sure and let it dry overnight before sanding (probably much less for most voids you'd encounter on your top plate but if you try and sand it before it's dry through and through, it will rub out and you'll be back at square one).
Sand the dried Bondo putty with aluminum oxide 220 grit then aluminum oxide 320 grit sandpaper and prime (the putty is dark red and difficult to cover so spot prime, lightly sand and re prime until the the fill is invisible.

For the alder that Bottlehead makes their bases from, an excellent filler is Elmer's Carpenter's Wood Filler. It comes in several shades and Golden Oak works very well with alder. If you happen to be working with something like maple, the Natural color is best.
Elmer's Wood filler is stainable and while nothing will look natural if the fill is too large and you can't "fitch" the woodgrain (using dry brush techniques with the appropriate stain or ink to imitate the wood grain), the color should match pretty well after you've stained and finished the repair.
Once again, it's important to be patient and give the fill(s) 24 hours to fully dry before sanding. It will look dry before that but the filler will be rubbery until totally dry and it will take twice as much sanding to level the surface. When you have to struggle sanding a fill, your always in danger of "cupping" the wood around it making the problem worse.
Once the fill is flush, be sure and lightly sand the entire side (with the grain) to even out the pores of the wood and get rid of any crossgraining from the sanding (causes crosshatching scratches to show up after staining.

I hope this helps some of you guys.

steve koto


Offline Mosez

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Reply #1 on: August 06, 2012, 06:21:38 AM
That's great advice - thanks Steve!

Daan Zweers


Offline Jim R.

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Reply #2 on: August 08, 2012, 09:28:56 AM
Steve,

Can I ask your advice on what would be the best way to fill the extra holes in thee transformer covers that BH supplies?  Sure, I can doit with bondo and some fine mesh stainless or brass screen, but how would I do it if I wanted something that could be plated over (conductive) or powdercoated (able to handle about 425 degrees for 30 minutes or so)?

Thanks,

Jim

Jim Rebman -- recovering audiophile

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Offline 2wo

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Reply #3 on: August 08, 2012, 12:32:53 PM
For powdercoat, I bet JB weld would work...John

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Offline ironbut

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Reply #4 on: August 09, 2012, 08:13:05 AM
Yeah, it might be worth sending an email to JBweld just to be sure before having someone powdercoat. If you're doing it yourself, heck,.. I'd give it a try.
If you want to electroplate it, you just about have to get it welded and ground. It would probably be much cheaper to just see if you could get a new cover. (after thinking about it, it would be easier in both cases to epoxy a fake screw head or something cool looking in the holes)
« Last Edit: August 09, 2012, 08:17:13 AM by ironbut »

steve koto


Offline Jim R.

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Reply #5 on: August 09, 2012, 08:16:36 AM
Thanks John and Steve.

Maybe I'll try filling the hole with some brazing rod and then grinding, etc.

-- Jim

Jim Rebman -- recovering audiophile

Equitech balanced power; uRendu, USB processor -> Musette DAC -> 5670 tube buffer -> Finale Audio F138 FFX -> Cain and Cain Abbys near-field).

s.e.x. 2.1 under construction.  Want list: Stereomour II

All ICs homemade (speaker and power next)


Offline RayP

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Reply #6 on: August 09, 2012, 10:18:03 AM
From the other end of the spectrum, the easiest way to make sure nobody notices the fine scratches in metal work is to drill an unnecessarily large rough hole (or two or three) in the plate. Works for me every time. Nobody ever talks about the fine scratches in my creations.

ray

Ray Perry