Promo cast grill smoothing?

[Foxer]

I'm working on a '51 Plymouth promo and need to smooth out the cast metal grill/bumper so I can alclad it. Every surface has to be glass smooth for chroming with Alclad. The surface has a bumpy texture that I have to remove. I have filed some of the surfaces but the deep inside ones are not easily filed smooth. I tried a wire brush on the Dremel but this just works over the whole surface and not smoother level.

I'm just looking for some ideas on how I might do this, crazy or not.

Thanks in advance.

here's a couple shots with different lighting

[MGL]

If you want to keep it as original as possible I don't have any ideas other than a thin polishing wheel on a dremal with coarse polish but if your not concerned with keeping it original you could grind out those areas from the back and open it up like the 1/1 grill. I guess you could also leave it alone and paint it flat black after the alclad. I should add they make small conical shaped grinding stones and polishing bits for a dremal.

Edited April 22, 2016 by MGL

[Foxer]

Original is not in the cards for this one ... the promo collectors would have heart attacks viewing my On the Workbench thread!

I'll have to delve into my polishing bits and see if anything small.

Thanks for the comments.

[MrBuick]

Shouldn't the deepest part of the grille be black\hollowed out anyway?

[sjordan2]

Have it re-cast in resin?

[Foxer]

Shouldn't the deepest part of the grille be black\hollowed out anyway?

yes .. not too worried about that flat area. The sides going down to that are the area I need to smooth.

[Foxer]

Have it re-cast in resin?

Its rough enough that it would be in the resin, though resin would be easier to smooth. I love the casting in metal. I could just polish it to a chrome luster if it was done without the texture on it.

[MrBuick]

yes .. not too worried about that flat area. The sides going down to that are the area I need to smooth.

Ah...I wonder if filing down the back and opening the flat area would make that easier...maybe those sides would be more accessible that way? Or, another idea is depending on how rough it really is, I wonder if some polishing compound applied with a q-tip would work...or for that matter, some fine grit sandpaper wrapped around a q-tip. Also, maybe an old toothbrush could be utilized to help knock some of the roughness down. 

[StevenGuthmiller]

Being as there is not a lot of fine detail, I would just prime it & then shoot it with several fairly heavy coats of Testors gloss black enamel for your base.

Everyone always talks about how enamel paints hide too much detail, well, this would be a good instance to make that work "for you".

The enamel takes a long time to dry & will level well so it should fill in that "roughness" that you're talking about & give you a smooth shiney black finish.

Exactly what you need for Alclad.

 

Steve

[oldnslow]

Colby, has the right idea, taking out the lower surface is the way to go, then you'll have access to all the surfaces to get them as smooth as you want.

[Foxer]

I do like the idea of sanding the back away. It seems to be around .04 or so thick and a few strokes say the metal is fairly soft. I would also be able to get the raised areas around the turn signals away. Mounting pins are directly behind the turn signals. It would give easy access to file down the rough surfaces.

With Steve's paint suggestion on top, it may come smooth this way. Lets see if I can talk myself into all that filing .. the grill WILL look better for it.

I really appreciate you all thinking thru this with me. Good suggestions.

 

[Ace-Garageguy]

Had exactly this problem on an old Pontiac promo I bought specifically to convert Revell's '50 Olds to a Poncho. I bead-blasted the flaky stuff off and primered the whole thing in several coats of SEM self-etching black primer. It's not a high-build primer, but it builds enough to get all the pitting out with minor sanding...if it's not too deep.

NOTE: If the pitting is REALLY bad (which mine was) all you gotta do is shoot it in a high-build or "scratch-filler" primer (Duplicolor, SEM, etc) over the self-etch before sanding it slick.

The self-etch is hot and ensures good adhesion. The high-build fills. Get it slick, shoot it in gloss black, and Alclad.  

[Ace-Garageguy]

 

PS. It doesn't have to be all that hard to take the 'filled' areas out of the back, either. Just gently support it in a vise with the backside facing up, and attack it with a Dremel drum sander. You remove the thickness of the metal 'wall' in the back of the part, once the 'holes' are opened up you file the back flat, and then lightly dress the edges with smaller files from the front. Goes fast.

[TomZ]

Please show us how your efforts turn out! I'm really curious about this one.

[Foxer]

Had exactly this problem on an old Pontiac promo I bought specifically to convert Revell's '50 Olds to a Poncho. I bead-blasted the flaky stuff off and primered the whole thing in several coats of SEM self-etching black primer. It's not a high-build primer, but it builds enough to get all the pitting out with minor sanding...if it's not too deep.

NOTE: If the pitting is REALLY bad (which mine was) all you gotta do is shoot it in a high-build or "scratch-filler" primer (Duplicolor, SEM, etc) over the self-etch before sanding it slick.

The self-etch is hot and ensures good adhesion. The high-build fills. Get it slick, shoot it in gloss black, and Alclad.  

This piece has bumps and not pits. Filing away you comments on pitting.

 

PS. It doesn't have to be all that hard to take the 'filled' areas out of the back, either. Just gently support it in a vise with the backside facing up, and attack it with a Dremel drum sander. You remove the thickness of the metal 'wall' in the back of the part, once the 'holes' are opened up you file the back flat, and then lightly dress the edges with smaller files from the front. Goes fast.

ah Bill ... glad you recommended using the drum sander ... was my thought and it IS going to be done.