Help with Dent in Sheet metal (steel)

[catalytic]

Hi GJ'ers

I just started a complete rebuild of a Burr King 760 belt grinder. Apparently, the previous owner let a rather large piece of angle iron fall onto the motor's capacitor cover, giving it one big dent and another smaller one (I've been through the motor and it's otherwise fine). The rest of the machine is getting polished/painted/bearings and all mechanicals replaced or re-machined. What are your thoughts on whether and how I can make these dents disappear such that they're not an eyesore on an otherwise nice restoration? (I know I could slather on auto body flller under the new paint, but that feels like cheating). Alternatively, if someone knows of a source for OEM replacements, I would love to hear about it (my searches have turned up empty).

I have access to a fully equipped machine shop, but relatively little experience with sheet metal.

The machine (prior to restoration):


The dents:

 

[CJM8515]

Pound it out, bondo, primer and paint.

 

[73surffisher]

These are "almost generic", just get one from another motor , , you'll be happier you did it, , , almost any bone yard will have an old motor junked

 

[rsanter]

Take a chunk of wood, hardwood prefered
Sand to a profile that will fit inside if it was not dented.
The wood only needs to be about 2" wide not the full width
Once you have that you can tap the wood into the cover with the dent down to the bench.
Once you have the wood driven in and the dent mostly out you can do a little hammering on the outside of the cover around the dent not right on it using the wood as a sort of form to help work the remainder of the dent out.
Once you have most of it to use epoxy as a filler not bondo as epoxy handles heat better

Or just buy a new cover...

Bob

 

[ZRX61]

I don't get it, you have access to the inside so just knock the dents out.

 

[lilredex]

Make up a "TEE" anvil that closely fits the shape...then go to work.

Something like this..

http://www.ruffrodders.com/forum/showthread.php?p=407006#post407006

 

[Kevin54]

I was going to say...get a large socket, or some object that is just about the same diameter, and press it out. Then take a wood dowel and round off the end and use it to tap the smaller dents out. You can run across the surface with a file to see you high and low spots, and tap from there. Once you get down to very minimal spots, use the belt sander and clean the surface up. Then you can prime and paint.

 

[Hpozzuoli]

I was going to say...get a large socket, or some object that is just about the same diameter, and press it out. Then take a wood dowel and round off the end and use it to tap the smaller dents out. You can run across the surface with a file to see you high and low spots, and tap from there. Once you get down to very minimal spots, use the belt sander and clean the surface up. Then you can prime and paint.

I agree. Something small like that can be pressed easily.

 

[Zeke]

You need the right hammer to bump that out and I bet you don't have one. So, you can use a metal dowel rounded off and hit that with any hammer (wear eye protection). The thing is you need both hands to do that so you'll have to figure a way to clamp the work on a piece of wood. The best place to beat against is the end grain of a large piece of wood or a flat stump. Just work your way around unclamping and clamping until the dent is bumped out.

We say 'bumped' because you don't wail on metal, just persuade it.

Let me add: when removing a dent think of how it happened and reverse the process, i.e., start at the edges or end where the last part of the dent was formed. The last part you straighten is the first part that the object hit, in your case it is the crown.

 

[Tucko]

You need the right hammer to bump that out and I bet you don't have one. So, you can use a metal dowel rounded off and hit that with any hammer (wear eye protection). The thing is you need both hands to do that so you'll have to figure a way to clamp the work on a piece of wood. The best place to beat against is the end grain of a large piece of wood or a flat stump. Just work your way around unclamping and clamping until the dent is bumped out.

We say 'bumped' because you don't wail on metal, just persuade it.

Let me add: when removing a dent think of how it happened and reverse the process, i.e., start at the edges or end where the last part of the dent was formed. The last part you straighten is the first part that the object hit, in your case it is the crown.

Zeke is correct. And for any body filler, I would suggest using ALL Metal which is like Bondo, but it's metal based and stands up to heat. (Great for powder coating).

 

[zkling]

Make up a "TEE" anvil that closely fits the shape...then go to work.

Something like this..

http://www.ruffrodders.com/forum/showthread.php?p=407006#post407006

This. You have access to a machine shop, turn a slug the same radius of the cover, then press or hammer it against a highly polished piece of steel (acts as an anvil). Just don't use too much pressure as it will stretch the metal. Me personally I'd just go at it with a end rounded piece of ~1/2" stock, polished and a hammer.

 

[kingchevy]

That is most certainly unfixable, rendering the machine worthless. I would be glad to give you scrap value plus shipping to clear it out of your garage.

 

[catalytic]

This. You have access to a machine shop, turn a slug the same radius of the cover, then press or hammer it against a highly polished piece of steel (acts as an anvil). Just don't use too much pressure as it will stretch the metal. Me personally I'd just go at it with a end rounded piece of ~1/2" stock, polished and a hammer.

Thanks guys -- I'll give this a try. Also, cool idea to use the belt grinder in slack belt mode to smooth it out afterwards -- this had not occurred to me. Usually I'm pretty happy when my tools can be used to fix each other, but I don't think I've ever had a tool that could fix itself.

 

[catalytic]

Your advice worked. I cut a 3" section of mild steel round. I happened to have the size in stock that gave a tight fit inside the capacitor cover, so there wasn't even a need to chuck it in the lathe (I imagine they used the same standard sized die to make it). After 45 minutes of tapping with a dressed sheet metal hammer and a ball peen, you wouldn't be able to tell there was ever a dent in it (well, save for the paint)