Filler for rough castings?

[MushCreek]

Mostly just curious- What is the filler they used on old machine tool castings to smooth them out? On machines like my Bridgeport, you can see how thick the stuff is. I imagine they just slathered it on, sanded it smooth and painted it. It kinda looks like Bondo, but I'm pretty sure I've seen it on machines that pre-date Bondo. Anyone here know what they used, and what the process was?

 

[Firebrick43]

bondo has been out since the 50's. That is what I have seen on machines. Havent seen too many machine tools that haven't been repainted at least a few times since that time so the chances are many, even if they didn't have filler originally do now. Cars used lead as fillers prior to bondo but I doubt it would be easy nor wise to get a casting up to soldering temp to apply.

 

[MushCreek]

My Bridgeport is early 60's, with the original finish. There's some kind of thick filler visible where it's been chipped.

 

[wrenchr]

No expert but I doubt it was any kind of secret sauce used, I would just research what was common during the 60's and go with that. I would suggest using the different color hardener. if original is pinkish/gray it was the red stuff. so you know if you are over sanding by the different color.

 

[The Cobbler]

probably some type of high build coating that was slathered on , had lead in it among other treats and sanded off sans masks , ...

 

[Junkdrawer Dog]

When I built industrial gearboxes for a living, we fixed bad/rough castings with JB Weld!

 

[MShaw]

Machine tools had their castings filled and smoothed since, at least, the early 1930s. If you see a wartime machine tool it will have a tag on it stating it conforms to "wartime finish requirements". This means they did not fill and sand to an automotive finish for economy and speed advantages. My father worked for Pratt & Whitney machine tool division during the war and explained the meaning of the tag to me.

 

[isb cornbinder]

My big WF and John Barnes camel-back drill press has been smoothed with a little filler. The DP is dated 1876. I had the DP blasted with ground walnut shell media. The casting was surprisingly smooth. I painted over the bare metal with Tremclad.
At this time, I have about 5 Camel-back drill presses.

 

[MushCreek]

If I recall, chunks of it that I've looked at had an almost crystalline appearance, if that makes sense. Maybe some kind of mineral filler in a liquid binder of ????