white vinegar derusting disaster

[Round in circles]

Recently I bought some vintage machinist calipers on Ebay. There were some spring type toolmaker's style by Lufkin and some Yankee style by Starrett from two different sellers. Some of both lots were lightly rusted and grimey so I thought I'd try using vinegar for rust removal. I had read that it does a good job without removing base metal and I hoped that it would remove the rust without otherwise marring the finish. I soaked several of them in regular household white vinegar overnight. As advertized, the vinegar did a great job on the rust. Unfortunately, I found 4 of the spring "bows" snapped in two. One of four Starretts broke (the other three seem fine) and all 3 of the Lufkins. I have the utmost respect for these old tools and am saddened to think I (unwittingly) destroyed them by trying to return them to a usable state. I found a similar Starrett caliper in their current catalog so I am hoping that I can get a replacemet bow. I am not so hopeful for the Lufkins.

Can anyone explain to me what happened? I am completely mystified as to what would cause the bows to break whilebsoaking in a mild vinegar solution. Also, if anyone knows how I might obtain replacements for the Lufkin bows, I would be grateful.

Here's a picture of the damage:
View attachment 88385

if you can't get the new bows ...
It could be an interesting exercise in bench fitting to make some new bows and then harden & temper them as for spring steel
( done as part of my apprenticeship nearly 50 years ago )

 

[rick9345]

rusting is metal removal
rust removal of any kind will not replace the metal that has already gone away
any rust removeal compound/soloution hastens/encourages more metal removal

 

[John_Dennis]

I have always bees surprised at how a strong piece of metal can be cracked by a liquid. One of the strangest instances of this is that if a liquid metal, mercury or solder for instance, is applied to a piece of metal under stress, it may crack. (Liquid Metal Fracture)

If you put a brass bar in your vise and hang a weight on the end of the bar causing a slight deflection and put a drop of mercury on the bar, it will shatter.

When soldering or brazing, if the parts are a press fit or there is uneven cooling, then the molten metal can cause the same effect although it will be less obvious and perhaps invisible till the part fails under use.

 

[Flammable_Solid]

I have always bees surprised at how a strong piece of metal can be cracked by a liquid. One of the strangest instances of this is that if a liquid metal, mercury or solder for instance, is applied to a piece of metal under stress, it may crack. (Liquid Metal Fracture)

If you put a brass bar in your vise and hang a weight on the end of the bar causing a slight deflection and put a drop of mercury on the bar, it will shatter.

When soldering or brazing, if the parts are a press fit or there is uneven cooling, then the molten metal can cause the same effect although it will be less obvious and perhaps invisible till the part fails under use.

What happens in the cases listed above happens at the atomic level. The liquid metal is wicked into the grain boundaries of the base metal. Throw in a temperature change or phase change, and the base metal is forced apart at the grain boundaries.

 

[coolidge]

You could also give Evapo-rust a try. It's not acidic and shouldn't cause embrittlement, I have had great success with it. It is a bit more expensive than vinegar though.

Just a thought,

-Ron

^^^ if you think MAGIC isn't real just buy a gallon jug of Evapo-rust and you'll become a believer.

 

[JR49]

Can Evaporust be re-used ? As in, using say 2" of it poured into a flat pan in order to submerge a rusted tool or steel plate. Once the part is "done" can the remaining liquid be poured back into the container and saved for the next de-rusting job? Merry Christmas, JR49

 

[ScrapMetal]

Can Evaporust be re-used ? As in, using say 2" of it poured into a flat pan in order to submerge a rusted tool or steel plate. Once the part is "done" can the remaining liquid be poured back into the container and saved for the next de-rusting job? Merry Christmas, JR49

Yes, you can keep re-using it until it turns dark brown. Mine never makes it that far as I tend to suffer a bit of loss every time I try and pour it back in to the bottle.

-Ron

 

[CoopVA]

Can Evaporust be re-used ? As in, using say 2" of it poured into a flat pan in order to submerge a rusted tool or steel plate. Once the part is "done" can the remaining liquid be poured back into the container and saved for the next de-rusting job? Merry Christmas, JR49

Yes, you can keep re-using it until it turns dark brown. Mine never makes it that far as I tend to suffer a bit of loss every time I try and pour it back in to the bottle.

-Ron

I keep it in a Rubbermaid "pan" with a lid. Actually, it's time for me to get some more....


Sent from my iPad using Tapatalk

 

[docn8as]

fwiw.....OLDETYME ANSWER TO DULL FILES WAS TO DELIBERAYELY RUST THEM,,,,,,,gain SOME ADDITIONAL LIFE
BEST WISHES
DOC

 

[18w]

This thread is what prompted me to finally sign up for this sight. I wanted to warn everyone about my experience. I placed 8 dividers and calipers (Starrett, Brown&Sharpe, and Lufkin) in a Evaporust bath for about 5 hours. These just had a slight hint of surface rust. No pitting or cracks. To my horror when I removed them 3 had broken spring clips. Evaporust is a great product but I learned the hard way that I will never place springs or spring steel in any kind of chemical deruster. As benign as Evaporust may be the results to these tools ruined my day. If they are broken when removed from the bath it is too late to bake the hydrogen out. The one thing I did not do was release the tension totally prior to my placing them in the bath. Perhaps that may have contributed to the problem.

Darrell