What do do with my slightly beat up cylindrical square?

macardoso said:
God, I’d be really worried about damaging the precision finish. I do not believe it is chromed, only lapped, although I could be wrong in that regard.
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The precision finish may be dulled and you may indicate a loss of approx .00005 but it should be better than the rust which sits proud by I’m guessing .0003. Just a thought. You might just try good old vinegar and a tooth brush.....


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I was going to suggest pickling vinegar and a brass brush. Don't rub too hard, even with a tooth brush because the rust is much harder than the steel, and turns into lapping compound. Just flush it a lot and you'll be fine. For stubborn spots, a razor blade is very helpful - but don't use it like a chisel... Instead drag it across the rust , pulling it at 45 degree angle. With some pickling vinegar, it will help loosen most of it.

For the really stubborn spots, it is okay to make them subsurface.... Paint a single drop of evaporust directly on the rust spot, being careful not to use too much, only on around 50% of the rust. In 5 minutes or so, you can rinse with a cloth with clean water on it. then try mechanical again.

One technique I use that I didn't see mentioned is to get WHITE 3M pads: they are supposed to have no 'grit' in them, and use spray WD40 with a white pad. It takes off all but the worst rust without marring the surface finish. You don't 'bear down' on the pad just light pressure. I cleaned up a rusty gauge block like that (thank goodness it was a spare), and the difference couldn't be measured, it just wouldn't 'ring' any more.
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My opinion is based on my most severe interpretation of the photos. Possibly, if I saw it in person, I might suggest a different approach.
I see my opinion will be unpopular, however you did ask for "tips".

First, very locally, I'd stone the area of the ding (ignore the rust) to be sure that no point was proud of primary base plane. Don't worry about trying to match the primary base plane. A small area recessed from the primary base plane will be of no significance.

Then, I'd soak it (completely submerged) in Evaporust for, probably, a day. My intention would be to kill any rust, for good.
It would probably come out with a slight grayish hue but the hue won't change the practical serviceability.

On a suitable reference surface, verify that primary base plane has no high spots and that there are no points proud of the cylindrical surface.

It's a blemished cylinder square that you bought real cheap. If "blemished" isn't satisfactory, new are available.
 
macardoso said:
They’re pretty cool. I worked in a metrology/inspection lab for an old job and we had a few. One was 18” tall and weighed probably 60lbs.

They’re a reference surface for comparing squareness and are excellent for use in machine alignment.
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I have to look for pictures but we used one at one shop that was four foot tall!
 
Might look at cleaning it up with a precision ground flat stone. That reminds me I need to get a set of those.
 
Daring to go where only the ignorant will, I would ask of the metrology aficionados, is not a cylinder square a "self proving" thing, which works by having the ends turned concave, with only a relatively narrow rim to stand on the surface plate?

Provided the cylinder curved surfaces are in good condition, not having to be reliant on how straight are the ways of a lathe, then if turned between centers, facing and finally lapping the rim in Y-Axis theoretically forces a square when standing on it's end, even if the rim is theoretically not flat. So long as the end surface feature "rings" go all the way around, it will still stand square.

Of course, it is much nicer to have the rim ends as flat as possible, and a square as possible to the cylinder, but not essential. The region is narrow, and so long as spun between centers, the cylinder will stand up square, forced by the geometry of being constrained between two points when made.

Proving it with a dial indicator on a surface plate will reveal whether one has made a metrology version of the leaning tower of Pisa.
I get it that one is talking about serious actions on an expensive metrology item, but is not the risk of re-finishing the ends minimal?

Also - while talking of vinegar, would not abut 5 microns of nickel prevent this happening again? The next question is, why are such things not given plating protection in the first place?
 
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@graham-xrf None of the high quality cylinder squares are plated. Plating wears unevenly and can flake off. This is far worse than having to occasionally dress it if it gets dinged.

There is an expectation that the precision equipment will be cared for - such as oiling and proper storage. When it has been abused, it becomes hobbyist fodder; it isn't worth paying the labour to fix it.

This is an easily salvaged square, even if it can be a bit tedious.

I'm sorry @extropic this lazy way to take the rust off will only destroy it. You are free to treat your own tools that way, but it is not a good idea to recommend it to others. Highly polished lapped surfaces can easily be ruined by the etching action of the rust removers. You depend in part of the ability to see light between the cylinder surface and a part surface. If light is present, a correction is required. An etched surface will always pass light, giving you a false reading. It would be fine only if you exclusively used a square gauge.
 
Several of the previous suggestions made me cringe a bit. Here's what I would do:
  1. First use a burr file to gently remove the majority of the rust. If you don't know what a burr file is let me know.
  2. Then use a precision ground flat stone to finish taking down the rust spots even with original geometry. Use as much of the stone area as possible as you work around the circumference gently. The precision flat-stone will allow you to feel any remaining burrs and bring them down to the cylindrical plane or the flat plane on the ends. It will not remove all stains, but will take down any high spots to the correct geometry. If you don't know what a precision flat-stone is let me know.
  3. Then use the unblemished areas only.
Use of chelation methods to remove rust may damage the ground finish. I do not recommend that unless you are planning to regrind the CS.

There is a video somewhere from one of the toolmakers from Suburban on how to adjust the CS. He uses a lapping plate on the ends. If i can find it I'll update with a link. Here it is Checking and Adjusting Cylindrical Square

Incidentally, Some CSs are ground differently on one end. On that type there will be markings indicating degrees of error. If your CS has no markings then no need for concern.

Oh and BTW you are a lucky dog with that purchase from HGR. Lucky I didn't see it first. Good for you!

Best Regards,
Bob
 
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I'd stay away from even X-fine steel wool.
Green Scotch Brite pads with Kroil or Ed's Red (shop made Kroil) slower going than wool....
Make some coffee and listen put some gentle music on to establish a rhythm. Make a day of it.
Be sure to keep changing the direction of movement and don't round the flat edge, work the circumference.

Daryl
MN
 
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