View Full Version : Measuring tool rust

08-17-2001, 07:47 AM
I was given a pile of older starret measuring tools. Some has bad rust on it. Whats the best way to remove rust from precision instruments. I dont want to sand or sandblast ,dip in acid . Any ideas. Thankyou

03-06-2006, 11:09 AM

J Tiers
03-06-2006, 01:16 PM
I am assuming (you said "bad rust") that you have no intention of trying to USE the tools for accurate measurement......

Either phosphoric acid (yes I can read what you wrote...) or electrolysis will remove the rust, but nothing will put back the metal and restore the tools to accuracy.

If they are spring calipers, that may not be an issue... micrometers, etc, would be another matter.

Either phosphoric or electrolysis will have some small added damage due to formation of a dark coating that will need to be removed. That comes with teh territory.

Phosphoric leaves less surface gunk, but can etch surfaces that have stresses in them, such as case-hardened parts, along the stress lines. It won't harm HSS at all, I've left HSS in for days.

Electrolysis is dirtier, leaves more surface gunk, and takes more equipment, but may be better on materials with locked-in stresses.

Neitehr one will do more than stop snd remove the rust.

[This message has been edited by J Tiers (edited 03-06-2006).]

Paul F
03-06-2006, 04:04 PM
I would start with some light oil and some 0000 steel wool, and gently rub off the loose rust, keeping the steel wool well oiled.

Then you can see how much is surface rust, and how much is deep down pitting.

I would try some formulation of phosphoric acid that is very weak first. Brownells (gunsmithing supply) sells a product, I THINK its called Steel White, that is a mix-it-yourself blue and rust remover. You can mix it quite mild.

After rust removal, I'd take stuff apart as far as you're comfortable with, and clean and oil with a light oil.

As J Tiers intimates, I would be highly suspect of the accuracy of any fine measuring instruments that are "badly rusted".
You MAY find, however, that you have more surface rust than you thought, and they will clean up with just the gentle oily-steel-wool rubbing and a clean up.

Paul F.

03-06-2006, 04:30 PM
I dunno Mike, why would you want to measure the rust on tools?

03-06-2006, 05:40 PM
Cheap & simple = soak them in plan old Vinegar. Find a glass or plastic container that the tool will fit in and put in enough vinegar to cover the item. Depending on how deep the rust is it may take from a few hours to over night. When you remove the item it will be black, wash in water. Rub with a rag then oil.

03-06-2006, 09:01 PM
As long as the rust is not on the measuring surface it shouldn't be a problem. Light oil and Crocus cloth works well, or perhaps some fine scotchbrite first. Light rust on the measuring surface isn't too bad. If you will be using the tools for your own work and know the basics of calibration, you can check them. You can get a cheap set of Gage blocks on E-bay for $50.00 to check them. Alot can be learned by cleaning up tools, calibrating them and repairing them. Unless you have more money than time, take the time, spray them with oil and work on one at a time until they are all done. Just my thoughts.


03-07-2006, 12:13 PM
The Starrett tools all have carbide tipped ends. Thankfully the carbide doesnt rust. Its primarily the spindles. I have shunned these tools to a seperate location as to not contaminate my good stuff. I was thinking a reverse electroplating idea might aleviate the surface rust. Any thoughts Thanks For The Replies.

03-07-2006, 12:39 PM
Sounds like carbide-tipped micrometers? You can remove the spindle and thimble. Chuck the spindle in a lathe and use very fine silicon carbide paper with some oil to clean it up.

Then, wrap the thimble in masking tape, chuck it up, and clean off the end of the spindle. Clean up very carefully -- no grit left anywhere. If the rust isn't deep, the spindle will still be a good fit and the markings on the thimble will be legible. In some cases, almost new-looking.

If the mics aren't chrome plated - just steel - then something like a DMT or 3M diamond hone is good for the flat surfaces of the frame. A bit of carbide paper hand held can restore other bits.

03-07-2006, 05:48 PM
Evaporust is what I use. You soak your items in it, apart or assembled. It will even work through a slight amount of oil. You can leave things soaking for 2 hours or two weeks, no harm if you forget about it for a while.
Doesn't hurt anything, rust just turns into a black film that rinses off leaving bare metal, plus a rust-preventative coating. If the steel has a high carbon content you will have a dark-gray surface that almost resembles parkerizing. I find it very appealing.

Good stuff

J Tiers
03-08-2006, 01:01 AM
Sounds like evapo-rust is similar to or same as phosphoric..... Phosphoric does that same coating on certain steels.

03-08-2006, 02:09 AM
Where do you buy evaporust and also where do you get phosphoric acid. Thanx Guys

03-08-2006, 11:43 AM
Last time I bought it I just used Froogle and took the best deal. At least I thought it was good until my "Gallons" arrived as quarts. My mistake.
Check their website for local dealers, usually industrial supply houses.
Expect to pay about $18/gallon.