How to clean up the rule in a combination square?

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Forum topic by DonnyBahama posted 06-24-2011 11:02 PM 22065 views 5 times favorited 30 replies Add to Favorites Watch
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215 posts in 2557 days

06-24-2011 11:02 PM

Topic tags/keywords: rust combination square discoloration

I’ve got a nice Starrett 4-piece combination square that I got a great deal on because it had some rust. I got everything cleaned up pretty nicely with some steel wool, but the rule is discolored and hard to read as a result. If anyone has a good tip for restoring it back to its original luster, I’d appreciate hearing it.

-- Founding member of the (un)Official LumberJock's Frugal Woodworking Society -

30 replies so far

View Don W's profile

Don W

18754 posts in 2593 days

#1 posted 06-24-2011 11:29 PM

I’ve used a fine wire wheel with good luck.

-- - Collecting is an investment in the past, and the future.

View Mike's profile


406 posts in 2713 days

#2 posted 06-24-2011 11:36 PM

if the marks are indented on the ruler, here is a little trick that I use. Take some black paint and paint the entire ruler. While the paint is still wet, take a paper tower and wipe off the surface gently. The indents / marks should be the only thing that has black paint. Let it dry and your all set.

-- look Ma! I still got all eleven of my fingers! - -

View Minorhero's profile


373 posts in 2631 days

#3 posted 06-25-2011 01:11 AM

If you are trying to remove the discolorations left on the steel rule by the rust then there are 2 things to try. 1 buy some Evaporust and soak the rule for 24 hours completely submerged. The other thing to do is buy some bar keeper’s friend and make a paste with it and rub the rule with a green scotchbrite pad.

View ChefHDAN's profile


1067 posts in 2875 days

#4 posted 06-25-2011 03:06 AM

I’ve gotten good results with a buffing wheel in my drill press

-- I've decided 1 mistake is really 2 opportunities to learn.. learn how to fix it... and learn how to not repeat it

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Steven H

1117 posts in 3086 days

#5 posted 06-25-2011 04:37 AM

What Minorhero said

View gfadvm's profile


14940 posts in 2716 days

#6 posted 06-25-2011 05:07 AM

I would use a 6 or 8” hard cotton buffing wheel with white compound in my bench grinder. Mine wasnt a Starret but I cleaned the rust/black stains off an old square with this technique. Wholesale Tool is my source for buff wheels and compound. The wax in the buffing compound leaves a nice finish and helps prevent future rust.

-- " I'll try to be nicer, if you'll try to be smarter" gfadvm

View KBX500's profile


35 posts in 2588 days

#7 posted 06-25-2011 06:13 AM

I’ve had 20 – 25 Starrett combination square sets that I’ve restored over the years
for resale or to use myself. I’ve found that if your going to actually use it for shop
work, and the blade is really discolored, corroded and/or pitted, you’re probably
better off buying a new blade. The 12” rule with quick reading 32nds & 64ths in
the satin chrome finish, Catalog # B12R, is $38.50 at Amazon. The satin chrome
is much easier to read for older eyes. It’s also a good time to consider a longer
blade. Starrett offers 12”, 18”, 24”, 36” and 48” blades in satin and regular finish.

If you’re cleaning it up for show, Evaporust is a good product to use, if it’s still
rusty or has rust particles on it. Follow that, if necessary, with a light sanding with
a fine grit, or a 3M Scotchbrite product or something similar. Then the previously
mentioned paint tip to finish it off.

Starrett’s #32 catalog has lots of good info in it, plus all their products, of course.
I ordered another one recently and had it in 3 days.


View BentheViking's profile


1782 posts in 2590 days

#8 posted 06-26-2011 12:40 AM

After reading this post I got inspired to try to clean up an old very rusty combo square rule today. Sat it in a bath of CLR for a few hours and came back just had to use a wire brush to finish off a couple of extra grimey spots but most of it came off just sitting in the chemical. Just have to wonder how long it will stay clean

-- It's made of wood. Real sturdy.--Chubbs Peterson

View WayneC's profile


13754 posts in 4123 days

#9 posted 06-26-2011 12:42 AM

Use a little wax or oil on it to keep the rust at bay.

-- We must guard our enthusiasm as we would our life - James Krenov

View oblowme's profile


91 posts in 2589 days

#10 posted 06-26-2011 05:18 PM

This is REALLY not for the faint of heart so if you do not feel comfortable or have a single doubt in your mind about it stay way away from it- Muritic Acid will eat up any corrosion in a big hurry, it’s the active ingredient in allot of ‘rust removers’. Mind you it’s not one bit user friendly and can be very dangerous stuff if you don’t know what you are doing.
Should you want to screw around with it there are a number of things you need to know-

1- Not only will it eat up rust it will eat you up too, eye protection (or better yet a face shield) rubber gloves (preferably the long gauntlet type) and a respirator are mandatory.

2- Only use it outdoors, the fumes will literally take your breath away, stay up wind at all times. Do not store it anywhere near anything you’d like to remain corrosion free, the little bit of fume that escapes from an unsealed container will go to work on any bare metals near it. Be absolutely sure children can not get to it at any time.

3- Keep 2 containers of water/baking soda solution at hand, (at least a half cup of sode in 5 gals of water) the soda neutralizes the acid immediately, one bucket in case you get any on you and the other to kill the action of it on whatever you are cleaning, wiping it off will do no good, you have to kill it. Also be aware that if allowed the acid will build up in the dunk bucket enough to over come the soda and therefore will need to be changed.

4- Be prepared to apply oil, grease, wax or what have you to the cleaned metal as it will start to rust very quickly, I know it doesn’t make sense, but that’s what happens.

5- It does not work through grease or finish coatings very well.

6- Wear old clothing, just like with battery acid they can come back from the wash with mysterious holes in them.

7- Work with it a little at a time, dip the piece a minute then wash it off and be sure to get all of the soda off. Be sure you do not allow the undiluted soda and acid to come in contact with one another, the reaction can be quite violent. Do not drop a piece in it and walk away, given enough time whatever’s left when you get back will be hotter than the hinges of modern day hell and probably useless.

8- The only safe containers for it are plastic.

9- It can be diluted with water to make a weaker solution, more water less action but safer to work with.

Now with that said I do not recommend it to anyone, use at your own risk. It works very well and will remove every last speck of rust right down to the white metal. I learned how to use it in doing auto body work.
A set of lathe tools that came to me with an old Delta that were so rusted it was kinda hard to tell what they were, 20 minutes in the acid and they were near new again.

Don’t bother coming after me about how dangerous this stuff is, I think I stressed that about as far as it gets. Before going into it I suggest Googling Muritic Acid and get all the info you can find.

One more time- If you have any question in your mind about any aspect of this DO NOT go anywhere near it.

-- A TOOL JUNKIE- There, I just admited it to myself...

View BlankMan's profile


1490 posts in 3379 days

#11 posted 06-26-2011 06:06 PM

I third what Minorhero said. I keep a few gallons of Evapo Rust on hand, buy it from HF when I get 25% off coupons.

Careful about soaking it for 24 hours though, I do that too that but sometimes the piece will get a black coating on it that takes some work to then get off.

-- -Curt, Milwaukee, WI

View DonnyBahama's profile


215 posts in 2557 days

#12 posted 06-26-2011 11:59 PM

Thanks for all the great suggestions, everyone! I have some Barkeeper’s Friend so I’ll try that first. (Thanks, Minorhero!) I also have hard cotton buffing wheels for my Dremel tool so I may give that a try. (Thanks, gfadvm!) I’d never heard of EvapoRust before but if HF has it (thanks, BlankMan!), I’ll pick some up. The Muritic Acid sounds a little scary. Worst of all, it sounds like there’s a good chance I could FUBAR my rule, so I think I’ll skip that technique. (But it was an interesting read – thanks, WoodRMe!)

@Mike – That’s a really cool trick! I may decide to do that no matter what else I do. I wonder if I could put it on with a foam brush, then remove the excess with a clean/empty foam brush?

@KBX500 – I’m pretty broke right now, so replacing the rule isn’t really an option – but it’s cool to find out that Starrett offers them in several other lengths! I ordered a Starrett catalog – thanks for the tip!

@BentheViking – CLR… is that the stuff that’s sold primarily as a lime remover?

-- Founding member of the (un)Official LumberJock's Frugal Woodworking Society -

View Belg1960's profile


1072 posts in 3091 days

#13 posted 07-14-2013 12:57 PM

Guys, I searched for how to clean a rusted square and found this old thread. I just wanted to add my results and one more option. I used a product called Flitch metal polish, and some abrasive pads. I experimented on a framing square here are my results. I cleaned it first with some mineral spirits to clean the surface rust and dirt.

-- ***Pat*** Rookie woodworker looking for an education!!!

View bold1's profile


293 posts in 1873 days

#14 posted 07-14-2013 02:02 PM

I use a wire brush on the surface, then baking soda in my sand blaster to clean the indents and spray with white enamel, that I wipe off the surface. I used to use black but it doesn’t show up as well as the white. I finish by using a good car wax after the paint is dry.

View macgee's profile


49 posts in 1663 days

#15 posted 01-27-2014 02:50 AM

I’ve tried several different ways to clean my rulers and squares. So far the best is using double stick carpet tape & sanding blocks.

Taping the ruler onto a flat surface, then using klingspor Sandflex sanding blocks (coarse & fine versions) to sand/clean up the surface. They work very well and makes cleaning steel surfaces almost a pleasure. As mentioned in earlier posts Starrett rulers have pretty deep engravings so your rather safe cleaning up the surface without damaging the ruler marks.

I finish the ruler off with Maas metal polish creme, awesome stuff and highly recommend it and should be in everyones cleaning supplies. Using the metal polish removes oxidation and leaves a clear coating after polishing to help it from further tarnishing.

The biggest problem is pitting, almost all of the older rulers I’ve come across has pitting to some degree. You’ll spend most of the time removing the pitting. I definitely will use the coarse version of the Klingspor block the most. I think I prefer the more satin finish of the coarse block than the more mirror like finish of the fine klingspor block. I found using the sanding blocks to clean the ruler the best. I try to avoid using chemical cleaners as they removing the painted marks on the ruler and they don’t remove the pitting.

Three problems with cleaning old steel rulers:

1. Most likely the bad pitting can not be removed without removing/damaging ruler markings.
2. While sanding/cleaning the ruler, you will remove to a degree some of the paint in the markings. Highly recommend to apply black paint and wipe off to the ruler after sanding.
3. I don’t like the shiny chrome like finish you get after refinishing rulers. There very shiny and pretty to look at but seem harder to read because of glare but substantially better than a old dirty ruler.

My favorite ruler and square is “Products Engineering Corporation” (PEC) satin rulers and squares, very easy to read and very easy on the eyes. You can buy a new 12” replacement blade on ebay for about $20

I hope this is useful for other members.

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