Cleaning old Starrett tools

[Ellen Benkin]

I have some old Starrett combo squares which are pefectly good except that the rules are almost unreadable. They have some kind of dark stain on them and I cannot figure out how to get it off without also removing the "paint" from the number and line marks. Does anyone have any brilliant ideas? I'll also appreciate good ideas.

Thanks.

[Mike Swindell]

Ellen,

I used a 3M light deburring wheel to clean up the scales I had neglected. You could use sotch brite pads, try the grey ones first they equal about 320 grit paper. Don't worry about the paint, you can always refill with some enamel, just rub on and wipe off, the paint will stay in the graduations. You can use the paint from model shops, litle 1/4oz bottles.

Good Luck and Happy New Year
Mike

[Ray Thompson]

Klinspore sells an eraser just for this purpose. They come in 3 grits coarse, medium, and fine. I mostly just use the fine, but for a heavy build up start with the coarse and work to the fine. Use them just like an eraser, they work fine on Starrett and other stained and oxidized metals.

Ray

[Wade McDonald]

I've cleaned up lots of machinist rules from a negelected state, including many combo square rules. (Yes, I have too many combo squares!) I now am able to make them look great other than possibly some pitting, no way to get that out and leave it readable/usable. Also, they look uncleaned, as in not a trace of overcleaning which to me can look garish. Just a nice clear semi shiny surface finish similar to what they started out with, and completely readable. One aspect easy to neglect is a rounding over effect on the edges that really makes it harder to see the graduations as clearly. The rubber erasers work okay sometimes, but leave a surface finish well short of what I'd prefer if there's more than a spot or 2.

I use 320 (or 400 if little cleaning needed) grit wet/dry sandpaper on a hard rubber sanding block with WD-40/ mineral spirits. I am careful to lay the rule on a flat surface and to hold the sanding block so it lays completely flat on the rule while rubbing. Note that it is best if the sandpaper has been used slightly, as it starts out with peaks that can tend to round over edges, though you don't have to be too obsessive for this application. Assuming there is only stain and no rust, rub until the rule gets reasonably shiny near the edges and the graduations are all nice and clear. Now switch to a small piece of the same grit sandpaper, use finger pressure to rub out additional stains in the middle of the rule but keep it away from the edges unless you have a small local area that the first part couldn't get to. But quality rules tend to clean up very evenly as they were made flat to begin with. With "local work" you can get an area shinier than the rest, just go back over it with the block to even it out. This grit usually leaves a scratching pattern fine enough to not be visible, but you can move up to a final 600 for an extra polishing effect.
If there is rust buildup, I add WD 40, and scrape it with a razor. Then if still lots of buildup, I might use a 220 grit on the sanding block to start rust/stain removal. (With the lower grit, definitely use the sandpaper on something else first for a bit.) Sometimes I use steel wool or a rust eraser instead.

And on to the edges- scrape with razor, then lay sandpaper on flat surface, add WD 40 and rub the rule along the sandpaper, but making certain the the 1/8" wide edge lies totally flat on the surface. You might try a trial first without the sandpaper to get used to keeping the rule perpendicular to the surface so it doesn't rock from side to side as you move it back and forth. This will clean off dirt and grit from the ages and if done with care will substantially improve the accuracy of an older combo square. Doesn't matter if its a Starrett, if dirt or rust are on the rule edge, or if its not quite flat it won't be right.

BTW- don't do the above to a satin chrome rule, though they shouldn't need to be cleaned.

The above advice also works well for neglected try squares. Though their graduations are much less vital, rounding over their edges during cleaning makes them much less useful, and straightening an edge does wonders. These often benefit from significant edge flattening to get a nice crisp corner between face and edge- many weren't ground so carefully in the first place.

Wade
making his first Sawmill creek post

[Lou Morrissette]

Ellen,
I've had pretty good luck thru the years using the type of eraser found on ballpoint pens.

Lou

[Ted Shrader]

Hi Wade -

Welcome to the Creek. A great place to hang out and exchange ideas.

Thank you for the detailed and easy to follow description of rule restorations.

Welcome,
Ted

[Ellen Benkin]

Wow! Thanks, Ted for all the detailed advice. Welcome to the Creek!

I decided to treat the rule just like an old plane iron. I took sticky backed sandpaper and put it on a piece of plate glass. I then used double stick tape and put the rule on a wider piece of flat wood that I could use as a handle. I rubbed the rule on the sandpaper until I took off the stains and got down to "raw" metal, just as I would with a plane iron. I started with 320 grit sandpaper and went through 400 and 600. I really didn't care if the rule was beautiful, just that I could read the markings enough to use it. As it turns out, the markings on Starrett rules are deep enough so that this kind of treatment doesn't get near them. I then put a light coat of wax on the rule to prevent further staining. Everything looks great and I have "restored" an old tool so that it us going to be functional for a long time.