View Full Version : Finish for Restored Starrett Dividers

Paul Alciatore
03-14-2010, 01:41 PM
I have a pair of Starrett dividers and a matching inside caliper that date from the WW2 era or slightly thereafter. My dad gave them to me. Or perhaps even earlier, I don't know how or when he got them. They had a pretty good coat of rust/grime/oil/whatever on them.

I cleaned up the dividers and used gun blue solution on them some years ago, but left the caliper till later. Last night I have removed most of the rust and grime from the caliper and it is now bare metal with some small pits from the rust. There is probably a bit of rust in the pits, but other wise it is clean.

They appear to be made of a hardened alloy but I have no idea what it is. The calipers appeared to have some kind of finish or plating that may have had a color somewhat like brass: it was hard to tell with all the rust etc. Both cleaned up to a steel like color.

What I want to ask is what kind of finish they originally had and what would be recommended for refinishing them. Of course, I can use the gun blue again, but it didn't take evenly on the dividers. That may be my fault for not cleaning them well enough. The other problem here is the various parts are probably different alloys and in some cases, I can not separate them. So if one goes in a bath, several will.

Oh, and is there something that will remove the remaining rust from the pits before I apply the final finish?

03-14-2010, 02:37 PM
Did you use the electrolysis treatment to remove the rust?
That seems to usually work pretty well, but it does require some finesse to brush the pits clean of the black residue afterward.
I've sometimes resorted to naval jelly (or is it navel jelly :D) after the electrolysis, and then scratch around with a sharp pointed scribe. But other than that know of no magic formula, since I have no sand blasting gear.

03-14-2010, 03:54 PM
I have several originals. The older ones are a beautiful color case hardened finish.

03-14-2010, 05:25 PM
I know of no Starrett spring or lock joint calipers or dividers that had any finish applied. All were polished bright steel. The springs were heat blued and adjusting and clamping hardware was blued or color case hardened.

03-14-2010, 05:53 PM
Anybody thought of asking Starrett? I bet they will know for sure. Duffy

Paul Alciatore
03-15-2010, 03:39 AM
I know of no Starrett spring or lock joint calipers or dividers that had any finish applied. All were polished bright steel. The springs were heat blued and adjusting and clamping hardware was blued or color case hardened.

Hmmm! The calipers definitely had something applied. I could clearly see spots where it was and where it had worn or rusted off. Perhaps by a previous user?

So, if I leave them bright, wouldn't they be prone to rust with small spots of rust remaining on them?

03-15-2010, 08:30 AM
They are a good quality of steel as are other Starrett instruments. Light oiling and dry storage will keep the rust away. Part of the reason behind the wood tool chests was rust prevention.

03-15-2010, 08:43 AM
All of the several Starretts,and the ones in their catalog,look like they were sanded with 400 grit wet or dry paper. Never saw a case hardened Starrett. That might have been done by an owner who had access to a furnace at work.

I wouldn't advise case hardening calipers which are already made of high carbon steel.

03-15-2010, 09:16 AM
Likewise, all the ones i have is what i'd call a bright finish - as smooth as you can get it without it being reflective...higher that 400 grit imo, well maybe a well worn piece of 400 :). My favorites are the round leg ones, they are so nicely made I seek out occasions to use these tools

As a practical matter, why would one bother case hardening dividers? useless at the business end after the first sharpening. I would think the hold unit would benefit from being of hardened and tempered tool steel, the body to avoid dings and the points to stay sharp

having said that, Paul wants to restore so looking at whats in our tool boxes isn't evidence of wwii era calipers unless one knows their age. Maybe they did some calipers like that or maybe even as a special edition 70 years ago? I think Duffy had the best idea, see if Starrett knows.

03-15-2010, 03:30 PM
The ultimate finish would be hard chrome. It can be nearly any degree of gloss you want depending on the original steel finish before it goes into the plating tank. As used on firearms, the plate is only about .0002-.0003" thick so function is unaffected. The most popular is finish is bead-blasted satin or brushed satin.



03-15-2010, 04:46 PM
If the calipers got too hard,their tips,and maybe even the legs could get broken off.

I thought about saying 600,but I'm not sure mine were polished that finely.

Paul Alciatore
03-16-2010, 01:47 AM
Just to be clear, I am not necessairly "restoring". I'm not a collector, I use them in my shop and I don't want them to rust. I only mentioned the approximate age to give an idea of how old they were and to possibly avoid a conflicting finish.

03-16-2010, 10:23 AM
My set of 6" inside, outside and dividers acquired over 50 years ago had built up a "patina" of rust. A few years ago I took them apart and went over them with some previously used cloth backed # 400 and lots of oil. The resulting finish turned out quite well with that slight mat finish.

I just checked them and the inside calipers were made by Millers Falls. Wonder when they were last made.


03-16-2010, 11:31 AM

Calipers and Dividers are listed from pages 272 through 280 in the Starrett Second Edition Catalog No. 27, Copyright 1957. In the listing of "Yankee" type calipers and dividers the finish was described as "well finished" no mention of color was found.

I believe the Starrett Catalog was presented to ny father in 1957 by a sales representative of the Salt Lake Hardware Co., Salt Lake City, Utah.

Ray Patterson