Need A Centering Square: What Do You Guys Recommend?

Watch Ebay. I purchased my 12" vintage Starrett, then bought the other pieces as they came up. Protractor and centering square, all hardened steel versions, complete. I would use the finest tip scribe I can find. Most times, but not all, the lines won't intersect to the center, but will put you somewhat close depending on how concentric the stock is. The smoother the finish, the better the scribed lines. I use a vise when I can, to hold the tool/work.
 
Bought the Union Tool square with a centering head for 20 bucks off eBay. An added bonus is that the rule is 18" long. Got the part marked up
in the shop this afternoon.


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- great buy! I was late to the discussion, but I was going to suggest for a good mitutoyo or Starret combo square kit. The do come up regularly, at less than 1/2 the new cost. Mine is a 12" Mitutoyo set, and I love it.
 
I saw a NOS Starrett rule with the centering head for 100 bucks the other day and was tempted, but this set was a no brainer at the price.
 
Bob, do you think they mixed a Union rule with Starrett parts?
Well, just looking at it in the pic you posted, it looks Starrett. Look closely at the heads for a maker's name. If they are Starrett, they would be the forged, hardened, and ground steel heads, not the cast iron ones. They are expensive, much more so than the cast iron heads, and are finished to high tolerances. So, I would grin instead of worry if the heads turn out to be Starrett. Between the various brands, speaking of older USA made ones here, some/most will interchange components with a good fit, some will not. With the locking screws loose, the heads should still be a fairly tight sliding fit on the blade. I like the fonts used on the older Union stuff. They definitely look vintage.
 
I had a look at the heads on the new tool: the centering head was marked "Hardened". There was no text on the square. Both parts look
well made to me. The rule is marked as a Union tool.
Here's a pic of both tools. As you can see, the square on my Dad's old tool looks quite different. It has an older, more ornate look.
I looked at a pic of a newer Starrett square, and you're right, they look almost exactly the same.

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The fit of the tools to the rule is pretty snug, particularly the centering head, but perfectly useable. So, you're probably right that this
thing is a mongrel, but that's fine with me.
 
this
thing is a mongrel, but that's fine with me.
It is a 'thoroughbred mongrel.' Use it with loving care. Next you need to make the missing scriber to fit the 90/45 degree head... Knurled brass head, hardened steel drill rod shank brought to a sharp point with a sexy curved taper. I made mine longer than the original $tarrett ones, there is quite a bit more depth available for a longer scriber, and it is a lot easier to actually use.
Edit: photo is of a genuine Starrett scriber.
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Nicely done Bob: I like the look of your scriber. I'll have to add that to my list of projects.
 
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