Can anyone identify this style of indicator? It is used for align boring. (Starrett)

[Ec1]

I have a bunch of different ways to align bore, mostly engine work. I have never used this style indicator in the pic but I know it somehow aids in easily aligning the boring bar to the housing bore. Usually I rough in with boring then I finish with honing. I hope to make some of my own setups for oddball situations and would like to know if this style of indicator is obtainable right from Starrett (or other brands)... I couldn't find any other views of this from any other angle:

 

[Bill D]

Looks like a standard bore gauge to me. Similar to a telescoping snap gauge. Put it in the bore sweep it around to the lowest number on the dial. The remove it and mike down the tip and back side until it reads the same number it had inside the bore. The reading on the mike is the bore diameter. I got a used one for cheap because it was metric. I use an english mike to read it.
Or it could be a coaxial indicator I suppose.
More thought says those two ideas always have the indicator oriented at 90 degrees to the long axis not like yours. I have no idea now.
BillD

 

[gbent]

Thats a single poor picture, much detail is missing. It looks like one of the back plunger indicators set up to be used for measuring valve seat runout.

 

[Dan from Oakland]

Most of those were custom made by the manufacturer of the line bore equipment. Tobin Arp, Berco and Sunnen all made similar indicators that were mounted in the bar support at each end of the block or head during setup and then you aligned to bore to the bar support. Sunnen may still offer replacement parts for the small cam bearing line bore machine they made many years ago, but I doubt it. You might check with Jameson Equipment as they sell used line bore equipment and you may get lucky.

 

[gappmast]

That is from the cylinder head cam boring machine that Tobin Arp made. They sold it to Sunnen and Sunnen redesigned the gauge. Sunnen will not have parts.

 

[Ec1]

Ok thanks I will look for Sunnen and Tobin Arp used stuff... I figured it was custom.