# Sorensen Center Mike



## John Conroy (Oct 11, 2017)

I got a good deal on a Sorensen Center Mike on eBay but the mahogany box was in rough shape. The finger jointed corners were all loose and the finish was in rough shape including some permanent marker writing on the outside. I re-glued all the corners then stripped, sanded and restained it then sprayed it with low gloss Varathane. I also cleaned up the measuring tool and  gave it a good coating of light machine oil to prevent corrosion. The tool itself is in great condition, the only real flaw is a number someone engraved on it and the standard. It worked out nicely I think.









































John


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## Jwest7788 (Oct 11, 2017)

Hey John

Would you mind uploading these attachments one more time? While trying to fix the auto-rotate issue I think I broken something. Just rolled everything backwards and am hoping you can help me check by re-uploading.

Let me know!


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## John Conroy (Oct 11, 2017)

I screwed up the first time I uploaded them but they look OK after I did it correctly the second time.


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## PeterT (Oct 11, 2017)

Nice work John. I like seeing instruments of yesteryear come back to their former glory. I bought one of those el-cheapo mini sand blasters, looks like an airbrush (ultimately for matt finishing certain parts of my radial). I've wondered to myself - if I made a nicely shaped mask out of some material like an elipse, could the mini blaster erase out the typical owners name or calibration date scribed in the body. It would have a different matt texture for sure, but maybe a bit purdier. Guess it depends on how deeply they scribed it.


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## John Conroy (Oct 11, 2017)

Thanks Peter, the engraving is quite deep so I doubt blasting media would remove it. I think I'll just leave it alone, the numbers are part of the tool's history. It is very accurate, I measured the distance between some holes in a sprocket then spent an hour setting the part up in my mill so I could measure the same distance using the DRO. The measurements were exactly the same within .001". Close enough for me.


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## PeterT (Oct 11, 2017)

Damn you. Because of this post I went on ebay.... just looking I swear! My mouse button finger accidentally slipped & I clicked Buy. I'm so <cough-not> disappointed with my carelessness. 
Seriously, I could have used this thing a million times already instead of mucking around with calipers & pins. I had no idea they even existed. Christmas came early this year!


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## RobinHood (Oct 12, 2017)

Great job, John!


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## Alexander (Oct 14, 2017)

Someone gave me a similar tool it is a 60 inch Vernier they called it a flange groove Vernier. I have not used it yet.


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## Dabbler (Oct 15, 2017)

nice!!!


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## PeterT (Nov 5, 2017)

As mentioned, after seeing Johns post I ventured onto ebay & got myself a Sorensen for reasonable price IMO. Once the crud was removed with WD40 & superfine abrasive pad, tooth picks, Q-tips etc. it cleaned up & slides quite nicely. The contacts had that rubbery protection stuff on it. Once removed it looked fine, not polished shiny but in good shape. The box is a bit grotty so I will get after that one day when I'm bored. 

On to measuring. It came with a reference bar marked 10.9993" (center to center). I guess they aim for 11" but give you exact number to 10-thou to calibrate however it works out. It took me a while to figure out the measurement sequence (assuming I did this right). First you have to note the closed position starting value which must be subtracted off from final readings. It has the familiar vernier but the measurement scale itself is 2X. I attached a pic of my notes. The bottom line is I measured 0.0002" larger than the standard. OK that's pretty dang close. I don have many things in my shop to a known standard in this range but spot checking some Asian 123 & 246 blocks were within 0.001" which who knows if they are ground within that spec. Anyway, for those troublesome center-center hole pattern distances or any larger caliper distance for that matter, this thing is deadly. Good score!


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