New Toy - Rahn Repeat - O - Meter

#1
Last week I inquired for a friend about a granite surface plate here in Ontario. I asked the typical questions including what grade it was and wether it had been calibrated recently. The owner got back to me, that if I wanted, for a whistle, a song and some bread crumbs he’d throw in this “tool” he had for measuring surface plates. I asked for his number and couldn’t dial fast enough. I told him that I had been inquiring about the plate for a buddy but what was the “tool”. I already have an autocollomator and I had my fingers crossed that he wasn’t going to say “autocollimator”; he didn’t. He said (I was dying in the suspense). The second he starter with the Rah..... sound I knew what it was and I wanted to finish the sentence for him, but I bit my tongue. If any of you fish, (I try but am horrible) it is like when you get a really big fish on line that is in no way supposed to be able to handle the fight you now have on your hands. You’re excited, scared, and a bunch of other emotions all at the same time.... I digress

....n Repeat -O - Meter. I told him I’d take it and asked for his coordinates to sent the E-Transfer and within 15 min I had some pics, he had payment (1 whistle, 1 song, and a healthy handful of bread crumbs). By lunch it was on it’s way and I had a Canada Post tracking number.

It arrived today, nicely packaged and both safe and sound. I poured a cup of tea and went down to the shop and opened the package like an 8 year old on Christmas morning. Here it is...... in all it’s glory; and in what I would describe as “brand new” condition.

I count myself fortunate to have this awesome little piece of kit. Thanks for reading to this point..... my wife thinks it is a stupid chunk of metal, and when I tried to explain she just laughed, called me a nerd and walked away. Just wanted to share with some of my “Pals”.

Cheers all, no you can’t borrow it. LOL.




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#8


On the Rahn, it came with a .00002 Mahr Surpramess indicator. I have these other 2 indicators as I was planning to scratch build a Repeat-O-Meter. I’m guessing I’ll keep the Millimess but I plan to sell the Supremess.


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#9
I tested my Brown and Sharpe 20 x 30 cast iron plate. It was indicated + .0002 to - .0003. Moved on to the Taft Pierce 13 x 15 cast iron plate. It indicated + .0002 to - .0002. Both will be scraped and with some luck I will get them under .0001 total flatness. I have a Starrett 24 x 36 and a Starrett 12 x 18 that I’ll check tomorrow. It’ll be interesting to see how far down the rabbit hole I end up, but I’m guessing that I will find I am in good company on the way. Cheers all.

Derek.


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#10
Nice kit!!

I have a granite 18X24 mitutoyo AA plate I bought used, but I will one day build a repeatometer and check it. There are no metrology labs in the West that can check a surface plate. sigh**.
 
#13
Craig, you use a autocolumnator to measure local slopes, but that device cannot measure directly what the mechanical deviations are. the repeatometer does this. It doesn't certify the plate by itself: local deviations can be cancelling or be cumulative, the autocolumnator will show this. it can only be used alone when the deviations are very small.

TOgether they can be used to certify a surface plate.
 

Crankit

Active Member
Premium Member
#16
Lol...Got to love stumbling across great tools! Keith Rucker just did a video on getting his Repeat-o-meter and had been watching out for one for almost a couple of years. Enjoy the life of high precision!!
 

PeterT

Ultra Member
Premium Member
#19
Nice score.
Just for kicks one day if the opportunity presents, I'd like to see a real life reading of Busy Bee (or similar) cheapo granite. They claim good numbers within the specified grade reference, but I mean who really knows. Not advocating relative value, more just morbid curiosity. Of course a Monday BB granite might be different than a Friday granite too LOL
 
#20
Nice score.
Just for kicks one day if the opportunity presents, I'd like to see a real life reading of Busy Bee (or similar) cheapo granite. They claim good numbers within the specified grade reference, but I mean who really knows. Not advocating relative value, more just morbid curiosity. Of course a Monday BB granite might be different than a Friday granite too LOL
Shars granite squares were out of spec by a lot, Some members of another forums posted.