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New Toy - Rahn Repeat - O - Meter

TOBARApprentice

Super User
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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YYCHM

(Craig)
Premium Member
Your wife calls you a nerd to eh:p Nice score!

Now you have to explain what one does with it:confused:
 

Brent H

Ultra Member
Wow - it is like new - like off the shelf!!

I think Oxtool does a pretty good video on surface plates and the use of this particular tool

@TOBARApprentice :very nice acquisition!
 

Janger

(John)
Administrator
Vendor
What's the scale on that dial? 0.00002"? one fifth of a tenth? So how accurate is your plate?
 

Dabbler

ersatz engineer
@Janger, it was available with a Mahr indicator that read in 2 millionths and 20 millionths of an inch. Mine reads in millionths of a meter but *sigh* not repeatograph to go with (yet!)...
 

TOBARApprentice

Super User
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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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TOBARApprentice

Super User
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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Dabbler

ersatz engineer
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**.
 

YYCHM

(Craig)
Premium Member
So..... I looked this thing up and came up with this "Detects local error, not overall flatness". What's the point?

I thought the purpose of a surface plate was to provide a flat reference?
 

DavidR8

Scrap maker
Administrator
Moderator
Premium Member
The least you could do was put some dust on the case so we're less envious!
What a score!
 

Dabbler

ersatz engineer
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.
 

DPittman

Ultra Member
Premium Member
Cool like new and super precise..what a good combo. I wouldn't know what to do with it myself but I can appreciate the joy of owning one. Congrats
 

Crankit

Well-Known Member
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!!
 

Crankit

Well-Known Member
Anyone wanting a new one? Starrett has taken over the patent on the Rahn and selling for $1734USD!!
 

PeterT

Ultra Member
Premium Member
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
 

Proxule

Ultra Member
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.
 
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