Mystery NMTB50 Drive Gear
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  1. #1
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    Default Mystery NMTB50 Drive Gear

    I have a mystery NMTB50 drive gear that doesn't fit the vertical attachment on my Cincinnati Cinova 205-12, and knowing how rare drive gears for mounting attachments onto horizontal milling machines seem to be, I'm hoping that someone can identify it instead of having it sit on a shelf or worse, go to the scrap bin.

    100_1519.jpg 100_1518.jpg 100_1517.jpg 100_1516.jpg drive-gear-stamp.jpg

    A factory Cincinnati drive gear would have "Cincinnati Milling Machine Co." stamped into the taper, but this one does not. The only marking on it that I can find is the number "19" in a square box on the face of the gear (see images 4 and 5). The gear and the taper appear to be all of one piece, i.e. the gear was not made separately and then keyed and pressed onto the NMTB50 taper. If I had to guess, I'd say it was probably shop made, but very nicely done.

    The gear measures 5-1/16" outside diameter, and has 39 teeth, which calculates to a No. 8 diametral pitch. I'm assuming that it is a 14-1/2 pressure angle, but am not certain. The gear is 3/4" wide. The gap between the backside of the gear and the NMTB50 collar is 9/32", and the NMTB50 collar is 1/2" thick, so not much projection.

    The taper is in very good condition, as is the gear. The dog slots are clean and sharp. The drawbar threads are clean. It does not appear to have had much use.

  2. #2
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    I'd guess really old (NMT50 goes back to circa 1928) but never used

    Why?

    Straight cut teeth - almost unheard of only a bit later - and helical instead

  3. #3
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    John, thanks for the reply. No idea as to why it appears virtually unused. It was reportedly mounted on a larger (maybe No. 3) Cincinnati mill of unknown vintage, but the attachment that it powered had been removed.

    Most of the drive gears that I've seen (Cincinnati and K&T) have been helical, but the Cincinnati factory vertical attachment on my Cinova 80 (made in 1966) uses a straight spur gear drive.


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