9 Inch Model A Headstock Upgrade
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  1. #1
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    Default 9 Inch Model A Headstock Upgrade

    Had a problem with my 9 Inch Model A, CL644A (4-2-1956) with the sixteen speed V-belt pulleys. After I cleaned and painted her up I bought a linked belt instead of the standard continuous V-belt. When changing speeds it was very difficult to get the belt on the lowest speed sheave (the belt was thicker than the space under the rim of the sheave). I just did an upgrade to the quick change forward/reverse lever and got a new headstock casting. As an added benefit the casting base is only 1.5 inch thick compared to the original’s 2 inch. Photos show a comparison of the two castings and the belt on the low speed sheave showing plenty of room under the sheave. Maybe South Bend noted that it was tight with the other casting.

    John

    20190529_100559.jpg

    Comparison of the two castings

    20190529_100655.jpg

    The original 1956 casting showing tight clearances.

    20190608_101058.jpg

    Lots of room now for quick belt changes...

  2. #2
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    Interesting. So, any comments on the fiber V belt versus regular V belt in operation? Or, compared to the flat belt if that's what you had originally.

    When I was considering the V-belt cone pulley replacing my flat belt, it looked like a squeeze getting a V belt on that large pulley. I stayed with a serpentine belt because of costs. Also, there was 2 versions of the V-belt cone pulley. After about 1962 the largest v pulley was larger in diameter, per an old thread here.

    My serial is 406XX NAR9 and I was guessing 1956 manufacture. Is yours close to that? My forward/reverse lever is locked by the square bolt.

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    I have a model 744 R, circa 1950 I believe...same v-belt configuration. Headstock looks like your replacement one.
    When I purchased it and tore it down three years ago, I just went with an automotive V-belt. Not a huge job to pull the spindle to replace, but hell it's been three years, the lathe gets a lot of use and the belt is none the worse for wear.

    Never having owned a flat-belt driven lathe I cannot compare, but I can tell you that I recently repowered with a VFD and 1 hp inverter-duty motor- and I can stall that motor with a heavy cut before the belt will slip.

    No engineer, but from what I've read...v belts are not as efficient as flat belts, but can transmit more power without slipping.

    You may be lucky and not have an issue, but headstocks were individually scraped into alignment on the bed with which they were matched at the factory. "Swapping" one out can result in significant misalignment to the bedways in multiple axes.

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    Jim, this one has always been V-belt, s/n 38987NAR9, so only a little older than yours. I've only run it with the Fenner Power Twist linked belt; the old original solid V-belt was pretty cracked by the time I got the lathe set up (the lathe sat in a corner of my garage for about 30 years waiting for me!) It will slip if you have the back gear engaged with the bull gear locked to the pulley (which I do to tighten the 1A collets); so kind of like the flat belt in that regard, but without any tracking issues. They are supposed to be run only forward, but I have run in reverse with no apparent difficulties. I was going to loop the belt over the spindle when I reassembled it this weekend, but forgot. A minute or two fiddling with the twist lock and the belt was again around the spindle (although I can pull the spindle and replace in under 20 minutes).

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    Quote Originally Posted by tobnpr View Post
    You may be lucky and not have an issue, but headstocks were individually scraped into alignment on the bed with which they were matched at the factory. "Swapping" one out can result in significant misalignment to the bedways in multiple axes.
    I haven't put a test bar on it but initial parts look good to go.


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