SB 16 gearbox/leadscrew hard to turn - Page 2
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  1. #21
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    Well, found a perk of rebuilding the gearbox and cutting new shafts....

    Picked up a few 4096ppr encoders from the obsolete pile at work with some custom electronics I had designed.

    Found this:

    How To Turn Any Motor Into A Servo Motor (#075) - YouTube

    Also happen to have a few treadmill motors....

    I'll be extending the secondary shaft for a coupler to a treadmill motor hanging off the secondary/LH side of the lathe and have the encoder on the other side of the QCBG.

    The real question is where is the best place to put the encoder to measure spindle speed? I'm thinking the gear up from the one you change out for 48/24 tooth to do different threading. All said and done, it could still thread normally through the GB, or disconnect the first handle on the QCGB and run through the secondary shaft to the second handle. 1.5hp at some reduction as is in the 2nd stage should be plenty to move it along. I may have a line on an 8' ballscrew setup as well, but time will tell if I can snag that for cheap.

    Anyone done anything similar? I see some mention of electric lead-screw conversions, but haven't found anything real in-depth here.

    I'm not planning to go full CNC, just expand feedrate/threading capabilities, and the parts are free/cheap... and I have the electronics skills/knowledge to make it work. Am I sounding like an idiot here?

  2. #22
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    I've seen several versions of what you're proposing but attached to the leadscrew at the other end. I think it's a pretty neat idea - variable feed rate at the turn of a dial.

  3. #23
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    Made an absolute mess of things today

    Failed brazing attempt - Album on Imgur

    Attempted to fix the safety cover that was smashed, I THOUGHT this was cast iron, but the way the metal melts so close to the bronze rod I'm not so sure. Also could have been using way too large of a tip (using a cutting torch head, don't have a welding torch head).

    Trying to get this cover fixed up before brazing the GB casting back together.

    Suggestions?

  4. #24
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    Good attempt Good attempt - Album on Imgur

    Tried some known cast, works much better. Seems cover is some kind of pot metal with a bit of iron in it

  5. #25
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    Setup Setup - Album on Imgur

    Made it exactly this far only to run out of oxyacetylene. Next weekend I guess.

    Decided to go with a 1-3/8" OD and 1-1/8" ID needle bearing. The casting is too big to bore on my mill-drill. I'm thinking of drilling to 1-5/16 with a demming drill and reaming to a light press fit for the bearing, though we're talking about reaming 60 thou which is quite a bit. Thoughts?

  6. #26
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    Found a piece of straight 1-1/8 CRS in the junk pile at work and found some time to braze up on both sides. Other side i did vertical and has a shit ton more braze on it than necessary, not the prettiest but it'll hold.

    Needle bearings should come in the mail this week.

    Anyone have a bearing number for the little needle bearings in the handles?

    Brazing - Album on Imgur

  7. #27
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    Quote Originally Posted by Rockmonton View Post
    Made an absolute mess of things today

    Failed brazing attempt - Album on Imgur

    Attempted to fix the safety cover that was smashed, I THOUGHT this was cast iron, but the way the metal melts so close to the bronze rod I'm not so sure. Also could have been using way too large of a tip (using a cutting torch head, don't have a welding torch head).

    Trying to get this cover fixed up before brazing the GB casting back together.

    Suggestions?
    Some of those covers are actually aluminum. You might want to check it with a magnet.

  8. #28
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    braze1.jpg

    braze2.jpg

    Looks like I need to do some touching up as I didn't quite fill the vee on the backside on the one section. otherwise not bad for my first time attempting to braze something decent in cast.

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  10. #29
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    Regretfully,its a mess ...I doubt you have any fusion at all,and if it holds under gear load ,it will be a miracle.

  11. #30
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    Any tips John?


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