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Thread: My "what did you do this decade" thread - poly-V spindle sheave/ pulley for Atlas 618

  1. #1
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    Default My "what did you do this decade" thread - poly-V spindle sheave/ pulley for Atlas 618

    Just found the original thread that started this back in August 2016, so pretty much exactly 3 years ago:

    http://bbs.homeshopmachinist.net/thr...ighlight=atlas

    Also, gives me the chance to thank Stepside without which this might still have been possible, but probably would have taken at least another 3 years.

    Also thanks to the advice about bearing fit in this thread, a little newer:
    http://bbs.homeshopmachinist.net/thr...ighlight=atlas

    in the end I just used a Sharpie and a Dremel with a grinding stone. Lightly ground the ID of each bearing 3 or 4 times until it was a tight sliding fit on the spindle.

    Anyway, that done, the idea behind this was to replace the 4 step V belt spindle sheave on my Atlas 618 with a poly-v spindle sheave using sealed bearings and a separate gear that would mesh with the back gears (that was the bit that Stepside very kindly made for me 3 years ago - they've been sitting in a baggy since then). One big reason was that the 3/8 V belt on there was constantly slipping, another big one was having one less thing to oil/ throw oil everywhere/ get the belt oily so it would then slip. I originally thought I was getting some vibration because the spindle sheave wasn't 100% concentric with the spindle, but I think that was more likely vibration from the motor.

    First step was to make a blank big enough for the spindle sheave.

    Random chunk of alu


    ring trepanned out


    slightly smaller piece turned to fit


    pressed together. And that's how it sat next to my lathe, then in a moving truck and then next to my lathe for another couple of years.


    also made the countershaft sheave/ pulley, turns out with THE COMPLETELY WRONG DIAMETERS but I'd get to that later (not sore about it or anything, honest)


    ground a 1/4" HSS bit to the right shape for a J-section poly-v pulley and cut the grooves. Not very well, but that didn't actually matter for the most part.


    pretty though


    Fast forward 2 or 3 years.....

    ...and I needed to turn the ends true


    so I could bandsaw off the unwanted bit, face the cut side and then drill out the hole. As Dickybird once said, I'm so tight I take my glasses off when I'm not looking at something



    bored the various IDs for bearing fits and the like, plus made the holes for the bull gear pin. Not quite at the right pitch circle, but that was easily fixed on the mill later (one of the easier screw ups to fix). The indexable bull gear on these lathes + tool post drill = sort of rotary table. Surprisingly handy.


    Trepanned off the bits that I didn't need, see Dickybird quote above


    and roughed in the ODs


    pressed in a couple of bearings


    and then a couple more, separated by a 3mm spacer. Funnily enough the NSK bearing slid, just, onto the spindle without modification after I filed off various set screw divots. The cheap azz bearings all needed a few passes with a Dremel before they could do the same. Guess it wasn't just me


    mounted on the arbor I made to turn it between centers (itself turned between centers). The dowel pin fits in one of the bull gear holes to drive the work and there's a shaft collar at the other end to hold it in place. Just making the arbor took a while.


    ODs finished, ready for some grooving, he he he


    ta da! All done


    with Stepside's gear added, with a couple of set screw "pegs) to stop it rotating but allow it to be easily replaced. All of the gears he made for me were drilled in the same set up, so in theory they should be interchangeable. This one step led to much swearing as I stupidly put 5-40 set screws in a 4-40 set screw compartment, then used all the 4-40 set screws, so the ones left (5-40) were mistaken for 5-40. Then when they wouldn't screw in, for some reason I assumed they were M3-0.5, which is pretty similar. Screwed in part of the way, then allen key pinged across the garage never to be seen again. Lots of swearing. Went and had a drink, came back and made my own bloody set screws out of some M3-0.5 screws (that'll teach 'em!) with a hacksaw.


    Even more swearing ensued when I realised that I totally screwed the pooch when I calculated the pulley sizes, so the belt I ordered fit the large spindle/ small countershaft ratio just fine and flapped around in the breeze on the other two. So another arbor was made, some actual math was done, and the countershaft sheave/ pulley was turned down and regrooved.


    bit of a difference n'est pas? Even though I messed up one of the grooves in the center ratio, it was a blessing in disguise as a) it got me a really low ratio and b) the hole must of been drilled/ reamed slightly off axis as there was some procession (?) around the arbor. That was easily fixed for the small and medium ratios as they were simply turned down and regrooved, but the larger one was a bit of a fiddle. Turned out ok though.

    All done! Even the accidently purchased belt went on the motor pulley to replace the J4 belt that was on there. Both the belts are now J5, so slip should be a thing of the past.



    Had a play, very smooth, very little vibration and I think that what there is comes from the motor. Equal belt tension in each ratio, belt seems to fit well in each ratio and the spindle sheave/ pulley appears as concentric as I can tell by eye.
    Even the back gears are quieter with the delrin gear in there.

    New speed ranges (about 1/4 motor speed to full)
    Small pulley on the motor: low 130-650, mid 370-1730, high 690-3000+ (that was at about 3/4, didn't dare go higher)
    Large pulley on the motor: low 250-1150, mid 500-2450, high - didn't test
    Small pulley on the motor, back gears: low 19-100, mid 50-260, high 98-600 (yeah, not going to use that one)

    Some nice spreads there, particularly between low and mid on the small motor pulley in direct drive. It'll be interesting to see if I need to use back gears as much now. Haven't used it in anger yet, but I'm pretty confident that belt slip won't be as much of a problem as before.

    Also ordered some sealed bearings to replace the bronze bushings in the back gears, once less thing to oil/ spread oil around.

  2. #2
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    Looks great!

  3. #3
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    Well that came out well. Good job!

  4. #4
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    thanks chaps, glad to have crossed that one off the list. Looking forward to using it now

  5. #5
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    Quote Originally Posted by mattthemuppet View Post
    thanks chaps, glad to have crossed that one off the list. Looking forward to using it now
    Next week you are going to get irresistible deal on you-name-it lathe and you need to sell the current one to make space

    Nicely executed mod nevertheless!

  6. #6
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    Quote Originally Posted by MattiJ View Post
    Next week you are going to get irresistible deal on you-name-it lathe and you need to sell the current one to make space

    Nicely executed mod nevertheless!
    ha, that would be a nice problem to have! The thought did cross my mind, but I like sleeping in my own bed so it left my mind shortly after

    I was rather pleased when the spindle sheave fit the spindle with no radial movement and only a gentle persuasion with a rubber mallet. It was neat reading back through the original threads and seeing how well the advice played out.

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