Fitting A 1/4" Pulley On A 1/2" Shaft

Discussion in 'General Questions' started by 5-7HEAVEN, May 20, 2010.

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  1. 5-7HEAVEN

    5-7HEAVEN Guest

    I have a 4" jackshaft with 1/2" diameter, spinning at 10,000rpm. The aluminum belt pulleys I need to use are about 1" outside diameter with .25" bore diameter. The hub diameters range from .512" to .787". The pulleys are secured onto the shaft by two #8-32 setscrews.

    I have been unable to find correctly-sized steel pulleys which could be bored to 1/2" and welded onto the shaft.

    The 1/2" shaft is supported by bearings at each end. The pulley will be situated 1" from the outboard bearing.

    How would you suggest installing a 1/4" bore aluminum pulley on a 1/2" steel shaft?

    Should I bore the pulley hub to 1/2", then slip it onto the shaft? In one case, the hub diameter will only be .012". No hub support at all.

    Do I machine the shaft down to .25" bore, 1 1/2" on the outboard end? I could then slip the pulley onto the shaft. Then I would have to find a 1.375" bearing with .25" inside diameter.

    FWIW, the aluminum pulleys are only $6.22; the shaft is $40. The machine shop will probably stiff me to resize the shaft.:ack2:

    Thanks for any help.

  2. AussieSteve

    AussieSteve Active Member

    I have a similar problem, trying to fit a (6mm wide) timing-belt pulley onto my jackshaft, to drive a 12V 100W generator.
    Like you, by the time I bore the pulley, there's no meat left on the hub.
    My best solution so far is to bore the pulley, then attach it to the side of the existing sprocket with spacers. Can't think of another option. Also can't think of how to attach and centre it properly.
  3. 5-7HEAVEN

    5-7HEAVEN Guest

    Steve, what size is your pulley bore and jackshaft's diameter?

    On what part of the jackshaft is your pulley being mounted? End? Middle?

    I found a steel pulley. Maybe I can bore them out and weld them onto the shaft.:idea:
    Last edited by a moderator: May 21, 2010
  4. AussieSteve

    AussieSteve Active Member

    My jackshaft is 5/8"Ø, a Sick Bike Parts shift-kit.
    I haven't actually bought the pulley yet, but all the ones I've looked at have had either a ¼" or 8mm bore. They've all been made of aluminium or polycarbonate.
    My pulley needs to be about 48T and must suit a 6mm wide timing belt with a 3mm pitch. It will be located in the middle of the shaft, right next to the input sprocket. In my case, it can't be welded in place, either, even if I could find a steel pulley with the above specs.
    My best bet is to buy an aluminium pulley and an aluminium 5/8" collar, then bore the pulley and have it welded to the collar. (The type of collar with 2 grub screws, if they can be had in aluminium.)
    I've been working on the voltage regulator at the moment when I get a chance. The pulley is next after it's done.
  5. 5-7HEAVEN

    5-7HEAVEN Guest

    You're in luck, Steve. That website I mentioned has the exact pulley you're looking for. The hub diameter is 1.496" so can easily be bored from .315" to .625"(5/8"). They have them in aluminum or steel.

    It's HTD 3mm pitch, up to 9mm belt width. Pretty sure they have 6mm belt too.

    Here's your aluminum shaft collars:

    I just happened to oirder two aluminum collars from them. These are the friction/clamp-type with the bolt in them. Much better than grubscrerw-type.
    Last edited by a moderator: May 21, 2010
  6. AussieSteve

    AussieSteve Active Member

    Thanks, 5-7HEAVEN. Those pulleys do look good. I'd half-hoped for double-flange, but double-flange 48T only come in nylon/aluminium and the hub diameter is a bit small for boring.
    I'll just have to ensure that my belt alignment is extra good.
    Hopefully they don't mind shipping to Australia. (That's the expensive part.)