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Hi guys. I have a unique garage business selling hardware to builders and
repairers of upright basses. Check bass capos dot com for details. One thing
they need is a small but strong pulley wheel with a 1/8" dia. round belt
race. The ones I supply are brass with a sealed bearing and are a bit
overbuilt and expensive for the application. I want to arrange for a run of
a few hundred which would be more fit for purpose, and hopefully a bit
cheaper.

The plan is for a 7/8" dia. x 1/4" wide brass pulley with a 1/4" brass axle
and without the sealed bearing. There is a constant force of about 120 lbs.
on the shaft, but almost no rotation. Maybe +/- 1-2° a few times a day for
tuning, and no adjustments at all sometimes for weeks or months, and it must
be usable for decades. I think that simple brass on brass should work if
both parts are well machined/polished/lubricated, but there have been
anecdotal failures. So, I need to do something more if only for marketing,
but also I stupidly offer a ten year warranty. So, I must be very careful
about how I design and produce my wares!

Anyway, what are some options?

1. A polished SS shaft instead of brass? Good, but the customer needs to cut
the shaft to length and polish the ends. Not practical for most violinmakers
/repairers. They can always special order the needed length, so not out of
the question, but extra pain.

2. A bearing-grade bronze shaft with brass pulley? Seems like the most cheap
and practical, but how durable?

2. A greased bronze or SS sleeve between the brass shaft and the pulley?
Sounds good except that afaik it would have to be machined from solid round,
upping costs. Anyone know of bushing sleeve available in small diameters
like this?

3. Delrin bushing sleeve? This seems available in the size I need, but some
customers really don't want any plastic on their bass. I know. It's just
something you have to deal with in my world.

4. SS or bronze Pulley? sounds expensive.

Anyway, I hope there is someone out there with interest and understanding of
the specific issue I discuss, and who has the time to give advice.

Please do not post if you wish to warn me of:
A - the risks to life and limb of using metalworking machinery, or anything
else which uses electricity or has sharp cutting edges.
B - the liability risk of altering something without UL approval, or using
it for a purpose not described by the manufacturer.

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I think if I were doing this, I would press-fit the shaft into the wheel and
have the bushings at the ends of the shaft. That would prevent the wheel
from wobbling due to any clearance in the bushing. Perhaps the shaft could
have just a short section of the larger diameter in the middle to make
press-fitting during assembly easier. For the bushing, if you can not find
the right stainless sleeve, you could drill out an unthreaded stainless
steel spacer to the right size (or size the shaft to match). You could also
use some stainless tubing and drill it out to the right size (often then
have a weld seam that protrudes on the inside). Although one problem with
this whole concept is you would need a step in the shaft at each end to keep
the shaft from moving laterally, so that would require specific lengths that
you were trying to avoid.

Here's another idea: The brass wheel rotates on a short S.S. shaft made from
an internally threaded spacer. The ends of the shaft are made from hollow
brass spacers held to the center portion with screws from both ends (perhaps
brass for aesthetics?). The OD of the brass spacers could be larger than the
center portion of the shaft to provide strength and some lateral support
against wobbling.