Inspecting the Flyer Mechanism of a Spinning Wheel

Start the flyer inspection by disconnecting the drive band. With the flyer 
mounted in the maiden bearings, give the flyer a twirl and see how freely it rotates.
(You may need to turn the maidens a bit to position the bearings a little better).

Next remove the whorl from the flyer shaft. Most double drive flyers are left hand thread
(opposite from a normal bolt thread) although I've noticed some mass 
produce manufacturers use a right hand threaded whorl. Be careful not to use extreme
force if you are not sure which way the thread comes off. It should
be snug but if it appears it won't come off, try the other direction.
With the whorl removed, slip off the bobbin and take a look at the flyer shaft.
There should be no burrs or large machining marks visible.
Check the end that rides in the rear maiden bearing. Is the surface very smooth?
Polished? It should be very smooth with no burrs or sharp edges.
Next look at the shaft part on which the bobbin bearings (if provided) 
will ride on the shaft. Is there visible wear? Run a fingernail down the length of the shaft
to check for ridges that indicate bearing/shaft wear. This will indicate that either the
shaft material is too soft or that the bobbin bearing
material is not matched to the shaft hardness.

Flyer Shaft Materials:

Plain Steel (Cold rolled): (NOT BAD DEPENDING)
Easily machined and threaded. Too soft for most bearing materials, easily burred and scratched
Not hardenable by economical means so most likely will not be hardened.
Rusts easily kind of a dull metal color.

Brass: (POOR)
Very easily machined and threaded but very soft. Contrary to some advertisements, brass (by itself)
is not significantly hardenable. I strongly suggest you avoid soft brass flyer shafts.
If unsure how soft it is, try to scratch (somewhere unimportant) with
a nail file. Should not be scratchable if it is avoid it.
Probably a bright yellowish color.

Bronze: (BETTER)
Better than brass but still quite soft. There is one bronze alloy that can be
acceptable if using only soft bobbin material, (plastic, leather). Sorry do-it-yourselfers
but you'll have to do your own homework for the alloy number.
Color: Orangeish

Tools steels and drill rod: (BEST)
These are the best for long bearing wear and shaft smoothness characteristics. They
are easily hardened but depending on the composition type may not be very
round once hardened. These are normally hard enough for most bobbin bearing types
without additional heat treatment.
These are the only shaft materials I would approve of for using bronze bearings in the bobbins.


Common Bobbin Bearing Materials:

Wood: (POOR)
Some bobbins are supplied with only a close fitting hole drilled.
Avoid these. Very cheap construction method. Noisy with high friction coefficient.

Leather: (BETTER)

Bronze, Oilite: (BETTER)
These bearings are a porous sponge like material that are factory impregnated with oil 
and release the oil inside with heat generated from rotation on the shaft.
These should only be used with a tool steel or drill rod flyer shaft.

Cast Bronze: 
These need frequent oiling though personally I prefer these to "oilite"
Bright Orangeish color. Should only be used with a tool steel or drill rod shaft.

*Please note that Cooper Spinning Wheels is an environmentally conscious enterprise and all materials used are chosen for low impact on Mother Nature. We no longer offer (or encourage) the use of polymer (plastic) bearings on bobbins, brass is now our standard bobbin bearing material. Many makers still use these materials though so the following is given for those unfamiliar with the various compounds which are most often found on today's wheels.

Plastic Bearings:
So many varieties available though most makers and "craftsman" use the 
cheaper ones which have a higher coefficient of friction (they aren't as slippery).
As follows ratings with color and appearance.

UHMW (POOR)
White, white with visible burrs>

NYLON (POOR)
Milky white with visible burrs. Not very slippery.

DELRIN (BETTER)
Mostly black or white depending. Better than NYLON but not real good for a continuous motion bearing.

TEFLON (BEST)
Milky white but less translucent than NYLON. Easy to tell the difference as they are very slippery.

VERY BEST:
Any of the following colors of bearings are most likely very good bearings
for any shaft materials (if polished).
-GREEN
-BROWN
-ORANGE
-BEIGE

If you are new to spinning or want more info, we recommend this site as a starting point: www.joyofhandspinning.com

Another good place to visit is:
(http://www.woolfestival.com)
Woolfestival.com: get your festival fix at home!
Spinner's message board, calendar of events, guild listings, articles and a marketplace of small wool producers offering Roving, Yarn, Fleeces, and other supplies for the handspinner