Vince Pitelka on sun 22 feb 98
>speaking of squeaky wheels does anybody have any experience
>changing the top bearing on an old (20 yrs.+) Shimpo RK-2 ?
>I tried and failed to take the plate held by 4 Allen screws
>off the top, the heads are rusted off.
Jon -
In order to replace the wheel-shaft bearings you NEED to unbolt that flange.
In my years working as a mechanic for a city in Northern California I
developed a certain expertise in the removal of rusty and/or broken bolts.
There has never been a bolt so badly rusted or broken that it could not be
removed. If you have not already done so, you first need to remove the
wheelhead, and hopefully that is not also corroded in place. In all
situations, when removing corroded parts, the keys are heat and a good
penetrating fluid, like Liquid Wrench or WD-40. WE-40 is not a particularly
good lubricant, because it evaporates quickly and leaves no lubricating
material in place. But for removing rusty parts it is by far the best thing
out there, and I have tried everything. A word of caution, though - do this
work in a very well ventilated place, and use a fan to blow all burning
WD-40 fumes away from you. If the wheelhead will not come off, use a
propane torch on the wheel-hub beneath the wheel-head, and spray WD-40 on
the shaft just beneath the wheelhead. Place several foot-long sections of
2x4 underneath the wheelhead, and pry against the housing to apply upwards
pressure on the wheelhead. Don't use longer boards, because you could
distort the wheelhead. If necessary apply heat and WD-40 repeatedly until
the wheelhead comes loose.
You stated that the flange bolts on your wheel are Allen scews. Is that
really what you meant? Allen screws are the small headless screws used to
lock pulleys on shafts. All of our RK-2s have regular hex-head bolts.
Yours may have allen socket cap screws on yours, which have an allen socket
in the head. You need to make sure you clean all of the corrosion out of
these sockets very thoroughly, using a fine-pointed little chisel and an
air-gun to blow out all the residue. If the surfaces are not too badly
corroded, then an Allen wrency should still fit.
If you are positive that they are too badly corroded to remove with an
ordinary wrench, then proceed to plan B. This unfortunately requires an
oxy-acetylene torch with a small tip, and also requires a Dremel moto-tool
or a die-grinder with a thin disc grinding wheel. These grinding discs are
readily available - they are about an inch in diameter, and about 1/32 to
1/16" thick, and they fit on an arbor-shaft, with a removeable screw which
allows replacement of the wheels. Using this tool, cut a large screwdriver
slot in the head of the rusted bolt or screw (or bolt/screw shaft if the
head were broken off). Make sure you have a large screwdriver which will
fit this slot. Using the oxy-acetylene torch, heat up the bolt head until
it is red-hot. Allow it to cool a bit, and begin spraying on WD-40. The
WD-40 will give off powerful fumes, which may burst into flames, but it will
be very localized and will not cause any trouble. Continue spraying WD-40
on the bold/screw head as it cools. Repeat these two steps, periodically
trying to unscrew the bolt/screw with a screwdriver. Each time you heat the
bolt it expands. As it cools and contracts, it sucks WD-40 into the
threads. Do this enough times, and ANY rusted bolt or screw, or broken-off
bolt or screw, will come out. Even if it is broken off flush with a
casting, you can grind the screw slot into the exposed face of the broken
bolt/screw. A propane torch will not work for this method, because the heat
is not intense enough or localized enough. The idea is to heat up the
bolt/screw quickly, without heating the surrounding metal any more than
necessary. Good luck.
- Vince
Vince Pitelka - vpitelka@DeKalb.net
Home 615/597-5376, work 615/597-6801, fax 615/597-6803
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
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