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Flexi shaft not connecting


#1

Hi All,

I bought a top of the line GD flexi shaft (my first ever) a couple
of weeks ago and have used it only a few times since. Up until
today it has worked beautifully. Today, however, I suddenly started
experiencing problems with the wheel staying stationary when I
pushed down on the pedal… or, rotating but stopping the moment I
applied pressure to the wheel. After a while I was able to track
the problem to the connection between the motor and the shaft. It
appears that where the shaft locks into the motor the shaft has been
sitting too low and movement of the handpiece sometimes causes it to
slip completely downwards from the motor. There even appears to be
a little wear at the top of the point that connects the shaft to the
motor. By tying some string around the outside of the shaft about
halfway down and pulling it up and tying the other end to the motor
casing I have forced the connection in tighter. So far this seems
to be working okay. My question is though, is this normal? Or at
least a common problem? Should I get the shaft replaced or will I
just end up with a new shaft with the same old problem? Also, by
tying the string around the shaft and pulling upwards to tie it to
the motor casing there is a slight curve forced into the shaft -
over a long period could this cause permanent damage of any kind?

As always, I really appreciate any thoughts or advice anyone can
offer on this.

Tina


#2

Tina- I had the same problem and in my experience the shaft attaches
to the motor via a flat surface on the shaft and a hex set screw.
If operated too long with a loose screw the shaft will round and the
screw wear down. My advice is to closely access the damage, flatten
the shaft with a file, and if necessary (probably not) replace the
set screw. I doubt you have caused any permanent damage, but if you
think you have any reputable dealer would cover this under
warrantee.

Tom


#3
 My question is though, is this normal? 

Tina, no it’s not. However, these connections shouldn’t need
external strings to hold them tight. They have, or should have, set
screws to hold the connections together. On most flex shafts, there
is a set screw fitting where the innter shaft fits over the motor
shaft. You loosen that set screw so the inner shaft, which looks
usually like a spring wound around a cable, with a sleeve fitting on
the end with it’s set screw, is pushed all the way up on the shaft
of the motor, with the set screw tightened down against the flat in
the motor shaft. That should then be a nice secure connection.
Then, there should also be a set screw connection where the black
rubber outer casing connects to she screw on (usually) connector that
screws to the motor housing. This second connection lets you adjust
the position of the outer sleeve, which has the effect of adjusting
the amount of the flanged end of the inner shaft, which projects out
of the outer sleeve where you connect to your handpiece. You adjust
that length so the quick connect handpiece fully engages, but
without binding. If too much of the flanged end projects, then it’s
being pushed too far into the handpiece, and may tend to either heat
up, or push off the handpiece in use. If too little projects, then
it won’t drive the handpiece correctly. In a very few cases, you
might have to adjust the position of the inner cable/shaft on the
motor, if the flange doesn’t project out far enough. Just be sure the
set screw is positioned so it’s still fully on the motor shaft and
secure.

Peter