The metal alloy, the heat treatment and manufacturing techniques
determine if the products for flexshafts are safe or not.
If you spin these at slow speed they do not bend. It is the
velocity, the metal and also the lopsided load that bend it right
Most of these mandrels specially the ones from Grobet are made in
Germany. These are made on Swiss Screw Machines (Automatic) they spit
these out at high speed and are well balance plus the metal is strong
to begin with.
Recently there has been split mandrels made in India and they are
brass nickle plated. These are made on manual machines with cheap
labor. To begin with the metal is no good. The machines that they make
these with cannot turn out well balanced pieces. The slotting is not
done right and it is a disaster in waiting.
I would not blame the vendors alone. The market seems to be looking
for prices and most of the manufacturers in the third world countries
dont even know what you are using these split mandrels for or at what
speeds. We use to have 18,000 rpm and now with micro motors we are
spinning these at 30,000 rpm
Please Protect yourself with any of these German or Indian
46 Jewelry Supply.