On a typical machine it can be done 5 or 6 times before any extemporaneous steps need to be taken. It is necessary to check the gage line to the face of the spindle and the draw-bar pressure before and after each spindle requalification. This is a part of the service that we provide, and should be done by anyone who requalifies your spindles. As a reference it should be " from the face of the spindle. Various machine manufacturers may deviate from this number. If the gage line is negative more than .015", make sure that the draw-bar pressure is adequate and that the tool changer does not have any conflicts.
Not necessarily. The most palatable solution is to disassemble the spindle and hard chrome the taper. This process adds additional material in order to bring the gage line back to the original specification.
In normal use, it
should be checked every year, or if you are having problems.
Premature deterioration can be caused by heavy milling, worn tool holders,
foreign material getting into the spindle, declining draw-bar pressure, or
"bumps in the night."
We ask customers to not
"help us too much." Hand polishing to
remove the gaul that results from spinning a tool in the taper should be
undertaken with extreme care in order to not subvert the parent
surface. The material that has been "welded" as a result of the
spun tool will be extra
hard. While trying to remove the weld, make sure not to remove too much
material from the parent surface. If you don't have to hand-grind, please
don't. If is very difficult to hold a tolerance of .0001" by hand.
On a vertical machine: We need approximately 17-1/2" of height under the Z axis and a space on the table to bolt to that is about 14" long and 8" wide.
On a horizontal machine: We prefer to bolt to a blank pallet.
machines: The spindle needs to be able to turn at approximately 100 rpm
and the retention system needs to be operable. If a machine is equipped
with a rotary screw draw-bar that protrudes into the taper, then it needs to be pushed
back out of the way or it needs to be removed.
used as a baseline number to determine whether or not the spindle bearings are
losing their pre-load through wear. Contact the machine manufacturer to
find out what their recommendations are for the axial deflection on your
machine. It can vary significantly even for different serial numbers of
the same model machine due to internal feature changes by the manufacturer.
This can vary greatly even by serial number in the same model machine. We simply try to report what the actual value is and suggest for our customers to contact the manufacturer. Most of the draw bars contain Belleville Disc Springs (also know as Belleville washers, disc springs, conical compression washers, and spring washers), which are cycle sensitive. The more times they are flexed, the sooner they will go away. If the retention pressure is too low, you will need to replace the Belleville Disc Springs in the machine.
This is a
little-known fact in the industry. Yes. It
makes a difference. Use retention knobs that are ground on the
surface that matches the top of the tool holder. Also the surface where
the collet lands on the retention knob needs to be ground. If ground
retention knobs are not used, it can pull the tool off to one side and affect
In the best circumstances, the tool holder, the retention knob, the collet, and the spindle all turn together simultaneously. When the tool holder taper doesn't have a good match, the retention knob becomes the flexure point. You simply work the tool holder (it bends) and breaks due to fatigue.
As a practical matter, no. Only to the extent that you start to stretch the retention knob would it become too much pressure. For instance, a Haas style retention knob is well capable of withstanding 9000 pounds of draw-bar pressure and not stretching the knob, if it is made from any reasonable material.
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