Machine Tool No 50 Taper
Machine Tool No 50 Taper
(OP)
I am trying to find information regarding a recommended Maximum Radial Moment which can be applied to a No. 50 Machine Tool Taper. We have a Grinding/Cutting application working at the moment that is showing a lot of fretting between the Spindle and Tool at the Taper. Is there such a figure available.





RE: Machine Tool No 50 Taper
Thread281-81884 ? (Just curious)
It's not quite clear what you mean by "Maximum radial movement". If you mean relative radial movement between the tool and the spindle, that should be almost immeasurable, at least at the front. However, if fretting is occurring, there will be some very small amount of movement. If you look at the standards for a 50 taper tool and the corresponding spindle taper, you will find that the tolerance on the taper is .001" per foot on both, but that the male taper tolerance can only be applied in the direction which increases the rate of taper, and the female taper tolerance in a direction which decreases it. This means that, assuming the tapers are 3" long, that there could be, in the worst case, a clearance of .0005" on diameter at the small end of the taper. If you notice more fretting there, that is most probably the reason. Since only the spindle taper geometry is controllable from the point of view of a machine builder, the very best that can be achieved is .0025" at the rear. When the tool is pulled into the taper, the front of the spindle expands slightly, and this has the effect of reducing the rear clearance, possibly to zero. The amount of this expansion is of course dependent on the drawbar pull and the design of the spindle. Some spindles have a relief in the central part of the taper, so that the tool only contacts on front and rear lands. Whether this helps is questionable. If, with enough drawbar pull, you can achieve a perfectly fitting taper, then you should be able to eliminate any possibility of fretting. However, tool ejection is another problem you can run into with high drawbar pulls.
RE: Machine Tool No 50 Taper
However, my comments are not totally irrelevant. In the mean time, I will think about the "maximum radial moment" question. Sorry !
RE: Machine Tool No 50 Taper
RE: Machine Tool No 50 Taper
Kennametal originally published deflection values for their KM joint based on FEA results. Until we did a static test and found the numbers wrong they would not believe the joint was weaker then originally published. Kennametal did take back the defective parts for full credit and do not publish a load value.
So I doubt anyone will have good moment load information.