This pin is fabricated out of Delrin Acetal Rod.  The Delrin Acetal rod will not crack or break.  It is flexible, but very tough.  The little "pin" connects the power on-off-variable control knob/ handle to the actual electrical switch inside.  This pin is "force fit" onto the electrical switch ribbed spline/ shaft and "force fit" into the plastic Control Knob/ handle.  You could possibly require a pair of pliers for this.  It is plenty tight enough to remain in place for the up and down, on/off action of the power switch but, not so tight that it cannot be removed, which is necessary for top plate removal and cleaning.  This Delrin Acetal pin fits snug without any wiggle at all.

This pin installation is not for someone who does not have mechanical aptitude.  The pin will have to be "force fit" onto the electrical on/off/variable control switch ribbed stem.  It fits very tight.  Also the "D" half circle shaped end "force fits" into the control knob handle.  These pins have been tested for proper fit, i.e., removable but, will hold, especially for on/off operation.  If you file or sand this half circle section down for easier fit then you risk it separating while attempting to "pull" the switch to the "on" position.  The pieces do come apart for finish plate removal and cleaning but, again the fit is "tight".  If you desire to file or sand then you do so at your own risk.  Note: Make sure that the pieces are free of oils, grease and are clean and dry prior to installation.  This pin installation is at your own risk.  I will not be responsible for any damage you cause to your equipment while you are installing it.  This is a replacement pin only.  I have fabricated it.  I have installed many of them.  I have reworked these many times.  I have perfected them.  I tested them for smooth operation.  I have tested that they do not inadvertently separate during normal operation.  I have tested that the pins can be removed for finish plate removal and cleaning.

I have heard that people pay well over $90.00 for these pin replacements but, they're still having to use a pair of needle nose pliers to pull the switch to the on position, how sad.  Not the case with my pins.  

RETURN POLICY:
No worries guarantee; Hey, I am offering this for those of you whose kitchen power unit is rendered practically useless because of an old, cracked or broken part.  I want you to be completely satisfied with my part.  Shipping is so minimal that you really have nothing to lose.  If for any reason, you find this item not to your satisfaction then just return it and I will credit your money back, no questions asked.

ALTERNATE PIN & ADDITIONAL SERVICES:

Nutone Model 251 Control Knob Repair Service Ebay item # 130954923980  Send in the Entire Unit