Most of my bits are 1/2 inch but I went to use a 1/4 inch bit and find I cannot get it into the collet and none of my other bits will fit either. With some WD40 I can coax it in about an 1/8 of an inch, but that's it. (and we are cautioned not to put to bit too low because of overheating!! LOL) Anyone else run into this problem? Any known cures?