Replies

1. 
   JohnWW | Mar 25, 2008 02:41am | #1

   A drill press chuck is mounted on the end of a tube, about 1.5 to 2 inches in diameter, called a quill that has bearings inside of it that allow the chuck to spin easily. When you turn the feed handle, the entire quill assembly slides in and out of a large vertical hole bored in the drill's head casting. Ideally, for accurate work, the quill should be a smooth sliding fit in the head casting bore, but should have no extra play that would allow the chuck to vibrate or veer slightly off course.

   In most older drill presses and some of the better modern drill presses, the fit of the quill in the head could be adjusted. This was accomplished by cutting a slot down the front of the head casting and then running a bolt or two across the slot. Tightening the bolt would close the slot a bit and make the quill bore a bit smaller allowing one to fine tune the quill fit.

   I addition to allowing you to fine tune the quill's fit when the machine was new, the split head would also allow readjustment to correct for wear over time, an important feature in heavily use industrial machines.

   An added advantage was that by adding a second crossbolt with a lever handle, the operator could quickly and very solidly, lock the quill at a fixed height which was useful for certain set ups and machining operations. Many modern lower priced drill presses either don't have any provision for locking the head or just use a bolt that jams against the side of the quill which can both slip and also damage the quill's surface.

   Just by luck, I am answering another drill press question and one of the posts has a photo of a 1950's drill press with the slot and cross bolt clearly visible in the photo. The adjustment bolt is the middle of the three at the bottom of the head casting.

   John White

1. 
   LB | Mar 25, 2008 07:48am | #2

   Thank you John! Excellent and comprehensive answer. You are the "THE EXPERT".

   LB

    

1. 
   JohnWW | Mar 25, 2008 06:26pm | #3

   You are welcome, glad I could help.John W.