----- Original Message ----- From: "Win Wiencke" To: Sent: Thursday, July 29, 2004 12:55 PM Subject: Re: [AD]: (will be) Small CNC mill, controller and software for ~$500 > > > A simple backlash > > eliminator could also be added to all three axes in the process. > > This interests me because I've never actually seen a backlash eliminator. > What is it? Perhaps it could also compensate for the slop in the coupling > and you'd be in great shape. > In it's most simple form a backlash eliminator can be a nut that has a hole drilled and tapped in one face. The nut then has a saw cut put through the tapped hole for half the thickness of the nut. A pointed grub screw is inserted into the treaded hole and by tightening the screw the faces of the nut can be spread apart to take up the slack in the thread. 'Generally' only the taper tap is used and the thread is left tapered so that the point of the grub screw can bite into the taper and spread the nut. As the LS wears the grub screw is 'snugged' up to take up the slop. Other types exist that use a threaded bushing that is slit and a 'C' clip or circlip applies constant pressure so that it is self adjusting to some degree. This type generally has hollow dowels inserted into each half to allow mounting screws to hold it to the machine. Another rather neat way that some home CNC enthusiasts have come up with is to make a nut out of Delrin but instead of tapping it out with regular taps (which can cut oversize) they make a tap out of a spare piece of the LS material. By doing this they get an almost size for size thread in the nut and backlash is not a problem. Apparently the Delrin stands up to the wear of use very well. Larry Green -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu