Putting A Stop To Lathes

Putting A Stop To Lathes

Operators often struggle with keeping the end of bar work pressed against the length stop as the chuck actuates and the drawtube pulls backwards when working on a lathe. This slows the job down because operators, uncertain if the bar end is against the stop, will open the chuck and make a second attempt at properly positioning the bar.

One solution to this problem is mounting some sort of length stop in the machine's spindle drawtube. For instance, some shops bolt a block to the back of the 0.500-in. spindle liner or to the spindle itself. The block is threaded for a 1/2-13 rod running down to the chuck with a nut securing it.

However, be aware that the cylinder for actuating a lathe's chuck is often on the outboard end of the spindle, and the drawtube may go all the way through. The only part that does not move is at the end of the cylinder. Some lathes may have a pattern of tapped holes on the outboard end of the cylinder, used to bolt in filler tubes. This could be a place to bolt a stop.

Another solution that works is mounting a stop in the machine's milling spindle, if it has one. Program the spindle with the stop placed at the length the bar needs to stick out of the chuck, open the chuck, pull the bar against the stop and close the chuck. According to one shop, this takes less time than many would think, about 10 to 12 seconds to change tools and to move the stop to position.

For shops with lathes that have servo barfeeders, the solution is the feeder's push rod. Shops simply program the push rod to travel into the drawtube and stop at the end of the program. Then they change parts, pushing the new part against the push rod. The first command in the part program retracts the pushrod. When feeding tubing, shops put a flange larger than the tubing I.D. on the end of the push rod.
practicalmachinist.com

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