Round Column Mill Quick Depth Stop

[Paul Alciatore]

I believe that with round stock it could be made without a lathe and even that is not strictly necessary. You say you have limited metal stock. The nut could be made from the head of a large bolt, perhaps a 1" one. Those would be available at a well stocked hardware store. It would be best to use a lathe to form it, but it could be done with a file and some elbow grease. It does not have to be round. It could be left as a hex shape or you could file down the six corners for a 12 sided shape or whatever you like. You could even file a knurl pattern on the outside of it after filing it to shape. The rest is just drilling.

Likewise, round stock could be used for the button. It does not have to be precise and again, a large bolt could supply the needed stock. The rest of the work could be done on your mill and with some filing for the step for the spring. Or even that could be done on the mill with a bunch of rotations to form a bunch of straight cuts into a roughly circular notch. An inexpensive spring assortment would probably provide a suitable spring or just buy one at the hardware.

And yes, it could easily be scaled up or down. But you are working with the the basic thread size of the threaded rod you are using so that must be kept in mind. I find that the somewhat large diameter facilitates fine adjustments.

As for how it works, when the button is completed (step 2 in my drawing), the slot in the button has threads on the rear end of that slot but the rest of the slot has been enlarged to clear the threads on the threaded rod. Normally the spring holds that threaded part of the slot against the threaded rod and it acts like a normal nut. When you press the button in, the threads disengage and it is free to easily move up and down on the threaded rod. It is a very simple device and, as I said, it is available from tool supply houses in at least two sizes.

You might think that having a spring holding the threads in contact would not be reliable, but I have used this type of nut for years and have never had one skip a thread. It acts like a very positive stop.