You know, as much as this advice makes perfect sense and I see it given often, when I get a screw with the head broken off, it is rarely loose...
I'm actually surprised when I can tease out a screw that has the head broken off, as most of the time it's still jammed in the threads. Maybe I just have bad luck in this regard, but I would love to hear if other people find that screws with heads broken of are usually free and easily removed...
Cheers, Al
Al
Other than the ones mentioned by Skutt, most others that I encounter are not loose enough to be removed with a pick.
I mainly work on what others have not been able to easily remove and they do not want any visible evidence of removal or the part having been worked on. As such, I personally avoid the use of chemicals in favor of two other methods of removal.
(1) For larger pocket watch size screws, I use a SKS 300,000 rpm mini die grinder with a micro carbide bur to cut a screw driver slot. Size comparison of the grinder and bur can be seen in the first two photos.
(2) For smaller screws, I drill them out in a Small Milling machine configured per the third/fourth photo. In this case, the Mill configuration allows for very clear optical observation of the drilling procedure. In addition, this allows the use of the "X" axis for drilling that is far more comfortable and natural than the "Z" axis in the vertical configuration. In addition, it offers greater tool feedback.
(3) The critical part of drilling is to establish a "centered" center spot. In order to assure this, I first machine a flat spot on the threaded screw section with a center cutting stub endmill and then spot drill in the center for drilling. This allows the spotting drill to do its job without any rough jagged off center stresses. The screw can then be drilled and removed with an easy out or by drilling up to thread size and easily chipping out the remaining thread pieces. All tools are carbide specifically designed for hard steel. Fifth photo, shows stub endmill top, spotting drill center and drill third for appearance and size reference for anyone interested. None of these are available in Horological supply out lets, but readily available through reputable machine tool supply houses. They and other far more complicated/capable micro tools can also be viewed and sometimes demonstrated at international machine tool shows.
Hands on experience again for anyone interested, can be had at selected NAWCC workshops by contacting the educational director for further information.
Jerry Kieffer