Earlier in the year, I bought some fly cutters at a model
The intention was to tidy up some of the castings I’d made last year. The first issue was how to hold an irregular shaped piece whilst it was being cut. Given that I was planning on turning this into a handle, drilling and tapping two locations to support it seemed like a good idea. The casting was then bolted to a short length of bar which was in turn mounted in the tool post. One of the problems with machining lumpy items is that it’s hard to set the first pass, the problem is that you will be happily skimming off a 1/10mm only to hit a 1mm bump where the cutter justs digs in. To work around this either file the item flat first or make multiple passes over the metal to check for high spots to machine down first.
A couple of other issues were spotted in the process. The size of the item to be machined is limited vertically by the sweep of the fly cutter. The size of the item horizonally is limited by both the sweep and the amount of movement of the cross slide. So the size I can easily fly cut on this lathe is about 60mm square. To machine large areas the bar held in the toolpost would have to be moved. I made the error of flipping this over only to discover my mounting holes were not exactly perpendicular to the work. This produced an approx 1mm difference between the two sides. I’ve decided to abandon this process and cut this casting up into smaller pieces that can be used for various projects needing aluminium in the future
So in conclusion, yes it it possible to use this technique and it beats manual sawing and filing for quality of results. However, it’s not idea for removing large quanties of metal as it takes a lot of time, so I’d be much better off trying to improve the quality of my castings and just fly cutting any critical areas.
I’ve made some progress with regards to better castings with the petrobond sand, some good quality source metal. I now need to make some better patterns and to practice bedding them in the sand to get better results.