It's going to be a while before I get to cut metal, but at least I can now start to get things organised to do so.Īs an aside, the use of G91 caused me a few problems. If, in the code above, I specify a feedrate of 100mm/min will that apply to the Z axis only, ie, the cut will take 0.01 minutes, or does it apply to the distance round the helix, which is much longer, depending upon the thread diameter?
The next task is to generate some proper parts to be made, test out feedrates, and then cut metal! I need to test feedrates because I'm not sure how the code will be interpreted. If the cutter is first centred over the hole to be milled then by using G91 both X and Y are zero, as well as J, which makes the code much easier to read. It is interesting to note the call to G91, incremental mode. For a 1mm pitch thread 10mm deep it produces 10 circular interpolation calls, one for each thread pitch. I downloaded a thread milling wizard from the Vardex website and used it to produce code. What it should have done is make Z=1 and not used K at all. Can anybody see why? I'm operating in the XY plane, so the only arc modifiers I can use are I and J, the K value is illogical. Having eventually found an obscure switch in the program that allows helical paths to be generated either by linear segments or circular interpolation, I got the software to generate code using G03. Of course, that will achieve the correct toolpath, but it wasn't what I was expecting. Initial trials with the thread milling function in my CAM software produced code consisting of thousands of short G01 moves.
It seems smaller than I was imagining, the slightly fuzzy scale on the left of the picture is millimetres: It's a 60° version, so will do metric and unified. I've finally received my single point thread mill from Maritool in the US. This thread (good grief, a pun already) will describe my experiments in thread milling on a CNC mill.
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