How Many One Off Parts Can You Make Per Day?
by John
Obviously it depends how many machining operations are required per part, but these days I find that one or two parts per day is about all that I can manage. That includes deciding on then finding the material, drawing up the part in CAD, mounting the material and the cutter(s), then machining and finishing time.
Take today for example. My aim was make a steam pressure valve for the Trevithick Dredger Engine. It consists of a lead ball weight 30mm diameter, a lever arm with a hook, a simple stand with a M6 male thread, a movement restrainer, and the seat and valve. 6 fairly simple parts. I thought that I might get it all done in one day.
But at the end of the day, all that I had made was the arm, stand and restrainer. 3 simple parts.
The pressure valve arm, stand and restrainer in place.
Admittedly the arm is stainless steel of unknown grade. I broke 2 (4mm) cutters before I had slowed the milling feed rate to a snail’s pace 40mm/minute. Machining time for that part was over an hour! Then at least another hour of hand filing and finishing.
It is just as well that the worst day in the workshop is better than the best day of working!
And next will the interesting job of making the 30mm diameter lead ball weight. Still thinking about that one.
johnsmachines 
That is why I sold off my CNC equipment when I began making one off scale models. I found that on most occasions it took me more time to redraft the parts from the blue prints in a CAD program, export the g-code to a machine, set up the tooling, and run the parts then it did to simply read the print and make the part.
The only time I regret it is if there are a number of identical parts on a model. Then going the CNC route would be an advantage.
To answer your question: about one or two a day.
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Just about everything I have ever made has been one off, each piece unique – made by hand – even in production (with the exception of print pieces).
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Everything I’ve ever made is one-off. Some projects take years, some just minutes.
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