Screwdriver
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Screwcutting is a rite of passage for any would be machinist and metric threads on an imperial lathe gets you bonus points. To be successful you need to know a goodly chunk of everything there is to know about your lathe. I suspect we have all had our moments, I certainly did. In fact my "moment" lasted several years!
I studied everything, did my research, assembled all the right bits and dove in. Eventually I got to the point where my threads were pretty close which drove me nuts. When I say "close" I mean the thread I cut was within a few percent of where it ought to be pitch wise. I assumed like everyone here that I must be some sort of idiot, gave up and used a die.
Some time later I decided it was time and determined to make it work. Turned out the Colchester has a swappable driver gear, you can fit the 21 tooth driver for standard pitches and the 42 tooth one to double it. All those levers and you still have to physically swap over the gear but that wasn't the problem. The problem is, where do you keep the 42 tooth gear when not using it?
On the student it resides on the end of the final drive shaft on top of the actual screw cutting gear, a 35 tooth. It just sits there doing nothing as if its on a coat hook. But on mine, some wag had switched the two so that my "stored" 42 tooth gear was inside of the required 35 tooth, driving the lead screw at just ever so slightly wrong!
Oh how I laughed. Finally I was able to cut a perfect thread and crash into the workpiece at the correct pitch. Yep thats right, finally with the machine set up correctly I could confidently start making all the other mistakes we all do...
I studied everything, did my research, assembled all the right bits and dove in. Eventually I got to the point where my threads were pretty close which drove me nuts. When I say "close" I mean the thread I cut was within a few percent of where it ought to be pitch wise. I assumed like everyone here that I must be some sort of idiot, gave up and used a die.
Some time later I decided it was time and determined to make it work. Turned out the Colchester has a swappable driver gear, you can fit the 21 tooth driver for standard pitches and the 42 tooth one to double it. All those levers and you still have to physically swap over the gear but that wasn't the problem. The problem is, where do you keep the 42 tooth gear when not using it?
On the student it resides on the end of the final drive shaft on top of the actual screw cutting gear, a 35 tooth. It just sits there doing nothing as if its on a coat hook. But on mine, some wag had switched the two so that my "stored" 42 tooth gear was inside of the required 35 tooth, driving the lead screw at just ever so slightly wrong!
Oh how I laughed. Finally I was able to cut a perfect thread and crash into the workpiece at the correct pitch. Yep thats right, finally with the machine set up correctly I could confidently start making all the other mistakes we all do...
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