Technical Tuesday tech. My lathe. Why is metric screwcutting screwy???

Hello! Welcome to Mart's Garage. This one won't be for everyone, It's my lathe. It wasn't doing the metric conversion correctly for screwcutting. Guess what! I managed to fix it! As a bonus it was a zero cost fix! Always nice.
Back to the usual content on the next one. Mart.

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It's the operator.........lol

 

Isn't there is enough metric in the world without wanting to making more? Just asking for a friend.

 

The wife and I were having a pint or three in Kilkenny a couple years back and some Canadian women at the next table over were quacking on about the weather, it was Celsius this and Celsius that. I remarked, "what the hell is a Celsius?" And they responded "move away from the Americans!" It's kind of like that with me and metric.

 

Haven't watched the video now... but usually you use a 127 tooth gear to cut metric threads with an inferior, sorry, IMPERIAL lead screw, or vise versa. 127 because it's the lowest number where whole millimeters match whole inches, i.e. 127mm = 5".

 

Thanks for the responses fellas. I usually work in imperial. What prompted all this was trying to cut a spark plug thread. Hate to say it, but every time you have one of those puppies in your hand you're using METRIC. It was funny because I found 20tpi close enough to the pitch I wanted to do the job anyway.
It was in a previous video:


Mart.