Thread: Threadmilling...because threading on a lathe is for chumps :p

One of my jobs this past week was a batch of 3/8"-24 LH UNF shafts on our Mikron threadmill. Fun fact: the Swiss are so concerned about precision that, not only are the carriage ways and tailstock rail scraped, even the mating surface between the machine and the base is scraped to avoid any possibility of the casting being twisted the smallest amount.

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The first step is setting the gear train; the top set controls the pitch and feed direction, the bottom set controls the feed and spindle speed (along with another pair of gears on the spindle and a 2-step pulley on the motor)

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Next, the cutter is centralised on the axis of rotation of the helix angle adjustment and the helix angle is set. Good luck trying to set 2° 11' without a vernier scale, but with the magic of magnification we can make a pretty good approximation of it (and let's be honest, a few minutes either way is barely even measurable, it certainly won't have any impact on the function of the piece).

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Step 3 is setting the stops; the stop position is set with the rods on the front of the carriage, the start is set with the rods on the back. Either the top or bottom rods are used, depending on the feed direction, and because some of the stops are completely inside the machine and not able to be seen we manually wind the carriage through the full travel required to make sure it won't jam up and break something.

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All 19 oil points are topped up and it's time to touch-off, zero the micrometer depth adjuster and make a test cut, then it's just a matter of creeping up to size.

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Finally, each part is washed, deburred and checked with a ground go/no-go thread gauge.

Thanks for that Elan, interesting how different machines make an arduous task simple. It's a bit hard to see, but is the cutting head behind the lubricant/coolant rotating??
I like the floor there, you could just about eat your lunch off it.
Kryn

The cutter is spinning, the head itself is fixed at the helix angle