Kennmetal threading tools.

A pic is worth 1000 words ! ;)
 
I just re checked the compound, and i may have made the common mistake. I think it was set at the wrong angle, even though I knew about the imports using the other axis for marking the degrees.
So what does every one set to? 29, 29.5 or 30 degrees?
 
29.5 degrees , not that 1/2 a degree really matters . :grin:
 
Doc1976 said:
I just re checked the compound, and i may have made the common mistake. I think it was set at the wrong angle, even though I knew about the imports using the other axis for marking the degrees.
So what does every one set to? 29, 29.5 or 30 degrees?
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It's the way we were taught. The basic premise is that by feeding in at just slightly less than 30º, most of the cutting is taking place on one flank of the tool. This reduces the total area of tool contact which reduces tendency to chatter, and produces better chip flow since there aren't two equal chips crashing into each other. The reason for setting just slightly less than 30º is to allow the trailing edge to take a very thin cleanup on each pass, ensuring there are no steps on the finished surface, which may happen if the feed is set to exactly 30º. Many people don't bother with any of this, simply feeding straight in, and still produce perfectly good threads. When threading 4 in. 4 tpi fire-hose thread in 304 S/S, it seems to be important.
 
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I set mine to 29, as the loved "How to run a lathe" from southbend suggests. I scribed a mark for future reference. I will try to cut some threads later and see what happens. Thanks guys.
 
When I set my lathe compound to 30 on the dial, it’s 30 degrees off the axis of rotation of the spindle. I have to set 60 degrees on the dial, then the compound moves at 30 degrees from perpendicular to the spindle axis.

My first threads looked like right triangles, just as described by the OP.
 
Winegrower said:
When I set my lathe compound to 30 on the dial, it’s 30 degrees off the axis of rotation of the spindle. I have to set 60 degrees on the dial, then the compound moves at 30 degrees from perpendicular to the spindle axis.

My first threads looked like right triangles, just as described by the OP.
Click to expand...
EXACTLY. I have high hopes that this will solve my problem.
 
already covered, sorry, I write too slowly.

I use a 30-60-90 triangle, just a bit off to set my compound.
 
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Good news, I tried another 1/2-20 thread with the adjustment made to bring the compound to 29 degrees and it is wonderful. Threads now have the proper shape. Thanks again to everyone for their input, it is greatly appreciated.
 
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