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An Introduction to Tapping

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July 29, 2011
2:04 AM

comeausj

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July 27, 2011

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Tapping is all well and good. I find it pretty easy compared to dies. Dies and external threads in general have been kicking my but since I got my new lathe about 3 weeks ago. I finally got a pair of passable internal and external threads, but they are pretty loose. I think I cut the Major diameter down too much. Anybody got any tips for threading on a lathe?

Information that may be helpful:

Harbor Freight 93212, trying to make 3/8" Aluminum with 16 Tpi

July 29, 2011
8:11 AM

Tenn

Linden, TN USA

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April 19, 2011

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comeausj said:

Tapping is all well and good. I find it pretty easy compared to dies. Dies and external threads in general have been kicking my but since I got my new lathe about 3 weeks ago. I finally got a pair of passable internal and external threads, but they are pretty loose. I think I cut the Major diameter down too much. Anybody got any tips for threading on a lathe?

Information that may be helpful:

Harbor Freight 93212, trying to make 3/8" Aluminum with 16 Tpi

Check "Often" for your "fit" also when you get close take a few passes "without" advancing the tool post and check in between passes. I have the same problem of cutting too far when I needed to quit several thousandths back. Embarassed I have managed a few passable threads though. With taps and dies the "fit" tight or loose is determined at the factory and they come (those that are not standard) labeled as to their fit.

Someone chime in here with the proper terms.

Also there are dies that are adjustable to change the fit slightly.

The man who will not share his wisdom, however foolish it may seem, For the betterment of his peers and the improvement of his trade, Is not worth his weight in swarf ! Learn from others mistakes, you probably won't live long enough to make them all yourself. But I do think I'm making progress on a lot of them! ~Chris

July 29, 2011
10:19 AM

Jerry

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February 10, 2011

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Adjustable dies are called 'Split Dies'. They are mounted in a die holder which has three screws in it. The two end screws locate in dimples in the side of the die, and they act to close the die over, the centre one has a pointed tip, this wedges into the split and is used to open the die up.

Split dies are certainly my preference, as they allow you to tune the fit to suit. There is a trade off however if you're using a tailstock mounted die holder. To allow the die to be opened up the holder has to have a recess for the die that is larger than the die diameter, this means that the die is held slightly off centre, and can result in threads that are not true, usually though they suffice for most things, as if you need true accuracy then single point cutting is the only way.

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