Thread Cutting?

Anybody got a link to a good thread cutting tutorial? Also, when machining
both the male and female items to be threaded, how much clearance do you
allow to start with between the two?
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I just made female threads on the lathe for the first time. I used a boring bar with a 60 degree bit that I ground.
I have a book "Machining Fundamentals" by John R. Walker that explains how to grind the bits and operate the lathe to make the cuts.
I ignored the book and made some on my own, but I got left hand threads. It is easier to just follow the directions.
Grady wrote:
Reply to
Clark Magnuson
Not exactly an answer to you question, but if possible, as you approach finished thread depth, stop and test fit (without taking the part out of the chuck). Then just take light passes until the fit is what you want it to be by feel. Make sure the thread are clean when you do this.
Of course, this does not work when one part already exists and is too big to bring near the lathe. Also, I'm assuming this is hobby work and the exact clearance is not critical.
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Umm. I did that the first time too.
Reply to
jim rozen
Second that, Clark! "Walker" is a great book but not quite correctly named. From the standpoint of my limited machining experience, he covers a lot more than fundamentals. Great book.
Bob Swinney
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Robert Swinney too.
It's better to be a red person in a blue state than a blue person in a red state. As a red person, if your blue neighbors turn into a mob at least you have a gun to protect yourself. As a blue person, your only hope is to appease the red mob with herbal tea and marinated tofu.
(Phil Garding)
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"When all else fails, but only then, try following the printed directions." :-)
Reply to
Ted Edwards
I read the books I could find and still couldn't figure it out till I threw the books aside and said screw it, it looks like I'm just going to have to wing it and it worked the first time !
I'm perplexed that in the information age why computers are like stabbing in the dark.
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That's what I do, try it. Lately, I'm cutting an internal sort of acme thread, 3/4" x 5tpi. "Sort of" because it is intended to fit mop handles, and they are NOT precise, at least to thread form, depth, etc. So I chopped off a $1.95 broom handle with a metal tip to test, then removed and tested on another handle with a plastic tip. Oops, have to break the edge and open up the i.d.
Picking up the thread again wasn't too bad. I just stuck the piece back in the collet, engaged the tool in the thread with the crossfeed with the boring bar loose and the threading dial at the right spot, then clamped the boring bar. To set the threading dial, I disengaged the drive and rotated the spindle (with the tool retracted out of the threads, of course).
I followed a suggestion I believe I read here a while back, and threaded in reverse on the back side. It worked very well, because the carriage travel was left to right, or out of the bore. At 5 tpi, it moves pretty quick, even in back gear.
Pete Keillor
Reply to
Peter T. Keillor III
Machinery's Handbook, or any other machinist's handbook will give you exhaustive information on thread turning. In general, I use a couple of thou. for clearance, but it makes a very tight fit. The class of the thread, based on strength requirements and size determines the clearance. It's a good idea to stick with published standards for interchangeability. Bigs
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What's an even better idea is to learn to properly apply thread wires so you can stick to the standards. They are of no use for internal threads, but perfect for outside measurements, and cheap to own. For those that don't understand, wires are the proper way to measure threads, and are used for calibrating thread gages. There is no better method.
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Harold and Susan Vordos
I have some information on using three wires on my web pages
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These web pages have been shamefully neglected for far too long but I plan to converto to a "rreal" web presence soon and will update and improve things on the pages.
Errol Groff
Instructor, Machine Tool Department
H.H. Ellis Technical High School 643 Upper Maple Street Dantieson, CT 06239
New England Model Engineering Society
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Errol Groff

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