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Low breakout torque thread

Low breakout torque thread

(OP)
Hello,

Im designing a milling/drilling machine that uses 1.750" diameter low alloy steel drill rods. Im needing a connection for connecting multiple drill rods together. currently, we use a 1" square drive and dowel pin, but I'm not totally happy with it. Does anyone know of a thread that will permit torque through etc, but will facilitate easy breakout? Im guessing it may be something like a twin start high helix thread or something similar to a 1" AMT thread.

regards

Matt

RE: Low breakout torque thread

Maybe a thread like that used to connect drill rod. I think it may be an API(American Petroleum Industry) specification. Or mining drill steel thread form.
Breakout torque will still depend on how tight the joint was made in service.
Ted

RE: Low breakout torque thread

(OP)
Thanks Ted,

Im fairly familiar with typical API threads (I work in the oil industry). However, most of them require being torques up and broken out with power tongs. I was wondering about the threads used in tool holders for live tooling?

RE: Low breakout torque thread

Quote (Mattm86)

I was wondering about the threads used in tool holders for live tooling?

If you're talking about typical CNC machines, the tooling is not directly held in place by a thread of any kind- there is almost always a tapered interface. Sometimes with keys, sometimes not. Thread forms are used only to pull the taper tight- the thread sees tension but does not transfer torque.

RE: Low breakout torque thread

If you want it easily removed but good at transferring torque look at the polygonal couplings.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

RE: Low breakout torque thread

(OP)
Imagine this as a borehole rig which may help, so a Morse taper is not really appropriate.

What I was referring to earlier is used on ejector drills (https://www.google.co.uk/imgres?imgurl=http%3A%2F%...)

Im leaning to a 4 start acme thread or something similar I think. A screwed joint is ideal for what I want, I just dont want the high breakout torque associated with it.

RE: Low breakout torque thread

Matt,
Consider one of the coarser Acme thread, but relieve/wipe the first two or three threads so that your pin(male) threaded post bottoms out in the mating (female) component.

Good Luck
Rick

RE: Low breakout torque thread

(OP)
Rick,

Thanks, although Im not totally sure what you mean?

I have modelled up and 3D printed a modified stub acme 4 TPI 4 start tapered thread which looks like it would work well. However, the lead is so steep that if the thread was not torqued up at all, the lower rod would unscrew from the pin and drop down under its own weight....

Its sort of a trade off between not backing off too easily, but not requiring too much torque to undo.



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