Swingup external threading tool

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Lykle:
I really love these kind of threads (pun intended)

Anyway, all we need to do now is design the same kind of tool for internal threading.
That's the one that always get's me into trouble.

It could be a rotating shaft with stops and maybe a light spring load to keep it down. Or a weighted stop?
I think it would require quite some modification on the relief side of the toolbit, to make sure it does not grab the material while retreating.

Hmm, nice little design project.

Lykle

andyf:
Hi Lykle,

It would be hard to make a swinging toolholder for internal threads. If it swings up, the tool will dig deeper into the side of the bore, unless the axis around which it swings is very close to the tip of the tool, so the radius of the arc described by the tip is rather less than the radius of the bore. I suppose it might be less difficult for threading holes of large diameter, but it would probably be easier to make a retracting toolholder like the one shown here http://www.gadgetbuilder.com/ToolHolders.html#Retracting , where the operator uses the ball handle at the end of each cut to slide the tool out of the thread so that the carriage can be wound back for the next cut.

Andy

Ned Ludd:
Hi Guys,
Anybody thinking of building one of those retracting tool holders, should think again. Although it is an interesting project and is indeed nicely designed, it can be replaced by a simple cross slide stop for MUCH less work. The idea of a retracting holder for internal threads has merit but of a completely different design. Something like a round boring/threading bar in an offset round sleeve, for fore and aft movement, but it would need some arrangement at one end to stop the bar rotating under load. I can see it in my mind but no time to make it real, where is Bogs when we need him?
Ned Ludd

Darren:
After building and using a swingup threading tool for external threads I wouldn't want to use anything else.

For the little internal work that I may or may never do I'll just do it the old fashion way or use slide stops. I'll work that one out when I get there.

ieezitin:
On the internal threading tool I don’t think it would be that hard to make here is a quick sketch on the mechanism that sprung to mind.

My theory is you only need to retract .050 - .070 max Linear to clear the cutter for extraction. The actuator could be at the end of the boring bar and a knurled wheel for rotation to seat and disengage.

The beauty is when you hit 0 and 90 of the cam you have great forces working for you so movement or backlash should be minimal if not zero.

All could be made on a lathe within a day maybe, the hardest thing would be the engineering of the cam and dimensioning after that its cake.

Any ideas please feel free to critique .

All the best. Anthony.

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