Maximum internal thread

[PaulR]

What's the maximum possible/advisable/sensible internal thread for a given size of bar and material. For example, would it be possible to cut an internal 10mm thread in a 1/2" round brass rod or is more 'meat' likely to be required? Seeing as it's perfectly possible to cut external threads of 1mm or less it seems like the inverse should apply. What about the same sizes in mild steel? Is there a rule of thumb?

Paul
(Someone has to ask the daft questions right?)

[Jasonb]

A lot will depend on what the thread is doing, if under a lot of load you would not want to go as thin as you would if there was little load.

But yes a M10 thread could be cut in 1/2" bar and still be quite strong.

[PaulR]

A lot will depend on what the thread is doing, if under a lot of load you would not want to go as thin as you would if there was little load.

But yes a M10 thread could be cut in 1/2" bar and still be quite strong.

Thanks for this. The use I was thinking of involves very little load, I was more concerned about tearing the material. If I had a scrap bin I'd give it ago but I haven't made any serious boo-boos in suitable material yet

[Jasonb]

You could always go with a finer pitch such as M10 x 1 rather than the usual M10 x 1.5 this is why pipe threads are finer than your typical fastener threads

[Admiral_dk]

It sounds wrong - but finer Pitch often has a bigger load capacity ....

Perhaps that is why 1mm. Pitch is used on a lot of big diameter threads for plugs ....

Per           

[dieselpilot]

The thing to keep in mind is that major diameter is greater than the nominal thread diameter, moreso with a sharp form. I could see M12 in a 1/2" rod, if load isn't a factor. A finer pitch doesn't change much in the case of the internal thread. Single pointing might be easier here. The only real trouble would arise if you were going to try to form tap.

I ran some M34x0.75 in a 36mm OD recently. I've single pointed many non-standard internal and external thread over the years.

Ever seen a Timesert for thread repair? The M10x1 insert uses a ~Ø11.2mm tap. The inserts are machined from my understanding.