Mis-matching thread angles and holding small tubing

[clarnibass]

Two unrelated questions...

1) Trying to envision what would happen when using a "screw" and a "nut" with different thread angles. The quotes are only because it's specific parts that are not exactly a screw and a nut but essentially the same. Maybe using the specific example: 9BA nut and a M2x0.4mm screw. Assuming nominal diameter (which isn't the case in reality) obviously the M2 screw would be too large for the 9BA 1.9mm diameter. Question is, what if the M2 screw was reduced (e.g. with an adjustable die) to 1.9mm and/or the nut threads would be slightly enlarged. Basically to the point where the 60 degrees of the metric screw vs. 47.5 degrees of the BA thread would be the only difference. Then, what if it was the other way around, 9BA screw in a theoretical M1.9x0.4mm, just in theory since a reduced diameter inner threads wouldn't happen. This case (adjusted M2 screw and 9BA nut) is a real case that sometimes can happen when it's not practical to get a BA die.

2) I might already answer this to myself, but I sometimes make bushings from nickel silver or brass. They are usually 4mm OD (OD is not critical) and ID varies anywhere from 2mm to 3mm, usually. I'm considering buying tubes to make them. It might be a silly question... but logically... as long as I'm able to hold the end part in a collet I should be able to hold a tube if the walls are not thinner...? Or is there a reason that at some point with thin walls it would be trickier to hold the tube more than it is for the collet to hold the part that was already held before? They are generally drilled and reamed, occasionally swaged to fit or even (rarely) lightly filed/sanded for final fit. Probably doesn't matter but each is manually made as a one off to fit a specific part.

Thanks

 

[hvnlymachining]

On the tube question, yes the collet will work fine with the tubing, especially with such a thick wall to diameter ratio.

I make sleeves for repairing large-ish bearing housings in electric motor end bells (often 6-8" diameter) these are made from relatively thin tube and turned even thinner. The wall thickness varies from .035"-.125". I make these on three and four jaw chucks with careful force application or special chuck jaws and occasionally a mandrel. On the rare occasion of smaller sleeves (under 1-3/8") I use my collet chuck on walls as thin as .010"

It all comes down to how hard you clamp, with a collet, you could swage that tube if you tried. But just a little effort to do it right will make things go smoothly even with very thin walls if the need arose.

 

[henrya]

Holding thin tubing in a collet gets lots easier with a wooden plug in the part.

As for the thread differential, what you are asking will affect where the threads make contact but won’t matter much for light duty use. I used to make threaded adapters for old well worn optical parts that had threads not readily measurable to a standard thread. I just made them to feel good. Not tight, not loose. Trial and fit.

 

[clarnibass]

Thank you.

I'm not sure what's considered thin or thick wall for a tube, I guess around 0.5mm for 4mm OD tube is thick?
I was just wondering if there's something I'm missing and holding a tube is trickier than still-holding a tube that became the same tube because it was drilled. I guess it's the same.
I can't use a plug in the tube because it needs to be drilled/reamed, that's all it needs really. I only want to change to tubes to save waste of material and a little bit of time.

Re the threads, yes it is light duty. Most of the load probably comes from the tightening, there is almost no significant load after that.

Thanks again