Expanding Lathe Mandrel for Large Tubes Pt 1

Cutting a large thick-wall tube to make antenna support rings on my lathe was a big challenge. Coffee and brainstorming resulted in an internal mandrel fixture that works a treat. I can now hold large heavy tube and machine the outside and both ends with ease. No steady-rest to get in the way, and it's a very solid, safe and adjustable way to hold big tubes on my ancient Colchester 1800 manual lathe. This is Part One. Please consider subscribing to the channel so you'll get notified about the next part and other rambling nonsense that I come up with.



To be clear, I am not saying that *THIS* is how to make a tube-holding mandrel thingy, I am saying that this is how I made *MY* tube-holding mandrel thingy. Making the thing was a huge pile of fun, and the fact that it works really well is a bit of a bonus.



Absolutely no originality is claimed for this fixture. It's probably got a proper name but I don't know what to call it. "Expanding Tube Mandrel" will have to do. Before anyone says "why not use a steady rest?", I haven't got one (yet) but more importantly, I need to machine the outside of the tubes and both ends, which is a bit of a faff with a steady rest.



Disclaimers apply: I have literally no idea what I'm doing when it comes to machining.

Also I'm an idiot, so don't copy what I do or what I say. My redeeming feature is that I give myself permission to fail and have no fear of failure. That seems to mean I get a huge amount of fun from playing with microwave ham radio and all of the electronics, maths, physics, electromagnetic simulation and propagation studies. I also have a jolly time messing about in my home machine shop making stuff.



SAFETY DISCLAIMER

On occasion, I wear flimsy nitrile gloves to help reduce the impact of allergic dermatitis from coolant, lube and fine metal shavings . That seems to trigger some folks who are sensitive to a purported (but not evidenced) physical safety risk to my life and limbs. Please don't bother commenting if you see me wear a glove sometimes.

Chapters:
0:00 Why I need a tube mandrel
1:15 Design ideas
6:55 Machining the shaft
14:01 Making the studs
26:00 Collars
35:55 Test fit!
37:48 Drilling the hole pattern
41:04 Haimer Time