Adding a thread to a round tube

[mjalaly]

I'm in the process of doing last-minute things before painting the chassis and one of the issues I've run into is adding thread to a round tube surface. The point is so that I can have ways to mount p-clamps, excetera 4 wiring harnesses and the like. I dont think rivnuts will work and i found some of these but everything is out of stock for a while.

https://shop.stafast.com/r14209cfur9

Im hoping for a near flush method as well.

These might also work for zip tying cables to the chassis. Any other thoughts?

https://www.cycle-frames.com/HYDRO-BRAK ... E-ZIP.html

[300D50]

You could look into getting a flow drill for the thread size you want, then tapping the resulting material.

It's done in industry quite regularly.

EDIT: https://www.mcmaster.com/flow-drills/

[FieroReinke]

https://www.mcmaster.com/nuts/surface-mount-nuts/steel-round-base-weld-nuts-9/

Can you use these and bend around the tube so they look like the ones from stafast?

[300D50]

Those seem to lack the curve to fit the tubing, but I'm guessing a mandrel/die set could be made for an arbor press to form that.

[mjalaly]

https://www.mcmaster.com/nuts/surface-mount-nuts/steel-round-base-weld-nuts-9/

Can you use these and bend around the tube so they look like the ones from stafast?

Totally forgot about these the only issue is that I would need to use a hand drill which I don't think that can work with.

[FieroReinke]

How are these different than those from stafast other than the curved top?

[rx7locost]

How many do you need to do? For flush mount, I would go DIY. Drill a hole large enough to clear the OD of a regular nut. Hold the nut in place using a piece of brass threaded rod. Weld all around, and then remove the threaded rod. Grind to your desired shape, flat or curved. Presto You're done. No waiting for special hardware that may or may not work.

For a finished flat surface that stands slightly proud of the tube, you could drill a small hole to clear the thread size desired, and weld or braze (your choice) a nut centered over the hole. If brazed, do not weld/braze with a screw in the hole.

For more threads, you could use a piece of threaded rod coupler in place of the std nuts.

[Miatav8,MstrASE,A&P,F]

Look at cable tie mounts or mountable zip ties that have a hole on the end to attach them to something with a pop rivet or screw.

If exposed to sunlight, it should be black plastic.

https://www.mcmaster.com/zip-tie-anchor ... -mounts-6/

[Nick94tt]

The kind of thing a machine shop could save you a ton of time and money on.

Pick a standard fastener head/thread/pitch and the sidewall you need for tensile strength. Have the shop (or great mini lathe project) turn some round stock and thread it. Part off to length flat. Countersink the tube hole (tube, not the insert).

Drill a hole straight through the tube a few thou over. Knock in the threaded tube, make sure you've got a disposable fastener in the hole (pan spray or mig spatter guard if you're going mig). Burn it in. Definitely more tig friendly - considering the tube bevel vs insert. Less likely to need a tap set.

Can grind it back to round/countersink/work the fitment to your level of interest.

Overkill with access to machining option, lol.

[NoahKatz]

How does a pointy tip make a cylindrical sleeve?

You could look into getting a flow drill for the thread size you want, then tapping the resulting material.

It's done in industry quite regularly.

EDIT: https://www.mcmaster.com/flow-drills/

[300D50]

From memory, so may be a bit off-base on actual, but...

Friction between the bit and the material heats the material to above the glass transition temperature, the hole happens when the stress overcomes the yield strength of the material, and then the material gets pushed out of the way as the bit is moved down.

Interesting process for sure.

[Sean in CT]

I think you need to use a drill press or milling machine machine to get a flow drill to work properly. Needs a lot of downward pressure.

[gto7419]

Sean in CT is mostly correct from my reading on flow drills. I've read that you can use a small enough diameter on a thin enough material in a high speed hand drill, but I've not seen anyone publish specs for that ability.