What process/tool required to put this pipe thread in sheet metal?

[Econdron]

Quoting this job, it could be pretty big. Part of the assembly requires these pipe thread mounts in the sheet metal. Is this some kind of a custom punch? Or maybe a "flow drill"? The sheet metal is only 18ga, but there's a good .25" of thread there. What would I need to copy this?

 

[doug925]

I believe you are correct on the use of a flow drill.
Without a flow drill, how else could you get upset metal thickness to .25" ??

 

[TKassoc]

It's two hits...first a pre-punch and then an extrude tool-->Extrusion | Punch Press Tooling Catalog | Wilson Tool Punch Press Job it to a sheet metal shop with a turret punch.

 

[Limy Sami]

Flow drill for pipe threads - they only list up to 3/4 Flowdrill - Products - Flowdrill

 

[DDoug]

Flow drill for pipe threads - they only list up to 3/4 Flowdrill - Products - Flowdrill

A couple of questions:
1. How does that put the threads on ?
2. how do you sharpen it (or even know when to) ?

 

[Clive603]

A couple of questions:
1. How does that put the threads on ?
2. how do you sharpen it (or even know when to) ?

1)Thats just the drill. The shank creates a tapping size hole in the upset material and the collar leaves either flat surface or raised bush depending on its shape. Use a cold forming tap to make the actual thread.

2)No sharpening needed. Its smooth point and side. Spin it fast to bring material up to red head and push hard piercing the sheet and forcing it to flow into a collar. I guess if it gets old and rough you could polish it.

Clive.

 

[Econdron]

They told me they want the assembly to be exactly the same, though they said the threaded holes were the only thing they would be ok with an alternative. I can't imagine a flow drill being efficient here. It's a piece that 64" L with 2 holes on both ends, they're wanting hundreds of these frames. Only other alternative I can think of is welding a pipe bushing to the back side of the hole? I have a turret punch shop down the road, I'll go ask them what they think.

 

[guest]

I've never used one of those friction drills, but I have seen them work. They leave a pretty nappy hole.

I would do the punch press thing, or better yet would be to punch the hole and use a bulkhead fitting instead of trying to tap that thin sheet metal.

 

[JRIowa]

We used the German version, Centerdrill: Centerdrill - Your specialist for flowdrilling
IIRC, Wilson Tool also sells something similar.
JR

 

[Clive603]

I've never used one of those friction drills, but I have seen them work. They leave a pretty nappy hole.

Process isn't quite as simple as the website make's it sound. Especially on larger sizes you frequently need some support to make the red-hot extrusion behave to get good finish. Of course a cold forming tap usually smooths minor imperfections out during tapping.

Such press has its own issues such as risk of work hardening the material. Collar to be tapped is only parent sheet thickness too which may be an issue.

Welding a bulkhead fitting on is slow unless you can arrange to spin weld it, an excellent process but you have to get it right.

For my money the flow drilling process is most forgiving. Pretty quick too with a good twin head drill having correct speed ranges. (Too many have three identical heads which is rarely right.)

Clive

 

[Peter from Holland]

Punch or lasercut a hole Then make a punch with 3 steps A lead that goes in the die to keep punch and die centered Then a step the same diam as the lasercut hole Then the biggest step is the diam of the hole you need to make
Very easy to make Does not even need to be hardended Some trail and error in scrap metal
I did make smaller ones to be used in a vice but this size I would do in a excentric press


Peter

 

[Yan_b]

In metal barrels industry there are stamped flanges solution for such things
try, Tri-Sure(R) More than Closures

 

[Ries]

I think you would be better off with a threaded rivet bushing- you punch a regular hole in your sheet metal, and then use a press of some sort to rivet a pre-threaded bushing in. Cheaper set up, time tested, and reliable. Several companies make these-
https://www.rgafasteners-psm.com/files//PSM.Files/anchor rivet bush.pdf
Anchor Rivet Nuts and Clinch Nuts - inserco.eu

 

[Econdron]

I think you would be better off with a threaded rivet bushing- you punch a regular hole in your sheet metal, and then use a press of some sort to rivet a pre-threaded bushing in. Cheaper set up, time tested, and reliable. Several companies make these-
https://www.rgafasteners-psm.com/files//PSM.Files/anchor rivet bush.pdf
Anchor Rivet Nuts and Clinch Nuts - inserco.eu

I thought about that, and I'll ask if that will work, but I think the flange on the "top" of the sheet would interfere with their setup.

 

[sfriedberg]

When you talk to the local punch shop, ask about "extrude".

 

[boslab]

We used to do somthing similar to extrusions, it was a round tipped punch that “drew” the hole, left the tube sticking out, it still had to be tapped, that’s where all the failures occurred so we went to rivnuts or rivicles I think they were called, they worked really well.
Mark

 

[rcoope]

Some great thoughts here but what size pipe threads are these? And they are actual NPT threads, not straight threads? They look about 3/4" in diameter which is larger than conventional PEM type fasteners.

 

[kilroyjones]

It's two hits...first a pre-punch and then an extrude tool-->Extrusion | Punch Press Tooling Catalog | Wilson Tool Punch Press Job it to a sheet metal shop with a turret punch.

This is what I would look at first. Farm it out to a shop with a turret punch.

Where I use to work we made a part that was a 16ga strip and we would use a spot welder to weld a 1/4-20 tab based weld nut to the strip. That may be an option.