Tool for drawing a tapered tube

Hi

I repair musical instruments and recently watched this video
YouTube

Starting at 0:45 you can see the brass tube (cone) over a steel mandrel is drawn through... something. This is a common method to make trumpet tubes and I guess many other things. I've never seen it done for a tube, or rather a cone with such a taper.

I'm wondering how that works i.e. how whatever it is on the outer side can change the diameter but still push against it? Someone suggested that it is lead and just deforms to press against the tube? Is this the standard method? I'm colourblind so not sure if the material in the video is even metal (looked like it but looking again it has a weird colour compared with steel).

Thanks

I checked out the video, and I'm guessing (and it's just a guess) that it's an elastomer ring that deforms against the enlarging taper of the brass tube and mandrel as it's forced through by the driving ram. I think lead would start to fracture with the amount of deformation shown, even with the lube applied to the outside of the brass.

I suspect the elastomer is a polyurethane or similar, as it needs good stiffness with elasticity.

For all the grandeur of the company name and that they make musical instruments, that seems to essentially be another sweatshop.

I believe that it is a lead slug, possibly backed with a soft steel washer.

There is a similar video from the Bach factory in Elkhart IN, showing the drawing of a trombone bell. This is drawing the tube down on the tapered mandrel from the outside, like the trumpet bell.

I had not seen the process used to expand a tube against the inside of a taped form, but it clearly works.

The referenced video also shows using high pressure water to expand a tube against a steel form. This was a Conn patent back in the 1930's (if I remember correctly). King also used hydraulic expansion for producing large brass (tuba, sousaphone, euphonium) tapered sections.

A few years back, a couple of the faculty of the Redwing MN repair school demonstrated a way of drawing a trumpet lead pipe using a boat winch to draw the pipe on a tapered mandrel through a stack of soft washers. I believe they were using soft steel washers Their device had a simple steel beam for a frame.

Its a one-shot process. The lead slug or washer is permanently deformed in the process. They get remelted and reused.

-Jess

Thanks. Whoever told me it could be lead also said it might be something like polyurethane. I guess it's not possible to tell from the colour or anything else in the video what it actually is.

Re being a sweatshop, I don't know. It's a Taiwanese company and I have no relation to them. The video was posted to show the hydro forming, which is now standard on quite a few parts by several wind instrument companies. I was just curious how this drawing works since I've never seen it on a saxophone, only brass instrument (just to clarify saxophone is not a brass instrument even though it's usually made of brass).

You can see that the ring is being deformed as the taper is being drawn through it if you look at the footage from the back side. They probably consider it to be a one shot tool.

I am curious as to what lead you say it is a sweat shop. Is it something in the video, or do you have any experience with shops like that, or what?

Milland said:

I checked out the video, and I'm guessing (and it's just a guess) that it's an elastomer ring that deforms against the enlarging taper of the brass tube and mandrel as it's forced through by the driving ram. I think lead would start to fracture with the amount of deformation shown, even with the lube applied to the outside of the brass.

I suspect the elastomer is a polyurethane or similar, as it needs good stiffness with elasticity.

For all the grandeur of the company name and that they make musical instruments, that seems to essentially be another sweatshop.

Click to expand...

EPAIII said:

You can see that the ring is being deformed as the taper is being drawn through it if you look at the footage from the back side. They probably consider it to be a one shot tool.

Click to expand...

Fair enough, I was thinking that there'd be enough shear through the (lead?) doughnut that cracking would show up on the inlet side. As I mentioned in my post, it was just a guess on the material.

I am curious as to what lead you say it is a sweat shop. Is it something in the video, or do you have any experience with shops like that, or what?

Click to expand...

Just prejudice* on my part - the unkempt aspects, the pace, and the repetitive nature of the work gave me that vibe. I'm spoiled because most of my work is prototyping or very low quantities, so I get a lot more variety in what I do.

*Please accept my word that race does not factor here, only what I mentioned.