Spinning aluminum

moonlight machine · Jan 9, 2021

I have not spun anything since high school. About 50 years ago! I need to make a set of stacks for an ancient Hilborn fuel injection manifold. Figured I would machine a split form that will clamp on a piece of 2 1/2" od aluminum tube. The form for the trumpet will be in the split form. First step would be to anneal the tube and clamp it in the split form, then clamp it in my lathe chuck. It seams in school we had forming tools that were a wood handle with a 1/2" or so rod with a ball on the end.
Will this sort of tool work ok when forming a trumpet on a tube. How many RPM? seems like the spinning lathe we had in 9th grade metals class was pretty fast but it was 50 years ago and I was just a pup so what do I know?

moonlight machine · Jan 9, 2021

Somebody here must do some metal spinning????

EmGo · Jan 9, 2021

moonlight machine said:
Somebody here must do some metal spinning????

I never did it but we had wheel covers spun, so I watched several times. It seems you want to take a tube and put it inside a mandrel then spin it outwards ? The guy I watched would have made a male mandrel, then used a piece of flat sheet, pushed the tailstock up against it to drive, and spun downwards over the flared male mandrel. I think that's how many light fixtures are done, too.

Can't do the full radius that intakes have now that way, but they didn't do that back then anyhow.

moonlight machine · Jan 10, 2021

EmanuelGoldstein said:
I never did it but we had wheel covers spun, so I watched several times. It seems you want to take a tube and put it inside a mandrel then spin it outwards ? The guy I watched would have made a male mandrel, then used a piece of flat sheet, pushed the tailstock up against it to drive, and spun downwards over the flared male mandrel. I think that's how many light fixtures are done, too.

Can't do the full radius that intakes have now that way, but they didn't do that back then anyhow.

Ya I want to use seamless 6061 .035 wall 2 1/2" diameter tubing. I would like to put a trumpet on it to about 3 1/2" diameter and around 2 1/2" long. I wonder if there is enough wall thickness to do this? The material to add an inch in diameter has to come from somewhere. If I can't get it to work I guess I could machine them and have them slip over the stacks. I would much rather make them from 1 piece.

EmGo · Jan 10, 2021

You should have an original to go from, what did they do ?

adh2000 · Jan 10, 2021

When I was working in Camarillo there was a shop behind us that did Al spinning. I used to watch sometimes during lunch. They turned the metal pretty slow, like half the speed you'd use if you were turning. The tool for crowding the metal had a bearing on the end. I think that's important otherwise too much friction. Also they didn't move the metal much before they took it off and put in an oven to anneal it. I'm not really sure but I think it was some 2000 series alloy, definitely not 6061, 2024 maybe. I got the feeling it was one of those things that looked easy because they had a process and worked the bugs out.

Rob F. · Jan 10, 2021

I have a spinning lathe but have only done flatish steel "dishes" with it. From what I have learned is you probably want to make an internal mandrel, could be hard tight grain wood, and start with a 3 1/2 tube and go down to the mandrel. Tool could have a roller on the end or just smooth ball, use lube.
Internal mandrel can be long slivers that nest together so they can come out one at a time, if there is a danger of them being trapped after spinning.

Watch near the end of the vid to see mandrel for these water bottles:
Copper bottle manufacturer in India - YouTube

Trueturning · Jan 10, 2021

moonlight machine said:
I have not spun anything since high school. About 50 years ago! I need to make a set of stacks for an ancient Hilborn fuel injection manifold. Figured I would machine a split form that will clamp on a piece of 2 1/2" od aluminum tube. The form for the trumpet will be in the split form. First step would be to anneal the tube and clamp it in the split form, then clamp it in my lathe chuck. It seams in school we had forming tools that were a wood handle with a 1/2" or so rod with a ball on the end.
Will this sort of tool work ok when forming a trumpet on a tube. How many RPM? seems like the spinning lathe we had in 9th grade metals class was pretty fast but it was 50 years ago and I was just a pup so what do I know?

It is really something all of the real world machining that has existed which is now unused and largely unknown. Thus is a large part of what manufacturing has become and so true skill and craftsmanship is largely the realm of enthusiasts today. I was trained by the guys who had lived that level of contribution.

They were the very best and the times they would step out of retirement to do their own projects or to help the shop are things of the past. Today most companies would not allow it out of fear a old timer may get hurt and then the shop could be sued.

EmGo · Jan 10, 2021

moonlight machine said:
I wonder if there is enough wall thickness to do this? The material to add an inch in diameter has to come from somewhere.

Seems like Rob has the better idea, start with larger tubing and spin it down.

moonlight machine · Jan 10, 2021

EmanuelGoldstein said:
Seems like Rob has the better idea, start with larger tubing and spin it down.

with an open tube I think it may be hard to resize it an inch smaller over an 8"
long area

moonlight machine · Jan 10, 2021

EmanuelGoldstein said:
You should have an original to go from, what did they do ?

I have an original, it is steel and shows no sign of how it was made.

EmGo · Jan 10, 2021

moonlight machine said:
I have an original, it is steel and shows no sign of how it was made.

Turned from solid (or thick wall tubing) on a tracer lathe ? Is that the kind that's threaded on the bottom with a lock ring ? I bet Norm Rapp had some originals piled in the back room

If you have any freedom in 'interpretation' you could make the staggered kind. Those are cool.

Rob F. · Jan 10, 2021

moonlight machine said:
with an open tube I think it may be hard to resize it an inch smaller over an 8"
long area

Are you using engine lathe? If so do the final sizing with the tool in compound to keep it straight.

Mount the tube in the lathe at double length, air spin the cone down to 2 1/2" all the way to the other end where the other cone is. This gives you tailstock support. Use power feed on your lathe to keep it straight. Cut in half when done.

If you have the 2 1/2 tube try to just air spin it out in the cone you need. watching for cracks , excessive thinning etc. Air spinning is with no backing mandrel. You just have to watch the size closely, if that works then make your split mandrel so they all stay the same.

moonlight machine · Jan 10, 2021

EmanuelGoldstein said:
Turned from solid (or thick wall tubing) on a tracer lathe ? Is that the kind that's threaded on the bottom with a lock ring ? I bet Norm Rapp had some originals piled in the back room

If you have any freedom in 'interpretation' you could make the staggered kind. Those are cool.

Ya, I used to work on a McLaren with an aluminum big block, those staggered trumpets look awesome. It's done to get a flatter torque curve, just what you need in a 1300lb car with an 800hp big block. No it is the kind that has 2 pieces of 5/16 x 1/4" tall braised on opposite sides and uses an 8-32 screw to hold it on. Doubt it is turned from solid, it's only .032 thick. I worked on an M8 with a DOHC Aston Martin V8 as well, don't know if it was any good as the driver was a wanker. (vintage "racing")

moonlight machine · Jan 10, 2021

I was thinking, Make a form for the inside, 3 1/2" dia. straight for 2", then the trumpet, then the 2 1/2 straight for 8" with a center hole for the tailstock. slip the 3 1/2" tubing over the straight and hold it in the chuck. slip a removable ring inside the 3 1/2" tube, have a good fit between the form and the ring. Remove the ring after most of the stack is formed. What do you all think?

machinistrrt · Jan 10, 2021

moonlight machine said:
Ya I want to use seamless 6061 .035 wall 2 1/2" diameter tubing. I would like to put a trumpet on it to about 3 1/2" diameter and around 2 1/2" long. I wonder if there is enough wall thickness to do this? The material to add an inch in diameter has to come from somewhere. If I can't get it to work I guess I could machine them and have them slip over the stacks. I would much rather make them from 1 piece.

I have a couple of pdf's on spinning. Pretty elementary, but they advise using 1100 or 3003, likely easier to form.
If you want copies, PM.

Rich

moonlight machine · Jan 10, 2021

machinistrrt said:
I have a couple of pdf's on spinning. Pretty elementary, but they advise using 1100 or 3003, likely easier to form.
If you want copies, PM.

Rich

I know
I can get 3003 in .035 wall I don't know how hard it is but it's easy enough to aneal.

3t3d · Jan 10, 2021

A lot of people out their seem to all do it the same way... Except the first link.

Velocity stack yapimi Turkey - YouTube

how to make a velocity stack - YouTube

How To Make Velocity Stacks - YouTube

Tim from Kelford Cams spinning his own velocity stacks - YouTube

Making velocity stacks on the lathe - YouTube

Making velocity stacks on the lathe - YouTube

72bwhite · Jan 12, 2021

I did something similar with simple die and a 20 lb hf press
Turned em out of mild steel polished em up good then used cherry red to case harden.

Now that was working with 304ss not Al.

More then one way to skin that cat

Garwood · Jan 12, 2021

Forming and 6061 don't belong in the same room.

Aluminum spinning I have limited involvement with uses 5052.

from tubing 6063 forms nice. not sure about spinning though.

Spinning aluminum

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