How can I make a 10" OD bowl with a 2" r 2" high side from 16 or 18 gauge CRS ?

How can I make a 10" OD bowl with a 2" r 2" high side from 16 or 18 gauge CRS ?

I need to make a bowl shaped piece with a 6" od bottom and a side that is a 2"r and 2"tall making the top 10" on the od. This piece will then be cut in four 90 degree pieces to be used in corners of a reproduction inner fender for a Diamond T pick up. I wold like to make about 32 or more of these 90 degree pieces. I have not been able to find any info on spinning mild steel, and don't know if this would be a possible answer. Have also thought about turning a male and female die to press them out,a lot of work with unknown results. I have a 100ton shop press ,mill,lathe welding and other machine tools and don't mind spending time on this project if I thought I was heading in the right direction.I am open to
all direction and suggestions .

Thanks, Richard

My friend and I played around with spinning some steel sheet on his 15" Clausing Colchester lathe. We were making caps for a cylinder, just 3 or 4 inches in diameter. With a wooden mandrel turned to the inside shape, it was no problem to turn 18 ga. (I think) steel into end caps with practically a 90º bend. I imagine your bowl would be easy. He forged an approximation of a "sheepsfoot" tool to use (he does blacksmithing too), but you could probably buy one.

Encouraged by some youtube videos like those below, I made a one-off spinning of approximately your spec's, on my 17" LeBlond. I was more than pleased with the results, actually surprised.

Setting up the tooling is so easy compared to preparing and fine tuning hardened punch & die for your press, I'd sure give it a try first.

Here is 3 minutes to completion on a cone with strictly hand tools,
Metal Spinning, - YouTube

.....while a near straight sided bowl with 88° turns would be harder but entirely doable as shown here with CNC.
Metal Spinning of a can with a CNC Spinning lathe in 21/2 minutes - YouTube

Pay special note to how in each example, a near total sweep of the disk is made in each pass. Also, I frequently kissed the spinning part with a paint brush dampened with oil. I have no idea if that helped, just seemed like a good idea.

I brazed a blob of HSS* to a CR bar, ground and polished it, removed the compound and bolted on a fab'd fulcrum.
*on one of my frequent cruises of ebay a few years ago, I saw a heavy, HSS blade about 4" X 36" X 1", that no one was interested in and won it for near nothing. It was new, kinda hurt when I cut the first chunk off with an abrasive saw. It's been a great resource.

I was forming a part to mate two different componets of unrelated shop vac's, looks factory.

Bob
Edit: turned hardwood form in place and made a flat-faced part that went on the nose of a live center for the tailstock.

Spin it. You might like to see the process I used to spin some rather thick copper into cups:
http://db.tt/2kRsiALi

Your steel is easy in comparison.
Jim

I have heard of using a concrete top die, pressed into a "rubber" bed. It may in fact be a product other than rubber and I think sometimes
experimentation is required to get the correct durometer hardness. This is about all I know of this process but I'm sure a search would turn up plenty
of results. I may just have to do some research for my own curiosity when I have more time!
Rick

Bob, Thanks for responding. I watched the videos and I have three questions. 1. Could you give me an approx. rpm? 2. I was thinking about using a 1/2" diameter ball bearing ball for the forming tool. Alternates that I have would be a piece of HSS or piece of bronze or 1/2" diameter carbide burr ground smooth. Which would you recommend? 3. One of the videos I saw used a lever plus the forming tool. The others just showed a forming tool. Which did you use or recommend?
Thanks..... Richard

Robert Campbell Jr. said:

Encouraged by some youtube videos like those below, I made a one-off spinning of approximately your spec's, on my 17" LeBlond. I was more than pleased with the results, actually surprised.

Setting up the tooling is so easy compared to preparing and fine tuning hardened punch & die for your press, I'd sure give it a try first.

Here is 3 minutes to completion on a cone with strictly hand tools,
Metal Spinning, - YouTube

.....while a near straight sided bowl with 88° turns would be harder but entirely doable as shown here with CNC.
Metal Spinning of a can with a CNC Spinning lathe in 21/2 minutes - YouTube

Pay special note to how in each example, a near total sweep of the disk is made in each pass. Also, I frequently kissed the spinning part with a paint brush dampened with oil. I have no idea if that helped, just seemed like a good idea.

I brazed a blob of HSS* to a CR bar, ground and polished it, removed the compound and bolted on a fab'd fulcrum.
*on one of my frequent cruises of ebay a few years ago, I saw a heavy, HSS blade about 4" X 36" X 1", that no one was interested in and won it for near nothing. It was new, kinda hurt when I cut the first chunk off with an abrasive saw. It's been a great resource.

I was forming a part to mate two different componets of unrelated shop vac's, looks factory.

Bob
Edit: turned hardwood form in place and made a flat-faced part that went on the nose of a live center for the tailstock.

Click to expand...

rovinton said:

Bob, Thanks for responding. I watched the videos and I have three questions. 1. Could you give me an approx. rpm? 2. I was thinking about using a 1/2" diameter ball bearing ball for the forming tool. Alternates that I have would be a piece of HSS or piece of bronze or 1/2" diameter carbide burr ground smooth. Which would you recommend? 3. One of the videos I saw used a lever plus the forming tool. The others just showed a forming tool. Which did you use or recommend?
Thanks..... Richard

Click to expand...

As best as I can remember, about 70RPM spindle speed, which equates to 275SFM at the OD of a 15" diameter disk. I can't imagine that I went faster and I did work up to the eventual speed as my fear subsided. Once the part begins to enfold the form, there is little chance of it becoming dislodged.

Like I said, Richard, "I brazed a blob of HSS* to a CR bar, ground and polished it, " going on to discribe it as having been cut from a flat of 1" thick HSS. It was about an 1-1/4" button, an inch thick, brazed to the approx. 36" CR bar. I think 1/2" would be too small, you want to push the metal, not groove it. You might take your cue from the videos by comparison to the size of things you recognize in the films.

Though I didn't try it, I'd feel comfortable "upsetting"* a say 1-1/2" head on a 1" bar of cold rolled steel and polishing it. It must be smooth.
*heat about an 1-1/2" with torch to cherry red and stand on end over a anvil or resonable substitute and pound the heated region to increase its diameter. Grind and polish it smooth, I chucked it up with the bar through the lathe spindle to finish it. That and a lubricant film will do it. While I was lubing with oil, I thought I might try rubbing a bar of parrafin on it, should I do another.

Don't try to match the speed of either video in forming it, take your time and make a near full sweep of the disk each time. Start each sweep where you are convinced the part is against the form and pull a little more in.

Dont waste the opportunity to do any lip forming and/or trimming while its still bound to the form.

If by forming tool, you mean the rounded wheel, that might be good. At least it would get you well over the 1/2" working point you referred to above. It might be harder to "steer". I'd "caster" it back a little for increased control, unless YOU are the hulk or a CNC machine.

Bob

A broken off shovel handle can also be used. Any good hardwood can be used as a forming tool. That is what I would try for the first attempt. No need to to over think this for a first try. make sure your form has some taper so the part can come off. Floor wax on the form and the tool can help.
Kind of hard to center up the blank, I believe it is often put in place then the outer diameter is trimmed down with a wood lathe bit. Not sure if that will work with ferrous metal.
Bill D.

Guy down the road spins for a living, has a "assisted" hand unit (never seen it he described it)
hydraulically power assist to tools.

One offs in heavier material is the main market, not enough qty to justify a set up of a c.n.c. machine.

He did a simple "pizza pan" shape for us in 1/8" thick material, which sounds similar to what you need.