Newbie from Canada

[Karl]

Hello everyone. New to the forum and trying to get some insight into metal spinning. Run a machine shop in Barrie Ontario and by necessity need to learn to spin simple end caps in stainless. Have done a few but having some difficulty with getting 90 degree bends. Always has a slight taper and not sure how to overcome this. I'm hoping someone might have some suggestions. Have not tried annealing as we are trying to keep the material from obvious heat discoloration. Doing these in 304 SS x .035" thick. Flat diameters range from 4" to 6" with 1/2" long skirt.

[Peter Tommasini]

Hi Karl welcome to the forum
Peter

[cliffrod]

Welcome to the forum, Karl.

[neilb]

hi karl, welcome to the forum.

i have no idea about metal spinning but love the process, have you tried to create a slightly wider angle on your die, so you can go past 90 deg? i ask as just sitting thinking about the process the centrifugal force is going to want to pull that edge back out from the centre line.

just a guess and maybe something to try?

[Karl]

Thanks for the welcomes.

Going to try and add some photos of what I am doing. The taper I am getting is at the open end so my 4" cap is 4.020" at the opening. To compensate for the size we turned the aluminum mandrel smaller by .020". The open end comes out to 4.00" but it has this taper, which I don't care for. Being a bit of a perfectionist I would like to, if possible, totally eliminate or reduce this taper considerably.

Here's the setup I have. Tried spinning at 312, 558 & 765 rpm but didn't find much difference in the performance, not that I noticed anyway.


The 3 sizes I'm working on at present are 4.00", 6.00" & 8.00" O.D. all with a 1/2" long skirt.

[neilb]

[QUOTE=Karl;147722]Thanks for the welcomes.

Going to try and add some photos of what I am doing. The taper I am getting is at the open end so my 4" cap is 4.020" at the opening. To compensate for the size we turned the aluminum mandrel smaller by .020". The open end comes out to 4.00" but it has this taper, which I don't care for. Being a bit of a perfectionist I would like to, if possible, totally eliminate or reduce this taper considerably.

Here's the setup I have. Tried spinning at 312, 558 & 765 rpm but didn't find much difference in the performance, not that I noticed anyway.[QUOTE]

does the die you are working on have a side face 90 deg to the main face?

[neilb]

Originally Posted by Karl

Thanks for the welcomes.

Going to try and add some photos of what I am doing. The taper I am getting is at the open end so my 4" cap is 4.020" at the opening. To compensate for the size we turned the aluminum mandrel smaller by .020". The open end comes out to 4.00" but it has this taper, which I don't care for. Being a bit of a perfectionist I would like to, if possible, totally eliminate or reduce this taper considerably.

Here's the setup I have. Tried spinning at 312, 558 & 765 rpm but didn't find much difference in the performance, not that I noticed anyway.

does the die you are working on have a side face 90 deg to the main face?

[Karl]

Hi Neil,

Yes the side is 90 degrees to the face. One thing I forgot to mention is that we cut the stainless discs just slightly over the finished size. All the caps have the 1/2" skirt so we cut the discs to the required finished diameter + 1+ and give an additional 1/8" per side for finishing.
Example on the 4", we cut the disc slightly over 5 1/4" in diameter and once mounted we machine the diameter true to 5 1/4".

The tool we use is a bearing mounted wheel, 2" diameter x 5/8" thick. I have tried 2 different type of wheels. The first one we used had a large corner radius and a second one with a 1/32" corner radius.


The larger radius wheel leaves a smoother finish and the smaller radius wheel gives a tighter size. After we adjusted the mandrel by the additional .020" we achieved a 4.00" opening with the large radius wheel. When I used the small radius wheel we got a size of 3.98" opening. but both have this .020" taper over the 1/2" skirt length.

The cap on the left was done with the larger radius tool and the one on the right was with the small radius tool.

[neilb]

like I say I have never had anything to do with spinning but steel is steel, there will be some sort of spring back in the steel I'm guessing, along with dealing with the centrifugal force, the taper you have in the part of .020 I would try it with that about taken of your mandrels side angle instead of having a 90 degree it would be 85 degree or what ever it is.

Just thinking about It now if your part fitted to the mandrel exact with the 90 degree corner it would be a pain in the proverbial to remove it from the mandrel. having that under cut angle you could wiggle the part free?

but I'm just guessing here