I'm stumped .

I have a reuleaux shaped piece of 3/16" plate.  The reuleaux is 8" on the side.  There is a 3-1/2" circle cut with a bias toward one corner.   I am trying to forge a bowl from the plate and then 'suspend' a 3" brass plate inside the circle in the bowl.  Currently I am forging the bowl shape using a fly press and 'smushing' the plate between two bowl shaped swages.  The result is a nice bowl shape from the reuleaux plate.  The plate is heated thoroughly to try to keep the metal flowing evenly during forging.  

Unfortunately the original circular hole is distorted during the smushing.  I'm thinking I might be able to reforge the hole if I had a cone. However, no one within 4 hours of me has a cone I can borrow.  

Short of making a conic section from some strap, I'm a bit stumped about how to maintain the circular characteristics of the hole. Is there any thoughts on how to selectively heat portions of the plate to recover the circular shape?  

Image 1 (far left, B/W) is the flat reuleaux plate with the brass disk. Image 2 (middle) is the best I've been able to achieve and the pic looks better than it is. Finally, the image on the right is sort of a before and after picture of a second attempt which ended up even worse.  

Thanks for any suggestions, 

Dave
Iron Rain Forge
www.IronRain.us

[For the curious, these are awards for a juried sculpture show in our artsy little town. The brass plate will be etched with info related to the show, date, place, etc. and will be suspended in the hole using small copper loops.] 

 

Forge first then cut the hole.  When forging, think about the metal's resistance to movement.  It'll always move at the point of least resistance.

Selective heat may help if you made the mistake of cutting a bunch of these shapes before forging.

The result of forge first then cutting looks like ... well, really bad even when done by a real pro with a plasma torch.  

Mistake?  I bow to your superior judgement. 

Custom fit the brass plate to each hole! Each award would then be unique in its own way! 

Try cutting the hole with a carbide tipped hole saw with a steel rod in place of the pilot bit.

8 hours ago, RogueRugger said:

The result of forge first then cutting looks like ... well, really bad even when done by a real pro with a plasma torch.  

Forge first, cut hole undersize, shape hole with files and/or die grinder.

 

If you still have, or can get them, you might try tacking the slug back into the hole. Then dishing the piece, then removing the slug. The mass of the slug will help with the hole distorting. Al

if you plan to make a lot of these your going to have to make press type tooling just for it

 

Idea weld some hole slugs together then weld to bottom dish then cut hole in top dish die &

taper slug stack so pieces will not lock down into jig also mite need punch out hole so you can get part out of jig

a bit of work to make ! should work though ! Ho use forging lube to will help in removing part from jig

Hole saw after forging the bowl shape.

If torched out use a trepanning tool to get the proper layout first. Besides rotating it will also need to move up and down. Easy enough to make one. Then use the slug to lay out the others.

Have them milled at a machine shop

If you want to cut the hole first then backwards engineer your finished sample. This will tell you how much "bad" draw you got (Out of round).  Subtract the "bad" surface area from your original round hole. 

Meaning, and as a quick guess, you need to start with a horizontal oval, not a circle.

Actually, if you have a lot to do, this will save you much heartache and cleanup.

Try it in modeling clay first to see how it reacts. But I would go with a hole saw myself.  Keep it simple.

On 6/15/2018 at 5:52 AM, Judson Yaggy said:

Try cutting the hole with a carbide tipped hole saw with a steel rod in place of the pilot bit.

yeah, I think this is what I'm going to do.  Sorry to be dense, but any reason for the steel rod replacement?  

Thanks to all for the great suggestions.  I actually had made a few blanks with and without the pre-cut hole.  I hadn't expected quite this much distortion, and want to still figure out how to keep it from happening.However, running into a time crunch on this and need to get moving on this. Too many things in the queue.  

 

Any suggestions on a good source for quality hole saws?  

 

Thanks again for the ideas. 

14 hours ago, BIGGUNDOCTOR said:

Try it in modeling clay first to see how it reacts. But I would go with a hole saw myself.  Keep it simple.

Clay is always a great idea for stuff like this and I hadn't thought if it.  Unfortunately a quick test didn't quite react the same, which I don't quite understand either. so much confusion. sigh.  

As you say, simple is good and am going to go with the hole saw. 

 

1 hour ago, RogueRugger said:

.  I hadn't expected quite this much distortion, and want to still figure out how to keep it from happening

You cannot keep it from happening. You just need to know how to cut your original hole to get what you want to end up with,,, as I explained above.

When you bend a piece of iron, some edges will be upset and other edges will become drawn out. This is basic blacksmithing  and you cannot change or prevent this. Thus you can only learn how much draw and upset you will get and where, then apply this to your original hole.

Or, not worry about it and cut it out after you shape your piece.

 

 

I suspect the reason for the rod in lieu of the pilot bit is so you can gain the necessary length to align the hole saw.  If it were long enough, you could potentially route the rod through a guide hole underneath the piece.  Assuming you're using a drill press, you'd have the saw locked in like a spit-roast which would minimize any wander as you cut on the sloped surfaces. 

DO NOT HAVE HANDS NEAR THE WORKPIECE WHILE CUTTING THE HOLE.  Can you have them laser cut or waterjet cut after shaping?

Thanks to all for the suggestions. While the hole saw seemed to be the consensus as the easiest approach, it got a bit complicated when considering the safety aspects of drilling through the bowl.  I almost tacked a couple of cross pieces, somewhat like the suggestion by +IronWolf. I should have kept the slugs for no other reason than I could have used them for something else; hindsight is always 20/20. I think the cross pieces would have worked pretty well. 

I ended up simply accounting for the differences in the expansion of the different sections and finished all three pretty quickly.  Some selective cooling and heating. Not prefect, but pretty close.  (someone suggested this was not possible and I don't understand that word as well as I probably should.) There still some clean up to do on the ironwork, the etching, and of course, the attachment. 

Thanks again for the great suggestions. 

 Dave

Iron Rain Forge
www.IronRain.us

[Edit: the large distortion of some of the holes in the picture is due to perspective.] 

That looks very nice. In a sense, the irregularity of the forged hole adds to its charm, especially contrasted to the mathematical perfection of the brass disk.

Gorgeous work, Rain.  I think they came out perfect, and the little oddity to the steel circle only makes the piece look better.  Something of a Japanese aesthetic, I'd say.

My suggestion when just now seeing this thread was the same as Anvil's..    Figure out the amount of distortion and subtract it.. This is the way I have done this kind of thing.. 

After seeing the replies and you being happy with the results is good enough for me..  Well done.. 

Practice makes perfect. The last one looks fine.  If you think you can or need to get it better. You will.

Hmm in the future what about using the deformation to make an eye with a golden pupil? A good award for art!

 

On 6/22/2018 at 12:17 AM, RogueRugger said:

While the hole saw seemed to be the consensus as the easiest approach, it got a bit complicated when considering the safety aspects of drilling through the bowl.

Isn't just a case of...

Putting a bit of wood on your bench, put the bowl on that face down & clamp it to the wood/bench so the convex side is face up (and you're not damaging the corners with steel on steel), get the hole saw, offer it up & draw around it, find the centre, drill a pilot hole the same size as whatever size bit goes in the holesaw, put the hole saw on a cordless drill along with the pilot bit/replacement pilot rod in the centre...and drill.

Thought there might be some interest in the final result.  Ran into a time crunch due to a series of health scares, so i had to compromise on the design a little bit.  Still reasonably happy with the results.  FWIW - These are the awards for the Creede Sculpture Show this weekend. 

 

 

Nice!

Excellent!

Are you from Creed, or the surrounding area?