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Ovals
Feb 28, 2007 13:57:28 GMT
Post by alanstepney on Feb 28, 2007 13:57:28 GMT
I need to produce several pieces of oval metal, some aluminium, some steel. They have to be 3/8" x 3/16" and lengths between 3" and 8".
I have a couple of ideas, but would welcome suggestions.
Easy with CNC (I assume) but as I dont have that and dont want to pay someone else to do it, any other ideas?
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Myford Matt
Statesman
There are two ways to run a railway, the Great Western way, and the wrong way.
Posts: 621
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Ovals
Feb 28, 2007 14:02:43 GMT
Post by Myford Matt on Feb 28, 2007 14:02:43 GMT
Do you mean oval 'extrusions' 3" to 8" long with an oval cross-section of 3/8" by 3/16"?
MM
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Ovals
Feb 28, 2007 15:17:02 GMT
Post by Jo on Feb 28, 2007 15:17:02 GMT
Get them red hot and use rollers?
Custom milling cutter? Something like a DP gear tooth cutter. Cut either side then rotate by 180 degrees. That way you would only have to support the work at the dimension you already know.
Jo
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John Lee
Part of the e-furniture
Posts: 375
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Ovals
Feb 28, 2007 16:30:19 GMT
Post by John Lee on Feb 28, 2007 16:30:19 GMT
Alan,
You have excluded CNC, although as a completely separate topic a CNC mill gets arounds lots of difficult bits like this.
A copy lathe would be the "old" industrial tool of choice, can you adapt some ideas from that? The effort expended would need to be balanced against how many of these you need of course.
What are your "couple of ideas"? Perhaps comment on here could refine those, if needed, into a practical solution.
Regards,
John
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Ovals
Feb 28, 2007 18:52:16 GMT
Post by alanstepney on Feb 28, 2007 18:52:16 GMT
Matt, that is exactly what I mean.
John, I can imagine this being childs play on CNC. However, I dont have it and doubt my ability to learn how to programme one anyway.
The ideas so far are, 1) grind up a milling cutter to half the profile, then run the metal through in two passes, hopeing that the "joins" meet!
2) ditto but for the shaper. Much easier to make the tool for that.
2) Chuck the bar in the lathe and turn off the widest parts, thus leaving a rectangle with rounded ends. This ends to be the smallest radius.
Then make a jig to hold them at a wide radius, probably close to the edge of a faceplate, turn so as to machine one side to the large radius, then reverse in jig and ditto for the other side. Might be easiest, and better balance, to make two jigs and do two at the same time. Then, there would just be some hand work to blend the two radii.
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Myford Matt
Statesman
There are two ways to run a railway, the Great Western way, and the wrong way.
Posts: 621
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Ovals
Feb 28, 2007 19:25:13 GMT
Post by Myford Matt on Feb 28, 2007 19:25:13 GMT
A few things spring to mind.
1. What's it for, or rather how accurate does it need to be? 2. 'Oval' is not a strictly defined shape in a geometrical sense, in say the way an ellipse is. Does it need a particular profile? Is it symmetric in both axes (like an ellipse) - or not, like an egg. 3. The answers to these questions will determine how easy, or otherwise, it will be to make a form tool. 4. I’d take the corners off with a mill and then use a form tool, again in the mill
MM
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Ovals
Feb 28, 2007 20:05:41 GMT
Post by alanstepney on Feb 28, 2007 20:05:41 GMT
1. "Fairly" or within a thou or two. 2. OK, elliptical is perhaps what I should have said. 3. Form tools are, in my experience, never as easy as I expect them to be! lol 4. Possibly. I'm still trying to decide, and hoping that someone may have a brilliant and simple idea.
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Myford Matt
Statesman
There are two ways to run a railway, the Great Western way, and the wrong way.
Posts: 621
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Ovals
Feb 28, 2007 21:05:48 GMT
Post by Myford Matt on Feb 28, 2007 21:05:48 GMT
If you were to mount a piece of form tool steel at 30 degreees to the horizontal and drill down with a 3/16" bit, the shape of the hole (either side) would be an ellipse with the dimensions you specify.
Equally, with the same set up, you could use a 3/16" end mill and cut half an ellipse into the edge.
This might be the basis for a form tool (you would have to find a way to grind away material underneath the ellipse, which might be tricky.
MM
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SteveW
Elder Statesman
Posts: 1,399
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Ovals
Feb 28, 2007 23:15:04 GMT
Post by SteveW on Feb 28, 2007 23:15:04 GMT
Alan,
Are these things for show or will they be structural?
I occurs if the former you could make a simple set of rollers and attack some appropriately sized tube. This'll be practical for softened aluminum tube but would require a bit more grunt on steel tube.
The other solution would be as per a cam production jig from the Edgar T school of fiddling.
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Ovals
Mar 1, 2007 22:22:28 GMT
Post by alanstepney on Mar 1, 2007 22:22:28 GMT
I like the idea of using tube. One I hadnt thought of.
The suggestion of picking ETW's brains is also a good one.
Of course, a geometric chuck would work, if I had one!
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Ovals
Mar 29, 2007 13:14:19 GMT
Post by bar313 on Mar 29, 2007 13:14:19 GMT
Alan, An elliptical chuck on an ornamental turning lathe with the metal turning slide rest would do the job.
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