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Pherdie
03-11-2010, 05:53 PM
Is there a way for an HSM to produce an oval plate using a single setup??

I realize that three different realignments (foci/centers) can be used in totality to produce an oval (assuming you can get the multiple circumferences to properly transition at simultaneous tangental points!!), but I'm wondering if I'm overlooking an easier more precise approach, using just one set up. I'd like to produce a 2" x 1" oval, 1/2" in thickness (mild steel).

Fred

Black_Moons
03-11-2010, 06:02 PM
Sure, just build one of these:
http://woodzone.com/Merchant2/graphics/00000001/oval-jig.jpg
the two 'tabs' slide in the two slots and create an oval motion depending on the distance beween the two (where they are connected to the main 'beam')

JoeCB
03-11-2010, 06:27 PM
Well if you only have to make one and you are not doing this for a living.. I would start out in the lathe, make a 1/2 in thick mushroom head 2 " dia on a 1" dia stalk. Set this up in the mill and get out your computer,,, calculate and tabulate all the X - Y offsets based on say .005 steps in the X direction.. and have at it for an evening or two.

Joe B

Evan
03-11-2010, 06:36 PM
The term "oval" has no rigourous meaning. Therefore there is no formula or specific method to make one. It simply means a shape somewhat like the outline of an egg since the word is derived from "ovum" which is Latin for egg.

If what you want is an elipse then it is a different matter. The coordinates for an elipse may be calculated to what ever degree of precision you require.

KiddZimaHater
03-11-2010, 06:37 PM
Just brainstorming, but an arm attached to the mill near the spindle could be used as a crude tracer, (kinda like a Pantograph), to trace a stencil mounted on the table next to your part?
??? Maybe ???
http://img717.imageshack.us/img717/8765/armv.jpg

lazlo
03-11-2010, 06:44 PM
There's a great article in HSM magazine within the last 3 years about making a ellipse jig. It was called "Something is out of round," or some such. At a 10,000 foot level, it was the jig that Black Moons posted with acme screws to set the major and minor axes. I'll see if I can find it...

Black_Moons
03-11-2010, 06:55 PM
Just brainstorming, but an arm attached to the mill near the spindle could be used as a crude tracer, (kinda like a Pantograph), to trace a stencil mounted on the table next to your part?
??? Maybe ???

Thats a pertty cool idea actualy. Especialy if you did something like mount a TDI on the end of the arm. just align TDI to X axis, continualy feed Y axis and adjust TDI to constantly read 0. swap X/Y axis once you pass 45 degrees around the template :)

Of course, then you need an oval template to start off with.. but whatever.

If accuracy is not as criticial, just a printed sheet and a needle could likey produce an oval accurate enough to just require some light sanding to make it 'appear' perfict.

easymike29
03-11-2010, 10:15 PM
A cross slide on a rotary table will do it.

Gene

Ian B
03-12-2010, 01:47 AM
Pherdie,

What's it for, how big, how thick? That might affect the suggestions on how to make it.

eg. if it's shim stock you're making it from, sandwich it between hardwood discs, bolt the sandwich to a rotary table. Mount the r/t at an angle on the mill's table, fit a long series endmill and just mill away - you'll get an oval (ellipse?). It'll be an oblique slice through a cylinder. The more the angle, the less round the oval will be.

Ian

Astronowanabe
03-12-2010, 03:00 AM
make a "smoke grinder" or "bullsh!t grinder"

OR

cut a slice out of a 1" rod at a 26.5651 degree angle and mill or grind
anything that is not perpendicular to a face

MuellerNick
03-12-2010, 03:07 AM
Tilt the spindle about 30°, insert an appropriate tool for outside work (not boring here) into the head and feed at the Z-axis (NOT the quill).

Done.

Nick

oldtiffie
03-12-2010, 05:46 AM
Is there a way for an HSM to produce an oval plate using a single setup??

I realize that three different realignments (foci/centers) can be used in totality to produce an oval (assuming you can get the multiple circumferences to properly transition at simultaneous tangental points!!), but I'm wondering if I'm overlooking an easier more precise approach, using just one set up. I'd like to produce a 2" x 1" oval, 1/2" in thickness (mild steel).

Fred

Fred.

As good a method as any is to use the ("old-fashioned") manual drawing board method (4 tangential arcs) which requires a straight edge, a pair of dividers, a centre punch and hammer and some "Dykem" (blue mark-out fluid) or similar.