Milling an arc?

JeffF · Feb 28, 2013

I have searched the internet for days looking for how to do what I'm about to ask, but can't find anything for manual mills, only CNC articles. For some reason, I just can't get my head wrapped around this.

It will end up being two base standards to hold a flywheel between them. The flamelicker I am working on (the one Cogsy made) is the engine I am making these for.

Can someone tell me (or, even better point me to a video) on how to do this on the mill? I do have a rotary table, although I have yet to use it. Is this milled laying on it's side, or standing up?

I guess what I am looking for is a "how to" of how to mill ouside arcs on flat pieces.

Jeff

Mike N · Feb 28, 2013

Draw a little sketch of the arc you want to machine. It sounds like a rotary table job to me!

Jasonb · Feb 28, 2013

Rotary table laid flat on its back set the axis of the table to teh spindle axis, mark out all the centres of the arcs and locate each centrally under the spindle then offset the radius of the arc plus half the tool diameter.

J

cncjunior · Mar 1, 2013

If you want videos of rotary table use, youtube has some. Use the "rotary table" in search line. There are two below to get you started. The first is doing the radius by rotating by hand a plate. The second give you an idea though it isn't that great in instruction quality.

[ame]http://www.youtube.com/watch?v=am5774rnjtU[/ame]

[ame]http://www.youtube.com/watch?v=-RGyP6PYnGc[/ame]

It is hard to describe the operation without seeing a set up of rotary table use. They are very handy for arced profiles. Math is needed for the complex arcs thou switching from linear measurements to degree measurements.

JeffF · Mar 1, 2013

It is hard to describe the operation without seeing a set up of rotary table use. They are very handy for arced profiles. Math is needed for the complex arcs thou switching from linear measurements to degree measurements.>

Those were helpful. I have watched tons of videos talking about the rotary table in general, but can't seem to find any that show someone milling out an actual arc. The second video you linked too, does at least show a small version of that. I wish I could find one that shows how to set up a piece on the table to mill a top arch (like one would see on the top of a support piece for a flywheel) and then see the actual milling process. I am less concerned about getting an exact arc, than I am just figuring out how to make any arc at all, since in this case, it is decorative only.

Nevertheless, thank you!

Jeff

Brian Rupnow · Mar 1, 2013

In the book "The Shop Wisdom of Philip Duclos" ISBN13:978-0-941653-04-6 which can be purchased from Village Press in Traverse City, Michigan, USA. there are plans for a number of very neat engines, how to make your own piston rings, and an in depth article on how to make a curved spoke flywheel, which does indeed incoroporate the milling of arcs, and all of the attendant geometry for laying them out.---Brian Rupnow

Lakc · Mar 1, 2013

If you cant wait, the instruction pamphlet from the Sherline rotary table shows some of that, and should be available for download on their site.

gcude · Mar 1, 2013

As Jeff says, here is the Sherline page(s):

http://www.sherline.com/3700inst.htm

--
Gary

weez · Mar 1, 2013

Check out the following links. I found them quite informative.
http://www.homews.co.uk/page70.html
http://rick.sparber.org/rtcs.pdf

easymike29 · Mar 2, 2013

This doesn't explain how to mill an arc but may show you the concept.

MachineTom · Mar 2, 2013

Assuming you do not have a DRO with the software to do this, if you provide me the details of the arc, starting position will be 3:00 as on a clock with 6:00 being the Y handle 12:00 being the machine base, Radius of arc, size of EM, # of points that you would drill and total degrees of arc.

I'll copy the results in X-Y position, So you end up with a saw tooth profile from the holes, then file/grind the arc smooth. I have found that a pilot hole of .125" then follow with a 1/4"EM worked best, advance 60% of the EM Dia.

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