Milling circles/ holddowns?

[m8kingit]

I'm anewbie here and just curious what you guys are using for hold downs on your metal mills.
On my wood router, it's not much of a question, because i can either use contact cemet, fasten it to the spool board or use a vacuum clamp.

I have ane wcnc master's jr that i'm ready to fire up andhave already run into a few obstacles that i didn't think about.
Like i said I'm a newbie here, so be nice.

My main question concerns holding down a circle that's being completely cut from a piece of stock. I know , I can edit the g code and pause it part of the way around it, then reset and restart, but i was wondering if there is a way to do it without, changing the hold downs or pausing the software.
Thanks in Advance all help appreciated!
mark

[littlerob]

Originally Posted by m8kingit I can edit the g code and pause it part of the way around it mark

You will leave a "dimple" in the part if you do that.

I guess I don't understand the problem, why can't you use toe clamps?

[BobWarfield]

littlerob, if he toe clamps, he can't cut the circle all the way around, and will have to pause to reset the clamps and will encounter the problem you suggest.

If the circle really has no internal features that allow clamping (often a small feature is enough to allow bolting down), and you want to cut the whole circumference in one shot there are a couple of approaches.

First, you can cement the part down just as you do with you router provided the cutting forces aren't going to knock it loose.

Another approach is to use material slightly thicker than the finished part. Mill the circle to finished depth. This is going to leave your milled circle edge clean, but the part is still embedded in the workpiece by that difference in thickness. Flip it over clamp the piece down at the edges, make sure there's room for the part to drop, and then facemill that thickness away to drop the part out.

Yet another approach is to mill all the way around to partial depth, and mill widely enough that you can flip the workpiece and seat your disc (that much that is exposed) in a set of custom cut softjaws in a vise. Cut the rest with the part flipped.

There's a ton of other approaches, those are some simple ones to ponder a bit.

Cheers,

BW

[m8kingit]

Originally Posted by BobWarfield littlerob, if he toe clamps, he can't cut the circle all the way around, and will have to pause to reset the clamps and will encounter the problem you suggest. If the circle really has no internal features that allow clamping (often a small feature is enough to allow bolting down), and you want to cut the whole circumference in one shot there are a couple of approaches. First, you can cement the part down just as you do with you router provided the cutting forces aren't going to knock it loose. Another approach is to use material slightly thicker than the finished part. Mill the circle to finished depth. This is going to leave your milled circle edge clean, but the part is still embedded in the workpiece by that difference in thickness. Flip it over clamp the piece down at the edges, make sure there's room for the part to drop, and then facemill that thickness away to drop the part out. Yet another approach is to mill all the way around to partial depth, and mill widely enough that you can flip the workpiece and seat your disc (that much that is exposed) in a set of custom cut softjaws in a vise. Cut the rest with the part flipped. There's a ton of other approaches, those are some simple ones to ponder a bit. Cheers, BW

The dimple part is what i was originally gettting at, if i was to reset and restart.
What type of cement or glue would a person use, if i was to use that method. With the wood. I can use something simple then release it with a solvent, but with the metal what do you use that won't be user friendly in that it will allow you to remove it once you're done.

The latter method you described sounds like a good idea, but i'm still open to a couple more options.
thanks
Mark