MetalworkingFun Forum

I need to bore some 1" holes through the middle of a piece of aluminum/aluminium tubing. What's the best way to get the spindle of the mill over the highest point on the tubing? I've have one of these and have used it but I don't think it's accurate enough for this application.

Center Finder

Attached is a picture of the part I'm making.

Thanks,
Ed

[attachment=6315]

Answering my own question but after I posted the question I realized I could likely do it with one of these edge finders.

Ed

[attachment=6316]

I find it's more accurate to use a dial test indicator on a long arm. You might not be able to reach the tangent point of a 1/5" radius with one of those.

(09-04-2013, 12:43 PM)PixMan Wrote: [ -> ]I find it's more accurate to use a dial test indicator on a long arm. You might not be able to reach the tangent point of a 1/5" radius with one of those.

Ken,

That's my concern also.

My first thought was to use a dial indicator but how do you keep the contact point in line with the axis of the mill spindle?

Ed

finding center is easy once you get it lined up on the mill table so that its straight. I take that the holes have to be in alignment to the center of the tube right

DA

(09-04-2013, 03:45 PM)dallen Wrote: [ -> ]finding center is easy once you get it lined up on the mill table so that its straight. I take that the holes have to be in alignment to the center of the tube right

DA

Correct.

Ed

I do this:





But I use a full diameter 1/2" center finder and leave the .200" tip for small diameters.

Ed,

You can also use an dial test indicator to center a part. Just swing the indicator on each side of the part and adjust the table until it reads the same on each side. If you do it on a piece of tubing, set your quill stop so you can set the indicator to the same level in Z on both sides of the tube (preferably at the center).

Tom

I run the indicator up & down to find the high point of the radius and side-to-side to find the low point of the straight at centerline, then adjust the Y axis until the readings are equal.

If the work is too large for an edge finder, lean a square against it and reference from that. In a similar fashion you can reference from a vice jaw. You can also kiss the top of the work with a small endmill and eyeball it, the middle of the narrow line it produces will be center.