Finding center...

Measure it accurately and then just divide by two, only need to find one side that way. Offset in the vice to get one side touched off. Straight edge on 123 blocks should reach. Heck, a creative stack of just 123 blocks would work.


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shorton said:
Thansk guys.
My edge finder won't reach the middle
I can use a piece of drill rod and a feeler gauge, hadn't considered that.
Nervous about shaving an oval in it. I might screw that up.
The indicator plan sounds interesting.
The ring is about 6" OD, so I can't really get a straight edge up against both sides very well. It's exactly as wide as my vice so the vice mount gets in the way.
I could put a bigger square on 123 blocks or something, but I don't have enough room on both sides of my vise (without remounting vise), and my squares are limited, too.
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Try a 3/8" or 1/2" drill blank. depending on your chuck size. I have used a transfer punch. Make sure the pin is straight and true. If you had a DRO on your mill then just it zero out then move the table over until the pin touches the other side minus the diameter of the pin you chose to use. If I am thinking correctly that should give you the outside diameter. If your mill doesn't have a DRO then it is a little more paper work but the process is the same. I remember counting the number of turns of the dial on some of those older milling machines.
 
hvontres said:
if you use a mill that is smaller than the hole, the flat will be completely gone. Another potential advantage of this method is that you get a nice flat surface for the drill to start.
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A good and fast way to better see the flat is to color the piece with Dykem before to mill it.
 
If you are real conservative of your time or in other words lazy you might try this. Put your end mill in and find your cross center then go to the right or left to the point where you will not hit the pipe, rod whatever lower the end mill a little past the center line and get a piece of tissue or other thin paper put the paper against the side of the pipe and bring the end mill to barley torch on the paper not under power and you will be within a couple of tenths. The nice thing about this method is that there is always a piece of paper around and with a little bit of practice you will be amazed how accurate it can be, if you do it half ass not so much.
 
Also, why do you have to use your vise? Can you hold it down to the table?
 
Mount an indicator in the spindle and sweep back and forth left to right and the "highest" reading is top dead center.
 
Dataporter said:
Since you have a DRO, you could find center front to back with your edge finder. Then move off to one side on center. Lower the spindle down as far as you can. Come back and find the "edge" of the part at that height (even though the point of contact is somewhere along the arc of the part). Then go to the opposite side of the part, again at the center front to back, with the spindle/edge finder at the exact same height, and find the opposite "edge" at that height. Split the difference between the "edges" found. You will be pretty darn close! You could try the same process described above again at another height just to check yourself! A circle is a circle! One half is a mirror of the other.
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This is how I just did a arbor for my shop press.
 
A quick and dirty trick is to put a center drill in the chuck eye up center then place a 6"rule or stiff feeler guage under it bump the drill down to the rule/guage if it tips right or left it is not centered adjust till you get it centered. same thing as setting lathe tools on center. Mark
 
Although I've already posted twice in this thread, thinking about it more I have an idea.

Your mill has table slots, so find the center of the slot using an edge finder. Then raise the head and it will still be above and centered on the slot. The when you place the ring in the slot (use the slot like a v block) it will be automatically centered.
 
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