finding the center while in a vise

[cg285]

I’ll throw this out there,
How about finding center of a hole in the vise clamped part ?.

maybe there is something hidden in the "vise clamped part"

 

[jmarkwolf]

I'll admit, times that I don't need great accuracy, I'll chuck up a drill bit or gauge pin of the same size as the hole, and carefully adjust the table X & Y until I can lower the bit into the hole (not turning), then hit 0,0. Quick and easy.
If I need the accuracy, I'll sweep the hole with an indicator.

 

[dlane]

That’s kinda what I’ve been doing the dowel method

 

[projectnut]

Your statement is not entirely correct. You cannot take the word of the manufacturer that the size is correct. You arrive at that yourself with a mic. I have gotten wrong sizes at times.

"Billy G"

I would agree. In the last 10 years I can't count the number of pieces of stock I've purchased that have been slightly under or over sized. There was a time when a 1/2" piece of 6061 or 4140 round stock was .500". More recently it can be as little as .498" or as much as .503".

I was making some collet bushings for a Black Diamond drill Grinder last week. I picked a piece of round stock labeled 5/8". The base OD was supposed to be .562 so I set the cross slide to cut a depth of .0315". As an old habit I measured the finished diameter "just to be sure". I was a bit surprised when the micrometer read .565". I cleaned the micrometer and the stock a couple times, remeasured, and got the same results. I then went back to the original stock to find it was actually .628" rather than .625".

Every once in a while I still get caught thinking 1/2" = .500". That may be mathematically true, but in the real world it isn't necessarily so. Many times close enough is good enough. The only way to be sure is to buy stock that comes with certifications. If you've ever bought stock that has to be certified as to alloy content and dimensions you know it's considerably more expensive than off the shelf stock. I've found it more cost effective and less frustrating to just "measure twice and cut once".

 

[RJSakowski]

I’ll throw this out there,
How about finding center of a hole in the vise clamped part ?.

Is the hole vertical or horizontal? How big a hole?

 

[RJSakowski]

Vertical: If the hole s large enough, I use the edge finder. A smaller hole I would mount a test indicator in the spindle and sweep the hole. A still smaller hole, I would use my spindle mounted microscope to find the edges as I would for the larger hole and edge finder.

When I find the center of a hole, I will pick a y position close to the center by eyeball and find the edges in the x direction and set my x center zero. Then I move to x = 0 and find the edges in the y direction and set my y center zero. If I am really being picky, I'll redo the x zero but usually I'm dead on.

If I am not concerned with dead nuts accuracy, I'll lower a pin or tapered pin into the hole, adjusting x and y position until I get a good fit. Sometimes, I loosen the vise slightly so the work is free to move. I then lower a close fitting or tapered pin into the hole which will position the work parallel to the jaws. I then move the position perpendicular to the jaws until the work just touches the fixed jaw tightening the vise at the same time,

Horizontal: If it is a hole size that I have a pin gage for and is deep enough for a stable mount of the pin, I'll insert the pon and find the outermost positions of the pin. If I can't use a pin, I would mount a test indicator and move until I see a deflection of the indicator to establish one sid. Then do the same for the opposite side. Average the positions for the center line.

 

[hman]

If I am not concerned with dead nuts accuracy, I'll lower a pin or tapered pin into the hole, adjusting x and y position until I get a good fit. Sometimes, I loosen the vise slightly so the work is free to move. I then lower a close fitting or tapered pin into the hole which will position the work parallel to the jaws. I then move the position perpendicular to the jaws until the work just touches the fixed jaw tightening the vise at the same time,

For a close approximation, I've been known to use the pointed end of a center finder. Lower the cone into the hole, then feel both sides while adjusting X. Then feel both front and back while adjusting Y. I've read that it's quite easy to detect differences of less than a thousandth by touch. Both the shank of the edge finder and the full diameter portion of the pointed section are sharply defined, so misalignment is pretty easy to feel.