How to hold and drill 2 holes on a single diameter of a cylinder (thick tube actually)

[Parlo]

For future reference here are 3 different ways of using an edgefinder to find the centre of a round part in 1- 2 or 3 moves depending on the equipment you have. All these simple quick methods do not require a DTI or DRO and backlash is eliminated.

One move -

Two moves -

Three moves -

Hope you find them interesting and useful.

 

[dbb-the-bruce]

3 different ways of using an edgefinder to find the centre of a round part

I'll keep those in mind for the future. One thing I need to do is make a functioning stop for my vise, it doesn't have one yet and there have been times when it would have been useful.

Looking at the videos, with all the methods the workpiece is a finished cylinder and the diameter is accurately turned and can be measured. Of course this makes sense in most cases - if you have rough dimensioned stock, you don't really need a very precise alignment for it.

The first example video relies on having a gage block that's half the diameter of the cylinder, so works great on even sizes for cylinder if you have a complete set of gauge blocks.

It's not entirely clear to me how the second approach works, somehow the distance from the measured y to the center of cylinder is known? I guess it would be easy to measure the total and subtract half the diameter first. I get the side V block measurement + half the measured V width gives you that centerline. Is the V always accurately centered in the block it's cut from?

The last one is starting with the eyeballed center? This assumes that any error will contribute a tiny amount to the edge finder (cos error thing). This works fine until the diameter of cylinder being measured gets small - probably using an edge-finder stops working before you reach a point where the error would matter.

In my case, I should have found the Y center by measuring the jaw faces then found the X center at Y=0.

I try not to use extra measurements other than edges and DRO center function - It feels more direct to me any error is limited to how good a job I do with the edge finder. Using additional measurements and adding/subtracting offsets (for me) is an opportunity to introduce error or math mistakes.

I'll also do things like drill a small 1/8" hole on center on the lathe and then use a precision ground pin in an accurate drill chuck on the mill. Use the pin to hold the piece in place and then bring the vise up to it. Eye-balling a gap with a light behind it can be quite accurate.

Anyhow, thanks for the videos.

 

[Parlo]

I'll keep those in mind for the future. One thing I need to do is make a functioning stop for my vise, it doesn't have one yet and there have been times when it would have been useful.

Looking at the videos, with all the methods the workpiece is a finished cylinder and the diameter is accurately turned and can be measured. Of course this makes sense in most cases - if you have rough dimensioned stock, you don't really need a very precise alignment for it.

The first example video relies on having a gage block that's half the diameter of the cylinder, so works great on even sizes for cylinder if you have a complete set of gauge blocks.

It's not entirely clear to me how the second approach works, somehow the distance from the measured y to the center of cylinder is known? I guess it would be easy to measure the total and subtract half the diameter first. I get the side V block measurement + half the measured V width gives you that centerline. Is the V always accurately centered in the block it's cut from?

The last one is starting with the eyeballed center? This assumes that any error will contribute a tiny amount to the edge finder (cos error thing). This works fine until the diameter of cylinder being measured gets small - probably using an edge-finder stops working before you reach a point where the error would matter.

In my case, I should have found the Y center by measuring the jaw faces then found the X center at Y=0.

I try not to use extra measurements other than edges and DRO center function - It feels more direct to me any error is limited to how good a job I do with the edge finder. Using additional measurements and adding/subtracting offsets (for me) is an opportunity to introduce error or math mistakes.

I'll also do things like drill a small 1/8" hole on center on the lathe and then use a precision ground pin in an accurate drill chuck on the mill. Use the pin to hold the piece in place and then bring the vise up to it. Eye-balling a gap with a light behind it can be quite accurate.

Anyhow, thanks for the videos.

Thanks for the comments, the option used depends on the equipment available. All methods assume there is no dti or dro available. The one move method does not even need dials so could be useful sometimes. Without a dro available backlash must be considered and the methods evolved from continuing the axis movement in the same direction.
There is this unusual method from another YouTuber you could consider instead -

Regarding making an end stop, you could consider this.

I have a video that shows a stop that remains in position on the X axis even when re-positioned and another that demonstrates why a stop should always be as close to the centre of the datum face as possible. Hope you find them helpful.