I think you'll find the better light was because the un-machined perspex rod had a polished surface. When you machined it down to 10mm, you lost all the internal surface reflection, so only axial light passed through. The 10mm would have worked better if you had polished it, although diameter control would have been difficult.
Also, the more rod sticks out of the top of the holder, the more light is collected and passed down to the target.

Thank you, I like the center finder.

Allen, Excellent project. Something else to add to my project list. Thanks, Randall in Kentucky, USA.

Neat project! Came out very nice!

Thank's for this Allen, I'll be making one of these asap!

I remember one of these when I was doing fine limit work at a college when I was studying production engineering.
With one you could drill a hole to within one ten thousandth of an inch.
The device we used was made one of the instrument makers of the day.

Nicely done Allan.

What a great project to make thanks Alan...

Spot on Alan 😀, it'll make a nice project. Thanks.

A great idea and well executed

great job,
Alan this is a very nice video,very well explained.thank you for sharing

You could use leds  and button batteries for lighting.

I like it but I'm sure it wouldn't be long before I whacked the perspex with the hammer.

Enoct

The o-ring can come off pretty easily with just a straight sided cylinder to hold it.  If you tapered the recess inwards, the O-ring will actually seat into the taper and be less likely to come off easily.  Or you could machine a o-ring groove in the reduced end to capture the -o-ring but leave enough protruding to give you the no-slip surface you desired

John

Nice project Allen. Thank you for taking the time to make the video.

Absolute quality work mate I really enjoyed the way you made it look easy I’m a beginner in machining I’ve made a few tools but I’m gonna give this one ago if you don’t mind thanks for sharing you work god bless
P.s what was the optic material you used thanks

Good job Alan. Unfortunately you did't show how you applied the "red cross" , because that is the primal requirement for accuracy.

I have seen quite a few of these made and not one of them was silly enough to drill holes to allow light in.

where do you get the perspec rod from? Not available from amazon or master-car in the us

Hi, Alan, I see you are using a good old Set-Tru chuck, the same model as I have. Have you ever done a video showing the use of it?
I have read so much mis-information about using one, and I am sure, like me , you know how to use it properly. So many people believe you need to loosen and tighten screws in the back plate, and on my own they are not even accessible!