Thread: Another Gizmo

Hi Guys,

The weather turned a little milder today, so I managed to spend an afternoon in the workshop.

There seems to have been some talk recently about "Center Finders" ! In particular electronic, Laser based ones. So having seen and purchased a laser pointer from Aldi last week, I decided to have a go and make one.



This is the laser pointer. Unfortunately I forgot to take a photograph before I cut it in two. The top piece contains a pen in the end of a telescopic rod. Actually a radio antenna. It is the bottom piece that I'm interested in. This is the laser pointer itself. Its powered by three 1.5 volt silver cell batteries, type 364, with a push button switch on the side. It's actually very well made. I had to remove the pocket clip and discovered that the body is made of brass, matte silver anodised with a chrome plated brass cap and joint piece.



After a bit of digging in the scrap box, I found a chunk of aluminum that was a suitable size for what I have in mind.
The device is intended to be placed into the machine spindle and spun at about 500 rpm. Then by raising or lowering the spindle the laser beam will prescribe a circle that will converge to a spot. If this spot is aligned with a center punch mark the spindle will be directly above.



Since I didn't take any pictures of the marking out and machining of the aluminum block, I did a quick sketch.
I determined that the angle for the laser should be between 10 and 15 degrees. I chose 10 degrees which should give me a working height of about 5 inches. I had an off cut of 10 mm diameter silver steel rod that I am using as the spindle for this tool. It is simply a good hand push fit into a 10 mm reamed hole.

The laser pointer is 9.25 mm diameter. I actually drilled a 9.5 mm hole for it to sit in. So it is a loose fit. Since I didn't want it to fall all the way through the aluminum block I made the hole intersect with the 10 mm spindle bore at the bottom, so that it cannot fall through.



These two pictures show how the device looks. You can see that the laser pointer is stopped and secured by the bottom of the spindle. ( the lumps at the sides are a couple of batteries that I used to hold it up whilst I took the picture ).



In order to clear the on/off switch, I milled a 3.5 mm wide slot down the outside. I just need to make the "U" shaped spring clip to hold the power button down.

Having tested the device, I can say that it does work as intended. I did however note a couple of interesting effects whilst playing about with it. At the right combination of spindle speed a circle appears as a string of dots. This effect had me puzzled for a minute or so, until I realised that it was a strobe effect because of the florescent lights in the workshop. Turning the lights off however only changed the number of spots. This was because the LED machine light was still on.

The other thing that I noted was that the laser pointer spot had a very tiny black center, far smaller than you could make the red spot. I'm not quite sure what causes this effect but it improves the potential accuracy of aligning the spindle. So much so that I could see the movement when I tightened the gib locks on the machine headstock.

My conclusion is that it was worth the afternoons work to make this device.