Rotary Laser centre finder

Anyone got a link to a suitable laser?

When I bought a little laser pointer, it came with a couple of dozen end caps, each projecting a different shape, stars moons fairies, and cross hairs.

Ian S C

I'm not sure it's legal to machine a fairy is it Ian?

Have built a small laser pointer built into a No2 Morse Taper blank with softened end fitting, and available from most tool suppliers, very useful to use except the dot and cross hair projection is too fuzzy to give accurate true location to a point.

I understand that by fitting a Polaroid film over the laser end will cure the fuzz, any help from our kind hobbyists who may have cured the problem this way including sources of Polaroid used would be most welcome.

Terry S.

http://www.ebay.co.uk/itm/10pcs-650nm-6mm-5V-5mW-mini-Laser-Dot-Diode-Module-Head-WL-Red-uk-/231266733398?pt=LH_DefaultDomain_3&hash=item35d8924d56

Might be a good place to start. 10 for £1.88. These are just the laser module on a couple of leads, so better than buying a pointer then unpicking the casing perhaps.

Steve

I had a crack at building a laser centre finder from a £3 pet shop pointer. After some experimentation I found that reducing the battery voltage made the most difference to the flare. I simply reduced the battery count to 2 by substituting one of the three LR44's with a brass dummy battery. I also reduced the aperture (the brass appendage can just be seen in photo) in the laser's path; a No. 58 drill I think, which gave me a well defined dot as shown in the photo.

Regards

Phil

Edited By CotswoldsPhil on 24/03/2015 19:51:44

I have aquired 12 Laser diodes with an integral driver board. They run off 3 V dc but the Laser beam is lozenge shaped when lit and would need additional lenses to collimate. These I understand are available on Ebay for about £2 to £3. I have not tried these, these Laser modules are 47 mm long and the Laser diode is mounted in an Alu. housing 17.5 Dia, stepping to 14.5 Dia and then to12 Dia.The alu part is 16 mm long and the remaining length is taken up by the driver board which is 8 MM wide. connection is by 2 pins at te end of the driver board. It could all be accommodated in a tube of 17 mm Dia. Batteries make extra length. You would need to make some arrangement for lateral adjustments

I would need an SAE to send and I am not expecting any payment for them. If you would PM me with your needs and I will supply my address for sending -- it would fit in a small jiffy bag of 120 mm x 140 easily.

Just out of interest they originally cost £71.each

Clive

Some of the ones on eBay can be "focussed" according to the description, I wonder how sharp the dot is with these?

Clive

I was under the impression that the light from these laser diodes did not conform to normal optical rules and could not be focussed. How do the lenses you mention work? and if you have a link please could you post it here.

Ian P

The commercial one I have has the trade name SDA on the side and is made by a firm at lasercenteredgefinder.com - a few UK companies were selling them.

With its polarising cap to reduce the spot to its smallest, and projecting over a useful 12", I estimate the spot diameter to be 0.008" at most, by traversing it across a line and noting the mill DRO. I usually recon to position it on a scribed cross to around +/- 0.002". Similarly you can quickly find an edge, with the spot half on and half off, to +/-0.002". With effort perhaps that precision can be +/- 0.001" and I think the manufacturers suggest that, but the limit is calibrating it on the centre line in its holder; i.e. when rotation causes no deviation. Mine has not moved out of alignment after a couple of years use and a battery change, so it has been good.

I often use an electronic edge finder in preference, but the laser pointer can be very handy for fixing a coordinate on certain jobs.

Norm.

.

Clive,

[assuming that you will be using it in the rotary device that was the subject of this thread] ...

Don't worry unduly about the shape of the spot, it's only the sharpness that matters. ... Back on page_3 of this thread, Billy Mills made this very perceptive comment:

"A point that may have escaped- pointers often have non-round beams and fuzzy edges. However because we are rotating the beam, the defects only produces a wider ring when the cone hits something. Say the beam was a small picture of David Clarke, as we rotated the beam it would then appear to be a series of rings but always rotating around the true axis of rotation."

MichaelG.

This is just one of many I've seen on eBay.

http://www.ebay.co.uk/itm/5mw-Red-Laser-Module-Focusable-Red-Dot-/291073032589?pt=LH_DefaultDomain_3&hash=item43c54e018d

Here is my attempt at the completed device. It's balanced to within the weight of an M4 nut.

The main problem I find with it is, I can't get close enough (to the rotating mass) to achieve the accuracy I can achieve with a sharp point held in the chuck.  The other is I've yet to find a suitable white marking fluid Correction fluid (TippEx) flakes off. 

Phil

Edited By CotswoldsPhil on 26/03/2015 21:00:25

For anyone interested in beam-shaping optics, etc.

This is a very good place to start.

MichaelG.

Edited By Michael Gilligan on 26/03/2015 20:58:51

I am only offering a Laser module and not an answer to centralizing the beam, I leave that to you to play around with.

In use this tiny Laser module is used at 1.6 Mtr. and is rotated using one end of the beam as a marking point for surveying purposes, our tolerance is 0.5 mm rotational and theses when mounted in the base of the Theodolite as an assembly were outside that tolerance. There are no further optics fitted as such apart from a small glass window to stop dust and dirt getting back up inside the Theodolite.

Clive

This is what I'm getting from my work in progress, looks like it will work pretty well I think.

Hi Vic

Now that is a very nice clean image of a circle.

What laser did you use? was it the one you posted from E bay.

Go Vic!

Regards
John

It's the one in this picture John, 1mw 6mm from eBay. UK seller and cost a few quid if I remember.

Vic,

What is the spacing between the rails, to give some idea of scale and did you need to use anything to focus this with please ?

Hi John, it was tracing a circle of about 23-24mm on the bed of my mill. I made a small aluminium "can" in which the laser sits. The bottom of the can has a .65mm hole drilled in it to "clean" up the Laser output. Without it most lasers give you a rather large oval than a dot. This is what you get with a suitable aperture: