Rotary Laser centre finder

Hi ALL

Re Lasers in general

In most states of Australia; and I live in Victoria one of the stricter states, laser pointers are regulated if above one milliwatt. any bigger and I would need a gun licence and paperwork. Laser Diodes not fitted in a battery powered pointer holder are not, well so far anyway. The restrictions were put in place due to individuals shining them at aircraft and traffic. One incident apparently caused a fatal traffic accident two were killed when a driver ran off the road. So the regulators stepped in.

So it looks like I will be building the Rotary laser tool from scratch. In a way this is a good thing. Dan Gelbarts design is very compact with the laser built within the body of the device it does not protrude less likely to be damaged or catch a finger. I plan to mill out a solid piece of material to hold the battery's, the laser diode body and some form of angle adjustment. It looks like Dan G adjusts the angle of the laser with a mirror or maybe the laser is mounted on an adjustable stage and that is angled. Note the small knurled screw that projects from the tool body in the video.

A 10 milliwatt device is available at a local supplier in Melbourne at a modest price, **LINK** (I have no connection with them). There are many suppliers on eBay at differing prices offering a similar item. They also sell a collimating lens to suit I plan to get them and experiment. The circuit is simple but I believe you must limit the current to within the device spec or it will fail.

First I have yet to ascertain if a 10mw laser is safe to use (I will certainly not be looking into it) however there is the possibility of reflection from a shiny metal surface, a number of sites mention the most damaging radiation is in the infrared spectrum and that an infrared filter should be used. I have yet to find a source for the filter if it is needed.

Link On Safety:
http://www.repairfaq.org/sam/lasersaf.htm#saftoc

Maybe others on this forum are more technically informed re the use and safety of lasers.

This has turned out to be an intriguing project.

Regards
John

Link On Safety:
http://www.repairfaq.org/sam/lasersaf.htm#saftoc

This site has a fair amount of information on solid state lasers from small to very big.**LINK**

Laser Colour chart Link:
**LINK**

Edited By John McNamara on 31/01/2014 11:08:24

Hi I have a lazer gun sight on my air rifle ,It came with the gun without instructions The spot of light is about 1/8"across and very bright and it gives a spot of light more than 50 yards away. .I think it is much too powerful

for what we want .I had to try it didn't I ? Keep trying. it looks as though it is a useful addition.

Maurice

Just off to build one of these.

You can reduce the dot size by putting a piece of tape over the end and pushing a pin through the tape to make a tiny hole.

I was going to make s stepped shaft to fit in different sized collets. Bnt now I'm making something that fits round the spindle so I can leve it in permanently.

< condensed quote >

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John,

I don't want to be a spoil-sport, but I would strongly advise against using anything so powerful in any situation where there is reasonable risk that you could look directly into the beam, or at its specular reflection.

Unless you are planning to work outside in the Australian sunshine; I suspect that a "safe" laser pointer will be adequate. ... Please try one of these first.

Laser damage to the retina can happen much faster than the Blink-Reflex kicks in.

MichaelG.

Hi ALL

PLEASE NOTICE

I have spent the last hours researching lasers on the net and have decided to use a one miliwatt diode NOT a ten milliwatt device.

From the research it appears the 10mw will not be safe.

Some sites also mentioned that Asian manufactured diodes might be marked one power but actually be another higher power. They simply sell whatever they can get so finding a reputable supplier is also important.

I do have a Leica Rugby 100 laser level.
**LINK**
Having looked up the specifications for that, I found that the laser inside it is a 98MW Class 2 Bright red, beam (635 nm) device.

I guess Leica have done their homework. In daylight the 360 deg rotating beam is hard to see outside but it is ok but not that bright in a large room. bright at a few metres. in fixed spot mode the beam is quite bright.

Normally I use it with a receiver/detector that works in full sun to 300 Metres but you cannot see the beam

I should have thought of the level in the first place anyway it has set the starting point for me.

Regards
John

Edited By John McNamara on 31/01/2014 12:52:51

Edited By John McNamara on 31/01/2014 12:55:37

Thank you Michael

You beat me to it

I should mention you should not look directly into any laser.

Regards
John

Edited By John McNamara on 31/01/2014 12:52:08

For anyone experimenting with LASERs ...

This, from Loughborough University, is an excellent guide, with links to regulatory guidance. Loughboro' was an early-adopter of lasers for Holography, so it's reasonable to assume that they've "been there, done that, and got the T-Shirt".

MichaelG.

The simplest target is a cylinder. A small cylinder with a vertical axis gives higher sensitivity than a larger cylinder. It is also simpler than a cone and can be the rod that you have or are going to turn. The patented device with the laser on the outside of a chuck i.e. say 30mm from the axis of rotation produces very low sensitivity on targets of 1-20mm. My suggestion in the two year ago thread implied that the laser is much closer to the axis of rotation. Indeed this is what Chris made and exhibited at AP. He spun the device in a Myford 3 jaw witha beam just off axis to demonstrate. The beam hit the tailstock centre and gave a nice slanted line across the cone. Not quite the same animal as the patent, but the patent allows drills & mills to be held while being aligned.

The geometry of the device is the key, Think of the axis of rotation then a beam crossing the axis at 45 degrees and hitting a round rod also having the same axis as the beam rotation. We would see the circle drawn around the rod. If we move the rod 5mm at a right angle to the axis of rotation then the circle is tilted into resembling an elipse, with the high point 5mm up and the low 5mm down on the other side of the rod.

Now if we move the pointer so that it makes an angle of 5.7 degrees ( roughly 6 will do fine) we only have to move the rod 0.5 mm to get the same apparent movement of the beam . If we can set about 1.1 degrees then the 5mm displacement happens with 0.1mm ( 100 microns) of movement so this a sensitive arrangement but demanding on beam quality.

The vertical displacement for a given displacement is only related to the beam angle from the axis of rotation so a smaller target makes the sloping elipse proportionally steeper so easier to see.

Fuzzy spots do limit shallow magnification, as suggested earlier increasing the background illumination will help. There are some well known optician tricks such as stopping the source down or placing an occluder in the beam path to produce sharper spots, worth a try.

The beam colour will not make any great difference for a given beam quality, absolute sensitivity is not an issue.

Engineer's Buttons don't need mods, you can use a shallow angle on the sides - which should have a lovely smooth surface. But a sensitive arrangement might have a very round plug in the hole as a target , a turned step around the hole or use the hole( the top feature allows several buttons to be located without moving the buttons which could be bolted down.) .

Another suggestion that was made originally was to be able to change the angle by changing spindle speed to avoid the need to keep stopping and starting. This idea was shot down by a few people in the original thread without much ado they said that they thought that vibration and other issues would afflict the device. It actually works very well indeed, the implementation was a bit more complex than I described but it allows much easier actual use when working with shallow beams, in effect the speed control is a remote beam angle control .

So if you want to make one of these gizzmos I would suggest that you fix the pointer to a rod so that you can move the pointer from the axis of rotation outwards and that you can adjust the inclination to an almost vertical angle.

Billy.

PS Many thanks MG for the quadrant detector link, I was mighty impressed by their price tag, thinking of knocking out a few....

.

John,

I'm sure it's just a typo

98MW would be very bright !!

... should presumably be mW

MichaelG.

Got me again Michael!

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Hi, Billy

Maybe the price for the finished product isn't too bad [depending upon who makes it], but I was very surprised to see the price of the basic detector package.

Given what you said earlier, about CD/DVD, I was expecting them to cost pennies

... any recommendations for realistically priced components ?

... or is it a hack the DVD job ?

MichaelG.

Hi Billy M

It is all about the geometry and the angle of incidence.

As long as the surface on the object you are centring on, be it the face of a cone or the side of a cylinder, intersects the beam by a small angle, if the centre of rotation is off axis the error will be more magnified than if the beam strikes the surface at 90 degrees if a cylinder. It matters less if it is a cone, The smaller the angle the better if the beam spot is small. If it the spot is fuzzy a greater angle may be better.

In the Dan Gelbart video he has located the laser on the side of the chuck within the flat housing of the laser tool. If you were to focus on a small conventional toolmakers button; mine are half inch diameter, you would have to locate the centre finder in a collet or chuck, you could not mount it outside the chuck. because the angle would be too great. Having the tool close to the axis of rotation would also mean that you could not focus on larger items unless you have very long travel on the quill, unless you changed the angle.

You idea for changing the angle by speed is interesting a bit like an old engine governor although you would need an opposing force I guess a spring would do. **LINK** You would also need a VFD, or are you proposing some sort of swash plate?

Regards
John

Edited By John McNamara on 31/01/2014 13:55:06

Hi

To modulate the brightness of a laser beam all that is required is a small polarising filter, same as used in photography and lens filters. As the laser beam is naturally polarised rotating the filter will attenuate the energy transmitted/intensity and therefore can be used to set the brightness to suit the conditions. As far as I am aware the frequency/wavelength/colour of a laser is by its nature very pure, therefore a RED Visible laser does not radiate any significant energy in the Infra Red region.

Cheers

Martin

I made this up, it fits on the spindle rather than in a collet to save swapping things over. A piece of tape with a pin hole in narrows the beam. It works ok, but I wouldn't use it for anything that needs to be accurate. The holes are to attempt to balance it slightly.

The laser was £1.55 posted from ebay.

Looks like that laser has killed your horse ?

John, did you work in the lasagne factory? That looks like a bovine horse if I am not mistaken......

Mark

All tastes the same to me if you buy your pies from Tesco

ROFL

Chris,

Very stylish construction

...But could I please ask about the pinhole ?

Theory suggests that what you have done is more likely to degrade the spot [by diffraction] than to improve it. But, as always, it's what happens in practice that's important.

If you have suitable "macro" facilities, would you kindly photograph the [stationary] spot in as much detail as you can ... and also let me know the size of the pinhole.

Many thanks

MichaelG.

Chris: Nice job, well done. I agree that fitting it around the spindle collar has benefits. I find that my R8 toolholder mounted one is not too inconvenient to swap and will carry on like that. The main problem is that you need a shallow angle (I use 9 deg) which means the spindle has to be lifted well away from the job. You then find out how much horizontal error you have in your supposedly vertical mill column!

Regarding the diffraction of the beam, you just need to ensure it is still a reasonable spot of around 1- 2mm at 200mm. When this hits the vertical work face you are simply looking at whether this 'wide red paint brush line' is sort of horizontal or not.

Billy: Your last posting said a lot of good things and clearly this was all looked at two years ago. Your comment to have an adjustment for the displacement of the laser from the centre line is sensible as this can overcome having to move it too far from the workpiece. You are right that it is more sensitive at lower workpiece diameters. On my mill it works well on small 3/8" diameter objects (buttons ?) that stick up as little as 3/16" from a workpiece (providing the surface is not freshly machined and shiny). Your comments about the lathe made me realise the usefulness of a laser rotating in the lathe headstock to align the tailstock - thank you!

Norm