Laser centreing

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Laser centreing

This topic has 30 replies, 19 voices, and was last updated 15 January 2012 at 23:48 by chris stephens.

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4 January 2012 at 09:34 #81215
Wolfie
Participant
@wolfie
OK now I’m wondering why when we spend so much time looking for the centres of things that noone has yet built in a laser centre into a machine.

Think about it, have a laser pointer pointing down the centre of your mill spindle will shine a tiny red dot on your job. Sorted!

I will now assume that its been done already and I simply haven’t ran across it yet
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4 January 2012 at 09:34 #5836
Wolfie
Participant
@wolfie
4 January 2012 at 09:54 #81217
Dusty
Participant
@dusty
Question; Where does the drawbar go?
4 January 2012 at 10:17 #81221
Springbok
Participant
@springbok
Drawbar!! I would presume it would go into a collet and once the centre was spotted

fix your XY remove the spotter then get to work.

Wolfie a very interesting idea worthy of some further research. I am sure that the Chinese who watch this forum will pick the idea up.

Bob
4 January 2012 at 10:23 #81223
NJH
Participant
@njh
Hi Wolfie

Go to the Chronos site and search for ” Laser Centre Finder “

Regards

Norman
4 January 2012 at 10:26 #81226
John Baguley
Participant
@johnbaguley78655
Laser Centre Finder

John
4 January 2012 at 10:35 #81229
Les Jones 1
Participant
@lesjones1
Hi Norman,

You just beat me to that suggestion. I thought I had seen them advertised somewhere so I tried Ebay and found Chronos. For Wolfie here is the link.

Laser centre

I do not think the spot would be small would be small enough for accurate work.

Another optical method that some people use is a USB camera in an accurate mounting that fits into the spindle or a collet chuck. One of the USB microscope cameras would probably the best.

Les.
4 January 2012 at 10:39 #81230
Clive Hartland
Participant
@clivehartland94829
A much better system is an optical telescope with a X graticule. With an inbuilt prism they can be looked through at right angles to the target.

They are very easy to adjust/check by rotating 180deg.

Lases are much better suited to long distant sighting, like 20/30 mtrs.

If you go to an auction/sale and see a Tribrach with an optical plumb attached then that optical plumb will sight down to .5mtr.

I have already modified one for my own use.

They can be modified quite easily and attached to a M2 taper for use in a tailstock.

Remember to clamp your tailstock if you use one, as a loose tailstock will not align correctly.

Clive
4 January 2012 at 11:24 #81236
chris stephens
Participant
@chrisstephens63393
Hi Guys,

Thinking of Lasers, what would be useful is an attachment that instead of projecting a point, projects an adjustable circle/disc of light. This would aid when having to drill out broken bolts or screws, something I have to do regularly for a friend in the motor trade.

I suppose the alternative would be find where I put it and then finish building the Hemingway kit of a centring microscope. It’s been about 3 years since I stared it, so it must be getting near to the top of the must-get-around-tuit list.

chriStephens
4 January 2012 at 13:52 #81243
John Shepherd
Participant
@johnshepherd38883
I have just submitted an article on this very subject.

It uses a cheap laser module that produces a focused cross beam. The module is mounted in a carrier that fits in a collet and has adjustments to align the two beams.

I looked at a commercial version and decided it was too long for my small mill and I wasn’t convinced that the spot was fine enough.

I wont pretend that my version is high precision but the lines are fine enough for most applications and it is proving a useful aid for both the mill and the lathe.

Regards

John
4 January 2012 at 14:29 #81245
David Clark 13
Participant
@davidclark13
Hi There

John’s laser attachement is in MEW 186.

regards David
4 January 2012 at 14:55 #81249
Clive Hartland
Participant
@clivehartland94829
The emitter of a diode laser is half moon shaped and when projected gives a lozenge shaped point of light.

They need a focusing arrangement and we set them to rotate about one end of the lozenge image. Our lasers can be rotated so it is easy to determine where the laser is pointing.

Please bear in mind that looking into a laser is bad for your eyes and over a prolonged time can leave permanent laser burns on the retina.

The power of the laser is the governing factor and I doubt anyone is going to use a laser of 1Mw or I hope not!

Clive

Edited By Clive Hartland on 04/01/2012 14:56:09
4 January 2012 at 17:17 #81260
Billy Mills
Participant
@billymills
Chris,

If you mounted any old laser pointer on a rough old bit of wood with sticky tape stuck in a milling chuck then the circle generated when the machine runs would be perfectly aligned with the axis of rotation, size of circle is adjustable by tilting the laser. No expensive German Precision needed, all done by simple geometry.

You don’t have to worry about the image shape being less than a perfect circle either because the whole image rotates about the axis of rotation. Expect to see your new laser circle generator for lathes, mills and drills at AP, I’m sure it will be yet another beautifully made object of desire.

The trick of rotating the source to define a cone around the axis of rotation can be very handy in setting up all sorts of tools.

Billy.
4 January 2012 at 18:55 #81266
Jim Greethead
Participant
@jimgreethead
Good one Billy, I should think that the eye is capable of centring the punch mark (or whatever) within the circle to at least 0.02mm – it is very good at that.

I made a centre finder using a webcam a couple of years ago but had great difficulty aligning it on the axis and along the axis (not coning). Eventually, I gave up when I realised that the resolution of the webcam would not allow me to resolve 0.02mm because there were not enough pixels in the window.

When last I checked the laser pointers, they were not sufficiently accurate either.

But I must check MEW 186 and think about Billy’s brilliant scheme.

Thanks to all for the input to this thread which is very illuminating (Ha).

Jim
4 January 2012 at 20:45 #81277
chris stephens
Participant
@chrisstephens63393
Hi Billy,

Like all the best ideas, once explained, are very simple. I think you should change your name to Sherlock.

As for having one for A-P, perhaps not.

As for another beautifully made etc etc, you flatter me, but you should know that flattery will not work on me, I am too used to it.

chriStephens
4 January 2012 at 23:44 #81291
Ed Duffner
Participant
@edduffner79357
Forgive the beginners questions, but how accurate would using a laser be which is aligned by eye? Doesn’t the projected ‘spot’ have a large diameter in engineering terms? How would you know you are within tolerance?
5 January 2012 at 00:26 #81294
Jeff Dayman
Participant
@jeffdayman43397
Clive –

If you were to use a 1 MW laser you will have a hole in the table before long….

But your caution about lasers and eye exposure to them is exactly right. Over time, even a 0.1mW laser can cause eye damage.

I have tried a few laser centre gizmos and find the dot is always a little too fuzzy for even a few thou resolution in metalwork. Great for woodwork though.

For general locating and positioning to lines and centre punch marks I often use a simple piece of unhardened silver steel 1/4″ dia, turned in the lathe with a sharp conical point concentric to the OD of the rod. This pointed rod is placed in the drill chuck or a collet, with the point close to the work. The point can be aligned surprisingly accurately to lines and centre punch marks by eye if sighted from a few angles with a good light and a magnifying visor. If the tip gets banged up or bent, it can be re-turned to sharpen it anytime.

One note about this trick – it pays to turn on the drill or mill to be sure the point is running true to the spindle, if it isn’t true, the tip will wobble and your layout will be off.

If the chuck or spindle does turn up wonky, you can still locate your work to true spindle centre with a piece of clay and a pin. You place the clay close to center on the end of the chuck or tool, start the machine and with your finger, push gently on the side of the pin until it runs true. Don’t touch the pin again. Sight the end of the pin over your mark as above by moving the work or the table. Lock the table/work when it is aligned. Take away clay and pin, fit the tool or drill and the spindle is still aligned to the mark.

Both methods cheap as chips and these tricks work, they were taught to me many moons ago by a master machinist using totally clapped out machines but still making good work.

JD
5 January 2012 at 01:01 #81296
Nicholas Farr
Participant
@nicholasfarr14254
Hi Jeff, I’ve used the pin idea very often. My one is an unused plunger that holds and reciprocates the needle in an industrial hand operated paper bag stitching machine. It just happens that it is precison ground 1/4″ with a integral pin vice end, and fits nicely into a collet in my vertical mill, and as you say spinning it wil show any wobble on the needle point, but it is easy enough just to correct it by bending the needle with finger pressure.

Regards Nick.

P.S. can’t get much cheaper than freebie surplus to requirement scrap spare parts.

Edited By Nicholas Farr on 05/01/2012 01:08:02
5 January 2012 at 01:10 #81297
Billy Mills
Participant
@billymills
Pins work fine for locating centres up close however lasers can be used to check the alignment of all sorts of machines at various distances. The fuzzy spot can be down to excessive brightness and is easily reduced by stopping down or by crossed polarisers.

The trick of rotating the pointer turns the fussy blob into a fuzzy ring, the centre of the ring being the true centre of rotation. It is very easy to see the centre. Defects in the beam shape also don’t matter with this method.

You can greatly improve the sensitivity by using a round or conical target, eg a dead centre in a rotary table or a steel ball. When the cone from the rotating pointer forms a horizontal line around the centre’s point then you are on axis. Same works for checking lathe alignment with a tailstock mounted centre along the ways. Nothing expensive needed.

There are more accurate methods for detecting the cone of light, the resolution is usually limited by vibration and other noise which can be averaged out, micron resolution is then attainable.

Billy.

Thanks Chris and Jim for your kind comments.

Edited By Billy Mills on 05/01/2012 01:22:35

Edited By Billy Mills on 05/01/2012 01:31:16
6 January 2012 at 20:29 #81442
Sub Mandrel
Participant
@submandrel
I bought a laser pointer in aboot sale for £1.I was thinking of fitting it to my air rifle, but to be honest the standard scope is fine for my needs (shooting small objects, now that the chickens have gone and the rats with them).

It came with about 40 crummy little hologram caps that projected skulls, hamburgers and other images when you fit them to the laser. really useful. Except, one of the images is a cross hair. I might try adapting it as a centre finder.

Neil
13 January 2012 at 17:16 #81954
chris stephens
Participant
@chrisstephens63393
Hi Guys and in particular Billy,

There is now a working prototype of the broken-bolt-drill-centring-laser-finder and it shows great potential. So thanks to Billy for the inspiration and if I ever write it up you will get due credit.

Oh, and I might have one in my pocket at Ally-Pally.

chriStephens
13 January 2012 at 18:39 #81959
John Stevenson 1
Participant
@johnstevenson1
Terribly old hat.

Just went way back on the HSM forum and on the 16th of April 2008 I posted the following pictures but the first one which is an overall shot of the setup is missing.

So brief description.

Two lasers mounted on the side of the spindle on the CNC router at 45 degrees pointing towards the spindle, These are cross hair lasers with fine lines via an engraved graticule.

As you higher or lower the Z axis these two cross hairs blend together.

Please note you MUST have the Dambusters sound track on in the background.

When lined up you just move the table to get whatever in the cross hair beam.

Simples and nearly 4 years too late.

John S.
13 January 2012 at 18:58 #81963
chris stephens
Participant
@chrisstephens63393
Old hat it may be but it is nothing like your cross hairs, as it projects an adjustable circle which you can centre on a sheared or broken stud/bolt/screw.

chriStephens
13 January 2012 at 20:55 #81975
Billy Mills
Participant
@billymills
Chris- one further thought. If the laser is mounted off centre and is able to move then you can adjust the circle diameter by changing the spindle speed.

Billy.
13 January 2012 at 22:02 #81980
chris stephens
Participant
@chrisstephens63393
Hi Billy,

That’s too complicated for me, a simple eccentric will do I think. If I had variable speed on my mill it might be a different matter, but I don’t, yet.

chriStephens
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