Laser centre finder

[BufferParticipant @buffer]

Anyone know why you can’t seem to find those laser centre finders for milling machines any more?

[bernard towersParticipant @bernardtowers37738]

SDA manufacturing. Calafornia based.

[Phil PParticipant @philp]

There are a couple on ebay if you want one. Item numbers below.
The first one has a polariser included.

800251141975

278093664030

[BufferParticipant @buffer]

Ok Thanks.

They were sold by the usual suppliers but they don’t seem to list them now.

 

[Clive FosterParticipant @clivefoster55965]

Buffer

I imagine there are some laser safety regulation issues getting in the way of widespread commercial sales to tech casual user.

Fundamentally these devices involve pointing a decently collimated laser beam at, usually, a fairly effective specular reflecting surface. The users eye is quite close to the surface.

Regulations for unenclosed low power lasers, pointers et al, basically assume a diffuse or scattering reflecting surface where much less power is thrown about into the human eye aperture.

That sort of thing tends to get the laser safety folk excited however low the laser power is. 25 – 30 years ago when i was working with lasers in an optics lab we had quite enough trouble with the safety officers panicking the moment they saw “laser” and refusing to accept rational discussion of the real hazard level. Around about that time some of my co-workers were involved in re-working the safety regulations to cover laser pointers and other applications of the then new packaged laser diodes. The controversy was less than pretty.

Presumably its impossible for a commercial product to demonstrate conformity with the regulations unless sufficient shielding is interposed so as to make the set up largely useless.

Clive

[Phil PParticipant @philp]

I have had one for many years, to be honest it does not get a lot of use. I am always a bit wary that the dot size is bigger than I would like for accurate work.
It does come in handy when centering work on a faceplate if you hold it in the lathe tailstock.

[John HaineParticipant @johnhaine32865]

IMHO the dot size is a major impediment, also the need to get the laser centred in the holder.  My approach is to have a 6mm silver steel “point” – about 50mm long with a sharp cone turned on the end (angle not critical).  Centre in 4 jaw or hold in collet so the point is as close as possible to the axis.  Put in milling collet and use to pick up the marking on the workpiece, with the aid of a strong magnifier and plenty of light.

Another approach is a centering microscope, which could use a webcam to make viewing easy.  There are apps around that can put “crosshairs” on the image.  A refinement would be to mount the ‘scope permanently on the mill head to one side and measure the X/Y offsets to the spindle axis – really need DROs to make this work.

What is not helpful is a device that is mounted on a taper such as MT3 or R8, as it can be impossible to remove it when you have centred the work when it’s held in a vice if your mill/chuck has limited headroom.  (Unless you have a DRO so you can recover the position.) Ideal device is as short as possible and on a parallel shank to fit in a collet.

[duncan webster 1Participant @duncanwebster1]

Old men like me use a sticky pin, a darning needle attached to the end of the cutter with plasticine, use the end of your ruler on the rotating pin to get it to run true. You can also use the pointy thing on a wobbler (ebay item 492842) but then you have to take the cutter out of the collet

[Dave HalfordParticipant @davehalford22513]

Too many idiots trying to protect their stash shining them at police helicopters.

[DiogenesParticipant @diogenes]

I made one ages ago, rejected because even with a dot as small as I could get it, it wasn’t as accurate as the ‘eyeball and point’ method outlined by John Haine – I really like the ‘double-ended’ (827MB) Starrett edge-finders for this, they are usefully short.

[JasonBModerator @jasonb]

Pointy bit in a wobbler for me. Though I try to avoid marking out where possible and use an edge finder on the work and move to the required position rather than mark the position and the try to locate the mark. Sometimes you can’t avoid having to work with a point but not that often.

[Mark EasingwoodParticipant @markeasingwood33578]

Like Duncan, ‘cept a decent size sewing needle and Blu-Tack works for me, when needed.

[Robert Atkinson 2Participant @robertatkinson2]

Issue with lasers is, as others have said, is spot size. Note that this is the apparent spot size, not the beam diameter. Local reflections and interference at the surface make the spot look much bigger than the actual beam diameter.

Robert.

[Nicholas FarrParticipant @nicholasfarr14254]

Hi, did someone mention needles.

These are a few I saved from being scraped, they were used in industrial hand sowing machines, that stitched up open ended paper bags after they were filled, the machines fell largely out of use, once self sealing bags became the norm, and soon never got used again a while afterwards. I think I’ve got one of the old machines somewhere, but don’t know if it is of any use now though, but I often use one of the needles to line things up on my mini milling machine.

I’ve even got cut down rod that held them, with a needle fixed in it, which can be held in a three jaw chuck or a collet chuck.

Regards Nick.

[Robert Atkinson 2]

On Robert Atkinson 2 Said:

Issue with lasers is, as others have said, is spot size. […]

They are wonderful when the application is suitably proportionate

Gunsights, Building construction, etc. … but near-useless for most MEW jobs

MichaelG.

.

P.S. … some may remember that when the NatWest tower [now known as Tower 42] was being built, they used lasers for the “straightness” checks
… Now THATrepresentsproportionate use of the tool.

[Robert Atkinson 2Participant @robertatkinson2]

nicholasfarr

My barbecue charcoal still comes in bags with a sewn top so some are still doing it.

michaelgilligan

Most laser alignment systems use some kind of electronic detection. typically photodiode arrays. Those for jigs and the like use quadrants:
https://www.hamamatsu.com/jp/en/product/optical-sensors/photodiodes/si-photodiode-array/segmented-type-si-photodiode/S4349.html
As long as the beam is circular it is centred when the output of all four diodes is the same.

The sensors used with levels for suspended ceilings and the like use linear array.

Robert.

 

[Michael GilliganParticipant @michaelgilligan61133]

Thanks for that link, Robert … I have grabbed the data-sheet

MichaelG.

 

[Robert Atkinson 2]

On Robert Atkinson 2 Said:

[…]  As long as the beam is circular […]

 

A fundamental problem with the laser diodes that most hobbyists might use !

MichaelG.

[bernard towersParticipant @bernardtowers37738]

Having used one for a considerable no of years I fail to understand Michaels comment on their suitability for model engineering.

[Nicholas FarrParticipant @nicholasfarr14254]

Hi Robert, yes many paper bags are still sewn up, but the ones that the company I worked for, were filling 1cwt bags, which were hand filled and sewn, but when it all changed to 25kg bags, relatively a short period later, new plant was installed, and the filling process became semi-automatic, and using self-sealing bags, and hence sewing machines were no longer needed. these bags contained a total industrial product. The plants that produced the product, no longer exists in the UK, it all went, you’ve probably guess it, to China.

Regards Nick.

 

[bernard towers]

On bernard towers Said:

Having used one for a considerable no of years I fail to understand Michaels comment on their suitability for model engineering.

I wold be interested to see the size and shape of the laser-spot that you are using, Bernard.

Perhaps we are thinking about different use-cases, but a fuzzy rectangular spot seems like a poor “finder” to me.

MichaelG.

[renardiere7Participant @renardiere7]

I remember, as a student, stitching my left thumb into the top of a potato sack. After doing so many hundred of the things I was firmly on autopilot. It was inevitable.

[bernard towersParticipant @bernardtowers37738]

Mines not fuzzy at all and with a polariser and the the use of an head magnetiser my parts seem to turn out ok.

[Phil PParticipant @philp]

How does the head “magnetiser” work Bernard ?
I need to get on of those by the sounds of it. I can just imagine bits of swarf sticking to the end of my nose !!

You did mean magnifier ?

Phil

[bernard towers]

On bernard towers Said:

Mines not fuzzy at all …

I am envious, Bernard

… is it a commercial item, or something you built from parts ?

MichaelG.

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