Anybody build Dan Gelbart angled laser centre finder?

[Andrew Wildman]

Pekka,
I have not had much of a chance to fiddle about with it yet, but it appears to produce a stable circle and the laser can be focussed to a fairly fine point.

I think these devices are most useful when centering a cylindrical object that is normal to the table.  The angle of the laser to the surface of the object means that it can be quite sensitive in this mode.  The shallower the angle of the beam to the surface of the cylinder is the more sensitive it will be.  Accuracy is determined by how well you can judge how parallel the laser line is to the bed.  Just using it projected on to a flat surface means sensitivity is limited to how well you can determine the edge of the laser.   I am treating this as a rough positioning device for non critical applications though.  If any accuracy is required it is time to get the dti or edge finder out!

I used  £3 focusable laser module from ebay.  This was good as the spot can be focussed.  I also found out that the case of the device is bonded to the positive input.  The module is at one end of a 12mm hole, two cells stacked up to the case and then the negative is connected to the other side of the cells with a screw in a threaded hole, to act as a crude but effective switch.  There is also scope to convert this to centripetally operated switch arrangement in the future.

[AussieJimG]

This thread just keeps getting better and better. Very interesting.  Thanks to all of you.

Jim

[BaronJ]

Here is a laser centre finder that I put together.  Most parts were 3d printed.


It looks a bit like a laser guided toilet seat for mice but the strange shape is allow it to be used on a number of different machines with different spindle sizes.  The centre finder is fixed to the spindle with magnets and is very stable when running, even on the drill where it looks a bit precarious!

Hi Andrew,
Look very futuristic    I like your description though,  I can imagine a mouse sat on there.   

[vtsteam]

Any concerns about magnetizing spindles and chucks?

It may not be a problem for everyone, but I've been on a concerted effort to reduce super magnet usage in the shop, since I find more and more tools and fixtures attracting iron and steel filings and grit. True, a degausser can help, but it isn't always possible to use those on hidden and internal parts. And magenetism seems to get transferred from tool to tool if you aren't diligent in demagnetizing. Magnets are a nice convenience, but in many cases a simple clamp will work in their place without the assocated magnetc field. I believe Gelbart's laser finder used a clamp.

[Arbalist]

Dan's original design is very elegant with just a couple of pieces of spring steel to hold it in place.
Most folks that have built these have used a spindle design for use in various fixtures instead though.
I'm torn between the two concepts but will probably go the spindle mounted route as most others have as it's easier for me to make and more economical on materials. We shall see though! No progress from me on this lately as I've not been too well recently. The hospital ED say it's nothing life threatening though so it's just finding a way to deal with the symptoms.

[PekkaNF]

Good to hear you are fine.

I did a little something.

1) Idea is to use 0-ring and close fitting to hold it on it's place. It is fairly close fitting. Ironically I walked on the workshop today and got a piece of springy steel band from the strapping machine. I would go that way now.

2) I may design an adjustable angle to the laser, I'm working now with r=40 mm and 10/15 decree inclination, which will give me Goldilocks range. Really try aim 15 degrees +/-5 degrees of adjustment.

Screws are not countersunk yet, centre of the plate is not cut out and plate is way too big, but I want to test few configurations first.

Pekka

[PekkaNF]

Well, I think I have a way.

Pekka

[PekkaNF]

Well sort of...

Led candle battery holder and swich are pretty low quality. Hope they will last this test.

Screw up royal with hole saw. You can see decorative markings on mounting plate.

All screws are M4 eccept small screws that hold the laser lever detent. And led candle gubbins. Tried to get away with only one thread size and screw length, but used two different length and slot head screw to test the detent mechanism.

I used reamer FOUR times to green nylon piece. Can't beleive how much it deforms during milling and fitting. Almost screwd it up too. Measure once and cut twice error. Had to make slot for laser beam bigger than I had planned, because I managed so seat laser holder (shaft) 1 mm too much down. herefore oval hole allows this shaft to rotate in this recess.

Laser angle adjustment works pertty good. Have to see if the range is usable. I may make the detent a slighty stonger on middle part.

All adjustments are to be done tomorow. It has not been balaced either....

While making it I got few better ideas.

Pekka

[Arbalist]

Some interesting ideas there Pekka, well done.  Be interesting to see some pics of it in action.

[PekkaNF]

Well the part I build works and the part I bougt doesnt.

Fought bit more than hour with battery holder/switch. It works intermitently. Plastic battery holder cap looks fine designwise, but apparently the lid is too thin and contact points may be not the best material for this purpose.

Any suggestions for single 3V battery or two small 1,5V battries?

Also I knowe that these laser modules does not generally have the laser beam axially to the body, laser beam exits more than one degree out of mechanical axis. Lucily on this design you can turn the laser module and the beam will be on the central plane, few degrees error here does not matter at all.

I used tape to hold down the wires.

I could not find from mthe hardwarestore or plumbing shop 52 mm ID 2,6 mm thick O-ring. I used short about half that size, cut half and a litlle tack to hold it in the grove. Even half of ot held the unit really nicely on the spindle. This one works.

Also the angle adjustment works. No problem there. The 10-20 degree angle is just about enough. I would not complain about bigger range. The mechanism works and there seem not to be any magic on the angle, just to find one that suits for that particular purpose.

Progress so far.

Turns out to be a mechanically a good testbed.

Pekka

[vtsteam]

Good work! Looks like you've got a working device as a prototype, Pekka. How accurate are you able to locate a center with it at this stage?

[PekkaNF]

it all really depends how you can read these, but intially it looks like under 0,15 mm on flat features. On round features it looks very acuurate. Needs more testing.

On that black cylinder even spec of dust flares up. On bright flat a centre punch is not that easy.

Any suggestions of test? No DRO.

Pekka

[Steamer5]

Hi Pekka'
   Looking good, I've been quietly following from the side lines. Ok to make you marks show up, colour the surface in blue of you choice, scratch your cross lines, center punch or what every as the laser crosses from blue to the scratch mark the dot will go bright. My laser center finder has blue card with a white cross on it to use for checking / adjusting it ,working on this idea.
In this part of the world you can buy oring material off the roll & make your oring to what ever size you need ......glue with a contact adhesive, getting the ends lined up is a bit of a trick but in this instance it's probably not that important. Hope this is of help

Cheers Kerrin

[PekkaNF]

Hi Kerrin,

Thanks for the tip. I got the most part of it and will try....I have't got layout-blue yet. Almost got it two years back, but the shop would't air mail it to me. But'll find proper substitute. I allready have engineers blue and then two different stuff for scraping. I hope I will not emerge frm the shop all blue and join VT:s army of blue.

I have noticed that surface quality has a lot of do how easy it is to line up stuff, also the brightness of the beam is a big thing. Evolution version will have a filter or linear polarizer.

The last part escaped...would you alaborate a little bit more on "oring material off the roll & make your oring to ...." Sort of laser printable transparent material or cross hair printed on it, possibly on mylar or any non streching material?

Thanks,
Pekka

[Sid_Vicious]

oring = O ring. It means rubber material on a roll in different thicknesses. You choose your length and glue it together into a ring.

[Arbalist]

I've got a bottle of Layout Fluid somewhere as backup but haven't used it yet.
These are far cleaner and quicker unless you're marking out large sheets Pekka.

[vtsteam]

Total agreement on layout blue switch to markers for small stuff. I went through two metal bottles of Dykem before switching over. The last one wouldn't seal at the cap, it leaked solvent into the shop drawer -- always smelled when you opened it, and the blue actually crawled out of the cap threads.

Markers are much cleaner and easier (for small areas). I would imagine black might be even better than traditional blue for use with a laser dot.

[awemawson]

I bought a re-fillable marker specifically intended for layout fluid - big broad felt tip, push on cap and the tip assembly screws out of the body for re-filling. JLA if I remember correctly.

[Steamer5]

Hi Pekka,
Happy to help, sorry about the confusion on the lay out blue, different countries different words! Arbalist put you on the right path, I used to use a vivid permanent marker, then found one simallar to Arbalist's much better as it covers a bigger area in one pass, I find the vivid good to use in the lathe if doing a ruff mark up as to we're you want to approximatley end up
Sid sorted the o ring out, cheers Sid, you might have to go hunting but hopefully you can find some off the roll

Cheers Kerrin

[PekkaNF]

Thanks guys

I'm off to try some permanent marker pens.

I did a little internet search on layout blues and hobby solutions and got even a little more confused than I were before. I have some acrylic and oil colors, as well some blue pigment powder, I may try something later.

I did think of o-ring as a one continuous ring, I'm more used to them like that. I know that there is this material on reel, maybe I can buy somewhere a few metres or so.

Now I'm torn between just mounting a new switch and to make a battery holder or completely different design altogether.

Pekka

[vtsteam]

Pekka, for layout you want a fast-drying  thin-build hard solvent-removable color.

Oil colors are slow drying and undergo chemical change to harden. They are not solvent removable once cured, They tend to flake when scratched, rather than leave a thin line. Acrylics are faster but also also not solvent removable, and very elastic, so hard to scratch in a clean line. Both are high build. Neither is a good choice for layout work.

Usually real layout colors are dissolved by alcohol or stronger solvents like acetone. They flash dry as the solvent evaporates.  They often use dye colors, not opaque pigments to keep the build low. They scratch with clean lines. If you are going to try to make your own from pigments and common ingredients, you might consider shellac with a lot of thinner (denatured alcohol/meths) as a starting point for a vehicle. And a dye pigment would be better than opaques, since they are finer.

But markers are so much easier and available, I'd say if it isn't just a matter of curiosity, just use markers. Markers and layout colors are very similar -- fast dry solvent based dyes.

I can understand the internet confusion -- it relates to the difference between layout and spotting. Spotting colors used for hand scraping are not supposed to dry, but to transfer marks from one surface to another. Therefore they are oil based -- and non-drying oils at that. So the two kinds of "blue" (layout blue and spot blue) are completely different in composition and purposes.

[Arbalist]

Here in the UK we normally refer to them as Marking Blue (non drying) and Layout Fluid. If memory serves "Micrometer" brand marking blue came in small flat tins or small tubes. It's all messy stuff though if you're not careful. Glad I switched to markers! I have both Blue and Red ones but much prefer Blue.

I've decided to go with a spindle mounted Laser as it suits my needs better. I've come up with an adjustable angle setup as well, just need to think about what battery to use. Sadly other chores are getting in the way at the moment, hopefully work on it starts soon, maybe next week some time.

[appletree]

As Instrument fitters we used to put a ring of marking blue on the eye end of a Watchmakers eye glass and say to the Apprentice come and look at this, they walked off with a ring of blue round their eye.
A tube of marking Blue lasts forever, I doubt the Engineering profession all put together have used a full tube, it's a bit like Dog Poo it gets everywhere.

[vtsteam]

I finished off a tube of marking blue in this present lathe construction (bought in 2001), and had to switch to artist's Prussian blue oils (which I had on hand).

[PekkaNF]

I finished off a tube of marking blue in this present lathe construction (bought in 2001), and had to switch to artist's Prussian blue oils (which I had on hand).

How do you work with that? I tried some scraping long time ago and tube of oil color was what I tried. I had hard time getting a thin film of color on steel and aluminium. I think I tried pretty much everything only way that work somewhat was a little dot of color on glass, some turpentine a little on brayer and then rolling on clean class until it was all spread and then constant pressure application with brayer onto transfer surface. Palm worked better but blue does not fit to my complexion 

Generally too many variable and I gave up because I lost faith on what I was doing.

Pekka