Crosshair laser

[throbscottle]

I'm wanting to equip the pcb drill I'm building with a cross hair so I can always hit the right spot. There are some 5mw laser modules around equipped with a cross hair lens, such as this: **broken link removed**

5mw is rather high, but lower powered lasers are a lot more expensive. So I was wondering about power reducing schemes. Most obvious choice is reducing the current, but I'm guessing there's a point at which it cuts off. Next option is to give it a pulse train as it's power supply, so it's only on for a small percentage of the time. I have no idea how much of a reduction in it's ability to blind me that would actually confer.

Or is the fact that the beam is spread out into a cross shape a sufficient safety margin in it's own right?

The other option is to get one of those cheap 1mw laser pointers and use the diode out of that with the lens out of the module. The lenses themselves are relatively expensive, I found. Crazy situation.

So, as always, what does anyone think?

 

[jpanhalt]

How are you going to make the cross-hairs co-axial with the drill bit at all distances? How wide will the cross-hairs be?

Several years ago, I bought an optical device to do exactly what you seem to want to do, but not for PCB's. I have never used it. You can easily get 0.005" accuracy or better with just a center punch. If I need better than that, I use a mill with DRO.

As for PCB's, use something like drill-aid.ulp (Eagle). It will allow you to easily get a #66 (0.033") drill in the center of a TH pad.

John

 

[Scotophor]

My dad's drill press came with a laser crosshair device installed. It actually projects two individual lines from locations 90 degrees apart, to get around the parallax problem alluded to by jpanhalt.

 

[atferrari]

My dad's drill press came with a laser crosshair device installed. It actually projects two individual lines from locations 90 degrees apart, to get around the parallax problem alluded to by jpanhalt.

I always wanted to know how. Now I know.

 

[Joe G]

I just use the shadow from 2 small leds mounted above and to the side of the chuck. It makes a shadow of the drill bit similar to a cross-hair ....as per what Scotophor stated. I also use a really good magnifying glass......

 

[atferrari]

I just use the shadow from 2 small leds mounted above and to the side of the chuck. It makes a shadow of the drill bit similar to a cross-hair ....as per what Scotophor stated. I also use a really good magnifying glass......

Could you show a picture?

 

[Joe G]

https://www.electro-tech-online.com/threads/any-info-on-these-motors.135168/
I've changed it around since then a few more times added the second led...now no leds.... depends on what I'm drilling......

 

[throbscottle]

Well, given that there is very little variance in the thickness of what I'm drilling, the laser doesn't actually need to track. It can be fixed to a bracket off the upright part, alongside the drill's chuck - or possibly put a small mirror there and mount the laser elsewhere down a little tube. The tilt of the thing would be small enough to not make any difference to me. Actually thinking about it a half-silvered mirror could lose some of the light into bit of black stuff, couldn't it.

If it did need to track, i like Scotophor's suggestion, but it would be easy just to make an arm that tilted it the right amount as the drill moved up and down.

Joe G, (ah yes, I remember that conversation!) didn't you find that the light from one LED would fill in the shadow created by the other one? Also, you would have had a V shape, rather than a cross, wouldn't you????? Otherwise it seems like a really good idea

Oh and John, this is simply an aid so I can put the pad on the board I'm positioning with my fingers, where the drill is going. Centre punching won't make a difference, nor will any software - but thanks for the response, you always give me something to think about

Anyway, no-one's come up with an answer to my question yet

 

[picbits]

I've tried doing this - the lines are generally too bright and not accurate/thin enough to pinpoint a PCB hole to be drilled.

I had a little more success with limiting the current to the bare minimum and using a much dimmer laser projection -less glare.

 

[Joe G]

yes, throbscottle, you are correct, It was a V shape.

and you may be able to use 2 laser pointer with a line filter on each one, and align both up with a drill bit? I remember seeing some small pointer that you could order different
image caps....smily face....crosshair were two I remembered....it's been a long time ago, the pointer was a key chain type that took 3 button batteries.

 

[jpanhalt]

Are these going to be single-sided or double-sided boards? If single-sided, you might put a bright light below the board. If you then use drill-aid.ulp, you could tell when the drill was occluding the tiny spot of light.

John

EDIT: Corrected spelling drill-aid

 

[throbscottle]

Aha! I think John might have it! But I don't know what drill-air is? Anyway, if I make the spot of light small enough and bright enough it should be a good enough indicator anyway because it will be either hidden or obviously wrong, unless it's in the right spot.
Picbits - thank you for the most useful reply!
Joe - it did occur to me to combine a beam splitter with 2 line lenses and get an arrangement like scotophor's dads drill press, but using only one laser. So it's an interesting point. Though I looked for laser pointers with different pattern caps, could only find decorative, not useful, ones. Though it does occur to me I could make a tiny cross shaped slit in a bit of metal and shine the beam through that. Diffraction might be a problem though.

 

[KeepItSimpleStupid]

Oh and John, this is simply an aid so I can put the pad on the board I'm positioning with my fingers, where the drill is going. Centre punching won't make a difference, nor will any software - but thanks for the response, you always give me something to think about

I've heard that some PCB programs have the ability to "dimple" at the holes. Meaning the holes are exposed less and etch slightly more. You have to do photo exposure though. Would that help?

 

[throbscottle]

Mmm, not really, KISS, but thanks for the suggestion. All my holes are etched anyway. So I can see them perfectly. I just need a means to align them with the drill bit.

 

[jpanhalt]

Have you tried what I suggested about using a small center punch/dimple/guide hole -- whatever you want to call it -- or are you just rejecting that suggestion on theory? In the situation where you have a handheld board on a smooth table surface, if you get the drill tip anywhere within the area of a etched hole in the copper plating, it will tend to pull the board and center the hole. The movement is not great, just a few thousandths, but you can both see and feel it. The speed of the drill also can make a difference on that centering effect.

On the other hand, if you have a very rigid set-up, like the board clamped to a CNC milling table, then the effect may be to bend the drill and make a crooked hole. I am assuming that is not the case here.
John

Edit: I don't often photograph my just etched boards -- I wait until I cover my mistakes with solder--, but I found two examples. The holes are #66 (33 mil). None are perfectly centered, but they were OK. Done with drill press, drill-aid.ulp, and just a goose-neck lamp attached to the drill press column to give good lighting. Traces on the left image are 24 mil. The #66 drill is the hole size I use for a typical 0.1" on-center, square-pin header. The redish tone on the right example is due to the photoresist I use that has not yet been removed.

 

[atferrari]

https://www.electro-tech-online.com/threads/any-info-on-these-motors.135168/
I've changed it around since then a few more times added the second led...now no leds.... depends on what I'm drilling......

Sorry Joe. I could not find what I believe is your setup, in that picture.

Any recent one where I could see how the LEDs are placed?

My concern is that whatever you do and no matter how you look at it you never could be exactly above the point where the bit should do its job.

I am affraid the CNC was invented for that..

 

[throbscottle]

Hi John

Had a very long couple of days.

I didn't mean to dismiss your suggestion out of hand. I actually have a moderately good drill that I made last year I have been using as you describe, but the holes are etched so no need to centre punch, the dimple is adequate. The new drill is for use the tungsten carbide bits, so I want to get the alignment correct before the bit touches the board. Oh damn my battery's going and it's not charging.

 

[throbscottle]

Right, finally managed go log in using phone. Pest this is. So, years ago I centre punched all my holes so I could align dry transfers on the marks, worked very well, drilling usually went well though the drill was hand-held. But with having got the carbide bits, and knowing their reputation for being very fragile (I got a cheap set, thinnest is 0.3mm, I look forward to trying that out!) I want to reduce lateral pull on the bits to a negligible amount. Same reason I don't want the bump around a centre punch spot, if I'm slightly off it could be disastrous. Also I don't want to have to keep centre punching! Hence the desire for a target which is coaxial with the drill.

 

[shortbus=]

As long as your PCB's are all the same thickness, why would you need cross hairs? Just on single 'dot' at the point where the drill meets the board would do what you want. A laser pointer with a mask over the lens to make a dot is all thats needed. A laser sight for a gun doesn't have cross hairs.

 

[4pyros]

Yes use a point of light.
You should be able to dim your lazer be reducing the current.