The Shop > Tools

Anybody build Dan Gelbart angled laser centre finder?

<< < (15/34) > >>

PekkaNF:
It is actually pretty stable, least at 200-600 rpm, much smaller rpm is a bit more problem, because eye does not "make" the dot track continuous. I first put the drawbolt only on finger tight and because this unit is not balanced it would shake it loose and I could see it it on the laser beam. Hmm...wonder how small dynamic runout (imbalance) it could show........ :smart: It might make better dynamic balancer fixture :lol:

I'm just trying prove here the concept and figure out what it is for me.

My first attempt is flawed, because I want to dispense with the arbor. It should be mounted over the bottom part of the spindle or such to allow drill/mill bit to coexist. It also has sharp edges and design is dangerous. I was thinking of using a holes saw to make a disc out of plywood and drill few holes to different angles to mount the laser. But it would have been slower to make.

But sheet metal is easy to fabricate, easy to bend to try out different angles and such.

Now I have to try it out with whole lot more ambient light to proved myself will that simple askew mounted 5mW laser work for me or not. Lucily this 5 mW laser is probably way under nominal value, but it's not the problem here.

If it doesn't then I have to look for 1mW unit or start thinking of attenuating it with ND filter or polarizing filter. If I choose filter approach, then I'm very tempted to fold the optical axis with prism or two. This would have a whole lot more involved structure with mounting the prisms and other optics, but it would be easier whole lot more versatile.

I took the collimating lens of the laser and the exit beam from the laser diode was really really wide and oval. Collimating lens has really big impact on dot quality. Not sure how deep I would like to get on this one.

Pekka

rotorhead:
Hi Lads,

I have to admit to agreeing with Rob and the Sheriff of Nottingham, telescopic gauges, wobblers and a coax indicator are all I've needed, mind you I don't make owt needing tooooo much accuracy...

appletree:
I am about to undertake the building of one, I bought one of those ones like chronos sell made by SDA manufacturing. I wanted it to use as an edge finder but the dot was to big, I bought a polariser (spelling?) which made the dot dimmer/smaller. For the current project I bought a 5mw red focusable laser the dot is a bit big/bright I tried the SDA polariser to v good affect, to that end i have ordered a phone repair sheet polarising sheet from that well known auction house, sheet is about 80mm x 55mm. 

Arbalist:
The Laser I ordered arrived yesterday so I've just tried it out to see what sort of image it produces.
First shot shows the setup with Laser about 150mm from the bench and powered by a single CR2032 button cell. The unit itself looks very similar to the one Pekka bought. I paid £5.20 for it. You can get them cheaper but this one came from a UK supplier so arrived in only a couple of days and the vendor checks all units before sending them out.



When first powered up the unit produced a short "line", after rotating the lens you can get it to produce the oval shown in the two pictures below. Without the lens it produces a very dispersed rectangle shape with a bulge in the middle. I thought all lasers produced a beam but this one doesn't without a the lens, the light is spread about a lot!

This is the focused "dot", which stays pretty much the same shape over a distance of perhaps 150-200mm so quite useful but clearly too bright.



This is the same setting but with a ND10 filter (very dark) held in front of the lens. Too weak for practical use but it clearly shows how small the "dot" is without any flare. It may be possible to make it smaller/more round over a short distance.



The lens is in a threaded plastic mount which is not very tight in the barrel, as a result when you tighten the metal cap to lock it in place it rotates the lens altering the focus point! There is a spring behind the lens but it doesn't stop it rotating. I expect that some type of loctite will hold the lens in place so perhaps it's not too much of an issue?

Not sure whether to make a mount for this or try another type of laser first. The other type I've seen are only available from China so it could mean a 3-4 week wait. In the meantime I've ordered a cheap ND4 filter to see if that yields a useful output.

vtsteam:
If using an elliptical dot, you could arrange the minor diameter of the dot parallel to the axis of the fixture to minimize the line width when spinning.

I was thinking that maybe two lenses at 90 degrees would make a round dot, but then realized the above would take care of the line thickness problem as well.

In use, these things are always spinning to get a target, right? You don't stop them to find a scratched mark after finding the right quill height to minimize spot size. Or do you? Because if the first is true, then a round spot isn't necessary. The second would maybe benefit a little from a round spot.  Just askin....

Navigation

[0] Message Index

[#] Next page

[*] Previous page