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How Usefull are the Older Shadow Graphs?

Ox

Diamond
Joined
Aug 27, 2002
Location
Northwest Ohio
Is something like this still of much use compared to the newer units?

20131023110314333_L.JPG



One feature that I like is "Surface Illumination" that I have only seen on "newer" units.
Would these have had such a thing?

If not - a guy could simply add something on to it eh?
There's nothing special about the rest of the unit is there?
Just a cpl little light bulbs is it eh?


Anything else?


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Think Snow Eh!
Ox
 
Many older comparators were equipped with surface illumination. That was an option you could order or not. It should not be too tough to come up with lights to give this effect.

Mounting a set of digital readouts will make life much easier.
 
Biggest deal is X-Y-Z stage and the old ones tend to be better.

Ring light will give you surface but these machines never do good at front lighting at high mags.
For front lighting you need to pump a lot of power into these guys at 30+X.

Is this a 30 screen? I ask because the readout looks tiny in the picture
OGP?
Looks like a very nice piece.
Bob
 
That one is down right new compared to this one that I picked up Friday at an auction. I've been looking for something small for the 3 times a year I need to check a radius. It only had the 20X lens with it. It does have surface illumination! For $60 you can't beat it.
micro vue.jpg
 
Yeah, I have an old MicroVue (model 300?) like the one Archer120x shows. Sometime soon, I'll replace the conventional bulb with the head off a small LED flashlight, and will add surface illumination with a 2nd head while I'm at it.

Despite being small, dim, and antique, I find mine very handy. Wish I could get an additional lens power for it, but not bad enough to even check what the lens mount is.
 
One feature that I like is "Surface Illumination" that I have only seen on "newer" units.
Would these have had such a thing?

If not - a guy could simply add something on to it eh?
There's nothing special about the rest of the unit is there?
Just a cpl little light bulbs is it eh?

Not quite 'just a cpl light blubs'.

A shadowgraph relies upon collimated backlight for its precision.

Reflected 'front' lighting is anything but collimated. In this case the precision relies upon the surface defined by the cones of focus, which probably isn't planar.

Shadowgraphs cheat Seidel abberations by utilizing parallel rays.

distortion.gif
 
I use a 1963 Watson Mannesty and it is well worth having IMO ,use it quite a bit for checking tool rads and other detais hard to check any other way.

Mine has surface ilumination but all it is is a specially shaped glass ring which fits around the main lense, the back side of it is mirrored to reflect the light from the main bulb ,I have only messed about with this ,not really needed to use it.
 
Pretty sure that I have seen surface illum done via two flexible leads with LED's or similar on the end.
Certainly nothing calbrated about that.

Did I not see that?
Am I imagining that?


---------------------

Think Snow Eh!
Ox
 
Pretty sure that I have seen surface illum done via two flexible leads with LED's or similar on the end.
Certainly nothing calbrated about that.

Did I not see that?
Am I imagining that?


---------------------

Think Snow Eh!
Ox

That instrument must have had more advanced optics than the run of the mill projector, or had a section in the operators manual that advised that precise reflected light measurements can only be made along the optical axis of the machine, and then proceed to present instructions on how to find the optical axis.

A normal shadowgraph is focused at infinity (parallel rays/collimated light). Front illumination turns the device into a projection microscope focused on the object. The object is usually 3-dimensional and the projected image is 2-dimensional.

You just have to take that in perspective.
 
Ok, now we know the theory which is good. Ox, what would you use it for? Great for the "hand animals" that we used to make on the wall. I use mine for small angles, radii, thread detail, etc when I use the surface or T&C grinder.

Tom
 
Pretty sure that I have seen surface illum done via two flexible leads with LED's or similar on the end.
Certainly nothing calbrated about that.

Did I not see that?
Am I imagining that?


---------------------

Think Snow Eh!
Ox

You definitely didn't imagine it. We've got one with the flexible lights. I've never been able to get all that clear of a surface image with it. I've never really looked into how that feature is supposed to be used though.

I've found it handy for checking turned parts mostly.
 

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I grind a lot of intricate (sort of) small core pins for molds, and use a Comparator daily. Just as essential as a mill, lathe or grinder, IMHO. With a Metronics DRO, easy to check radii, angles, just by clicking on a few points.. DRO does the calculations..
 
Ox, what would you use it for?

Tom


This and that I s'pose.

I don't have one. I've been here for <25 yrs and have gotten away this long.

I have needed a CMM more than a comparator for features that [standard] hard tooling just can't measure.

But is something that would be nice to have.

I have used the surface illum somewhere on some part. I don't recall what or where anymore, but I doo know that it is a feature that I would want. So if it would not be retrofittable, then I wouldn't bother even looking at such an item is all.

Just a thought that sparked through accrost my mind and figgered that I should check into it a little for future ref.


--------------------

Think Snow Eh!
Ox
 
Biggest deal is X-Y-Z stage and the old ones tend to be better.

Ring light will give you surface but these machines never do good at front lighting at high mags.
For front lighting you need to pump a lot of power into these guys at 30+X.

Is this a 30 screen? I ask because the readout looks tiny in the picture
OGP?
Looks like a very nice piece.
Bob

It sure looks like an OGP, but it is labeled as an Excello.

???


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Think Snow Eh!
Ox
 
about 20 years ago I worked at a defense contractor. They would make "templates" that they would put on the screen. I would make about 3500 rounds of ammo per shift. We would lay a round in the fixture that was mounted to the table and turn on the light. As long as all features fell within the high and low limit lines drawn on the template.....voila....good form on the bullet. Obviously we also had to mic. the critical diameters. But this worked very well for the body of the part which had many odd rads, angles and chamfers on it.
 
Inspector where I used to work used high reflectance silver paint and dull black to create contrast when using the surface illumination.

The optical comparator is just another tool along with CMM's and toolmaker's microscopes that are nice to have if you can afford them and space to put them. Your eyes are a valuable part of the inspection system that machines just cannot duplicate.

Tom
 
I replaced my old shadowgraph some years back with a new Deltronic comparator and it was like going from watching a 13" black and white Tv with rabbit ears and a pair of pliers to change the channel to a 60" hdtv with a remote and surround sound. But if you don't have much need for one it will certainly work and that one looks to be in great shape.
 
On these things the "collimating or telecentric view" is done in both the back light and the lens system.
The collimated back light is a very big deal on round parts.
Due to the fact that lens systems will also try to extract only light rays going straight you need to pump a lot into the surface illumination.

Yup, a couple of fibers on a decent size source work just fine at reasonable mags.
For surface viewing at 100X you need an absurd amount of light, at 20-32.5x it's easy with a 150-250 watt source and some fiber "arms".
One of these or better yet one with two arms would most likely work just fine for ya.
Fiber Optic Illuminator Microscope Ring Light Source | eBay

Is it a good price and in the "expendable cash"?
If so just buy the darn thing. To me these are like a bench grinder, everybody should have at least one.
Bob
 








 
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