Centering Scope For Milling Machine: Handy or Not?

Centering Scope For Milling Machine..... Have never used one, have never seen one in use. How they are used in general? And are they something useful to have around?

I assume they could be used for picking up a edge, intersection, small hole, punch, etc, that you couldn't PU with an edge finder or test or coax indicactor, etc. The ones I have seen have like a .500 inch shaft that is gripped by a collet in the spindle, eyepiece at about 45* angle to spindle.

I already have the basic edge & hole finding tools. Two BestTest indicators, cylindrical & pointed edge finder, and an Indicol.

So just want to hear opinions and experience using them. Photos of yours would be good.

If I were to get one it would probably be used. What should I look for in terms of a decent scopes attributes? What about magnification? 5X, 10X, 20X, etc ?

I had one - gave it away! Found that a Co-Ax dial is much easier!
The one I had was adjustable -needed to be calibrated, you had to look through -it banged my head, I just found it to be a PITA.
I suppose if its free, like mine was ,its worth trying.

mt2,

The advantages over conventional methods are few, if any. Mainly I will list the disadvantages...

* For maximum accuracy they have to be 're-zeroed' every time they are chucked in a collet.
* You need clearance on mill-head in order to be able to swing the scope 90* for zeroing.
* They necessarily have a very shallow depth-of-field and it can be difficult to impossible to pick up edge features reliably. A good quality edge finder used carefully is just as accurate.
* They are only as good (with some loss of accuracy) as your layout lines and center-punch marks.
* There is this invention called a DRO (or some arrangement of dial indicators and gages) that render the centering scope obsolete.
* In order to pick up side edges of features or holes the edges have to be sharp and no bevels. As I said... there are quicker methods that are at least as accurate.

You will be better off getting a DRO installed if you don't already have one.

At one time they would have been handy... before DROs were invented... if, say, you had a cast part that had uneven edges (can't use an edge finder), and the part had a flat machined surface parallel to the table travel, and the part had carefully made layout lines scribed in it. The you could zero on designated spot/crossed lines, move to the first feature (say a bored hole), remove the scope, drill and bore the hole. Then put the scope back in and re-zero it. Move to the next feature. Drill and bore. Repeat. Gets pretty tedious. Even if the scope maintains acceptable zero there will be a LOT of knee cranking going on between features.

For max accuracy they would have used machinist buttons instead of a scope.

I own a couple of them. One is very similar to this one: Skoal Centering Scope | eBay on eBay. At one point I thought they might be handy until I discovered how limited they are. Perhaps someday I will think up of a good use where they are the ideal tool for the job. It hasn't happened yet.

I hope someone who has used them can tell us about a good use.

-DU-

Probably the most unused bit of equipment I ever bought. ISTR mine needed calibrating too, defiinitely end up banging your head when you need to look through to set it up 180(?) deg apart.
Honestly, it may well be a essential piece of kit for some people. I tried it a few times and it's gathered dust on the shelf ever since. If you were in the UK I'd be happy to sell you mine cheap.

I have a Skoal like the one pictured........just don't know why.

One good use is for work where you transfer hole locations from an existing part or template. A DRO won't help you there and the centering scope can be a bit faster than trying to pick up punch locations with various types of indicator.

I suppose they could also be used, with table motions and a DRO, as a poor man's inspection scope; if you happen to have a mill where the ergonomics wouldn't be a total pain. Find one feature, zero the DRO, then crank to find another feature . . .

Otherwise, as David and others have said, a DRO-equipped mill or CNC has generally replaced hand layout and punched hole etc. locations. There are better methods of picking up the single origin point typically needed.

My answer the question in the title to this thread is, yes, they are handy. As an example of a job where a DTI wouldn't have worked, I needed to extract a broken screw (approx. 6-32, although it was an odd metric size) from a housing where damaging it would have been completely unacceptable. The jagged portion of the screw partially protruding from the housing made use of a DTI impossible, but with a centering scope it was trivial to center the spindle directly over the broken screw.

If you don't bump the adjusting screws there is no need to "calibrate" (i.e. re-zero) the centering scope each time it is used. However, it is easy and fast to do it so I do it every time. It takes no longer than the process to zero the DTI when using one of them to center the hole.

As for magnification, you have to decide what you're likely to use it for. Higher magnification gives higher resolution, but it also give a smaller field of view. My Titan model Y-1 is 20x, with 0.001" marks and a 0.38" field of view. That is, I can center it over holes up to ~3/8" dia. to within 0.001". Personally, 0.001" is sufficient for me (and, I have a separate 3x eyepiece magnifier when needed, if centering over a much smaller hole), so I would not want to give up field of view to have a higher magnification (40x would give 0.0005", but with a 0.19"-dia. field of view).

Unless someone has a specific, immediate need for it, I wouldn't recommend a centering scope to be their first purchase for centering purposes. However, unlike some of the other replies, I would very much hate to be without mine. For certain specialized tasks there is no substitute that I am aware of.

I should add that my mill has a 4-axis DRO. Having the DRO does not eliminate my need for the centering scope.

opscimc said:

My answer the question in the title to this thread is, yes, they are handy. As an example of a job where a DTI wouldn't have worked, I needed to extract a broken screw (approx. 6-32, although it was an odd metric size) from a housing where damaging it would have been completely unacceptable. The jagged portion of the screw partially protruding from the housing made use of a DTI impossible, but with a centering scope it was trivial to center the spindle directly over the broken screw.

If you don't bump the adjusting screws there is no need to "calibrate" (i.e. re-zero) the centering scope each time it is used. However, it is easy and fast to do it so I do it every time. It takes no longer than the process to zero the DTI when using one of them to center the hole.



As for magnification, you have to decide what you're likely to use it for. Higher magnification gives higher resolution, but it also give a smaller field of view. My Titan model Y-1 is 20x, with 0.001" marks and a 0.38" field of view. That is, I can center it over holes up to ~3/8" dia. to within 0.001". Personally, 0.001" is sufficient for me (and, I have a separate 3x eyepiece magnifier when needed, if centering over a much smaller hole), so I would not want to give up field of view to have a higher magnification (40x would give 0.0005", but with a 0.19"-dia. field of view).

Unless someone has a specific, immediate need for it, I wouldn't recommend a centering scope to be their first purchase for centering purposes. However, unlike some of the other replies, I would very much hate to be without mine. For certain specialized tasks there is no substitute that I am aware of.

I should add that my mill has a 4-axis DRO. Having the DRO does not eliminate my need for the centering scope.

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You make a good point! I can see where it would work well for that.

It is not something you use instead of an edge finder, 3d taster, touch probe, or indicator.

It IS something very handy for certain tasks, sometimes kind of bizarre, where those things won't help you. I have a titan, looks a lot like the skoal, may be nicer, may not be. I won't be giving it away so long as I have mills (most of which are CNC and the other has a DRO.)

I would NOT suggest you buy one until after you have a 3d-taster, and/or a touch probe, and a good indicator with good mounts for it.

I have a few 1/2 and 5/8 dowel pins that I turned to a point. I find them handy when I have to work off scribed lines. I thought about buying one but I would like to try it before I spend money on one.

I bought a Japanese centering scope about 35-40 years ago. I also bought a Blake Co-Ax indicator. I use the scope whenever I have scribed lines marking drilled hole locations that need to be accurate. The Blake is not so good for that job because it needs a center punch mark. The scope is more accurate than I can punch mark the intersection of scribed lines, even with the cute little Starrett magnifying hammer.

A little blob of modeling clay and a sewing needle can't be beat for speed if you only need a few thousandths of location accuracy.

The Blake indicator is great for locating on an existing bore, which is not nearly as convenient with the scope.

I have no DRO on my mills. I don't see where one would help find scribed lines. I did put a DRO on one of my lathes, so I am not totally rejecting progress.

Larry

I have had one like the Skoal ~5 years, and have used it exactly twice. Both times to pick up scribe marks on a part where using the scope was the only way to do it. I don't use it much, but when needed, they can be hard to beat. However, all the downsides others have mentioned apply: recalibrating, banging your head, small field of view, small depth of field, etc, etc. Before you get one, decide if you have work where you need one for something you can't do any other way, or for which the hassle of using a scope is less than the hassle of finding the location any other way.

Cheers,
--Hawk

Our toolmakers at the plant use them when they have to drill out a broken screw, usually a 2-56 or an 0-80. They have a small box with several hundred removed screws that they save for entertainment.

As someone who has spent way too many hours looking through microscopes: eye relief and field of view are just as important as magnification and depth of field. These two specifications are often buried in the back off sales fliers if they are published at all.

Eye relief is especially important for those of us with older eyes. Often older scope users have to have their scopes modified so their tired eyes can still focus when using the scope. Microscope use is a task for young eyes. I was very privileged, as I got middle-aged, to have younger-eyed subordinates to look through the scopes for me.

I've used small precision drills units with a binocular microscope that sat on top of the drill head and looked through the spindle. This was a very useful arrangement and pretty easy to use. The little toy scopes that chuck in the collet on the BP are a kludge at best. Should I come across the need I would mount a quality Leica or Nikon binocular head on an arm outboard of the spindle and focused on a wiggler. By looking down alternate axis one could easily pick up a scribed cross to tenths.

Are scribed lines as good as +/- 0.001" (or even +/- 0.002") ? I really don't know. Scribed lines have a variable width and the center of the line is not always at the center of the dimension. Some scribes are V shaped and some are more V shaped (that is an edge of the line is at the dimensional location. )

Since I do mostly prototypes and one-two offs I almost always use layout dye and scribed lines on my work ... at least as a 'sanity check'. But when it comes to accuracy better than +/- 0.005" I use DROs, gages, DTIs, micrometers, etc. For +/- 0.005" and up scribed lines, wigglers, calipers, and edge finders work fine. I use a magnifier when using a wiggler.

I could see them being handy for approximately centering over a broken screw or tap.

Don't get me wrong. I DO use measuring microscopes in my work for measuring features on objects that can't really be physically contacted to pick up an edge or probed. Stuff like small printed circuits with fine features, slit width and spacing for optical components. That is usually done a special microscope that is designed for such use and as Starbolin said, really good quality optics.

-DU-

Our shop will be installing video cameras with macro lenses on the mills in the future. They saw them in use at a sister plant, and they make it a lot easier to see what's what. They still have microscopes, but they do enough small parts that they are looking forward to the cameras.

starbolin said:

The little toy scopes that chuck in the collet on the BP are a kludge at best. Should I come across the need I would mount a quality Leica or Nikon binocular head on an arm outboard of the spindle and focused on a wiggler. By looking down alternate axis one could easily pick up a scribed cross to tenths.

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Sorry, but as a long-time user of many types of microscopes, and as a designer of optical instruments, I disagree. Mounting a a binocular microscope on the head is no more equivalent of a centering microscope than a binocular microscope is equivalent to a metallurgical microscope. And it's not an issue of "toy" optics vs. quality Leica or Nikon. The design that allows a reticule to be accurately centered over the center of rotation is a fundamental difference between a centering microscope from a microscope outboard of the spindle. Further, a microscope mounted outboard intrinsically views the surface at an angle, which is problematic because of the limited depth of field at the necessary magnifications involved.

David Utidjian said:

Don't get me wrong. I DO use measuring microscopes in my work for measuring features on objects that can't really be physically contacted to pick up an edge or probed. Stuff like small printed circuits with fine features, slit width and spacing for optical components. That is usually done a special microscope that is designed for such use and as Starbolin said, really good quality optics.

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A centering microscope certainly can be used to pick up an edge or a line even though that's not making use of them for what they are designed to do. They are "special microscopes" in your terminology. Also, the mechanical design is an issue, but the quality of the optics is not. My Titan Y-1 centering microscope wouldn't function any better if the optics in it were made by Zeiss. I say this as an owner of at least six distinct types of microscopes made by Zeiss, Nikon, Olympus, Bausch & Lomb, Gaertner and Titan.

David Utidjian said:

I could see them being handy for approximately centering over a broken screw or tap.

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Because of the design I can center the spindle of my mill over the center of a broken screw or tap to no worse than +/-0.001". If you call that 'approximately', than so be it. However, are you aware of an alternative method or tool that does this particular job at a similar level of accuracy?

I use mine a few times a year. I have a Skoal. Can't figure out why they didn't put a lock of some sort on the calibration ring on their centering scope. It is hard not to move the ring when boxing, mounting, un-mounting and re-boxing it. Anyone have a aftermarket lock suggestion?

Ken

KMoffett said:

<> I have a Skoal. Can't figure out why they didn't put a lock of some sort on the calibration ring on their centering scope. It is hard not to move the ring when boxing, mounting, un-mounting and re-boxing it. Anyone have a aftermarket lock suggestion?

Ken

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Suggestion. Have not actually done this myself: Tape spanning from the ring to the body of the scope and wrapping 2/3 of the way around the scope. the eyepiece arm prevents a full turn.

Denis

opscimc said:

Also, the mechanical design is an issue, but the quality of the optics is not. My Titan Y-1 centering microscope wouldn't function any better if the optics in it were made by Zeiss. I say this as an owner of at least six distinct types of microscopes made by Zeiss, Nikon, Olympus, Bausch & Lomb, Gaertner and Titan.

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Assuming of course that the quality of the optics, mechanical design of the scope and surface/edge features of the part are are all amenable to their use. This is not always the case...

Because of the design I can center the spindle of my mill over the center of a broken screw or tap to no worse than +/-0.001". If you call that 'approximately', than so be it.

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... and, speaking for myself, certainly isn't in this one. What feature are you centering on? Some "point" of the broken screw or tap? Is that "point" +/- 0.001" with the center of the original hole? The "edge" of the hole? The "edge" of a threaded hole is not +/- 0.001" round unless you work with finer threads than I can imagine. How would you even verify that? If you can pickup the center of a tapped hole with a broken screw or tap in it to +/- 0.001" then that is great. I do not have such confidence in my equipment or abilities.

However, are you aware of an alternative method or tool that does this particular job at a similar level of accuracy?

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No, I am not. I just doubt my ability to achieve the level of accuracy you are claiming. BUT I WILL try and use my scope to get close to the center should this situation come up again that it would be useful. Most of the time I already know the location relative to a reliable feature or I can determine the location from other features. All that said I rarely have tapped holes that need to be located better than about +/- 0.005 and 'eyeballing' with a pin in the chuck that is the minor diameter of the tapped hole is good enough for that and a heckuvalot quicker.

-DU-