Fine Centering Scope

I have an Enco version of this, but I'm sure I didn't pay remotely near $170 for it. Got it some years ago, though.

I don't think it's as accurate as a centerfinder and use it only seldom, but there are times when it's invaluable -- as in locating from a feature that can't be "felt" with any precision. It's also good for measuring between features that are difficult to get hold of. Find feature, zero DRO, move to other feature after perhaps adjusting quill or knee as necessary, read DRO, do such math as is indicated. This is very useful now and then. I'd regard it as +/- .002 or so, often close enough for much of what I do.

They are definitely adequate for finding scribe lines or punch marks, because those are seldom closer than .005". Mine aren't anyway, YMMV.

I had a fancy centering scope from an SIP jig borer that sat in its box for many years before I finally sold it on ebay, and I haven't missed it since. Learn to use an edge finder, a test indicator, and a wiggler, then worry about the scope if you still think you need it.

Same for the coax indicator in your other thread. I have a Blake, but would still be using an Indicol and DTI if I hadn't found the coax for $40.

I'm just an amateur machinist and rarely do anything that requires extreme accuracy but I use something similar to this and love it!

They sell them with different shank sizes but they also have a Starrett collet adapter that lets you use the 3/8" version in collets from 1/4" to

1".

Best Regards, Keith Marshall snipped-for-privacy@progressivelogic.com

"I'm not grown up enough to be so old!"

I've got the Enco model, bought from a sale flyer at 10% off. I had a reference to a Model Engineer article on building one, but decided it'd be a lot cheaper and faster to just buy one.

It's made by SKOAL, in Korea, and works fine in both mill and lathe. The tip has to be almost exactly an inch from what you're trying to focus on, so I keep a little 1" square of cardboard in its box.

Tove

That is an issue. I do have difficulty seeing exactly where things are without getting rather too close to things for comfort.

Hmm.

I don't have any problem getting the wiggler needle to settle on axis. The problem is seeing *exactly* where the point is with respect to a set of scribed lines and/or a punch dimple. It takes forever, lots of fiddling, and sometimes fails, yielding misplaced holes.

Edge finders I also have, and they work on edges, but not on scribed lines.

The Indicol (which I have, or a knockoff) works well, but not quickly. The claimed benefit of the Co-Ax was speed and convenience.

One question on the Co-Ax: What is the minimum spacing between mill collet and workpiece? They look a bit large.

Joe Gwinn

========= Invest in a binocular magnifier, possibly with the auxiliary magnifier loop.

for an example see

1_3/4 to 2_3/4 power that can be boosted to about 18-25$US. Cheaper ones are available but the optics are not so good and you will get a headache after wearing/using for a while in my experience. These are not that expensive and will make a world of difference. Also try getting more light in your work area. For some reason many home shop machinists fail to get enough light.

You may find this of interest

(I don't have one)

For center/prick punching locations from scribed lines get a punch with a magnifier. If you are using a coax indicator you just need a light prick punch mark, and you will damage the special punch with the Skidmore unit if you give it a mighty blast with a heavy hammer. I like the cross hair type click on

has a magnetic base which helps when using on steel.

there are also some that use a plastic magnifier.

see

Unka' George [George McDuffee] ============ Merchants have no country. The mere spot they stand on does not constitute so strong an attachment as that from which they draw their gains.

Thomas Jefferson (1743-1826), U.S. president. Letter, 17 March 1814.

On Thu, 19 Jul 2007 00:03:10 -0500, with neither quill nor qualm, F. George McDuffee quickly quoth:

Ditto for woodworkers and other hobbyists. Are we secretly afraid of seeing our mistakes in the bright lights? ;)

I saw this one at Lee Valley years ago and should have bought one when they were at a much better exchange rate. They're only $34 now, tho.

I have one of these (by some brand), with glass lenses. It works well, but it's too clumsy to work on the mill table. I've tried.

Yep, got that. I put a fluorescent fixture on the ceiling right next to the mill, and a gooseneck machine light on a nearby wall, shooting sideways and down at the business end of the endmill in arbor. It helps a lot, but still there are many contortions needed, and if the light isn't just right, it's hard to see both the scribed lines and the wiggler needle point at the same time.

Nor do I. I gather from other comments that such laser edge/center finders do work well, but are somewhat less accurate than other methods. Although the accuracy is adequate for most HSM applications.

I have one of these, made by Fowler. It works very well, and I use it a lot. It has a dot and ring, not a crosshair.

It is not useful for lining mill spindles up, though.

The Fowler unit looks like this.

As does this, although the Fowler unit came with only one magnifier and one punch, and cost $47 (if memory serves).

I'm leaning towards the Enco Fine centering Scope, I think. The key seems to be vision and reduced contortion. I also liked the suggestion that one could use it with a DRO on the mill as a largish toolmaker's microscope.

DRO. I'm in the process of installing a 3-axis Jenix DRO on the Millrite MVI. I have the X (side-to-side) scale installed, and am working on the Y (in-and-out) scale. X was easy, because there are machined parallel surfaces to attach to. Y is harder, as only half the machined surfaces are available. Z will be a bear, as nothing is flat and nothing is parallel.

Joe Gwinn

Very nice looking and I am sure it works well. Unka' George [George McDuffee] ============ Merchants have no country. The mere spot they stand on does not constitute so strong an attachment as that from which they draw their gains.

Thomas Jefferson (1743-1826), U.S. president. Letter, 17 March 1814.

I bought the one from Enco many years ago and use it often. The stated accuracy is 0.0001, but is more like 0.001. But I still find it useful where edge finders, wigglers, and the like are useless. I do cast injection molds which might need some machining or changes after casting. With the scope I can alien the mill spindle with an edge of a small cavity or the tangent of a hole. Using contact devises could easily damage the mold and most features would be too small to use an edge finder anyway. I do have 3 axis DRO to help position the cutter. I use collets for the scope and cutter. The run out of the collet also effects the accuracy. Using the scope effectively will require a lot of time and practice, and twisting your head around to see through the eye piece is frustrating. There are much more accurate scopes available but they are also 10 times the price. If you are only trying to locate over a mark on the workpiece, setting up the scope will take a lot longer than the other methods.

One cannot do better than the runout and angular error of the spindle (and collet) of the mill in question, so I won't do better than 0.001" either.

I assume that the 0.0001" Enco guarantees is measured in a far better machine than I will own any time soon.

Very good point.

Why is getting eye to scope harder than getting eye positioned to see the scribed marks and wiggler needle, with bad lighting and the bulk of the mill in the way?

Does the eyepiece arm of the scope interfere with the mill? It looks like it wants to interfere with the quill.

Flexbar has one for $425:. This is only 2.5 times. What other makes and models do you know of?

Google yielded , which is ~$1,000. And Deckel makes a really good, but pricey one.

I think it would be best to put the money into a better mill first.

Really? I find the other methods (wiggler over scribed marks) very slow and fiddly. And error-prone. But I haven't used a scope either. Please expand a bit.

The bottom line remains that you do use it a lot, and this is encouraging.

Thanks,

Joe Gwinn

Here's the problem. You may notice a black knurled sleeve just above the lower lens housing; you turn this to move the image in the lens along the same axis as the eye piece barrel. This is because the cross hair is not automatically centered with the spindle. It must be adjusted when after you put it in the collet. Because you can't get your head between the mill column and the table, you swing the eye piece in line with the x axis of the table, find a y edge, then adjust the swing until the now y hair is on the edge, swing the scope 180, if the hair is not on the edge, turn the sleeve 1/2 the distance, move the table to line up, swing to the other side, if not lined up, repeat until both sides line up. The other hair will not necessarily be centered, there is backlash in the thing, and you have to remember to turn backward then forward just like a mill table. I usually just use the one hair and zero both x and y. The scope will turn freely 360 on my Bridgeport, it just misses the DRO Z scale. Sorry about this description, but it's the best I can do from memory. I would hope that the more expensive scopes would not have this problem.

If I only need to find the edge of a block of material, I use the standard edge finder. For a center punched mark, I would use the pointed end edge finder. They would be faster than the scope.

Maybe because of the type of machining I do, trying to locate odd features. There may be other methods I'm not aware of but the fact that the scope is non-contact is a big plus when you need to locate off an existing, delicate feature on a cast mold. On a machined mold, you would have provided locaters when you began the mold so it could always be set up without touching the untouchables.

Ouch. Sounds like a crucial design flaw. This is just as fiddly to use as the wiggler.

Yes. This goes in the checklist for sure.

I don't yet have this problem. Nothing I make is untouchable. Or untouched.

Maybe the better solution for me is the laser dot generator a number of people have suggested. Cheaper, too. Here is one:

.

Any opinions, anybody?

Joe Gwinn

According to Joseph Gwinn :

[ ... ]

O.K. One difference between this and the earlier ones is that it has an adjustment for the particular spindle in which you are mounting it. Put it in the spindle, move it up or down until you have a sharp image of a scribed line under it, crank the table until the line matches the hairline in the scope, then rotate the spindle 180 degrees, and check whether the hairline is still on the scribed line. If it is not, adjust it half-way to meet the line, and repeat the test. Once you can rotate the spindle 180 degrees with no obvious change, it is calibrated to that spindle and collet, and you have the center of rotation directly over the scribed line. So zero the dial on that axis, then rotate it 90 degrees, and zero the other axis to a scribed line at right angles to the first.

Of course -- this does not correct for any errors in concentricity when you remove the scope and install the milling cutter, which may exhibit runout of its own, thus changing the width of the cut. But you are at least zeroed to the axis of rotation of the spindle.

Oh yes -- the "focal length 5/8" part of the specs shows that you have to add 5/8" to the length extending beyond the collet. At a rough guess, that would be about 3-1/2 inches if the shank is fully inside the collet.

Enjoy, DoN.

According to Joseph Gwinn :

[ ... ]

This is to adjust out any lack of concentricity in the collet, so it will indicate the true point around which the spindle rotates. (You can still have runouts introduced by the collet and burs or chips in the spindle, but at least you know that you are centered over the spindle's true rotation axis if you have the adjustable type and take the time to adjust it.)

With a truly good spindle nose and collet, you would not need the adjustment.

Don't count this against the scope. I think that the more expensive ones are *more* likely to have that, since they are also likely to have greater magnification, so the spindle errors are easier to spot.

[ ... ]

I don't think that would be as accurate as the kind which was just discussed with the knob to adjust the centering to be truly on.

Enjoy, DoN.

OK. I see why one would do this, but what escapes me is that if the fine centering scope isn't a whole lot better at something than a wiggler, why would anyone buy a scope? I guess what's emerging is that the advantage is accuracy (and reliability), but not speed. And I was hoping for all three.

I imagine that you are right. The question is if it's good enough, and sufficiently faster to use to be worthwhile. Does anyone have experience? I recall one poster reported that it was good enough for his non-stringent purposes.

Joe Gwinn

If this is what the expensive unit does, what does the $170 unit do? I thought it used the same 180 degree moves and difference splitting.

Yep.

And the quill travel is 4", so knee motion will be required.

Joe Gwinn

According to Joseph Gwinn :

I consider it a lot better for aligning to scribed lines, and scribed lines need not be that far from accurate, if you use a stack of gauge blocks and a rigid scriber sliding along a surface plate to scribe the lines.

The speed is not that bad. Normally you look at one position, adjust the axis to bring the scribed line up to the hairline in the scope, then rotate it 180 degrees and a quick look tells you that it is set right -- or occasionally (if the collet is poor or is seated on a chip or bur) that you need to tweak the setting by turning the knob to bring the hairline halfway between where it is and the scribed line. Once you've done this, you can also trust it rotated 90 degrees for zeroing on the other scribed line. You only need to check the zeroing of the scope once when you have just put it into the collet, or if you accidentally hit the knob after it has been zeroed.

And you'll get a feel pretty quickly how often you actually need to tweak it with *your* spindle and collets. In my case, I would be using it in a 30 taper end mill holder, since I don't have R8 collets in my mill.

It is a *lot* easier to see errors with this than with a wiggler, in part because you don't have to deal with parallax, which you do when trying to see the point of the wiggler and the scribed line from an angle. The only way around that is to bring the point down to

*almost* contact, which can be more fiddly than the zeroing of the scope. [ ... ]

That could perhaps be the less expensive ones without the zeroing knob.

I have one (which I had to machine out the old threads for a broken-off microscope objective and mount one which I had), but I need to finish the conversion of the mill -- it is no good at the moment with some stepper motors and some servo motors and a serious case of electronics Altzheimer's in the original controller. :-)

And my other mill is a horizontal spindle mill, which would be awkward to use this with.

Enjoy, DoN.

According to Joseph Gwinn :

[ ... ]

The URL for that one is gone, so I can't re-check it, but as I remember, it did not have the knob which is visible in the flexbar unit (opposite and a bit above the eyepiece tube's joining point). So, I think that those cheaper ones do not have this adjustment, and perhaps also have less magnification, so there is less need for the correction

-- unless you drop it, of course. :-)

[ ... ]

Unless you are using endmill holders of similar extension instead of collets..

Enjoy, DoN.